262 PROCEEDINGS OP THE AMEIilCAN ACADEMY 



tals on evaporation, or after standing for some time. Wlien, however, 

 a solution of potassic bromide is added in large excess, a deep orauge- 

 red crystalline precipitate is quickly formed in large quantity. The 

 salt exhibits the peculiar aurora-red tint which is often observed when 

 phosphoric acid or a soluble phosphate is mixed with a solution con- 

 taining both tungstic and vanadic oxides. The compound dissolves in 

 a rather large proportion of hot water, but at the same time undergoes 

 decomposition, and the solution after a time deposits a bright orange- 

 brown crystalline salt without the peculiar aurora-red tint. The first- 

 mentioned potassic salt, as precipitated from a cold solution, allowed to 

 stand twenty-four hours, then washed with cold water and dried ou 

 woollen paper, gave on analysis the formula 



18 WO3 . 4 V2O5 . 3 PjOj . 8 K^O + 32 aq, 



which may perhaps be written 



2 {6 WO3 . 2 V2O5 . P.p. . 3 K,0} + 6 WO3 . P^Og . 2 K^O . H^, 



the type of the first compound being 



8 WO3 . P2O5 . 3 K.p. 



1.1017 gr. lost on ignition with WO^Na^ 0.0973 gr. = 8.83% 



6662 100.00 



7:1:1 Series. — The bright orange-brown salt formed by the 

 decomposition of the 18:4:3 salt was in small distinct granular 

 crystals. Of this salt, — 



0.9773 gr. lost on ignition with WO^Na, 0.0780 gr. = 7.98% 

 1.0160 gr. gave 0.8205 gr. mixed oxides = 80.76% 



1.3077 gr. " 0.1037 gr. Yfi^ = 7.93% 



1.0113 gr. " 0.0958 gr. Pp,Mg3 = 6.06% P^O^ 



