58 PROCEEDINGS OF THE AMERICAN ACADEMY 



PHOSPHO-DIVANADATES. 



The salts of this series are formed under conditions which have 

 already been pointed out. They have frequently, at least, a fine 

 yellow color, and are decomposed by water with formation of salts of 

 other series. 



Phospho-divanadate of Ammonium. — This is the yellow crystalline 

 salt referred to as formed by the action of phosphoric acid upon 

 ammonic metavanadate. The salt dissolves in a small quantity of cold 

 water without apparent decomposition, but the reactions of the solution 

 are at best rather uncertain. Argentic nitrate gives a fine bright 

 yellow crystalline pi'ecipitate. In the ammonium salt, 



1.1259 gr. lost on ignition 0.2876 gr. = 25.54% NH. and H,0 

 1.0600 gr. " " with WO^Na.^ 0.2723 gr. = 25.69% 



1.0624 gr. gave 0.1676 gr. NH.Cl = 7.67% (NHJP 

 1.4112 gr. " 0.7534 gr. Vp^ =53.40% 



The analyses lead to the formula 



P,0, . 2 V,0, . (NIIJ.O . 2 H3O + 5 aq, 



685 100.00 



The formula given corresponds to the pi'ovisional assumption of three 

 molecules of water in the acid. 



ARSENIO -VANADATES. 



These salts are formed under precisely the same conditions as those 

 which determine the formation of pho^spho-vanadates. The general 

 characters of the salts are almost precisely similar. Like the phos- 

 phorus compounds, they are yellow or orange-yellow and crystalline. 

 They are decomposed by water, and yield deep orange-red salts of new 

 series, in which the proportion of vanadic to phosphoric oxide is largely 

 increased. 



