Chemistry and Physics. 79 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. The Relative Volatility of the Bromides of Barium and 

 Radium. — Stock and Heynemann have determined the temper- 

 atures at which the bromides of calcium, strontium and barium 

 begin to sublime in a quartz tube exhausted by the mercury pump 

 as follows : 



Calcium bromide, about 720° C. 

 Strontium bromide, " 770 

 Barium bromide, " 820 



These results showed that the temperature of sublimation rises 

 with the atomtic weight of the metal in these cases, and it was 

 inferred that barium bromide would sublime more readily than 

 radium bromide. This was found to be the case by fraction- 

 ally subliming several samples of barium bromide containing 

 varying quantities of radium and determining the radium in the 

 products by the electroscopic method. For instance, a sample gave 

 8*8 per cent of a sublimate containing 0*008 per cent of radium, 

 while the residue, 88*2 per cent, contained 0-015 per cent of radi- 

 um. In another case 17 per cent of sublimate contained 4*8 per 

 cent of radium, while the 83 per cent of residue contained 6*6 

 per cent of radium. The authors are of the opinion that frac- 

 tional sublimation may be of practical use in the preparation of 

 pure radium salts — Berichte, xlii, 4088. h. l. w. 



2. The Action of Light upon Hydrogen Chloride. — The 

 action of light in causing the combination of hydrogen and 

 chlorine gases is very familiar, hence it is suprising to find from 

 the experiments of Coehn and Wassiljewa that ultra-violet 

 light is capable of decomposing hydrochloric acid gas to some 

 extent into hydrogen and chlorine gases. These investigators, 

 having previously found a similar decomposition of S0 3 into S0 2 

 and 2 , passed pure HC1 gas through a quartz tube, where it was 

 exposed to the light of a quartz-mercury=vapor lamp. The gas 

 was then led through a blackened glass tube into potassium iodide 

 solution where the liberation of iodine indicated the formation of 

 chlorine, and the unabsorbed gas, collected in a eudiometer, was 

 shown to be hydrogen. The decomposition of the hydrogen 

 chloride in this way amounted to 0*25 per cent. No decomposi- 

 tion was obtained when tubes of glass, instead of quartz, were 

 used. Any suspicion that the liberation of chlorine here was 

 due to the presence of atmospheric oxygen, which might give the 

 reaction of the Deacon process, 4HC1 + 2 =2H 2 + 2C1 2 , was 

 shown to be without foundation since hydrogen was shown to be 

 present. — Berichte, xlii, 3183. h. l. w. 



3. The Ratio between Uranium and Radium in Minerals. — 

 Mlle. Gleditsch has studied this question, which is important in 



