,ellen ,s4 ,richards ,monographs ,no4 #b ,published by ,vassar ,college ,the ,discovery of ,radium ,it is my earnest desire that some of you shall carry on this scientific work and will keep for your ambition the determination to make a permanent contribution to science ,m4 ,curie ,address by ,madame ,m4 ,curie at ,vassar ,college ,may #ad1 #aiba ,illustration3 ,autograph ,,prefatory ,,note ,in her recent visit to ,america1 ,madame ,curie conferred a special honor upon ,vassar ,college by delivering in the chapel on the evening of ,may fourteenth the only extended address which she made in this country4 ,in a simple1 straightforward way she told the story of her great achievement4 ,one realized how1 closely environed by all the great realities of human experience1 in the face of tremendous difficulties and with limited resources1 she had pursued undaunted her search for truth4 ,the discovery of radium gave ,madame ,curie immediate distinction among scientists on account of the extremely significant contribution she thereby made to the great ultimate problem of physical science1 the constitution of matter4 ,the striking properties possessed by radium gave to its discovery a world-wide interest1 all the more intense because of the hope which was inspired by the possible healing qualities of the radiations from this new element4 ,that hope is being realized in large measure4 ,it is therefore fitting that this address should have been given by ,madame ,curie at ,vassar and that it should now be circulated among the members of the college under the foundation in memory of ,ellen ,s4 ,richards1 who devoted her life to the public health4 ,edna ,carter ,chairman of the ,department of ,physics4 ,,the ,,discovery ,,of ,,radium ,i could tell you many things about radium and radioactivity and it would take a long time4 ,but as we can not do that1 ,i shall only give you a short account of my early work about radium4 ,radium is no more a baby1 it is more than twenty years old1 but the conditions of the discovery were somewhat peculiar1 and so it is always of interest to remember them and to explain them4 ,we must go back to the year #ahig4 ,professor ,curie and ,i worked at that time in the laboratory of the school of ,physics and ,chemistry where ,professor ,curie held his lectures4 ,i was engaged in some work on uranium rays which had been discovered two years before by ,professor ,becquerel4 ,i shall tell you how these uranium rays may be detected4 ,if you take a photographic plate and wrap it in black paper and then on this plate1 protected from ordinary light1 put some uranium salt and leave it a day1 and the next day the plate is developed1 you notice on the plate a black spot at the place where the uranium salt was4 ,this spot has been made by special rays which are given out by the uranium and are able to make an impression on the plate in the same way as ordinary light4 ,you can also test those rays in another way1 by placing them on an electroscope4 ,you know what an electroscope is4 ,if you charge it1 you can keep it charged several hours and more1 unless uranium salts are placed near to it4 ,but if this is the case the electroscope loses its charge and the gold or aluminum leaf falls gradually in a progressive way4 ,the speed with which the leaf moves may be used as a measure of the intensity of the rays2 the greater the speed1 the greater the intensity4 ,i spent some time in studying the way of making good measurements of the uranium rays1 and then ,i wanted to know if there were other elements1 giving out rays of the same kind4 ,so ,i took up a work about all known elements1 and their compounds and found that uranium compounds are active and also all thorium compounds1 but other elements were not found active1 nor were their compounds4 ,as for the uranium and thorium compounds1 ,i found that they were active in proportion to their uranium or thorium content4 ,the more uranium or thorium1 the greater the activity1 the activity being an atomic property of the elements1 uranium and thorium4 ,then ,i took up measurements of minerals and ,i found that several of those which contain uranium or thorium or both were active4 ,but then the activity was not what ,i could expect1 it was greater than for uranium or thorium compounds like the oxides which are almost entirely composed of these elements4 ,then ,i thought that there should be in the minerals some unknown element having a much greater radioactivity than uranium or thorium4 ,and ,i wanted to find and to separate that element1 and ,i settled to that work with ,professor ,curie4 ,we thought it would be done in several weeks or months1 but it was not so4 ,it took many years of hard work to finish that task4 ,there was not one new element1 there were several of them4 ,but the most important is radium which could be separated in a pure state4 ,all the tests for the separation were done by the method of electrical measurements with some kind of electroscope4 ,we just had to make chemical separations