Gooch and Gilbert — Ammioniicm Vanadate. 205 



Art. XXIY. — The Precipitation of Ammonium Vanadate 

 hy Ammo7iiiLm Chloride; by F. A. GoocH and K. D. 

 Gilbert. 



[Contributions from the Kent Chemical Laboratory of Yale University— CX.] 



Berzelius was the first to point out and utilize in analysis 

 the fact, that when a vanadate in concentrated solution is treated 

 with a saturated solution of ammonium chloride, white insolu- 

 ble ammonium metavanadate is deposited."^ The method of 

 treatment was moditied by v. Hauerf in that solid ammonium 

 chloride was added to the solution of the vanadate, as concen- 

 trated as possible, until it failed to dissolve, the mixture allowed 

 to stand and then treated with a large amount of strong alco- 

 hol, the precipitate filtered off, washed with alcohol, dried, 

 ignited in a covered platinum crucible until all ammonium 

 chloride was volatilized, and the residue ignited carefully with 

 ammonium nitrate. Roscoe:): was unable to obtain exact quan- 

 titative results by this method on account of the solubility of 

 the ammonium metavanadate in the alcoholic mixture and the 

 danger of mechanical loss during the ignition. Holverscheit 

 also, in testing v. Hauer's method, § noted loss of vanadium, due 

 to solubility of the ammonium vanadate in the alcoholic liquid, 

 finding in every case vanadium in the filtrate by means of 

 ammonium sulphide or by hydrogen dioxide. In the average 

 of six determinations Holverscheit found a loss of 0*0015 grm. 

 calculated as Yfi^. Another modification of the method was 

 proposed by Ditte,|| who, finding that precipitation by an excess 

 of ammonium chloride was complete in a solution made color- 

 less by boiling with free ammonia, attributed the deficiency in 

 the amount of Yfi.^ found after precipitation under the pre- 

 scribed conditions, to volatilization of the vanadium during igni- 

 tion under the influence of ammonium chloride, and endeavored 

 to avoid liability to such error by making it certain that no 

 ammonium chloride should remain with the metavanadate at 

 the time of ignition. To this end, the solution made colorless 

 by boiling with ammonia was cooled to 30°-40°, nearly satu- 

 rated with ammonium chloride and finally treated with four 

 or five times its volume of alcohol ; the precipitate thus thrown 

 down was filtered off, washed with absolute alcohol until free 

 from ammonium chloride, dried and ignited, the carbonized 

 residue having been washed with nitric acid before the final 

 ignition. Holverscheit's criticism of Ditte's process consisted 

 in showing that losses which may occur in the ignition, and 



* Ann. Phys. xcviii, 54, 1831. f Jour. Prakt. Chem., Ixix. 388. 



X Ann. Chem. SuppL, viii, 101. § Inaug. Diss., Berlin, 1890, p. 11, et seq. 



II Compt. Rend., civ, 982. 



