,,laboratory ,,manual ,,of ,,glass-,,blowing ,mc,graw-,hill ,book ,company ,publishers of ,books for ,electrical ,world ,engineering ,record ,railway ,age ,gazette ,signal ,engineer ,electric ,railway ,journal ,metallurgical and ,chemical ,engineering ,the ,engineering and ,mining ,journal ,engineering ,news ,american ,machinist ,american ,engineer ,coal ,age ,power ,,laboratory ,,manual ,,of ,,glass-,,blowing ,,by ,,francis ,c4 ,,frary1 ,,ph4 ,d4 ,,assistant ,,professor ,,of ,,chemistry ,,university ,,of ,,minnesota ,mc,g,r,a,w-,,hill ,,book ,,company1 ,,inc4 #bci ,,west #ci,,th ,,street1 ,,new ,,york #f ,,bouverie ,,street1 ,,london1 ,e4 ,c4 #aiad ,,copyright1 #aiad1 ,,by ,,the ,mc,g,r,a,w-,,hill ,,book ,,company1 ,,inc4 ,,preface ,the purpose of this little book is to provide a clear and detailed discussion of the elements of glass-blowing4 ,many laboratories in this country1 especially in the west1 are located a long way from any professional glass-blower1 and the time and money spent in shipping broken apparatus several hundred miles to be mended could often be saved if some of the laboratory force could seal on a new stopcock1 replace a broken tube1 or make some temporary repairs4 ,many men in physical or chemical laboratories have occasion to modify some piece of apparatus designed perhaps for other uses1 or to design new apparatus4 ,to such also1 the ability to perform some of the operations herein described may be very valuable4 ,no originality is claimed for the methods here described4 ,they are those which the author has found most suitable and convenient in his own work1 and most easily learned by students4 ,the aim has been to describe each operation in such detail that a beginner can follow the process without help and1 with practice1 attain satisfactory results4 ,it is1 however1 much easier to perform any of the operations described1 after seeing some one else perform it correctly2 since the temperature1 the exact time to begin blowing the glass1 and many other little details are very difficult to obtain from a description4 ,it has not been thought worth while to describe the process of making stopcocks1 thermometers1 vacuum tubes1 etc41 as such things can be purchased more cheaply and of much better quality than any amateur can make unless he is willing to spend a very large amount of time in practice4 ,for similar reasons the manipulation of quartz glass has been omitted4 ,the author will be grateful for all suggestions and criticisms tending to improve the methods presented4 ,if some of them appear to be given in excessive detail1 the reader will remember that many things which are obvious to the experienced worker are not so to the beginner1 and that it is the little details in the manipulation which often spell success or failure in glass-blowing4 ,f4 ,c4 ,f4 ,,minneapolis1 ,,minn41 ,january1 #aiad4 ,,contents ,,page ,preface v ,,chapter ,i ,,materials ,,and ,,apparatus #a ,varieties and defects of glass--,devitrification--,annealing glass--,blowpipe and bellows--,light--,arrangement of exercises4 ,,chapter ,,ii ,,general ,,operations #g ,cutting1 bending1 constricting and flanging the tubing--,methods of rotation and blowing4 ,,chapter ,,iii ,,elementary ,,exercises #af ,joining two pieces of tubing of the same diameter--,the tee tube--,joining two tubes of different diameters--,blowing bulbs4 ,,chapter ,,iv ,,advanced ,,exercises #ce ,sealing a tube through another tube3 ,the gas-washing tube1 suction pump1 and ,kjeldahl trap4 ,,chapter ,v ,,modified ,,methods ,,and ,,special ,,operations #dc ,capillary tubing--,glass rod--,mending stopcocks--,closed circuits of tubing--,spirals--,ground joints--,sealing in platinum wire--,sealing vacuum tubes--,closed tubes for heating under pressure4 ,,index #ei ,,laboratory ,,manual ,,of ,,glass-,,blowing ,,chapter ,i ,,materials ,,and ,,apparatus ,one of the most important factors in the success of any piece of glass-blowing is the glass employed4 ,as is well known1 there are two general varieties of glass3 ,lead glass and soda glass4 ,formerly much apparatus was made of lead glass1 but at present it is very seldom met with1 except in the little drops of special glass used to seal platinum wires into the larger sizes of tubes4 ,lead glass is softer and more readily fusible than soda glass1 but has the disagreeable property of growing black in a few seconds unless worked in a strong oxidizing flame4 ,this may be prevented by using a hissing flame1 with a large excess of air1 and working in the extreme end of the flame2 or the black lead formed may thus be reoxidized1 and the glass restored to its original clearness4 ,almost all the soft glass on the market is a soda glass1 although sometimes part of the soda is replaced by potash4 ,most of the hard glass appears to be a potash glass4 ,the following qualities are desirable in a glass for ordinary working3 7#a7 moderately low working temperature1 7#b7 freedom from air bubbles1 striations and irregularities1 7#c7 proper composition1 so that the glass will not devitrify or crystallize while being handled at its working temperature1 7#d7 ability to withstand rapid heating without cracking4 ,the working temperature of different samples of so-called soft glass varies a good deal1 and is best determined by trial4 ,the glass should become almost soft enough for blowing in a flame that still shows a little yellow near the tip1 so that at the highest temperature of the flame it may flow fairly freely and thus easily eliminate irregularities in thickness4 ,if the glass is too hard1 the shrinking of the glass1 collection of material for a bulb1 and in fact most of the working processes will be slower1 and the glass will not stay at its working temperature long enough after its removal from the flame to permit it to be properly blown4 ,air bubbles in the original batch of glass are drawn out into long hair-like tubes during the process of manufacture4 ,when such tubing is worked1 the walls of these microscopic tubes collapse in spots1 and the air thus enclosed will often collect as a small bubble in the wall1 thus weakening it4 ,irregularities are of various kinds4 ,some of the larger sizes of thin-walled tubing often have one half of their walls much thicker than the other1 and such tubing should only be used for the simplest work4 ,some tubing has occasional knots or lumps of unfused material4 ,the rest of the tube is usually all right1 but often the defective part must be cut out4 ,the presence of striations running along the tube is generally an indication of hard1 inferior glass4 ,crookedness and non-uniformity of diameter are troublesome only when long pieces must be used4 ,devitrification is one of the worst faults glass can possibly have4 ,it is especially common in old glass1 and in glass which has contained acids4 ,it seems to be of two sorts4 ,one variety manifests itself on the surface of the glass before it reaches its working temperature1 but if the glass be heated to the highest temperature of the flame it will disappear except in the portion at the edge of the heated part4 ,the glass seems to work all right1 but an ugly crystallized ring is left at the edge of the portion heated4 ,this kind appears most frequently in old glass which was originally of good quality1 but has in time been superficially altered1 probably by the loss of alkalies4 ,the other variety of devitrification does not appear when the glass is first heated2 but after it has been maintained at or above its working temperature for a longer or shorter time1 it will be noticed that the outer surface has lost its smoothness1 and appears to be covered with minute wrinkles4 ,it will also be found that the glass has become harder1 so that it becomes impossible to work it easily4 ,further heating only makes the matter worse1 as does the use of a higher temperature from the start4 ,in fact it will often be found that a piece of comparatively soft glass which devitrifies almost at once in a hissing flame can be worked without serious difficulty if care be taken to use a flame still decidedly tinged with yellow4 ,even good glass will begin to devitrify in this way if heated too long at the highest temperature of the flame1 so care should always be taken 7#a7 to reduce the time of heating of any spot of glass to a minimum2 i4e41 get the desired result at the first attempt1 if possible1 or at least with the minimum of reheating and doctoring1 and 7#b7 avoid keeping the glass at the highest temperature of the flame any longer than necessary4 ,this may be accomplished by doing all heating1 shrinking1 etc41 of the glass in a flame more or less tinged with yellow1 and only raising the temperature to the highest point when ready to blow the glass4 ,this kind of devitrification is apparently due to volatilization of the alkalies from the glass in the flame1 and it is said that it can be partly remedied or prevented by holding a swab of cotton saturated with a strong solution of common salt in the flame from time to time as the glass is heated4 ,the toughness of glass1 i4e41 its ability to withstand variations of temperature1 depends on its composition and the care taken in its annealing4 ,in general1 large pieces of glass should be heated very slowly in the smoky flame1 and the larger the diameter of the tube the greater the length which must be kept warm to prevent cracking4 ,all large pieces should be carefully heated over their whole circumference to the point where the soot deposit burns off1 before being finally cooled4 ,after being thus heated they are cooled in a large smoky flame until well coated with soot1 then the flame is gradually reduced in size and the object finally cooled in the hot air above it until it will not set fire to cotton4 ,if thought necessary1 it may then be well wrapped in cotton and allowed to cool in the air4 ,if not properly annealed the place heated may crack spontaneously when cold1 and it is quite certain to crack if it is reheated later4 ,next in importance to the glass are the blow-pipe and the bellows4 ,any good blast lamp1 such as is ordinarily used in a chemical laboratory for the ignition of precipitates1 will be satisfactory2 provided it gives a smooth regular flame of sufficient size for the work in hand1 and when turned down will give a sharp-pointed flame with well-defined parts4 ,where gas is not available1 an ordinary gasoline blow-torch does very well for all operations requiring a large flame1 and a mouth blow-pipe arranged to blow through a kerosene flame does well for a small flame4 ,several dealers make blow-torches for oil or alcohol which are arranged to give a small well-defined flame1 and they would doubtless be very satisfactory for glass-work4 ,any good bellows will be satisfactory if it does not leak and will give a steady supply of air under sufficient pressure for the maximum size of flame given by the lamp used4 ,a bellows with a leaky valve will give a pulsating flame which is very annoying and makes good work very difficult4 ,when compressed air is available it can be used1 but if possible it should be arranged so that the supply can be controlled by the foot1 as both hands are usually needed to hold the work4 ,for the same reason the supply of air is usually regulated by varying the rate of operation of the bellows1 rather than by adjusting the valve of the blast-lamp4 ,on the other hand1 it will be found best to always adjust the flow of the gas by means of the cock on the lamp1 rather than that at the supply pipe4 ,the operator must have complete control over the flame1 and be able to change its size and character at short notice without giving the work a chance to cool1 and often without ceasing to support it with both hands4 ,glass-blowing should be done in a good light1 but preferably not in direct sunlight4 ,the operator should be seated in a chair or on a stool of such a height that when working he may comfortably rest one or both elbows on the table4 ,the comfort of the operator has a decided influence on the character of his work2 especially in the case of a beginner1 who often defeats his purpose by assuming uncomfortable and