Chemistry and Physics. 75 



We have, therefore, as the final product a mixture of metallic 

 silver with much H 3 Sb0 3 and little metallic antimony, while an 

 appreciable quantity of the antimonious acid goes into solution. 

 The reaction is precisely similar to that of hydrogen arsenide 

 with silver solutions, except that in the latter case the arsenious 

 acid, being more soluble, goes into solution. — Perichte, xlii, 1458. 



H. L. W. 



3. The Separation of Antimony and Tin. — G. Panojotow has 

 devised a simple and rapid method for the separation of these 

 metals, which can be used in all cases where the antimony is in 

 solution in the trivalent condition. To the solution is added 

 enough concentrated hydrochloric acid to give about 15 per cent 

 of the actual acid, then it is heated to 50-60° C. and a rapid 

 stream of hydrogen sulphide is passed in for 30 minutes. A 

 yellow precipitate appears at first, but soon the cinnabar-red, 

 anhydrous antimony sulphide is formed, which settles rapidly. 

 The liquid is then cooled below 30° C, and a very moderate stream 

 of hydrogen sulphide is passed in for 10 minutes. Then the 

 precipitate is quickly filtered upon a Gooch crucible, washed with 

 15 per cent hydrochloric acid which has been saturated with 

 hydrogen sulphide until the tin has been removed, then the 

 hydrochloric acid is removed by washing with strong hydrogen 

 sulphide water. After this the antimonious sulphide is washed 

 successively with alcohol, a mixture of alcohol and carbon disul- 

 phide, alcohol, and ether. It is then dried at 110° and weighed. 

 The tin in the filtrate is precipitated with hydrogen sulphide 

 after partially neutralizing with ammonia, diluting with water, 

 and heating. Test analyses gave excellent results with widely 

 varying quantities of the two metals. — Beriehte, xlii, 1296. 



H. L. W. 



4. The Purification of Sulphuric Acid by Freezing. — It is well 

 known that sulphuric acid containing about 94 per cent of the 

 "monohydrate," H 2 S0 4 , yields crystals of the 100 per cent acid 

 upon cooling to about —20° C, and upon this fact is based a 

 method of concentrating such acid upon a commercial scale. 

 Moeaxce has found that a considerabty weaker acid, if of just 

 the proper strength, will crystallize at a few degrees below zero, 

 and will yield a stronger and purer product than the original 

 material. In a case where an impure acid had been frozen so 

 that almost exactly equal weights of solid and liquid were pro- 

 duced, he obtained the following results upon analyzing the 

 products : 



Crystals Mother liquor 



Ignited residue 0-2320 0*5730 



Iron and alumina 0'0241 0*0825 



Arsenic 0-0275 0*2250 



Sulphuric acid 82-45 69*1 



The results show a particularly good purification from arsenic 

 by the crystallization. — Comptes Pendus, cxlviii, 842. 



H. L. W. 



