56 PROCEEDINGS OP THE AMERICAN ACADEMY 



7 : 6 Hydric Phospho-vanadate. — When a solution of phosphoric 

 acid is mixed with a strong solution of sodic divanadate, a yellow un- 

 crystalline mass is formed. This after standing some days becomes 

 distinctly crystalline, and may be washed with cold water until the 

 washings become orange-red. In a preparation of this salt, dried as 

 usual upon woollen paper, 



1.2172 gr. gave 0.4846 gr. V.O. = 39.81 % 



0.8553 gr. " 0.6487 gr. mixed oxides = 75.84% P.O. -f V^O^ 



0.6127 gr. lost with WO.Na, 0.1470 gr. = 24.00% water. 



The analyses show that the compound analyzed contained no soda, 

 and that it is a 7 : 6 phospho-vanadic acid, the formula of which may 

 be written 



7 pp. . 6 Vp, . 3 H^O + 34 aq. 



The formula requires : 



Calc'd. 



39.76 1 7-33 39.811 ^^g^ 



36.07) 36.03) 



24.17 24.00 



2756 100.00 



The sum of the phosphoric and vanadic oxides found by difference 

 is 76.00. After all saline matters are washed out, the acid dissolves 

 readily in water, and gives an orange solution, which changes color on 

 dilution in the manner already explained. I shall, after describing the 

 phospho-vanadico-vanadates and arsenio-vanadico-vanadates, return to 

 this and the preceding compounds. 



20 : 1 Phospho-vanadic Acid. — When a solution of phosphoric acid 

 is mixed with one of ammonic metavanadate, the liquid becomes orange, 

 but after heating for a time upon a water-bath lemon-yellow, and then 

 deposits a large quantity of a lemon-yellow crystalline salt. More of 

 this salt is deposited on evaporating the mother liquor, and again after 

 partially neutralizing with ammonia. The yellow salt may be drained 

 with the lilter-purap and then washed with a small quantity of cold 

 water. The salt presents fine yellow crystals which dissolve in a small 

 quantity of hot water. The liquid is at first yellow, but on adding 

 more hot water, and especially on heating, it becomes orange ; wath 

 more water, orange-red, and finally deej) garnet-red with a very strong 

 acid reaction. If this solution is evaporated upon a water-bath the 

 changes of color occur in the inverse order ; that is to say, the liquid 



