

324 Scientific Intelligence. 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. Qualitative Separation of Arsenic, Antimony and Tin. — 

 James Walker describes the following method for the analysis 

 of this group : The sulphides are dissolved in caustic soda and 

 the solution is boiled with sodium peroxide. This produces 

 sodium stannate, arsenate and antimonate. An excess of ammo- 

 nium chloride is then added, and the liquid is boiled. This 

 treatment precipitates all the tin as stannic hydroxide, and, 

 although the precipitate may contain a little antimony, the sepa- 

 ration answers for qualitative purposes. 



In separating the sulphides under consideration from the sul- 

 phides of the copper group by the use of sodium hydroxide, it is 

 necessary to add a few drops of yellow ammonium sulphide in 

 order that stannous sulphide may readily dissolve. It is to be 

 noticed, also, that mercuric sulphide is soluble in the solution, but 

 this is precipitated as such when the other sulphides are oxidized 

 by boiling with sodium peroxide. 



The presence of tin is confirmed by dissolving the stannic 

 hydroxide in concentrated hydrochloric acid, reducing to stan- 

 nous chloride by boiling with metallic iron, and testing with mer- 

 curic chloride, or also with hydrogen sulphide. 



To detect antimony and arsenic it is recommended to acidify 

 the filtrate from the stannic hydroxide, to warm until oxygen 

 ceases to be evolved, then to cool and pass in a rapid stream of 

 hydrogen sulphide. This treatment precipitates antimonic sul- 

 phide, which is filtered off. The resulting filtrate is then treated 

 with a few drops of sodium thiosulphate solution and warmed 

 until a precipitate begins to form. This may be sulphur alone, or 

 also arsenious sulphide. The precipitation of arsenic is then 

 made or completed by passing hydrogen sulphide. — lour. Chem. 

 Soc, lxxiii, 184. h. l. w. 



2. Arsenic JPentachloride. — Although phosphorus and anti- 

 mony pentachlorides are well known, all the numerous attempts 

 to prepare the pentachloride of arsenic have failed heretofore. 

 The apparent non-existence of this compound is considered 

 remarkable on account of the intermediate position of arsenic in 

 its relations to phosphorus and antimony. Baskerville and 

 Bennett now believe that they have succeeded in preparing this 

 much-sought compound. They placed arsenic trichloride in a 

 test-tube surrounded by solid carbon dioxide, then led in chlo- 

 rine. The trichloride, which had solidified at the low temperature 

 used, assumed a greenish yellow color and became liquid, and the 

 liquid increased in bulk, since the chlorine was liquefied. By 

 allowing "the excess" of chlorine to distil off at a temperature 

 two or three degrees above the boiling point of chlorine (— 33 -6°), 

 a residual liquid was obtained, in one case at least, which had a 



