71 Soientific Intelligence. 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



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

 — J. M. Wkm'ii and II. C. P. Weber have observed that the 

 method of Noyes and Bray which consists in treating the three 

 higher sulphides with concentrated hydrochloric acid on the 

 steam bath, thus leaving the sulphide of arsenic undissolved, then 

 diluting the liquid with about four volumes of water and pre- 

 cipitating sulphide of antimony in hot solution with hydrogen 

 sulphide, and finally precipitating sulphide of tin after further 

 dilution, does not give satisfactory results in many cases in t,he 

 hands of inexperienced operators on account of failure to adhere 

 to the exact conditions. They observed that when antimonious 

 and stannic sulphides happen to precipitate together they 

 frequently show a brown color which is not intermediate between 

 the usual colors of the two sulphides, but much darker. The 

 authors consider this dark precipitate as a characteristic test for 

 both tin and antimoiry, and they prefer to allow the hydrochloric 

 acid solution to cool while hydrogen sulphide is being led in, so 

 as to obtain this test if possible. To finish the analysis they dis- 

 solve the sulphides by evaporating or using an oxidizing agent, 

 then add oxalic acid (F. W. Clarke's method), precipitate anti- 

 mony with hydrogen sulphide, boil the filtrate with granulated 

 lead and test for tin with mercuric chloride. — Jour. Amer. Chein. 

 Soc, xxxviii, 1011. h. l. w. 



2. A New 3Iethod for Estimating Ammonia. — For determin- 

 ing ammonia in dilute waste liquors, G. E. Foxwell takes 5 CC of 

 the liquid, makes it up to 300 cc with water, puts 5 CC of the diluted 

 solution into a test-tube, and then adds l cc of 4 per cent phenol 

 solution and l cc of a dilute sodium hypochlorite solution and heats 

 by placing the test-tube in boiling water for at least l£ minutes. 

 A blue color is developed which is compared with a series of 13 

 test-tubes containing from O'l to 3 CC of a solution of ammonium 

 chloride containing 0*063 g. of the salt in 1000 cc , all of which are 

 diluted to 5 CC and treated in exactly the same way as the other 

 liquid. Free acid vitiates the test, while CaO has no influence. 

 The method is not recommended for larger amounts of ammonia, 

 and it is not as accurate as the distillation method for the smaller 

 amounts. It serves well, however, for control purposes, as a test 

 can be made in 3 or 4 minutes. As a qualitative test the method 

 gives a distinct coloration with less than 0-0001 rag. of NH 3 . — 

 Gas World, liv, No. 1654. h. l. w. 



3. Analytical Chemistry ; by F. P. Treadwell, translated and 

 revised by W. T. Hall. Volume I, Qualitative Analysis. 8vo, 

 pp. 538. New York, 1916 (John Wiley & Sons, Inc.).— This is 

 the fourth edition in English, which is based upon the eighth 

 German edition. The translator has not strictly followed the 



