Chemistry and Physics. 365 



tated as sulphides, and tliese are filtered, starting with a dry 

 filter, and washed with a solution of hydrochloric acid of the same 

 strength as was present during the precipitation. In order to 

 precipitate arsenic in the higher state of oxidation the filtrate is 

 heated and hydrogen sulphide is passed again. Then, after filtra- 

 tion if necessary, the liquid is diluted with an equal volume of 

 water, and hydrogen sulphide is passed again. This precipitates 

 the sulphides of tin and bismuth, which are filtered and washed 

 with hydrochloric acid of the proper strength. At last the acid 

 is nearly neutralized and the sulphides of cadmium and lead are 

 precipitated by means of a third treatment with hydrogen sul- 

 phide. Directions are given for the examination of each precipi- 

 tate for the detection of the metals in it. It appears that the 

 method is one which may be conveniently applied in certain prac- 

 tical cases, but for use in laboratories of instruction the necessity 

 of three precipitations by hydrogen sulphide under accurately 

 regulated conditions would seem to make its utility very doubt- 

 ful. — Bulletin, xix, 154. h. l. w. 



3. The Estimation of Vanadic Acid after Reduction by 

 Metallic Silver. — Gkaiiam Edgar has found that finely divided 

 metallic silver, prepared by precipitation or by igniting the oxide, 

 reduces vanadic acid in hot, dilute sulphuric acid solution to the 

 quadrivalent condition, and that three methods for determining 

 the amount of vanadium present may be based upon the reaction. 

 In the first place, a weighed excess of metallic silver may be used 

 and the loss in weight of the silver shows the amount of vana- 

 dium. The second method consists in the titration of the reduced 

 vanadium, which may be accomplished, conveniently and accu- 

 rately, by means of potassium permanganate solution. The third 

 method consists in determining the amount of silver in solution 

 after the completion of the reaction, for example by titration 

 with a thiocyanate solution. It is interesting to observe that the 

 three methods can be applied, in the order given, to a single por- 

 tion of a vanadate. The results obtained by the author in his 

 test analyses show an astonishingly close agreement in the three 

 methods not only among themselves but with the known amounts 

 present. It will not be attempted to give full details of the 

 process here, but it may be mentioned that solutions of sodium 

 vanadate containing not far from 0-1^ of V 2 O s were acidified with 

 about 2 CC of concentrated sulphuric acid, diluted to about *75 cc , 

 from 1 to 2 s of finely divided metallic silver was added and in 

 each case the liquid was boiled for about one-half hour in a small 

 flask. The reduction takes place quantitatively in the presence of 

 hydrochloric acid, but in this case the oxidized silver forms silver 

 chloride, so that the amount of vanadium can be calculated from 

 the gain in weight. It appears to be more accurate, however, to 

 use sulphuric acid solutions free from chlorides. — Jour. Am. Chem. 

 Soc, xxxviii, 1297. h. l. w. 



4. The Density of Radio-Lead from Pure Norwegian Cleveite. 

 — T. W. Richards and C. Wadswortii, 3d, have obtained from 



Am. Jour. Sci.— Fourth Series, Vol. XLII, No. 250.— October, 1916. 

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