strained positions4 ,steadiness and exact control of both hands are essential in most operations2 any uncomfortable or strained position tires the muscles and weakens the control of the operator over them4 ,in the arrangement of the exercises here presented1 several factors have been considered4 ,it is important that the first exercises be simple1 although not necessarily the simplest1 and they should teach the fundamental operations which will be used and amplified later4 ,they should in themselves be things which are of importance and commonly used in glass-work1 and they should be so arranged that the fundamental points1 such as the rotation of glass1 the proper temperature1 blowing and shrinking the glass may be learned with a minimum expenditure of time1 glass and gas4 ,it is therefore recommended that the beginner take them up in the order given1 at least as far as ,no4 #g1 and that each be mastered before attempting the next4 ,the beginner should not leave the first exercise1 for example1 until he can join together two pieces of tubing so that they form one piece of substantially uniform inner and outer diameter1 and without thick or thin spots4 ,from two to four practice periods of two hours each should suffice for this4 ,this chapter and the following one should also be frequently read over1 as many of the points discussed will not be understood at first and many of the manipulations described will not be necessary in the simpler exercises4 ,,chapter ,,ii ,,general ,,operations ,cutting the ,glass4--,for this purpose a glass-knife is preferred to a file1 if the glass is cold3 if it is hot a file must always be used1 and its edge slightly moistened to prevent drawing the temper4 ,the glass-knife is simply a flat piece of hard steel1 with the edges ground sharp on an emery wheel4 ,the bevel of the edge should be from #cj to #fj degrees4 ,an old flat file can easily be ground into a suitable knife4 ,the glass-knife makes a narrower scratch than the file but appears more likely to start the minute crack which is to cause the tube to break at that point1 and the break is more likely to give a good square end4 ,the scratch should be made by passing part of the knife or file once across the glass1 never by sawing the tool back and forth4 ,this latter procedure dulls the tool very quickly4 ,in breaking a piece of glass tubing1 many persons forget that it is necessary to pull the ends apart1 as well as to bend the tube very slightly in such a direction as to open up the minute crack started in the scratch4 ,care in breaking the tube is essential1 as it is impossible to do as good work with uneven ends as with square ones4 ,when tubing of large diameter or thin wall is to be cut1 it is often better not to attempt to break it in the usual way1 but to heat a very small globule of glass 7#a_/af to #a_/h inch diameter7 to red heat1 and touch it to the scratch4 ,this will usually start the crack around the tube2 if it has not proceeded far enough1 or has not gone in the desired direction1 it may be led along with a hot point of glass4 ,this is put a little beyond the end of the crack1 and as the latter grows out toward it1 moved along the path where the crack is desired4 ,this point of glass is also very useful in breaking off very short ends of tubes1 where there is not room to get a firm enough hold and sufficient leverage to break the tube in the ordinary way1 and for breaking tubes attached to large or heavy objects1 which would be likely to make trouble if treated in the ordinary way4 ,another way of cutting large tubing1 especially if it has rather thick walls1 is to make a scratch in the usual way1 and then turn on the smallest and sharpest possible flame of the blast lamp4 ,the tube is next taken in both hands and held horizontally above the flame so that the scratch is exactly over it4 ,the tubing is now rotated rapidly about its axis1 and lowered so that the flame is just tangent to its lower side4 ,after about ten seconds of heating1 it is removed from the flame and the hot portion quickly breathed upon1 when it will generally crack apart very nicely4 ,care must be taken to hold the tube at right angles to the flame during the heating1 and to rotate it so that only a narrow strip of the circumference is heated1 and the scratch should be in the center of this heated strip4 ,by this means tubing as large as two inches in diameter is readily broken4 ,griffin's glass cutter1 which contains a hardened steel wheel1 like that on any ordinary window-glass cutter1 and a device by which this can be made to make a true cut clear around the tube1 is a very handy article1 especially for large tubing1 and may be obtained from any dealers in chemical apparatus4 ,bending ,glass4--,inasmuch as this is one of the commonest operations in the laboratory1 it is assumed that the reader knows how to perform it4 ,however1 it should be noted that in order to obtain the best results a broad 7fish-tail burner7 flame should generally be used1 and the tube rotated on its axis during the heating1 and allowed to bend mostly by its own weight4 ,if large tubing is to be bent1 one end must be stoppered and great care used4 ,whenever the tube shows signs of collapsing or becoming deformed1 it must be gently blown out into shape1 heating the desired spot locally if necessary4 ,a blast-lamp is likely to be more useful here than the fish-tail burner4 ,drawing ,out a ,tube4--,most students learn this the first day of their laboratory work in chemistry1 but few take pains to do it well4 ,the tube should be heated in the flame of a ,bunsen burner1 or blast lamp 7preferably the latter7 until it is very soft4 ,during this time it must be continuously rotated about its axis1 and so held that the edges of the heated zone are sharply defined2 i4e41 it should not be allowed to move back and forth along its own axis4 ,when so hot that it cannot longer be held in shape1 the tube is removed from the flame1 and the ends slowly and regularly drawn apart1 continuing the rotation of the tube about its axis4 ,by regulating the rate of drawing and the length of tube heated1 the desired length and diameter of capillary may be obtained4 ,the tube should always be rotated and kept in a straight line until the glass has set1 so that the capillary may have the same axis as the main tube4 ,this capillary or tail is often a very necessary handle in glass-blowing1 and if it is not straight and true1 will continually make trouble4 ,in drawing out very large tubing1 say from one to two inches in diameter1 it is often necessary to draw the tube in the flame1 proceeding very slowly and at a lower temperature than would be used with small tubing4 ,this is partly on account of the difficulty of heating large tubing uniformly to a high temperature1 and partly in order to prevent making the conical part of the tube too thin for subsequent operations4 ,constricting a ,tube4--,where a constriction is to be made in a tube1 the above method must be modified1 as the strength of the tube must be maintained1 and the constricted portion is usually short4 ,small tubes are often constricted without materially changing their outside diameter1 by a process of thickening the walls4 ,the tube is heated before the blast lamp1 rotating it about its axis as later described1 and as it softens is gradually pushed together so as to thicken the walls at the heated point1 as in a1 ,fig4 #a4 ,when this operation has proceeded far enough1 the tube is removed from the flame1 and the ends cautiously and gently drawn apart1 continuing the rotation of the tube about its axis and taking care not to draw too rapidly at first4 ,the resulting tube should have a uniform exterior diameter1 as shown in b1 ,fig4 #a4 ,illustration3 ,,fig4 #a4--;,constricting a tube4 ,this method of constriction is not suited to tubes much over #a_/d inch in diameter1 since the mass of glass in the constricted part becomes so thick as to be difficult to handle when hot1 and likely to crack on cooling4 ,larger tubes are therefore constricted by heating in a narrow flame1 with constant rotation1 and when soft1 alternately gently pulling the ends apart and pushing them together1 each motion being so regulated that the diameter of a short section of the tube is gradually reduced1 while the thickness of the wall of the reduced portion remains the same as that of the rest of the tube1 or increases only slightly4 ,this pulling and pushing of the glass takes place in the flame1 while the rotation is being continued regularly4 ,the result may appear as indicated in c1 ,fig4 #a4 ,the strength of the work depends upon the thickness of the walls of the constricted portion1 which should never be less than that in the main tube1 and usually a little greater4 ,this operation is most successful with tubing having a relatively thin wall4 ,flanging a ,tube4--,this operation produces the characteristic flange seen on test-tubes1 necks of flasks1 etc41 the object being twofold3 to finish the end neatly and to strengthen it so that a cork may be inserted without breaking it4 ,this flanging may be done in several ways4 ,in any case the first operation is to cut the tube to a square end1 and then heat this end so that the extreme sixteenth or eighth of an inch of it is soft and begins to shrink4 ,the tube is of course rotated during this heating1 which should take place in a flame of slightly greater diameter than the tube1 if possible4 ,the flange is now produced by expanding this softened part with some suitable tool4 ,a cone of charcoal has been recommended for this purpose1 and works fairly well1 if made so its height is about equal to the diameter of its base4 ,the tube is rotated and the cone1 held in the other hand1 is pressed into the open end until the flange is formed4 ,a pyramid with eight or ten sides would probably be better than the cone4 ,illustration3 ,,fig4 #b4--;,flanging tool4 ,a better flanging tool is made from a triangular piece of copper or brass1 about #a_/af inch thick1 and mounted in a suitable handle4 ,such a tool is shown in ,fig4 #b1 being cut from a sheet of copper and provided with a handle made by wrapping asbestos paper moistened with sodium silicate solution about the shank of the tool4 ,it is well to have several sizes and shapes of these tools1 for different sizes of tubing4 ,the two sizes most used will be those having about the following dimensions3 7#a7 a #b inches1 b #a inch2 7#b7 a #a inch1 b #a inch4 ,when the end of the tube is softened1 the tool is inserted at an angle1 as indicated in ,fig4 #c1 and pressed against the soft part1 while the tube is quickly rotated about its axis4 ,if the flange is insufficient the operation may be repeated4 ,the tool should always be warmed in the flame before use1 and occasionally greased by touching it to a piece of wax or paraffin4 ,after the flange is complete1 the end must be heated again to the softening temperature and cooled slowly1 to prevent it from cracking4 ,illustration3 ,,fig4 #c4--;,flanging a tube with flanging tool4 ,illustration3 ,,fig4 #d4--;,flanging a tube with carbon rod or wire4 ,some glass-blowers use a small carbon rod1 about #c_/af inch in diameter1 as a flanging tool for tubes larger than about #c_/h inch diameter1 and a small iron wire or similar piece of metal for smaller tubes4 ,in this case the tube is heated as above described1 and the rod or wire inserted in the end at an angle and pressed against the softened part1 as indicated in ,fig4 #d1 while the tube is rotated about its axis4 ,for large heavy tubes a larger carbon would be used4 ,rotation of the ,tube4--,this is the fundamental manipulation in glass-blowing1 and upon it more than all else depends the uniformity and finish of the work1 and often the possibility of accomplishing the work at all4 ,directions for it will be given on the assumption that the reader is right-handed2 if otherwise1 the position of the hands is of course reversed4 ,the object of rotation is to insure even heating of the whole circumference of the tube at the point of attack1 to equalize the effect of gravity on the hot glass and prevent it from falling out of