1870.] 



Prof, lloscoc on Vanadium. 



319 



further evolution of CO, is observed, a tribasic vanadate remains as a white 

 crystalline mass. This mass dissolves easily in water, and on addition of 

 absolute alcohol to the solution two layers of liquid are formed ; the lower 

 one solidifies after a time, forming an aggregation of needle-shaped crystals, 

 which possess a strongly alkaline reaction. These having been washed with 

 alcohol, and dried on a porous plate over sulphuric acid in vacuo, were 

 analyzed with the following results : — 



Calculated. Found. 



Na 3 = 69-0 14-6 13'8 



V = 51-3 10-86 10*80 



0 4 = 64-0 13-56 



16H a O =288-0 60 97 60'44 



472-3 99-99 



The sodium in this and in the following compounds was separated from 

 the vanadium by precipitating the vanadic acid as the perfectly insoluble 

 basic lead salt hereafter described. This was dried at 100° and weighed, 

 then dissolved in nitric acid and decomposed by sulphuric acid, and the 

 solution of V 2 0 5 in excess of this acid gave on evaporation a finely crys- 

 talline mass. The filtrate from the lead precipitate freed from lead yielded 

 on evaporation sodium sulphate. Full analytical details of this method, as 

 well as of the other by precipitation as the insoluble ammonium meta- 

 vanadate, are given in the memoir. By frequent crystallizations the tri- 

 sodium vanadate is slowly decomposed into the tetrasodium salt, caustic 

 soda being formed. This singular reaction was most carefully examined 

 and the amount of sodium hydroxide liberated determined volumetrically. 



2. Tetrasodium Vanadate, Na 4 V 2 0 7 + 18H 2 O. — This salt crystallizes in 

 beautiful six-sided tables ; it is easily soluble in water, insoluble in alcohol, 

 and is precipitated by the latter liquid from aqueous solution in white 

 scales of a silky lustre. As long as the salt contains free alkali or tribasic 

 salt, it forms, on precipitation with alcohol, oily drops which solidify after 

 some time. The tetrasodium vanadate is always formed by the first fusion 

 of vanadic acid with excess of carbonate of soda, and can be easily prepared 

 in the pure state by recrystallization. 



Found (mean of many 

 Calculated. determinations). 



Na 4 = 92-0 14-58 14-61 



V 2 = 102-6 16-27 15-97 



0 7 = 112 0 17-27 



18H 2 0 . . . .= 324-0 51-38 51*80 



630-6 99-99 

 The salt loses 17 molecules of water at 100°. 



The corresponding Calcium and Barium Vanadates, