230 ILLINOIS STATE ACADEMY OF SCIENCE 



To test the efficiency of the solvent action of the three 

 halogen acids, the residues from the acid extractions 

 were analyzed for their barium content and were found 

 to contain practically the same per cent of that element. 

 Hence, it was concluded that the acid extraction was the 

 same in all cases and that the three solutions presumably 

 contained the same amount of radium. 



After several crystallizations of the three halide sys- 

 tems, equivalent amounts of the richest fraction of each 

 were placed in the case of a charged electroscope and the 

 time of discharge noted. The iodide discharged the elec- 

 troscope more quickly than either the chloride or the 

 bromide, but the work has not yet progressed to the 

 point which will permit a definite statement concerning 

 the value of its enrichment factor. Another decided ad- 

 vantage in the use of the iodide comes from the greater 

 solubility of this salt over the others; hence a given 

 amount of radium in the iodide solution occupies a much 

 smaller volume than it does in the chloride or bromide 

 solution. This permits the use of smaller crystallizing 

 dishes, a material saving on a large scale operation. 



The use of the iodide for radium concentration would 

 not be practical unless it were possible to recover a large 

 per cent of the iodine at the end of the process. Accord- 

 ingly, when the radium had been practically all removed 

 from certain fractions, the barium iodide solutions were 

 saturated with chlorine. The displaced iodine was fil- 

 tered off, dried and resublimed. The. barium chloride 

 solution was evaporated and the crystals were used in 

 the precipitation of the next batch of radium-barium 

 sulfate. The iodine was mixed with a little less than the 

 theoretical amount of red phosphorus, and water was 

 slowly dropped over the mixture. In this manner hy- 

 driodic acid Avas obtained, which was also used in the 

 next series. The recovery was satisfactory, indicating 

 that the operating cost for iodine would be quite reason- 

 able. 



Urbana, Illinois, April 25, 1922. 