shape when soft1 and to keep the parts of the tube on each side of the heated portion in the same straight line4 ,in rotating the tube1 both hands must be used1 so that the two ends may revolve at the same rate and the glass in the hot part not be twisted4 ,the rotation is performed by the thumb and first finger of each hand1 the other fingers serving to support the tube4 ,as it is almost always necessary to follow rotating and heating a tube by blowing it1 the hands should be so placed that it will be easy to bring the right-hand end up to the mouth without shifting the hold on the glass4 ,for this reason the left hand grasps the glass with the palm down1 and the right hand with the palm turned toward the left4 ,if there is any choice1 the longer and heavier part of the tube is usually given to the left hand1 and it is planned to blow into the shorter end4 ,this is because it is easier to support the tube with the hand which has the palm down4 ,this support is accomplished by bending the hand at the wrist so that it points slightly downward1 and then curling the second1 third and little fingers in under the tube1 which is held between them and the palm4 ,this support should be loose enough so that the thumb and first finger can easily cause the tube to rotate regularly on its axis1 but firm enough to carry all the weight of the tube1 leaving the thumb and first finger nothing to do but rotate it4 ,the hand must be so turned1 and the other fingers so bent1 that the thumb and first finger stretch out nearly to their full length to grasp the tube comfortably4 ,the right hand is held with the palm toward the left1 the fingers except the first slightly bent1 and the tube held between the first finger and the thumb while it rests on the second finger and that portion of the hand between the base of the first finger and the thumb4 ,rotation of the tube is accomplished by rolling it between the thumbs and first fingers3 the rotation being continued in the same direction regularly1 and not reversed4 ,it is better to roll slowly and evenly1 with a series of light touches1 each of which moves the tube a little1 than to attempt to turn the tube a half a revolution or so with each motion of the hands4 ,the hands must be held steady1 and the tube must be under good control at all times1 so that both ends may be rotated at the same angular velocity1 even though they may be of different diameters1 and the tube be neither drawn apart nor pushed together unless such a motion is expressly desired1 as it sometimes is4 ,the hot part of the glass must be constantly watched to see that it is uniformly rotated and not twisted1 nor pulled out or pushed together more than is desired4 ,care must also be taken to keep the parts of the tube in the same straight line1 or as near it as possible1 during the heating and all other manipulations4 ,when flanging a tube1 it is held and rotated with the left hand as above described1 while the right hand holds the flanging tool4 ,when part of the end of a tube must be heated1 as in ,exercise #f1 and rotation must be very carefully performed and continued during the blowing1 both hands are used4 ,the right hand is held as above described1 and the left hand close to it and either as above described or else with the palm toward the right1 grasping the tube in the same way as the right hand does4 ,this puts both hands in a position where the tube may be blown and rotated uniformly while its axis is kept horizontal4 ,smoothness and exactness are the two things for which the beginner must constantly strive in glass-blowing1 and they are only attained by a careful attention to the details of manipulation1 with a steady hand and watchful eye4 ,every move must count1 and the exercise must be finished with a minimum of reheating and retouching1 for the best results4 ,,chapter ,,iii ,,elementary ,,exercises ,,exercise ,,no4 #a ,,joining ,,two ,,pieces ,,of ,,tubing1 ,,end ,,to ,,end--,,first ,,method ,this exercise is most easily learned on tubing with an exterior diameter of #a_/d inch1 or a little less1 having moderately heavy walls4 ,a piece of such tubing is heated before the blow-pipe at a point ten or twelve inches from the end1 and there drawn out to a capillary as previously described 7page #i74 ,the capillary is sealed off about two inches from the main tube1 and the latter is cut near the middle4 ,care should be taken to get square ends where the cut is made 7page #g74 ,the flame is now so regulated that it is a little broader than the diameter of the tube1 the sealed half of the tube taken in the left hand and the other half in the right4 ,the open end of the sealed part and one of the ends of the other part are now held in opposite sides of the flame1 inclined at a slight angle to one another as indicated in ,fig4 #e1 and rotated and heated until the surfaces of both ends are just softened4 ,the two ends are then carefully and quickly brought together 7a1 ,fig4 #f71 removed from the flame and pulled apart a little1 to reduce the lump formed at the joint as much as possible1 as indicated in b4 ,the joint is then tested by blowing into the open end of the tube to see if it is tight4 ,if so1 the flame is reduced to half or less than half of its former size1 and the joint heated in it1 holding the tube and continually rotating it as directed in the last chapter 7page #ac74 ,illustration3 ,,fig4 #e4--,softening ends of two pieces of tubing4 ,illustration3 ,,fig4 #f4--;,joining two pieces of tubing end to end--first method4 ,as the tube softens and tends to shrink1 the two ends are pressed together a little and the walls allowed to thicken slightly1 as in c4 ,it is then quickly removed from the flame and gently blown as indicated in d1 continuing the rotation of the tube during the blowing1 and at the same time pressing the ends of the tube together a little so as to make a short thick-walled bulb4 ,the joint is then returned to the flame and reheated1 rotating as before1 shrinking to about the shape of e4 ,when this stage is reached1 the glass should be very hot and fluid1 and the mass of hot glass thick enough to remain at its working temperature for about five seconds after removal from the flame4 ,the glass is now reblown as indicated in f1 to form a bulb having walls of practically the same thickness as the original tube4 ,as soon as the bulb is blown1 the tube is removed from the mouth1 held horizontally in front of the worker1 and gently drawn out to form one continuous tube1 as indicated in g4 ,during both the blowing and drawing of this bulb the rotation must be continued1 and both blowing and drawing must be carefully regulated so that the resulting tube may have the same internal and external diameter at the joint as elsewhere4 ,discussion4--,in making the original joint1 7a1 ,fig4 #f71 care should be taken that the lump formed is as small as possible so that it may be entirely removed during the subsequent operations4 ,for this reason1 only the very tip ends of the two pieces of tubing are held in the flame1 and the softening should not extend more than #a_/af inch down the tube4 ,as soon as the ends are sufficiently soft to stick together1 they are made to do so4 ,the first drawing of the tube 7b7 should take place immediately1 and reduce the lump as much as possible without making the adjacent walls of the tube thin4 ,the whole purpose of the rest of the manipulation is to absorb or iron out the lump at the joint4 ,for this reason1 care is taken that this lump is always in the center of the flame while the joint is being heated1 and a small flame is used so that little of the main tube may be softened4 ,during the first shrinking of the joint 7c7 the walls next the lump1 being thinner than it is1 reach the softening temperature first and are thickened by the slight pushing together of the ends1 so that they taper from the lump to the unchanged wall4 ,upon blowing this joint1 these thickened walls blow out with the lump1 but as they are thinnest next the unchanged tube1 they stiffen there first4 ,then as the thicker parts are still hot1 these blow out more1 and with the lump make a more or less uniform wall4 ,by this first operation most of the lump will have been removed1 provided it was not too large at first1 and the tube was hot enough when it was blown4 ,beginners almost invariably have the glass too cool here1 and find difficulty in blowing out a satisfactory bulb4 ,under such circumstances the lump will be scarcely affected by the operation4 ,during the shrinking of this bulb1 the thinner parts of course are the first to reach the softening point1 and thus contract more than the thick parts1 so that practically all of the lump can be absorbed1 and a uniformly thickened part of the tube left as in e4 ,when this is just accomplished1 the second bulb must be blown during one or two seconds1 and the tube then drawn out as described1 so as to change the bulb to a tube4 ,the drawing must proceed with care3 portions nearest the unchanged tubes are the first to reach the proper diameter1 and must be given time to just set at that point before the center of the bulb is finally drawn into shape4 ,the drawing is perhaps best done intermittently in a series of quick pulls1 each drawing the tube perhaps #a_/af inch1 and each taking place as the thumbs and first fingers grasp the tube for a new turn in the rotation4 ,if the tube is not rotated during the blowing1 the bulbs will be lop-sided and it will be impossible to get a joint of uniform wall-thickness2 if rotation is omitted during the drawing1 the tube will almost invariably be quite crooked4 ,if the lump still shows distinctly after the operations described1 the cross-section of the tube will be as in h1 and the tube will be likely to break if ever reheated at this point after it becomes cold4 ,the operations d1 e1 f1 and g may be repeated upon it1 and it may be possible to get it to come out all right4 ,care must be taken not to blow the bulbs d and f too thin as they then become very difficult to handle1 and the joint is usually spoiled4 ,the wall-thickness of these bulbs must never be much less than that of the original tube4 ,if the joint as completed has thinner walls than the rest of the tube1 it will be more easily broken4 ,it should be remembered that the length of the finished tube must be exactly the same as that of the original piece1 if the walls of the joint are to be of their original thickness4 ,therefore the pushing together during the two operations c and d must shorten the tube just as much as the final drawing 7f to g7 lengthens it4 ,the interval between the removal of the work from the flame and the beginning of the blowing must be made as short as possible1 or else the portions next the main parts of the tube will set before they can be blown out1 and cause irregular shrunken areas4 ,,exercise ,,no4 #b ,,joining ,,two ,,tubes ,,end ,,to ,,end--,,second ,,method ,the method described in ,exercise ,no4 #a is very satisfactory for joining short lengths of straight tubing1 but becomes inconvenient or impossible when the pieces are long or bent1 on account of the difficulty in uniformly rotating such work4 ,in such cases1 this second method is used4 ,it does not usually give as smooth and pretty a joint as the first method1 and takes a little longer4 ,the joint is begun exactly as in the first method1 and the manipulation is the same until after the preliminary tight joint 7b1 ,fig4 #f7 is made4 ,the flame is reduced as usual1 but instead of rotating the tube in the flame1 only one part of the circumference is heated1 and this is allowed to shrink thoroughly before blowing4 ,it is then blown gently so that it becomes a slight swelling on the tube1 and the operation repeated on an adjoining part of the joint4 ,three or four repetitions of the operation will usually cover the whole circumference of the joint1 in a small tube1 the result being a swelling roughly similar to the first thick bulb in the first method 7d1 ,fig4 #f74 ,if all the lumps of the original joint have not been removed by this operation1 it may now be repeated upon such parts as may require it4 ,the