'220 Brownituj and Painiev — Vanadixmi as Silver Vanadate. 



Art. XXII. — T/te Gravimetrie Estimation of Vanadium, as 

 Silrer Vatiadate ; by Phimp E. Browning and Howard E. 

 Palmer. 



[Contiibntions from the Kent Chemical Laboratory of Yale Univ. — ocxv.] 



Silver nitrate lias long been known as a precipitant of solu- 

 tions of vanadic acid, but, so far as the authors are aware, no 

 method for the quantitative estimation of vanadium, based on 

 the use of this reagent, has been published. The work to be 

 described was undertaken to determine the conditions under 

 which vanadium could be estimated gravimetrically as silver 

 vanadate. 



For this work an exactly neutral solution of ammonium 

 vanadate was used, whose , standard had been determined by 

 evaporating accurately measured portions to dryness in a 

 platinum crucible and weighing as Y„0^ after gentle ignition. 



Attempts were first made to precipitate the silver vanadate 

 in acetic acid solution. The solution of ammonium vanadate, 

 acid with acetic acid, was heated to boiling, and a solution of 

 silver nitrate was added, with stirring to coagulate the precipi- 

 tate. The precipitate, after settling, was filtered off on asbes- 

 tos, washed thoroughly, and weighed after gentle ignition. 

 The experiments made in this way, under different conditions 

 of acidity, and with diflierent amounts of silver nitrate, are 

 recorded in Table I, and indicate a variation in the composi- 

 tion of the precipitate which is formed in acetic acid solution. 



Table I. 



(0 



(2) 

 (3) 

 (4) 

 (5) 



V2O5 taken 

 grm. 



0-0569 

 0-0569 

 0-1139 

 0-0569 

 0-0569 



Silver vanadate 

 found 

 grm. 



0-1978 

 0-1202 

 0-2275 

 0-2671 

 0-1717 



V2O5 found 

 grm. 



0-0871 

 0-0529 

 0-10(12 

 0-1176 

 0-0756 



Error 



grm. 



-h 0-0302 



— 0-0040 



— 0-0137 

 -1-0-0607 

 -1-0-0)87 



The effect was next tried of making' the precipitation in 

 exactly neutral solution as follows : The neutral solution of 

 ammonium vanadate, about 200'="^ in volume, was heated to 

 boiling, and a solution of silver nitrate was added in excess, 

 witli vigorous stirring to coagulate the precipitate. The pre- 

 cipitate was then filtered off on an asbestos felt contained in a 

 platinum crucible, washed thoroughly, ignited at a gentle heat 

 below the fusing point of silver vanadate, and weighed as 

 AgYO,. 



