41 (i Scientific Intelligence. 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. A New Volumetric Method for Silver. — Louis Schneider, 

 of the Research Laboratory of the Eastman Kodak Company, 

 has devised a method for titrating silver nitrate by means of a 

 potassium iodide solution and the use of palladium nitrate as 

 an internal indicator. His results show that the method as a 

 very convenient and accurate one and that the presence of mer- 

 cury does not interfere with it, as is the case with the well-known 

 thiocyanate method. As soon as the silver is completely pre- 

 cipitated as iodide the reddish-brown color of palladium iodide 

 makes its appearance. A very weak solution of palladium 

 nitrate, containing 006% of the metal was employed, and of this 

 dilute solution only about 1 cc in volumes up to 225 cc was 

 found to be required. Larger quantities of the indicator gave 

 a much slower establishment of equilibrium in the end-reaction. 



The method was found to be particularly well adapted to the 

 determination of very small quantities of silver. It was found 

 also that the presence of a little gum arabic in the solutions 

 titrated was advantageous in preventing the occlusion of silver 

 nitrate and potassium iodide by the silver iodide precipitate. — 

 Jour. Amer. Chem. Soc, 40, 583. h. l. w. 



2. Potassium Iodate Titrations. — George S. Jamieson of the 

 Bureau of Chemistry, U. S. Department of Agriculture, has 

 applied L. W. Andrews' method of titration of strong hydro- 

 chloric acid (11-20%) solutions with potassium iodate, using a 

 globule of chloroform as an indicator, to the determination of 

 arsenic in various insecticides and fungicides. For this purpose 

 the method has advantages over the usual iodimetric methods 

 on account of the ease with which the volumetric solution can 

 be prepared, its perfect stability on keeping, and particularly 

 from the fact that the titration is not interfered with by ferric 

 and cupric salts nor by most kinds of organic matter, so that in 

 most cases the determination of arsenious oxide may be made 

 directly by this method after dissolving the substance in hydro- 

 chloric acid. In cases where the arsenic was present, partly or 

 wholly, as arsenic acid the process was applied, after distillation 

 with cuprous chloride and strong hydrochloric acid, to the dis- 

 tillate. The results of many analyses showed excellent agree- 

 ments with an official method. — Jour. Indust. Eng. Chem., 

 10, 290. h. l. w. 



3. The Chemist's Pocket-Manual, by Richard K. Meade. 12 

 mo, pp. 530. Easton, Pa., 1918 (The Chemical Publishing Com- 

 pany). — This is the third edition of this useful handbook con- 

 taining tables, formulas, calculations, information, and physical 



