230 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1925 



Conjro mineral a method of extraction based upon the same princi- 

 ples as that of Mme. Curie but involving some original ideas in its 

 application. 



The dominant impurities in the first Belgian material were copper, 

 iron, lead, phosphoric acid, alumina, and silica. For their elimina- 

 tion at the beginning, the mineral is pulverized and submitted (for- 

 lowing M. Leemans) to tlie four following operations: 



1. Attack with acids for the elimination and separation of 

 uranium, iron, copper, and phosphoric acid. 



2. Treatment with a sodium chloride solution for the elimination 

 of lead with final precipitation of the metal and the regeneration of 

 the brine. 



3. Treatment with hydrochloric acid to eventually eliminate the 

 calcium, 



4. Treatment with sodium carbonate to eliminate the sulphuric 

 acid. 



At the conclusion of these operations the radium remains in an 

 insoluble form mixed with the silica. This insolubility of radium 

 requires either that it exists at the start as a sulphate in the mineral, 

 which is not very likeh', or that it is first changed into the sulphate, 

 for instance, by heating it with sodium sulphate as is done at 

 JoachinivStahl. It is then possible to eliminate the impurities by 

 treatment with acids. Hydrochloric acid, 13° Baume and warm, is 

 particularly recommended for this step. The chloride of lead 

 formed, being only slightly soluble in the hydrochloric acid solution, 

 can doubtless be eliminated by a concentrated solution of sodium 

 chloride solution with which it forms a double salt. The calcium 

 sulphate can be removed with warm hydrochloric acid in which 

 gypsum is quite soluble. Finally treatment with sodium carbonate 

 transforms the sulphates of barium and radium which are insoluble 

 with the silica, into carbonates soluble in hj^drochloric acid and they 

 can thus be removed from the silica. 



All this earlier part of the process, whicli entails some 40 opera- 

 tions — filtration, washing, etc. — are carried out in the first building. 

 There results a mixture of impure chlorides of radium and barium 

 in which the radium is mixed with one hundred and twenty-five 

 thousand times its weight of inactive matter. The impurities liave 

 been thus reduced one two-hundredth of their original amount. 

 From this point the process is continued as with the carnotites. 



In a second phase of the work the chlorides are purified by trans- 

 forming them several times into sulphates and carbonates, and 

 when the purification has become sufficient the last phase of the 

 process commences: the enrichment of the radium b}' fractional 

 crystallization at first in the form of chlorides and then as bromides. 