thickness of the wall in the bulb should be about the same as that in the original tube4 ,the whole of the expanded joint is now heated as uniformly as may be until soft enough so that it begins to shrink a little1 and the swelling is gently drawn down to the same diameter as the main tube1 as in the first case4 ,any irregularities in the finished joint may be corrected by local reheating1 shrinking or blowing as required4 ,discussion4--,in using this method1 especially with larger sizes of tubing1 it is very important to keep the whole circumference of the joint hot enough during the operation so that it does not crack apart at the part which has not yet been worked4 ,for that reason the first heating1 shrinking and blowing should be performed as quickly as possible1 leaving the resulting irregularities to be corrected later1 rather than attempting to reblow the same part of the joint several times in succession until it is satisfactory4 ,care must be taken in this as in the first method that the blowing follows immediately upon the completion of the shrinking and removal of the object from the flame3 delay in blowing will cause shrunken places where the joint meets the original tubes1 on account of the cooling and setting of the glass before it was blown4 ,most beginners err in being afraid to shrink the part of the joint enough before blowing it4 ,on small tubing1 the shrinkage may often extend so far that the inner surface of the shrunken part reaches the center of the tube4 ,insufficient shrinking results in failure to remove the lump formed at the original joint4 ,it is often of advantage1 after blowing out part of the joint1 to allow that part a few seconds to set before going on with the rest1 keeping the whole joint warm meanwhile in or near the smoky flame4 ,this helps to prevent the twisting of the joint1 or other distortion incident to the handling of a piece of work of awkward shape4 ,in making a joint on a very long or heavy piece by this method1 it is often advantageous to attach a piece of rubber tubing to the open end1 hold the other end of this tubing in the mouth during the process1 and blow through it1 rather than attempt to bring the end of the glass up to the mouth4 ,this enables one to keep closer watch on the joint1 and avoid drawing it out or distorting it in handling4 ,on the other hand1 the rubber tube is an inconvenience on account of its weight and the consequent pull on the end of the apparatus1 and makes rotation difficult4 ,,exercise ,,no4 #c ,,the ,,tee ,,tube ,the operations involved are two3 the blowing of a short side tube on a piece of tubing1 and sealing another piece of tubing on this1 by what is essentially the second method as just described4 ,illustration3 ,,fig4 #g4--,the tee tube4 ,the two pieces of tubing to be used each have one end cut square and the other sealed in the usual manner4 ,the longer of the two is now heated at the point at which the joint is to be made1 until it begins to color the flame4 ,a small flame is used1 and the tube rotated until the flame begins to be colored1 when the rotation is stopped1 and only one spot heated until a spot the diameter of the tube to be sealed on has become red hot and begun to shrink4 ,this is now gently blown out into a small bulb1 as in a1 ,fig4 #g1 and it will be noted that this bulb will have walls tapering from the thick walls of the tube to a very thin wall at the top4 ,the sides of this bulb1 below the dotted line1 are to form the small side tube to which the main side tube is to be sealed4 ,the top of the bulb is now softened by directing a small flame directly upon it1 and as soon as it shrinks to the level indicated by the dotted line1 it is removed from the flame and quickly blown out to form a thin bulb1 as indicated in b1 ,fig4 #g4 ,this will usually be so very thin that a stroke of the file or glass-knife will break it off at the dotted line1 leaving the side tube1 to which the short piece of tubing is now sealed according to the second method 7,exercise ,no #b74 ,in doing this1 care is taken to direct the flame partly on the main tube in the two crotches1 so that both tubes blow out a little and give space for the gases to turn in1 as indicated in c1 ,fig4 #g1 and at the same time increase the mechanical strength of the job4 ,on the other hand1 care is taken not to deform the main tube1 and not to produce such a bulge or bulb at the joint as will prevent the finished tube from lying flat on a table4 ,discussion4--,most beginners tend to err in the first steps of this operation1 by blowing too hard and too long when blowing out the little bulb4 ,the result is a large1 very thin bulb1 which breaks off in such a way as to leave a hole in the main tube1 occupying nearly half the circumference of the tube at that point1 instead of the neat side tube which they should have4 ,it is not difficult to seal a tube on this side tube1 but it is very difficult to seal a tube into a hole in another tube4 ,care should be taken here1 as in the two previous exercises1 that the lump obtained at the joint when the two tubes are put together is made as small as possible1 and reduced if possible by gently drawing on the side tube as soon as the tubes have actually joined4 ,it is much easier to prevent the formation of a lump at the joint than it is to remove the lump after it is formed4 ,the remarks previously made about blowing quickly after removing the work from the flame apply here with especial force4 ,a tee tube1 from its very nature1 is exposed to a good many strains1 so care must be taken that the walls of the joint are of uniform thickness with the rest of the tube4 ,the beginner will find it easiest to make this tube out of two pieces of the same tube1 about #a_/d inch in diameter4 ,larger or smaller tubing is usually more difficult4 ,if tubing much more than #a_/d inch is used1 the whole joint1 including part of the main tube1 must be heated nearly to the softening point at the close of the operation1 and well annealed1 as described in ,chapter #a 7page #c7 or it will be almost certain to crack4 ,in the larger sizes of tube it will be necessary to heat the whole circumference of the main tube frequently during the operation1 to prevent it from cracking4 ,in sealing a small tube on the side of a large one1 it is usually advisable1 after warming the spot where the joint is to be made1 to attach a small drop of glass to the tube at that point1 and direct the flame upon that1 thus supplying at the same time both a definite point to be heated and an extra supply of glass for the little side tube which is desired4 ,in this way it is also easier to blow out a side tube with a sufficiently small diameter4 ,if the diameter of this tube should be much greater than that of the small tube1 the latter may be enlarged with a carbon or a flanging tool4 ,,exercise ,,no4 #d ,,to ,,join ,,two ,,tubes ,,of ,,different ,,diameters ,in this case the first method 7,exercise ,no4 #a7 is to be used whenever possible1 as it gives a much smoother joint than the second method4 ,the directions given will describe the adaptation of this method to the problem3 if the second method must be used on account of awkward shape1 etc41 of the work1 the modifications required will be obvious to any one who has learned to make the joint by the first method4 ,after sealing or corking one end of the larger tube1 the other end is drawn out to form a tail as described on page #i1 taking care to have the tube uniformly heated1 and to draw the tail rapidly enough so that the cone is short1 as indicated in a1 ,fig4 #h4 ,the tube is now rotated1 a small flame directed against the cone at right angles to an element of it1 and it is allowed to shrink a little1 as indicated in b1 ,fig4 #h1 so that its walls will thicken4 ,when the tail is cut off1 at the dotted line1 the diameter of the opening and the thickness of the walls at that point should correspond with the dimensions of the tube to be sealed on4 ,as the glass is hot1 the scratch for cutting it must be made with a file 7moisten the edge671 and it often will not break square across4 ,before proceeding to seal on the small tube1 any large projections on the cut end are best removed1 by warming the cut surface a little1 directing the small flame upon each projection in turn and touching it with a warm scrap of glass4 ,it will adhere to this and may then be removed by rotating this scrap a little so as to wind up the projection on it1 and then drawing it off1 while the flame is still playing on the spot4 ,this must be done rapidly and care taken not to soften the main part of the cone4 ,illustration3 ,,fig4 #h4--;,joining two tubes of different diameters4 ,the large tube is now taken in the left hand1 the small one in the right1 the ends heated and joined in the usual manner1 taking care not to get any larger lump at the joint than necessary4 ,a small flame is now directed on the cone at right angles to its elements as before1 and the tube rotated so as to heat the whole circumference4 ,the flame should be just large enough to heat the whole of the cone4 ,as the latter shrinks1 the lump at the joint is brought into the edge of the flame1 and it and a very little of the small tube allowed to shrink with the cone4 ,when well shrunk and heated to blowing temperature the joint is removed from the flame and blown gently with careful rotation1 pushing the tubes together a little when the blowing is about finished1 so that the cone becomes a short thick half-bulb1 as shown in d1 ,fig4 #h4 ,this corresponds to the first thick bulb in the first method 7d1 ,fig4 #f71 and is treated similarly4 ,it is again heated and shrunk1 taking care not to involve either the large tube or the small one in the shrinking1 blown quickly to about the same shape as before1 7d1 ,fig4 #h71 and then gently drawn out into a smooth cone 7e71 exactly as in the first exercise4 ,care should be taken not to draw too rapidly or too far1 as then the resulting cone 7f7 is weaker than it should be1 and does not look well4 ,discussion4--,the beginner will find that this operation is best learned on two tubes which are not too nearly of the same diameter4 ,a tube about #e_/h inch in diameter and one a little less than #a_/d inch will be suitable4 ,both should have moderately heavy walls 7#a_/af inch or a trifle over for the large tube1 and a trifle less for the small one7 but the large tube should not be too heavy or else it will be hard to prevent melting down too much of the small tube1 and getting this drawn out too thin during the process4 ,one of the troublesome features of this exercise is the difficulty of rotating two tubes of different diameters with the same angular velocity1 so as not to twist the joint4 ,another difficulty is found in getting the cone uniformly heated to blowing temperature without overheating and overshrinking the small tube4 ,the reason for this is obviously the much greater circumference of the cone1 especially at its large end1 so that relatively much less of it is being heated at any time4 ,the beginner is also inclined to start with too long a cone1 or else heat so much of the large tube that part of its glass is included in the cone1 with the result that in order to get the right wall-thickness the cone must be made too long 7g1 ,fig4 #h74 ,this does not look well1 and usually will be irregular in shape4 ,,exercise ,,no4 #e ,,tube ,,for ,,condensing ,,sulphur ,,dioxide ,this is useful as a test of mastery of the preceding exercise4 ,a piece of #c_/af or #g_/cb inch tubing is joined to each end of a piece of tubing #e_/h by about #e inches1 and two constrictions made in the large tube1 by the method described on page #aj4 ,the small tubes are then bent in the same plane1 as shown1 and their ends fire-polished 7,fig4 #i74 ,illustration3 ,,fig4 #i4--,tube for condensing sulphur dioxide4 ,,exercise ,,no4 #f ,,bulb ,,at ,,the ,,end ,,of ,a ,,tube ,for this exercise tubing of #a_/d inch diameter and moderately strong walls is selected4 ,a tail is drawn out on one end of the tube1 and a piece of tubing about nine or ten inches long is cut off4 ,the tail should be carefully drawn