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LIV. The Origin of Radium, fi>/ Bertram B. Boltyvood *. 



IN previous papers t it has been shown that the quantities 

 of uranium and radium which occur together in certain 

 minerals are directly proportional to one another, and the 

 important bearing of this relationship on the origin of radium 

 has been pointed out. In the present paper the same general 

 method of investigation has been applied to twenty-two separate 

 samples comprising twelve distinct mineral species, and the 

 constant proportionality between the uranium and the radium 

 has been further confirmed J. 



In order to determine the relative amounts of radium 

 contained in any two samples of material, it is only necessary 

 to determine the activity of the maximum or equilibrium 

 quantity of radium emanation produced by equal weights of 

 the two samples. The ratio between the activities of the two 

 quantities ot emanation will Jje the same as that between the 

 quantities of radium which produced them. Since the 

 activity of a given quantity of emanation can be measured 

 with great ease and with extraordinary accuracy considering 

 the infinitesimal quantities of matter dealt with, the quanti- 

 tative measurement of the radium in this manner, through 

 the medium of the activity of its emanation, affords a most 

 convenient and accurate means of determining the relative 

 quantity in which this element is present. 



"When a solid substance containing a radium salt is allowed 

 to stand, the emanation which is formed is, for the most 

 part, occluded by the solid. If the solid is dissolved the 

 emanation escapes from the solution, slowly at ordinary 

 temperatures and rapidly if the solution is heated to boiling. 

 It is therefore possible in this way to completely separate the 

 emanation from the radium salts, and under proper conditions 



* Communicated by the Author. Read before the American Chemical 

 •tv. Feb. 10,190-1 

 Sngineeriiig and Mining Journal, lxxvii. p. 750 (1904) ; Nature, lxx. 

 (1904 ) : Amer. Journ. of Science, xviii. p. 97 (1904). 

 [ M •< toy has published (Berichte d. D. Chem. Gesell. xxxvii. p. 2041, 

 some numbers obtained from the direct measurement of the 

 radioactivity of a number of uranium minerals, which seem to show that 

 for the samples examined the activity is roughly proportional to the 

 content of uranium. He assumes on the basis of this proportionality 

 that the radium contained in each mineral is directly proportional to 

 tlie uranium present, a conclusion which, under the circumstances, is 

 only justified on the assumption of the further hypothesis that all of the 

 other radioactive constituents (polonium, actinum, radio-lead) are also 

 directly proportional to the uranium. This latter relationship still lacks 

 experimental confirmation. .McCoy's method is moreover quite un- 

 suitable for minerals containing any notable quantities of thorium, as he 

 himself acknowledjj 



