68 PROCEEDINGS OF THE AMERICAN ACADEMY 



It will be observed tbat tliis salt may be considered as derived from 

 twelve molecules of an arseuio-vanadate by reduction of one half the 

 vanadic pentoxide to dioxide and loss of seven molecules of ammouic 

 oxide, since we have 



12 {AsA . VA . (NHJ2O} = 



12 AsgO, . 12 VO2 . 6 VA • 5 (NH,)oO + 7 (NHJ^O + 6 0. 



This relation might be made available in the preparation of the salt. 

 Boiling water instantly decomposes this compound, and gives a deep 

 green solution, which on standing deposits crystals of a peculiar deep 

 olive-green color with a tinge of brown. The black salt corresponds 

 exactly in composition to a phosphorus compound above described, 

 except only as regards water of crystallization : 



12 P2O5 . 12 VO2 . 6 VoO. . 5 (NHJsO + 7 aq. 



9:9:8 Ammonium-salt. — When boiling water is poured upon the 

 black salt, it instantly becomes deep olive-green vipon the surface, and 

 then dissolves to a deep green liquid, which on cooling deposits crys- 

 tals with a dull olive-green surface color. These may be redissolved 

 and recrystallized a second time. The mother liquor from these crys- 

 tals has a bright green color, and contains much vanadic acid. In the 

 olive-green salt, 



0.4061 gr. gave 0.0167 gr. (NHJP = 4.12% 



(0.2871 gr. " 0.1370 gr. As^Sg " = 44.61% 



1 0.2871 gr. " 0.1393 gr. Yf>, by KMnO^ = 48.51% (complete 

 oxidation) 



0.1637 gr. gave 0.0259 gr. YO. by KMnO, = 15.82% 



The analyses correspond tolerably well with the formula 

 9 AsP- . 9 VO2 . 8 VA • 4 (NHJP + 11 aq, 



4687 100.00 