in the axis of the tube1 and in the same straight line with it1 as it is to be used as a handle in assembling the glass for the bulb4 ,this tail must be long enough so that it can be conveniently held in the left hand1 as described on page #ac1 and rotated about the same axis as the main tube4 ,holding the main tube in the right hand and the tail in the left1 the tube is rotated in a large flame so that a piece of it1 beginning where the tail stops and extending about an inch to the right1 may be uniformly heated to the highest temperature at which it can be kept in shape4 ,as soon as this temperature is reached1 the tube is removed from the flame1 continuing the rotation and taking care not to draw out the heated part1 and gently blown4 ,the rotation is carefully continued during the blowing1 holding the tube in approximately a horizontal position4 ,as soon as the tube has expanded a little the tail is pushed gently toward the main tube1 continuing the gentle blowing4 ,if this is properly done1 the heated piece of tube will become a short bulb of about double its original diameter1 and about the same wall thickness as the original tube4 ,it will have somewhat the appearance of a1 ,fig4 #aj1 when properly manipulated4 ,illustration3 ,,fig4 #aj4--;,blowing a bulb on the end of a tube4 ,the tube is now reheated as before1 taking care this time that the heating extends over all that part of the bulb to the right of the dotted line in the figure1 as well as part of the main tube adjoining4 ,if this heating has been properly placed1 when the operation of blowing and pushing together is repeated the result will be to lengthen the bulb into a uniform cylinder1 as shown in b1 ,fig4 #aj4 ,otherwise the result will be a series of bulbs1 as in c1 ,fig4 #aj1 separated by thickened ridges which will be almost impossible of removal later and will disfigure the final bulb4 ,this operation of heating1 blowing and pushing together is repeated several times1 until the cylinder becomes as long as can be conveniently handled 7about #a-a_/d inches to #a-a_/b inches74 ,if more glass is needed than is then contained in the cylinder1 the latter may now be heated as a whole1 and blown and pushed gently into a shorter cylinder of a slightly greater diameter1 and more glass then added as before4 ,when enough glass has been collected for the bulb1 it is all well heated and blown gently a couple of times1 pushing the mass together as required1 until a thick bulb like d1 ,fig4 #aj1 is obtained4 ,the tail must now be removed at the point indicated by the dotted line4 ,to do this1 a very fine flame is directed on the point where the tail joins the bulb1 and the tube well rotated as the glass softens at that point4 ,when sufficiently soft1 the work is raised a little1 so that the flame instead of striking the glass squarely at the point indicated passes below and tangential to it4 ,the tail is now drawn off slowly1 continuing the rotation1 raising the work just out of the flame whenever the thread of glass drawn off becomes too thin1 and lowering it again to the point where the flame just touches it when the glass stiffens a little4 ,by this means the tail may be drawn off without leaving an appreciable lump behind1 as indicated in e and f1 ,fig4 #aj4 ,when as much of the extra glass has been removed as is practicable1 the flame is brought to play squarely upon the little lump left1 the last of the tail removed1 and the lump heated and gently blown to a small excrescence on the main bulb4 ,the whole end of the latter is now heated until it begins to shrink a little1 and gently blown to make it uniform in thickness4 ,the whole bulb is then heated in a flame of the proper size1 so that it all may shrink to about two-thirds of its diameter4 ,the flame must be very carefully chosen and directed1 so as to shrink all the bulb1 right up to the main tube1 but not soften the latter4 ,as soon as this stage is reached1 the bulb is removed from the flame1 continuing the even rotation1 and blown to the desired size1 preferably by a series of gentle puffs following one another at very short intervals4 ,during the blowing1 the main tube is held in a horizontal position1 and any tendency of the bulb to fall out of line is corrected by the rotation4 ,if the shape of the bulb or its size are not satisfactory1 it may be shrunk again and reblown4 ,such shrinking should begin in a large yellow flame1 with just enough air to give it direction4 ,the amount of air may be gradually increased as the bulb shrinks and the walls become thick enough to bear it without collapsing4 ,if the bulb starts to collapse at any time1 it must be immediately blown enough to regain its convex surface1 before the shrinking proceeds further4 ,discussion4--,in collecting the glass for the bulb1 enough must be gathered to give the walls the desired strength4 ,since the area of a sphere is proportional to the cube of its diameter1 it is evident that doubling the size of a bulb diminishes the thickness of its walls to a very large extent4 ,the limit of diameter for a strong bulb on ordinary #a_/d-;inch tubing1 collecting the glass as above1 is about #a-a_/b inches1 and the beginner will do well not to blow his bulbs more than an inch in diameter4 ,the collection of the glass is one of the most important parts of the process4 ,if the mass of glass be twisted1 furrowed or ridged1 or lop-sided1 it is very difficult to get a good1 even1 spherical bulb1 no matter how many times it is shrunk and blown4 ,the greatest care should therefore be taken to get a uniform cylinder1 on the same axis as the main tube2 and to this end the rotation of the tube must be carried on very evenly4 ,for method of holding the tube1 see page #ad4 ,if a very large bulb is required1 it will often be economical to seal on the end of the tube a short piece of a large tube1 provided with the proper tail1 and use the glass in the large tube for the bulb instead of attempting to collect it from the small tube4 ,in this case part of the small tube will usually be included in the bulb1 so that the joint comes in the latter1 and not where it joins the tube4 ,as the amount of glass carried on the end of the tube increases in weight and size the difficulties of heating it uniformly1 keeping it in the proper position and handling it increase rapidly4 ,in collecting glass1 it is usually best not to leave the part of the cylinder next the tube with too thick walls4 ,this is always the coolest part during the preparation for blowing the bulb1 consequently it does not get blown out1 and causes an ugly thickened appearance on that end of the bulb4 ,if the bulb grows too long or pear-shaped1 it may be easily shortened by heating to the blowing temperature1 and then blowing gently with the main tube in a vertical position1 and the bulb at the top of it4 ,gravity will then shorten the bulb nicely4 ,the finished bulb should be a nearly perfect sphere1 with the axis of the tube passing through its center1 and the portion of the tube adjoining the bulb must not be distorted1 twisted1 or blown out4 ,in order to prevent the distortion of the tube1 care must be taken that it is never heated quite to its softening point during the process4 ,,exercise ,,no4 #g ,,blowing ,a ,,bulb ,,in ,a ,,tube ,the tube is selected and one end closed as in the previous exercise1 but it should be cut a little longer1 say about twelve inches4 ,beginning at a point about four inches from the closed end1 glass is collected and blown into a thick-walled bulb1 exactly as in the previous exercise4 ,greater care must be taken1 however1 that the cylinder collected and this thick bulb are of uniform thickness and set squarely in the axis of the tube4 ,instead of removing the tail1 the bulb must be blown in this case with both pieces of tubing attached1 and care must be taken that they line up properly1 i4e41 are in the same straight line1 and that this line passes as near as may be through the center of the bulb4 ,the tube is held in approximately horizontal position during the blowing of the bulb1 as in the previous case1 and especial care taken with the rotation4 ,both pieces of tube must of course be rotated at the same rate1 and their softened ends must be kept at exactly the proper distance from each other1 so that the bulb may be spherical and not elongated4 ,if the blowing of the bulb be quickly and accurately done1 it may usually be completed before the glass is quite set1 and the alignment of the two tubes may then be rectified while looking straight through the bore of the tube4 ,discussion4--,the two points of greatest importance are the collection of the glass1 and the uniform rotation of the tube4 ,a larger tube may be sealed in the middle of a small one when a large amount of glass is necessary4 ,the piece of tubing used for the exercise must be long enough so that the fingers may be kept on a cool part of the glass without getting uncomfortably near the ends of the tube4 ,it should not be any longer than necessary1 however1 as the extra weight and length make the manipulation of the hot glass more difficult4 ,when a string of bulbs are required on the same tube1 a piece of glass #ah inches long may be used at the start1 and the first bulb made near the closed end1 as described4 ,each succeeding bulb will then be in plain view during the blowing1 and when the open end becomes too short for comfort1 it may be dried out1 cut off1 and another piece joined to it1 starting as in the first method 7,exercise ,no4 #a71 but instead of drawing out the thick bulb to a tube1 it is made part of the glass collected for the next bulb4 ,if the string of bulbs becomes awkward to handle on account of its length and weight1 it may be made in several parts and these later sealed together by the second method1 preferably blowing through a rubber tube attached to the open end1 as described on page #bb4 ,very neat small bulbs may be made on tubing of a diameter of #c_/af inch or a little less1 but the beginner is advised to start with tubing of about #a_/d inch diameter4 ,the use of tubing with too thick walls usually produces bulbs which are thick-walled at the point where they leave the tube1 but inclined to be too thin at the point of maximum diameter 7perpendicular to the axis of the tube7 where most of the strain comes and strength is particularly needed4 ,,chapter ,,iv ,,advanced ,,exercises ,,exercise ,,no4 #h ,,sealing ,a ,,tube ,,through ,,another ,,tube ,first ,method--,making a ,gas-washing ,tube ,this first method can be used whenever one can work through an open end opposite to the end of the tube where the joint is to be made4 ,to illustrate it1 take a piece of rather thin-walled tubing1 about #c_/d inch in diameter1 and some pieces of rather strong tubing a little less than #a_/d inch in diameter4 ,draw off the large tube in a short cone1 then draw off the tail as in the making of the bulb on the end of the tube1 blow out the little lump slightly1 shrink the whole cone a little and blow gently to form a rounded end like that on a test-tube1 with walls about the thickness of those of the rest of the tube4 ,cut this tube to a suitable length1 say about six inches1 and provide two corks which will fit the open end of it4 ,now cut a piece of the small tubing of the proper length to form the piece which is to be inside the large tube4 ,for practice purposes1 this piece should be about an inch shorter than the large tube4 ,flange one end of this tube a little1 and anneal the flange well in the smoky flame4 ,bore one of the corks so that a piece of the small tubing will fit it1 and cut a couple of notches in the side of this cork so that air can pass between it and the glass4 ,pass a short piece of the small tubing through this cork1 and attach the flanged piece of small tube to this by means of a short piece of rubber tubing1 so that when the whole is inserted in the large tube it is arranged as in a1 ,fig4 #aa4 ,the piece of glass tubing projecting out through the cork is now cut off so as to leave an end about #a_/b inch long when the cork is firmly seated and the inner tube pushed into contact with the center of