60 PROCEEDINGS OF THE AMERICAN ACADEMY ^ 



to be described and oxidized with nitric acid and potassic hyperman- 

 ganate, I found the ratio of the arsenic to the vanadic oxide to be 

 as 7 : 6. 



1 1.2105 gr. gave 0.5825 gr. As,S3 = 44.99% As^O^ 

 X 1.2105 gr. " 0.3748 gr. V^O^"' = 30.97% 



The difference here cannot be taken as water, as some manganous 

 oxide was present ; but the acid may, like the corresponding phos- 

 phorus compound, be regarded as 



7 Asp^ . 6 yp, . 3 H,0. 



Since the publication of the preliminary notice in which I announced 

 the discovery of this class of compounds,* and threw the whole subject 

 open to chemists, a short paper has appeared by F. Fernandez,t in 

 which the writer describes an arsenio-vanadate of ammonium, which, 

 except so far as water of crystallization is concerned, corresponds to 

 the ammonic phospho-vanadate which I have described, so that we 

 now have 



PaO^.VA-CNHJp + aq, 



As.p, . V,0, . (NH,),0 + 1 1 aq. 



"Want of material has prevented a more complete study of the sub- 

 ject on my own part. 



PHOSPHO-VANADICO-VANADATES. 



The salts of this series are very readily formed by boiling an excess 

 of a mixture of vanadic dioxide and peutoxide with alkaline phos- 

 phates, when the mixed oxides dissolve to form red or greenish-red 

 solutions, which on cooling yield in many instances very beautiful 

 crystalline salts. The same result is obtained by fusing the mixture 

 of oxides obtained by igniting ammonic metavanadate with alkaline 

 phosphates; by partially reducing phospho-vanadates, or by adding 

 solutions of vanadic dioxide to solutions of phospho-vanadates. The 

 alkaline phospho-vanadico-vanadates are often very beautiful, and pre- 

 sent extremely well-defined crystals. They have usually a green 

 color, which may be so deep as to appear black in large crystals. By 

 oxidation they pass into phospho-vanadates. 



* American Chemical Journal, iv. 577. 



t Berichte der Deutschen Chem. Gesellschaft, xvii. 1632. July, 1884. 



