614 Scientific Intelligence. 



the volumes, and temperatures are known, while the pressures 

 are determined. — Jour. Phys. Chem., 22, 337. h. l. w. 



2. The Detection of Iodides 4n the Presence of Cyanides. — It 

 is a well known fact that cyanides interfere with the qualitative 

 test for iodides where the iodine is set free by means of an oxidiz- 

 ing agent and an acid, and L. J. Curtman and C. Kaufman 

 have recently studied the extent of this interference and have 

 found that it varies with different oxidizing agents. It is very 

 marked with potassium nitrite, much less so with the perman- 

 ganate, while it is intermediate in the cases of hydrogen peroxide 

 and chlorine water. Even under the best conditions it appears 

 that the test may fail in the presence of more than about 10 

 parts of cyanogen to one of iodine. Several methods have been 

 used for removing cyanogen before testing for iodine, such as 

 the ignition of the silver salts, which destroys the cyanide, or the 

 boiling of a solution of soluble salts with an excess of acetic acid, 

 which volatilizes the hydrocyanic acid, but the present authors 

 advise precipitating the cyanide of cobalt, together with the 

 ferrocyanide and ferricyanide, by the addition of cobalt nitrate 

 solution, adding asbestos fiber, boiling for half a minute, filter- 

 ing, and testing the filtrate for iodides after sufficient concen- 

 tration. — Jour. Amer. Chem. Soc, 40, 914. h. l. w. 



3. The Determination of Zinc as Zinc Mercury Thiocyanate. — 

 A gravimetric method based upon the precipitation of the com- 

 pound ZnHg (SCN) 4 by adding a reagent containing KSCN and 

 HgCl 2 to weakly acid solutions of zinc salts, filtering the precipi- 

 tate on a Gooch crucible and weighing it after drying at 108° C, 

 was described several years ago by Lundell and Bee. The pre- 

 cipitate was washed with water containing a minute quantity of 

 the reagent on account of its solubility in pure water. 



George S. Jamieson has now made a study of the method and 

 obtained results that indicate that it is very accurate, but he has 

 found that the dried precipitate is anhydrous instead of con- 

 taining a molecule of water of crystallization as supposed by the 

 originators of the process. Jamieson observes that cadmium 

 cobalt, copper, bismuth and manganese compounds also give 

 insoluble double thiocyanates, while nickel in small amounts and 

 arsenic in large proportions do not interfere with the method. 

 He has employed ammonium thiocyanate in the place of the 

 potassium salt in the reagent with equally satisfactory results, 

 and also he has applied titration with potassium iodate to the 

 precipitate, in the place of weighing it, with excellent results. — 

 Jour. Amer. Chem. Soc, 40, 1036. h. l. w. 



4. Principles of Chemistry ; by Joel H. Hildebrand. 12mo, 

 pp. 313. New York, 1818 (The Macmillan Company) .—This 

 text-book has been prepared for the purpose of teaching chemical 

 theories in connection with any other books dealing with the 

 facts of the science. This separation of the two features of 