the end of the large tube1 as shown in the drawing4 ,care should be taken that the little rubber tube which joins the two pieces is arranged as in the figure2 i4e41 most of it on the piece of tubing which passes through the cork1 and very little on the other piece1 so that when the cork is removed after the small tube has been sealed through the large one1 the rubber tube may easily come with it4 ,select a short piece of the small tubing of suitable length for the piece which is to be on the outside of the large tube as a continuation of the piece inside1 and another piece for the delivery tube4 ,a small bulb may be blown in the latter at a point about #b-a_/b inches from the closed end1 and the open end cut off about #a-a_/b inches from the bulb4 ,a cork or cork-boring of suitable size to stopper the small tube is prepared1 and laid ready with the other 7unbored7 cork for the large tube4 ,illustration3 ,,fig4 #aa4--;,gas-washing tube4 ,when everything is in readiness1 the rounded end of the large tube is slowly heated until it softens and joins firmly to the small tube inside4 ,after it has shrunk down well1 it is blown out to its original size1 placing the whole end of the large tube1 cork and all1 in the mouth4 ,now with a fine-pointed flame the glass covering the end of the small tube is heated to the softening temperature1 and then is blown out to an excrescence by blowing on the end of the small tube which passes through the cork4 ,the end of this excrescence is heated and blown off in the usual way1 so as to leave the small tube sealed on the inside of the large one and opening through it into this short tube which has been blown out4 ,the end of the small tube which passes through the cork is now closed with the cork prepared for it1 and the short outer tube is joined to the tube that has just been blown out1 so that the joint appears like b1 ,fig4 #aa4 ,use the first method 7,exercise ,no4 #a7 for this joint4 ,reheat the whole of the end of the tube nearly to the softening temperature1 anneal it a little1 and allow to cool a few seconds until well set4 ,now remove the cork1 short glass tube and rubber tube from the open end of the large tube and insert the solid cork in their place4 ,warm the joint and the whole of that end of the tube again carefully up to about the softening point1 then seal on the side tube for the delivery of the gas in the usual way1 taking care that the whole of the end and the joint are kept warm meanwhile4 ,when thoroughly sealed1 the delivery tube is bent up parallel to the tube through which the gas enters1 and then out at right angles to it1 as shown in c4 ,the whole of the end of the tube is now cautiously reheated and then cooled slowly to anneal it4 ,the cork may now be removed from the open end of the large tube1 this end heated in a large flame1 caught together with a scrap of glass tubing and drawn off into a cone so that the base of the cone is about opposite the end of the inner tube4 ,the lump of glass is drawn off the point of this cone and it is reblown to form a rounded end1 as previously described4 ,after this cools1 the tube through which the gas enters may be heated at the proper point and bent at right angles to form the finished apparatus as shown in d4 ,the ends of the small tube are cut off square and fire-polished4 ,discussion4--,after the joint has once been made1 great care must be taken that it is kept hot during all the subsequent manipulations1 and if it becomes somewhat cool at any time it must be reheated very slowly4 ,it is obvious that the rate of heating and cooling of the inner tube will be slower than that of the outer tube1 and this will readily produce stresses which tend to crack the tube at the joint4 ,the amount of heating and cooling which such a joint will stand depends upon its form4 ,the beginner should examine such a joint on regular factory-made apparatus1 and note the uniformity of wall-thickness and the clean-cut appearance of the joint1 as a model for his imitation4 ,a ragged joint1 where the line of joining of the inner and outer tubes wavers instead of going squarely around the tube1 is almost sure to crack during the cooling and heating unless extra precautions are taken with it4 ,the presence of a small lump of glass at any point on the joint affords an excellent starting place for a crack1 as do also the points on a ragged joint where the inner tube comes farther down on the outer tube than at other points4 ,in order to insure a joint which is square and not ragged1 it is essential that the angle between the inner and outer tubes at the joint be very nearly a right angle4 ,for this reason the two tubes should not be of too near the same size1 or if this cannot be avoided1 a small bulb should be blown on the end where the joint is to be made4 ,if this bulb be made with the same wall-thickness as the rest of the tube1 and somewhat pear-shaped1 it may be drawn out to the same size as the rest of the tube1 if necessary1 after the joint has been made4 ,this method is used wherever possible in preference to the second method 7,exercise ,no4 #i71 as it is easier to get a good joint with it4 ,it may also be used where it is desired to seal the tube through the side of a tube1 or for a tube sealed through the wall of a bulb1 as in a ,geissler potash bulb or similar apparatus4 ,where there is not space to join the inner tube to the blowing tube by a rubber tube1 this joint may be made with a small piece of gummed paper1 which can readily be broken when desired4 ,,exercise ,,no4 #i ,,sealing ,a ,,tube ,,through ,,another ,,tube ,second ,method--,making a ,suction ,pump ,select a piece of tubing #c_/h to #a_/b inch in diameter1 with walls about #a_/af inch or a little less in thickness1 heat a place about #d inches from one end and draw it out so that when cut off at the proper point it will look like a1 ,fig4 #ab2 the open end of the drawn out part being small enough to slip inside another piece of the original tube4 ,a small thick-walled bulb is now blown as indicated by the dotted lines1 and annealed4 ,a piece of the original tubing is now prepared1 #g or #h inches long1 with one end cut square off and the other closed4 ,a piece of #a_/d-;in tubing about #b inches long1 and drawn out at one end to a tail several inches long is also prepared1 to form the inlet tube for the air4 ,another piece of the #c_/h-;inch tube is prepared1 about #d inches long1 and provided with a tail drawn out as indicated in b1 so that when cut off at about #b-a_/b or #c inches from the main tube its inner diameter may be slightly less than that of the narrowest point of the tube a4 ,a small thick-walled bulb is blown at the point indicated by the dotted lines1 and annealed4 ,care must be taken in drawing the capillary and blowing the bulb in both a and b that the capillary tubes are in the axis of the main tube1 and in the same straight line with it4 ,illustration3 ,,fig4 #ab4--,suction pump4 ,the open end of the #h-;inch piece of tube and the bulb of the piece a are now warmed together1 the end of the tube only moderately and the bulb to about its softening temperature4 ,the tube a is now inserted in the open end of the large tube1 and the bulb softened with a suitable flame and pressed into good contact with the tube4 ,it is then reheated1 including the joint1 blown a little and pulled out to form a straight tube in line with the main tube4 ,by warming the joint a little1 and proper rotation1 the capillary may be brought into the same straight line with the rest of the tube4 ,keeping this joint hot1 a place about an inch from it on the tube a is warmed1 and the piece of #a_/d-;inch tubing previously prepared is sealed on at that point4 ,the joint is then well annealed and allowed to cool4 ,the tube a is now cut at such a place that when b is inserted in the open end the point will come near the end of the constriction of a1 as shown in c4 ,care is taken to get a clean square cut4 ,the side tube is now cut off about an inch from the main tube and corked4 ,tube b is sealed into the open end of a1 in the same way as a was sealed into the large tube1 and the joint carefully annealed4 ,discussion4--,as in the first method1 the secret of success lies in getting a square joint1 and having the inner tube leave the outer one at nearly right angles4 ,all the remarks about annealing1 lumps1 etc41 made under the previous method apply here4 ,this method may be applied in sealing a small tube into the end of a large one1 the latter being either drawn to a cone and cut off at the desired diameter1 or else given a rounded end like a test-tube and a hole the proper size blown in the center of it4 ,a suitable thick-walled bulb is to be blown on the small tube1 as in the case described above4 ,this method is also used in making the ,kjeldahl trap 7a1 ,fig4 #ac71 the small tube to be inserted being first drawn1 the thick bulb blown at its point of union with the main tube1 and then the small tube bent and cut4 ,the large bulb is best made with rather heavy wall1 being either blown in the middle of a tube1 and one piece of the tube drawn or cut off1 or else made on the end of a tube4 ,in the latter case a drop of glass must be put on the point where the joint is to be1 so as to get a hole of the proper size with enough glass around it to prevent it from growing larger when it is heated4 ,the author prefers to blow the bulb in the middle of the tube1 draw off one end of the bulb1 and blow out the desired hole where the tube was drawn off4 ,the whole bulb must generally be reheated and blown a little at the end of the process1 and well annealed4 ,illustration3 ,,fig4 #ac4--;a1 ,kjeldahl trap2 b1 suction pump on smaller tubing4 ,the suction pump can also be made on #a_/d-;inch tubing1 and one joint saved if desired1 by constricting the tube to form the raceway for the water and air1 as shown in b1 ,fig4 #ac4 7,see page #aj for method47 ,but it is more difficult to make a square joint on such small tubing4 ,,chapter ,v ,,modified ,,methods ,,and ,,special ,,operations ,,capillary ,,tubing ,this is commonly used in many forms of apparatus for gas analysis1 and one is often called upon to join two pieces or to make a tee on it4 ,the methods are nearly the same as with other tubing1 except that more care and patience are required4 ,the work must be done much more slowly on account of the thickness of the walls1 and open ends of the tube must always be enlarged before joining them to anything4 ,this is best done by carefully sealing the end and then blowing1 with several suitable reheatings1 to form a pear-shaped bulb as in a1 ,fig4 #ad4 ,the end of this is then heated and blown off1 and the piece is ready to be joined to another similar end1 or to a piece of ordinary tubing if desired4 ,the joints are best not blown too much1 as thick walls shrink very slowly4 ,much may be done by gently pushing the tube together or pulling it apart in the flame1 to remove lumps and irregularities4 ,it is necessary that the bore of the joint be approximately that of the main tube1 and care must be taken that the latter is not constricted at the point where the joint begins4 ,illustration3 ,,fig4 #ad4--;,capillary tubing4 ,especial care must be taken to warm the tube slowly when starting and cool it slowly when through1 as the thick walls frequently crack if not carefully handled4 ,for this reason the whole neighborhood of the joint must be heated somewhat so that there may not be stresses set up between the heated and unheated portions4 ,in making the tee 7b1 ,fig4 #ad7 the inability to blow the joint makes itself decidedly felt1 but if the side tube is properly enlarged as previously described1 a good joint can be made by alternately pulling and pushing on the end of the side tube1 and shrinking well4 ,very fine capillary tubing should be blown with a rubber bulb instead of the mouth1 so as not to get moisture into the tube4 ,the rubber bulb may also be used to advantage on some of the coarser capillary tubing4 ,when a bulb is to be joined to a piece of capillary tubing1 the joint is preferably made before blowing the bulb1 and will then be taken