OF ARTS AND SCIENCES. 253 



Of this acid, — 



{ 



1.0343 gr. lost on ignition 0.1342 gr. = 12.97% water. 

 1.0343 gr. gave 0.0363 gr. V.O^ = 3.51 9^ 

 1.2540 gr. lost on ignition 0.1617 gr. = 12.90% 



The formula requires : — 



5007 



The sum of the two oxides is determined by difference, which is the 

 most accurate method whenever applicable. In this, as in all the other 

 vanadio-tungstic compounds analyzed, the vanadic pentoxide was deter- 

 mined by boiling with chlorhydric acid in the manner already described. 

 The crystals of the 18 : 1 acid are readily soluble iu water, and may 

 be recrystallized without decomposition. 



The compounds which I have described appear to establish a com- 

 plete analogy between the vanadio-tungstates and phosplio-tungstates 

 already described. Rammelsberg * has described a salt which crystal- 

 lizes in beautiful brown-black cubo-octahedrons, and which he obtained 

 by saturating a commercial sodic vanadate with acetic acid and evapo- 

 rating spontaneously. According to his analyses, the salt has the 

 formula 



(NH,),0 . WO3 . 3 VPg + 6 aq. 



I suspect that it contains VO., as well as V^O^ . I did not succe'^d 

 in preparing it by synthesis, employing pure VOgNII^ and WO^(NH^).,. 

 It may prove to be the type of an entirely new class of complex acids, 

 and well deserves further investigation. 



PHOSPHO-VANADIO-MOLYBDATES. 



Triple acids of this class are formed when solutions of phospho- 

 vanadates are digested with molybdic teroxide; whenvanadio-molybdates 

 and alkaline phosphates are heated together in solution, especially in 

 the presence of an acid ; and when vanadic pentoxide is heated with 

 a solution of an alkaline phospho-molybdate. 



The salts of this class are as a whole less stable than the vanadio- 



* Berichte der Deutschen Chem. Gesellschaft, i. 161. 



