OF ARTS AND SCIENCES. 61 



Analytical Methods. — These are the same as those described for the 

 analysis of phospho-vanadates. The vanadic dioxide may be deter- 

 mined directly by titrition with potassic hypermanganate in dilute 

 solutions containing free sulphuric acid. In another portion of the 

 solutions the vanadic pentoxide is to be reduced with sulphurous acid, 

 and then determined by titrition. The whole quantity of oxides may 

 be found by mercurous nitrate and mercuric oxide after completely 

 oxidizing the vanadic dioxide with nitric acid. 



18 : 1 : 2 Phosjjho-vanadico-vanadates of Ammonium. — When a 

 solution of phospho-vanadate of ammonium is mixed with one of va- 

 nadic dioxide in chlorhydric acid, and the liquid is allowed to stand 

 for some time, beautiful deep green prismatic crystals are deposited. 

 These dissolve in hot water to a very deep red solution, and appear 

 to be decomposed exactly in the manner which has been explained 

 in the case of the phospho-vanadates. Of this salt, 



0.3647 gr. lost on ignition with WO^Na., 0.0938 gr. = 25.72% 



0.5318 gr. gave 0.3657 gr. V.p. and Y.h, = 68.76% 



( 0.4058 gr. " 0.0084 gr. VO, with KMnO^ = 1.68% 



1 0.4958 gr. " 0.0083 gr. VO., with iodine and COgNaH = 1.69 % 



0.4284 gr. "• 0.0325 gr. (NHJ.O = 7.59% 



The vanadic dioxide was oxidized with nitric acid before precipita- 

 tion with mercurous nitrate and mercuric oxide. The resulting per- 

 centage is to be corrected accordingly. The analyses correspond 

 fairly well with the formula 



18 VA . VO2 . 2 Pp, . 7 (NH,),0 + 50 aq, 



4925 100.00 



The phosphoric oxide is determined by difference only. The com- 

 pound may also be regarded as a double salt ; as, for instance, 



6 V.A . VO, . 3 (NH,),0 + 



2 {6 VA . P.O. . 2 (NII,),0 . 11,0} + 48 aq ; 