up a little way on the bulb during the process4 ,care must of course be taken not to constrict the capillary2 the pear-shaped bulb blown on the end 7a1 ,fig4 #ad7 may well extend back a little further than usual into the tube so as to prevent this4 ,if a bulb is required in the middle of a capillary tube1 the latter is usually best cut and a piece of ordinary tubing of suitable size sealed in to provide material for the bulb4 ,,glass ,,rod ,joints1 tees1 etc41 in glass rod are made on the same principle as in tubing1 except that of course they cannot be blown1 and regularity must be obtained by accumulating a small mass of uniformly heated glass1 and then drawing it to a suitable rod1 on the same principle as ,exercise ,no4 #a4 ,great care must be taken in heating and cooling this1 as in the case of the capillary tubing1 and for the same reasons4 ,by joining pieces side by side1 pressing with carbon plates or a plate and a rod1 and other suitable manipulations1 stirrers1 spatulas1 and other objects may easily be made from rod1 and its manipulation is relatively easy on account of the fact that one does not have to worry about the bore of the tube4 ,but the same general rule about not having thick and thin spots in contact1 and making all changes in diameter on a taper if possible instead of abruptly1 applies here4 ,thick pieces will cool and contract at different rates from thin ones1 and cracks are likely to develop where they join4 ,work which has been formed with any tool must always be heated to the softening point afterward before allowing it to cool in order to remove the stresses caused by the contact of the tool with the hot glass4 ,when it is necessary to join a piece of rod to the side of a piece of tubing1 the end of the rod is made very hot while the wall of the tube at the spot desired is heated to just below the softening temperature4 ,the rod can then be pressed into firm union with the tube and drawn a little to remove the excess of glass without deforming the tube4 ,,mending ,,stopcocks ,mending the ,plug4--,the plug of the stopcock occasionally falls out and is broken4 ,if the break is in the main part of the plug1 nothing can be done except to search for a spare plug of suitable size and grind it to fit1 as described below4 ,if only the little cross-piece at the end is broken off1 it can easily be replaced4 ,in most ordinary stopcocks the plug is solid1 but the little handle is hollow4 ,what has been said above regarding care in heating and cooling glass rod applies with especial force here4 ,it is usually best to wind the whole of the plug with several thicknesses of asbestos cord1 leaving bare only the end where the handle is to be joined4 ,this diminishes the danger of cracking the plug by too rapid heating1 and also makes it more comfortable to hold4 ,a piece of rather thick-walled tubing of suitable diameter is chosen1 drawn out so as to have a suitable taper 7taking care to heat enough of the tube so that the capillary tail has good wall-thickness and strength71 and then a corresponding taper is drawn to form the other side of the handle4 ,the result is shown in ,fig4 #ae1 a4 ,the capillary tail is now heated and bent back to form a handle which will be in the same straight line as the axis of the plug 7b1 ,fig4 #ae7 and the main part of the tube drawn off at the dotted line1 making a neat seal at that point4 ,the broken end of the plug is now slowly warmed in the smoky flame1 the heat gradually increased by a gentle stream of air from the bellows1 and the point at which this handle is to be attached finally brought to the temperature at which the glass flows freely4 ,in the mean time1 the little handle has been warmed almost to the softening point4 ,it is now quickly pushed into place 7c1 ,fig4 #ae71 taking care that its axis is parallel to the hole in the plug1 and then drawn away from the plug just enough to make a graceful neck instead of the bulging one indicated by the arrow in the figure4 ,with a fine pointed flame the little tail is now drawn off at the point indicated by the dotted line 7c1 ,fig4 #ae7 and the whole carefully annealed4 ,if necessary1 the handle can be blown a little before the tail is removed4 ,local heating and blowing at the point where the handle joins the plug is often necessary in order to make a smooth job4 ,illustration3 ,,fig4 #ae4--,stopcock plug4 ,regrinding4--,this is sometimes necessary to make stopcocks tight1 when the grinding has not been properly done in the factory4 ,for this1 a very little fine flour of emery or carborundum is the best and quickest4 ,if this is not at hand1 some clean sand may be ground in an agate mortar1 and if possible sieved4 ,only material which passes the #ajj-mesh sieve should be used4 ,it will be ground still finer in the process4 ,for the final polishing1 a little infusorial earth or even kaolin will do4 ,the surface to be ground is moistened with water and dusted over with a little of the abrasive4 ,the plug is now inserted in the stopcock1 and turned with a gentle pressure4 ,this turning should be in the same direction for several revolutions1 then in the opposite direction for several more revolutions1 etc4 ,as the abrasive becomes finer during the grinding1 a little more may be added if necessary4 ,in general1 only a little grinding will be required1 and one small pinch of carborundum or emery will be ample4 ,the beginner usually grinds too much1 and with too coarse material4 ,as the grinding surface becomes dry1 water is added drop by drop1 and the grinding continued until the abrasive seems to be reduced to an impalpable powder1 most of which has been squeezed out of the stopcock4 ,the two surfaces in the stopcock are usually grinding upon each other at this stage1 and inspection will show whether the contact between them is uniformly good4 ,if not1 the grinding must be continued with a little fresh abrasive4 ,if contact appears to be good1 the surfaces are ground together for a little with practically no abrasive1 so as to polish them1 and the joint is then washed out and tested4 ,in grinding in a new plug to replace a broken one1 the plug selected should have practically the same taper as the seat into which it is to be ground1 and should be a very little too large4 ,care must be taken to so distribute the abrasive material as to grind mostly on the places where the plug fits tightly4 ,sealing on a ,new ,tube4--,it frequently happens that one of the tubes of the stopcock is broken off close to the cock itself1 and a new one must be joined to the stub of the old one4 ,with care1 this may often be successfully done even where the break is within #a_/d inch of the stopcock4 ,the first step is to clean and dry the stopcock1 remove the plug1 cork the open ends of the stopcock sleeve and the other tube1 and wind a couple of layers of asbestos cord carefully over the sleeve and the most of the corks which close it4 ,a suitable tube1 having as near as possible the same diameter and wall strength as the one broken off1 is selected and a piece the desired length cut off4 ,the broken end of the tube on the stopcock is now squared off as well as possible1 by cutting or by heating and drawing off the projections1 and the new tube sealed on1 usually with the first method 7,exercise ,no4 #a74 ,if the break is very close to the stopcock1 very little reheating and blowing can be done1 on account of the danger of getting the stopcock sleeve out of shape1 and the work must be heated very slowly to prevent cracking4 ,the main reliance is then placed on making a good joint when the tubes are brought together1 and then drawing out this joint a little1 at once1 to get an even wall4 ,,closed ,,circuits ,,of ,,tubing4 ,in some pieces of apparatus closed circuits of circular or rectangular shape are required4 ,a similar problem is involved in apparatus like the ordinary ,soxhlet extractor1 where a small tube is joined to the side of a large one1 bent to form a siphon1 and attached again to a continuation of the original large tube4 ,the difficulty in all such cases is to provide for the contraction taking place as the last joint cools4 ,if part of the circuit has the shape of the letter ,s1 or is a spiral1 the natural springiness of the glass will take care of this4 ,if not1 the side of the circuit opposite to the joint and parallel to it must be heated also1 the two being finally heated together to the softening point after the joint is completed1 and then allowed to cool together4 ,to make the last joint1 the rest of the tube is made in approximately the desired form1 the two pieces which are to be joined to make the last joint being just enough out of the desired position to allow them to pass one another4 ,the final joint is preferably made in the middle of a straight piece of tube1 not at a tee4 ,the two pieces which are to be joined are bent so as to just pass each other1 marked at the right point with the glass-knife1 and cut there1 preferably with a small bead of hot glass4 ,one or both of these tubes are now warmed to the softening point in such a place that the tubes can be made to meet properly1 and the two cut ends pressed together4 ,they are now warmed in the flame1 and joined together1 either by simultaneously warming the opposite side of the circuit or some other suitable part1 so as to allow the two ends to be pushed together again after they are softened1 or by gently touching the places that do not unite with a hot bead of glass1 and using the glass to fill up the crack where the ends do not quite meet4 ,care must be taken not to leave knots or lumps of glass in the finished joint1 and the latter should be well reblown1 and if necessary left as a small bulb or enlargement1 rather than have it have too thick walls4 ,,spirals ,spirals of glass tubing are probably best made free-hand before the blow-pipe1 unless one has a great many of them to make1 and extreme accuracy is desired4 ,to begin with1 a piece of tubing of the desired size 7say #c_/af inch in diameter7 and a convenient length 7about two feet7 is selected1 one end closed1 and a right-angle bend made about six inches from the closed end4 ,holding the closed end in the left hand and the long open one in the right1 the spiral is begun4 ,the short closed end is to be parallel to the axis of the spiral1 and preferably in that axis4 ,using a moderate-sized flame1 of somewhat yellow color1 and taking care to heat the whole circumference of the tube1 the long open end is wound little by little into a spiral having the short end a 7,fig4 #af7 as an axis4 ,the bend at b1 where the tube changes from the radius to the circumference of the circle1 must be rather short1 but the tube must not be flattened or constricted here4 ,especial pains is to be taken with the first turn of the spiral 7b to c1 ,fig4 #af71 as the shape of this determines the diameter of the whole spiral1 and serves as a guide for the rest of the turns4 ,the winding of the tube is best accomplished1 after a portion has been softened1 by slowly turning the short end a a little about its own axis1 while the long open end remains where it was4 ,this winds the tube into a spiral1 just as if there were a solid cylinder in the center of it1 and this cylinder was being turned about its axis1 and was winding up the soft glass upon its circumference4 ,as the cylinder is not actually there1 the curve of the turns must be carefully estimated by the eye1 so that the spiral may be uniform and moderately smooth4 ,when the original piece of tube has been used up1 another piece is sealed on to the open end1 and the operation continued as far as may be required4 ,illustration3 ,,fig4 #af4--,making a spiral4 ,,ground ,,joints ,it is sometimes required to join two pieces of tubing end to end1 by means of a ground joint4 ,whenever possible1 a regular sealed joint should be used instead of this ground joint1 as it is quicker to make1 and more certain to be tight4 ,where a ground joint is necessary1 however1 it is best made in the conical form shown in c1 ,fig4 #ag4 ,if the wall of the tube to be used is not very thick1 it is thickened by collecting glass as for a bulb on