Chemistry and Physics. 413 



SCIENTIFIC INTELLIGENCE. 

 I Chemistry and Physics. 



1. A New Method of Separating Arsenic from All Other 

 Metals. — L. Moser and J. Ehrlich have been led by theoretical 

 considerations to a modification of the well-known method of 

 separating arsenic from other metals by the distillation of 

 arsenic trichloride. Instead of carrying out this operation in 

 a stream of gaseous hydrochloric acid, or also with the vapor 

 of methyl alcohol, they employ a stream of air with successive 

 additions of strong hydrochloric acid solution. 



The apparatus and the method of operation are very simple. 

 A flask of 300 cc. capacny is used as the retort, and this is heated 

 by placing it in boiling water up to the neck. A rubber stopper 

 with three holes closes the flask, with a glass tube through which 

 air is led to the bottom of the flask, with a glass dropping 

 funnel supplied with a stop-cock for the introduction of hydro- 

 chloric acid solution, and with a bulbed outlet tube which leads 

 to the receiver. The latter is a 400 cc. beaker containing 250 cc. 

 of water. 



Starting with the substance, with the addition if necessary 

 of a reducing agent, such as ferrous sulphate or potassium 

 bromide (which has been recommended by Gooch and Phelps 

 for this reduction), 50 cc. of hydrochlorine acid (sp. gr. 1.19) 

 are added, the apparatus is placed in the hot water, a rapid 

 stream of air is passed through, and, after periods of ten minutes 

 each, 20 cc. of the hydrochloric acid are added. With 0.15 

 to 0.25 g. of AsoO ;3 the whole of it passes over in about 40 

 minutes. Very good results were obtained by test-analyses 

 where the arsenic was determined volumetrically in the distillate, 

 and it was found that no antimony passes over under these 

 conditions. — Berichte 55, 437. h. l. w. 



2. .4 New Volumetric Method as Applied to Certain Problems 

 in Inorganic Chemistry.— Paul Dutoit and Ed. Grofet have 

 devised a method which is unique in furnishing evidence 

 of the existence of certain compounds. From a burette which 

 is thermally isolated a solution is delivered into a Dewar flask 

 containing another solution where a reaction takes place 

 between the two dissolved substances. A thermometer graduated 

 to 0.01° is read during the titration, and the burette reading 

 is plotted against the changes in temperature. Straight-line 

 curves are found, with sharp breaks at the ends of reactions. 

 Such diagrams show breaks when H 2 S0 4 is half neutralized by 

 sodium hydroxide, and also when the normal sulphate is formed. 

 The several stages of neutralization of LLPO t by NaOH are 

 clearly indicated. Addition of HNO : , to Na 3 P0 4 give curves 



