OF ARTS AND SCIENCES. 259 



days, large deep orange or garnet-red crystals separate in quantity. 

 They appear to be octahedra, and when first separated from the 

 mother liquor are very beautiful ; but on standing in the air they lose 

 their lustre, perhaps from a superficial eflfervescence, and become dull 

 red. The salt is readily soluble in water, giving a deep orange-red 

 solution, and crystallizes from the solution unchanged. The constitu- 

 tion of this salt is represented by the formula, 



16 WO3 . 3 V2O5 . PPg . 5 (NHJ^O -I- 37 aq, 



as the following analyses show : — 



1.0379 gr. lost on ignition with W0,Na2 0.1826 gr. = 17.59% NH, 



and ILO 

 1.2811 gr. gave 0.1264 gr. NH.Cl = 4.80% (NHJ2O 

 1.0652gr. " 0.1074 gr. V2O5 =10.08% 

 1.0130 gr. " 0.0419 gr. P20.Mg2= 2.64% PgOj. 



The formula given requires : — 



Calc'd. Found. 



16 WO3 3712 69.67 ^ 69.69 ^ 



3V2O5 548 10.28^82.62 10.08 >- 82.41 



PPj 142 2.67) 2.64) 



5 (NH,),0 260 4.88 4.80 



37 H2O ' 666 12.50 12.79 



5328 100.00 100.00 



Adopting the provisional hypothesis which I have proposed above, 

 that V2O5 as V2O2 . O3 may partially replace M0O3 or WO3 in these 

 combinations, and that, on the other hand, V2O5 also replaces P^Oj, we 

 may write the formula given above, 



8 WO3 . 2 V2O2.O3.P2O, . 3 (NH,)20 -f 



8 WO3 . V2O5 . 2 (NHJ^O . H2O + 36 aq, 



in which formula the first term is reduced to the type of 



10 WO3 . P2O, . 3 (NHJ2O. 



The presence of five molecules of ammonic oxide shows that the salt 

 belongs to the acid type so often met with in this class of compounds, 

 and upon the view which I consider probable,* that the formulas of 



* Proceedings, Vol. XVII. p. 89. 