the ends of two tubes 7,exercise ,no4 #f71 and drawing to form cones of suitable shape 7a and b1 ,fig4 #ag7 and of such relative sizes that a will slip about half way into b4 ,in order to make a straight and give it the proper angle1 it may be rolled when hot1 upon a hot plate of carbon4 ,blowing during this rolling is often helpful to remove depressions4 ,after b has been drawn to nearly the proper size and shape1 it may be smoothed by the use of a small carbon rod1 held inside it at a slight angle1 or better by the use of a truncated hexagonal pyramid of carbon1 whose edges have the proper slant to make the inside of the cone right4 ,the proper taper for both these cones is the same as that used in stopcocks of similar size4 ,the hexagonal carbon can easily be made by carefully filing down an electric light carbon1 and finally impregnating it with paraffin or beeswax1 and is extremely useful wherever a conical surface has to be formed from the inside of a tube4 ,illustration3 ,,fig4 #ag4--;,ground joint4 ,the tail is allowed to remain on piece a1 as a sort of guide in grinding1 and should therefore be in the axis of the tube and have rather thick walls4 ,grind with emery or carborundum1 as described under a previous head4 7,regrinding plug for stopcock47 ,if many such joints are to be made1 it will pay to have a little sleeve of brass made with the proper taper1 and rough down the plug a in it to about the proper size1 while b is roughed down by means of a brass or iron plug having the same taper4 ,this prevents excessive grinding of one-half of the joint in order to remove a defect in the other half1 and is the method commercially used in making stopcocks4 ,,sealing ,,in ,,platinum ,,wire ,very often it is necessary to seal platinum wire into the wall of a tube4 ,professional glass-blowers usually use a special sort of glass 7,einschmelzglas7 which is usually a lead glass1 and is made of such composition that it has the same or practically the same coefficient of expansion as platinum4 ,a little globule of this glass is sealed into the tube in such a way that it joins the platinum to the glass of the tube4 ,to do this1 the small globule of special glass is fused on the platinum wire at the proper point and the tube into which the wire is to be sealed is heated and a small tail drawn out at the point where the wire is to be inserted4 ,the lump of the special glass should be from #c_/cb to #a_/h inch in diameter1 and the tail drawn on the tube should have a slightly less diameter at the point 7about #a_/h inch or less from the tube7 where it is cut off4 ,there are now two ways of sealing in the wire4 7#a7 ,the wire with the globule of glass is placed inside the tube and the latter revolved until the end of the wire sticks out of the cut tail 7a1 ,fig4 #ah74 ,the latter is now gently heated1 and the two glass surfaces fused together1 taking care to use only the end of the hissing flame1 if the special glass contains lead4 7,see ,chapter ,i1 page #a47 ,the whole circumference of the tube is then heated and annealed carefully4 7#b7 ,the end of the wire which is to be outside the tube is attached to the end of a thin scrap of glass1 by heating the glass and thrusting the wire into it a very little way4 ,using this piece of glass as a handle1 the wire is inserted in the cut tail 7b1 ,fig4 #ah7 and the globule brought near to the end of the tail4 7,if the main tube is cold1 it must of course first be warmed47 ,with the end of the hissing flame1 as in the first method1 the globule of glass is melted and the end of the tail softened4 ,the wire is now pushed into place1 the handle removed by heating the end and withdrawing it1 and the tail reheated a little if necessary to make it shrink back into line with the walls of the tube4 ,the whole circumference of the tube is heated at that point and annealed as usual4 ,illustration3 ,,fig4 #ah4 ,the use of this special glass is not absolutely necessary if the platinum wire is small 7#a_/d millimeter or less in diameter71 and in fact it is often better in such cases not to use it1 unless the apparatus is to be subjected to a very high vacuum4 ,on small tubes1 especially1 it is undesirable to use the special glass1 as a lump of it will usually cause the tube to crack on cooling4 ,when such glass is not at hand or is not to be used1 the procedure is altered somewhat4 ,the tail which is drawn out is very fine1 having only a sufficient diameter so that when it is cut off the wire can be inserted in it4 ,such a fine tail is readily made by heating a small spot on the tube1 touching it with a warm platinum wire1 removing from the flame and drawing out the tail with the wire4 ,after cutting off the tail the wire is inserted in it1 being held on a scrap of glass as in the previous case1 and the wire and tail heated until the latter shrinks back into line with the walls of the tube4 ,if too great shrinkage occurs1 the place may be blown out gently after reheating4 ,thus the wire is sealed through the wall of the tube without changing the thickness of the latter1 and consequently without developing undue stresses at that point4 ,such a joint must of course be carefully reheated and annealed4 ,with fine platinum wire there is very little risk of the tube cracking if care is taken to avoid formation of any lump and to reheat the whole circumference of the tube at that point4 ,any glass adhering to the end of the platinum wire1 where the scrap of glass was sealed on for a handle1 may be removed when the glass has cooled by crushing it carefully with a pair of pliers4 ,,sealing ,,vacuum ,,tubes ,tubes which have been evacuated usually are sealed off while they are still connected to the vacuum pump4 ,the connection should be through a small1 rather thick-walled tube4 ,when this is to be sealed1 it is slowly heated toward the softening point4 ,as the glass just begins to soften1 the air-pressure will force it in1 and care must be taken that the softening is uniform over the whole circumference of the tube4 ,as the shrinking goes on1 the tube is gently drawn out to make a thick-walled cone at that place1 and the end is drawn off as soon as the tube is sealed4 ,the principal point to be guarded is the thickness of the walls of the cone1 and uniform heating4 ,a thin place or a hot place will give way under the air-pressure and be sucked into the tube4 ,,closed ,,tubes ,,for ,,heating ,,under ,,pressure 7,carius method for determination of the halogens and sulphur47 ,in this case the tubing used must have thick walls 7usually about #c_/cb inch7 to withstand the pressure4 ,its external diameter is usually about #c_/d inch4 ,one length will usually make two tubes of standard length for the cannon furnace4 ,especial care must be taken in heating and cooling it on account of the thick walls4 ,a length is gradually warmed in the center1 finally heated at that point until soft1 drawn out1 cut apart and annealed4 ,taking one of the pieces1 the cone is carefully heated and shrunk1 as in ,exercise #d1 until its walls are as thick as those of the main tube4 ,a flame with a little tinge of yellow should be used for this operation to prevent devitrification 7page #b71 as the thick glass shrinks slowly4 ,the tail is now drawn off and the whole end heated and gently blown several times to make a rounded end1 like a test-tube1 with walls as thick as those of the main tube4 ,this must be carefully annealed4 ,it is more important that the walls be thick than that the end be nicely rounded3 it may indeed be left somewhat conical in shape4 ,at a point about two inches from the open end of the tube1 it is slowly warmed and finally heated to the softening point4 ,grasping the open end with a pair of crucible tongs1 it is cautiously pulled out1 a little at a time1 usually during rotation in the flame1 to make a constriction of moderate wall-thickness1 but of sufficient internal diameter to admit the tube containing the substance4 ,after annealing this1 cooling and cleaning the tube1 the acid and salt are introduced 7the former by means of a long-stemmed funnel7 and the tube is inclined and rotated about its axis so that the acid wets its surface about half way up from the bottom4 ,the substance is now weighed out in a piece of thin-walled glass tubing1 closed at one end1 and about two inches long4 ,inclining the large tube at a suitable angle1 the small one is introduced1 closed end first1 and allowed to slide down the walls of the large tube until it reaches the place where the acid has wet the tube4 ,here it will stop1 and if the tube is kept inclined during the rest of the operation it will roll around inside the tube at this point and thus not get down where any acid is likely to get into it and produce any pressure by decomposing it before the open end of the tube is sealed4 ,now the tube is held in an inclined position1 taking care that the acid does not reach up to the substance1 the constricted portion cautiously warmed and shrunk4 ,it is finally shrunk and drawn out into a somewhat elongated cone1 with walls as thick as the rest of the tube1 and when this is accomplished the end of the cone is sealed and the waste piece drawn off4 ,anneal with great care1 and cool in such a position that the acid cannot reach the hot glass4 ,the shrinking of this cone takes a good deal of patience1 and is one of the most important parts of the process4 ,if the walls are left too thin1 the tube may burst when heated1 and the whole labor is lost4 ,if care is taken1 the same tube can be used for a number of determinations1 until it becomes quite short4 ,,index ,annealing glass1 #d1 #bd ,bellows1 #d ,bending glass1 #h ,blowing glass1 #ac1 #ai1 #bj1 #ba1 #bd1 #bi1 #ca with a rubber tube1 #bb ,blowpipe1 #d ,bulb at end of tube1 #bh in middle of tube1 #cb very large1 #cb ,bulbs1 string of1 #cc ,capillary tube1 drawing on larger tube1 #i1 #ed tubing1 working1 #dc ,carius method1 tubes for1 #ee ,closed circuits of tubing1 #dh tubes1 for heating under pressure1 #ee ,collecting glass for bulb1 #bi1 #ca1 #cb ,constricting a tube1 #aj ,crystallization of glass1 see ,devitrification4 ,cutting glass1 #g1 #be ,devitrification1 #a1 #b ,drawing out a tube1 #i1 #ah1 #ai1 #bg ,flanging a tube1 #aa1 #ad tool1 #aa ,gas-washing tube1 #ce ,glass1 annealing1 #d1 #bd ,glass1 bending1 #h blowing1 #ac1 #ai1 #bj1 #ba1 #bd1 #bi1 #ca collecting for bulb1 #bi1 #ca1 #cb cutting1 #g defects1 #b grinding1 #dg hard1 #a knife1 #g lead1 #a qualities desired1 #a rod and tube1 joining1 #de rod1 working1 #dd shrinking1 #ah1 #ai1 #bb1 #bf soft1 #a working temperature1 #a1 #ac1 #ai1 #bg ,grinding stopcock or joint1 #dg ,ground joints1 #ea ,handle on stopcock1 mending1 #de ,hard glass1 #a ,holding tube1 #ac1 #ad ,insertion of tube through another1 see ,sealing a tube through another tube4 ,joints1 ground1 #ea ,joining rod and tube1 #de tubing end to end3 first method1 #af second method1 #bj ,joining tubes of different diameters1 #be a new tube to a stopcock1 #dh ,kjeldahl trap1 #da ,lead glass1 #a ,lump of glass1 removed1 #ah1 #ai1 #bj1 #ba1 #bd1 #bf1 #cj1 #ch ,platinum wires1 sealed into glass1 #a1 #eb ,position for glass-working1 #e ,pressure1 tubes for heating under1 #ee ,quality of glass1 #a ,rod1 glass1 working1 #dd ,rotation of the tube1 #ac1 #ai ,rounded end of tube1 #ce1 #ch ,rubber tube used for blowing1 #bb ,sealing a tube through another tube1 #ce1 #ci ,sealing vacuum tubes1 #ee ,shrinking glass1 #ah1 #ai1 #bb1 #bf1 #ca ,side tube1 blowing1 #bb1 #be ,soda glass1 #a ,soft glass1 #a ,spirals1 making1 #ej ,stopcocks1 mending1 #de ,suction pump1 #ci1 #db ,sulphur dioxide tube1 #bh ,tail of glass1 drawing out1 #i1 #ed removed1 #cj1 #ce ,tubes1 closed1 for heating under pressure1 #ee ,tee tube1 #bb on capillary tubing1 #dc small side tube on a large tube1 #bd ,vacuum tubes1 sealing1 #ee ,working temperature of glass1 #a1 #ac1 #ai1 #bg ---------------------------------------- ------------------------------ ,transcriber's note3- ,words in italics are indicated by the use of underscores and words in bold by the use of equals signs as shown4 ---------------------------------------- ------------------------------