and to examine all products obtained with respect to their activity4 ,the product which retained the radioactivity was considered as that one which had kept the new element2 and1 as the radioactivity was more strong in some products1 we knew that we had succeeded in concentrating the new element4 ,the radioactivity was used in the same way as a spectroscopical test4 ,the difficulty was that there is not much radium in a mineral2 this we did not know at the beginning4 ,but we now know that there is not even one part of radium in a million parts of good ore4 ,and too1 to get a small quantity of pure radium salt1 one is obliged to work up a huge quantity of ore4 ,and that was very hard in a laboratory4 ,we had not even a good laboratory at that time4 ,we worked in a hangar where there were no improvements1 no good chemical arrangements4 ,we had no help1 no money4 ,and because of that the work could not go on as it would have done under better conditions4 ,i did myself the numerous crystalizations which were wanted to get the radium salt separated from the barium salt with which it is obtained out of the ore4 ,and in #aijb ,i finally succeeded in getting pure radium chloride and determining the atomic weight of the new element radium1 which is #bbf while that of barium is only #acg4 ,later ,i could also separate the metal radium1 but that was a very difficult work2 and1 as it is not necessary for the use of radium to have it in this state1 it is not generally prepared that way4 ,now1 the special interest of radium is in the intensity of its rays which is several million times greater than the uranium rays4 ,and the effects of the rays make the radium so important4 ,if we take a practical point of view1 then the most important property of the rays is the production of physiological effects on the cells of the human organism4 ,these effects may be used for the cure of several diseases4 ,good results have been obtained in many cases4 ,what is considered particularly important is the treatment of cancer4 ,the medical utilization of radium makes it necessary to get that element in sufficient quantities4 ,and so a factory of radium was started to begin with in ,france1 and later in ,america where a big quantity of ore named carnotite is available4 ,america does produce many grams of radium every year but the price is still very high because the quantity of radium contained in the ore is so small4 ,the radium is more than a hundred thousand times dearer than gold4 ,but we must not forget that when radium was discovered no one knew that it would prove useful in hospitals4 ,the work was one of pure science4 ,and this is a proof that scientific work must not be considered from the point of view of the direct usefulness of it4 ,it must be done for itself1 for the beauty of science1 and then there is always the chance that a scientific discovery may become like the radium a benefit for humanity4 ,but science is not rich1 it does not dispose of important means1 it does not generally meet recognition before the material usefulness of it has been proved4 ,the factories produce many grams of radium every year1 but the laboratories have very small quantities4 ,it is the same for my laboratory and ,i am very grateful to the ,american women who wish me to have more of radium and give me the opportunity of doing more work with it4 ,the scientific history of radium is beautiful4 ,the properties of the rays have been studied very closely4 ,we know that particles are expelled from radium with a very great velocity near to that of the light4 ,we know that the atoms of radium are destroyed by expulsion of these particles1 some of which are atoms of helium4 ,and in that way it has been proved that the radioactive elements are constantly disintegrating and that they produce at the end ordinary elements1 principally helium and lead4 ,that is1 as you see1 a theory of transformation of atoms which are not stable1 as was believed before1 but may undergo spontaneous changes4 ,radium is not alone in having these properties4 ,many having other radioelements are known already1 the polonium1 the mesothorium1 the radiothorium1 the actinium4 ,we know also radioactive gases1 named emanations4 ,there is a great variety of substances and effects in radioactivity4 ,there is always a vast field left to experimentation and ,i hope that we may have some beautiful progress in the following years4 ,it is my earnest desire that some of you should carry on this scientific work and keep for your ambition the determination to make a permanent contribution to science4 ,m4 ,curie4 ,illustration3 ,photograph ,with my friendship for the ,students of ,vassar ,college-- ,m4 ,curie ,transcriber's ,notes --,silently corrected a few typos4 --,retained publication information from the printed edition3 this e,book is public-domain in the country of publication4 --,generated cover and spine images from elements in the printed edition4 --,in the text versions only1 text in italics is delimited by underscores4