Chemistry and Physics. 479 



preparation of this compound from commercial calcium cyanam- 

 ide, CNNCa. This is due to the difficulty of evaporating water 

 solutions of cyanamide, even at low temperatures at diminished 

 pressures, on account of the decomposing influence of water 

 upon the substance. He has, therefore, devised a new method 

 for the operation, which gives very satisfactory yields. In the 

 first place, the amount of pure acetic acid necessary to neutralize 

 a gram of the commercial calcium cyanamide is determined, then 

 to the proper amount of pure acetic acid diluted with nearly 

 its own weight of water in a large mortar a charge of 100 g of 

 calcium cyanamide is gradually added in portions of about 15 g 

 with constant stirring while the mortar is kept standing in cold 

 water to avoid much rise in temperature. A pasty mass is 

 finally formed, which is well kneaded and allowed to stand in 

 the air for 24 hours. At the end of this time the mass becomes 

 friable and is coarsely powdered. It is important that a slight 

 excess of acetic acid should have been used, so that the material 

 is faintly acid throughout. The mixture is then extracted with 

 ether in a Soxhlet apparatus, the ether is evaporated at a gentle 

 heat by distillation and finally evaporated to dryness in a 

 desiccator over sodium hydroxide. In this manner a yield of 

 95.6% of the theoretical cyanamide was obtained. — Jour. Chem. 

 Soc, cix, 1325. H. L. w. 



3. A New Method of Separating Tin and Tungsten.—M.. 

 Tea VERS has described a method of analysis which he has applied 

 to wolframites containing tin. The very finely divided substance 

 is fused with anhydrous sodium sulphite in a porcelain crucible 

 at a bright red heat. The decomposition is rapid and perfect, 

 even with minerals containing as much as 50% of tin. The 

 mass is extracted with boiling water, then diluted to 700 to 800 

 cc, and then slightly acidified with acid. The excess should not 

 be more than 20 cc of normal acid. Brown stannous sulphide 

 is thus precipitated. This carries down a little silica and sul- 

 phides of iron and manganese, but it is entirely free from tung- 

 sten. It is purified by solution in yellow ammonium sulphide, 

 and the tin is determined as oxide in the usual way. The 

 tungsten is determined in a separate sample, starting again with 

 a fusion with anhydrous sodium sulphite. The complete details 

 of the operation need not be given here, as the principal object 

 of this notice is to call attention to the novel method used for 

 decomposing the mineral. — Comptes Bendus, cxlvi, 1408. 



H. L. w. 



4. Yellow Mercuric Oxide as a Standard in Alkalimetry. — 

 G. Incze states that this oxide is a reliable substance for use in 

 standardizing acid solutions, as it is readily obtained in a pure 

 condition, is free from water of crystallization, and is not hygro- 

 scopic. Its use depends upon its reaction with potassium iodide : 



HgO + 4KI + H^O = K^Hgl, + 2K0H 



