264 PROCEEDINGS OF THE AMEllICAN ACADEMY 



34 WO3 . 3 V2O5 . 2 P2O5 ; but a determination of the trimethyl- 

 animonium oxide will be necessary in order to settle the formula 

 completely. I am indebted to the kindness of Prof. Arthur Michael 

 for a supply of the trimethylamin salt, which has proved of great 

 service to me. The disposition of the corresponding oxide to form 

 well-crystallized salts makes it a valuable test, and it should become 

 an article of commerce for chemists' use. 



VANADIO-VANADICO-MOLYBDATES. 



The salt about to be described constitutes the type of a new and 

 extensive series of complex acids, which contain two different linking 

 oxides, embraced respectively under the formulas R^Oj and R'Oo, in 

 which, however, R and R' may be identical. The general formula 

 for this class of molybdenum compounds may be written 



m M0O3 . n Rfi^ . p R'O, . x W'.f>, 



which, in the case of the identity of R and R', becomes 



m M0O3 • '^ ^2^s . JO RO2 . a: R^'^O. 



I shall show that these are corresponding salts, containing tungsten 

 in place of molybdenum. Vanadio-vanadico-molybdates are very readily 

 formed by boiling a mixture of the two oxides of vanadium with an 

 acid molybdate ; by the partial reduction of vanadio-molybdates ; or by 

 digesting solutions of acid molybdates with solutions which contain 

 vanadic dioxide and pentoxide. 



28 : 4 : 1 Vanadio-imnadico-molyhdate of Ammonium. — When pure 

 ammonic divanadate is ignited in an ojaen platinum vessel, and the 

 remaining mass is boiled with an excess of a solution of 14:6 acid 

 ammonic molybdate, a greenish solution is formed, which after fil- 

 tration and evaporation yields on cooling a pale greenish-yellow 

 crystalline salt. After draining on the filter-pump, the salt may be 

 redissolved and recrystallized, when it presents very distinct gran- 

 ular greenish-yellow crystals. The solution is bright yellow. Of 

 this salt, — 



1.4613 gr. lost on ignition with WO.Nag 0.2527 gr. = 17.29% 

 1.3326 gr. gave by titrition 0.1423 gr. (NHJP = 10.68% 

 1.2031 gr. " " 0.1288 gr. " =10.71% 



2.1968 gr. " 0.2184 gr. Yjd, = 9.95% VO., + V^O^ 

 0.9980 gr. " 0.0607 gr. VO2 = 6.08% VO2 



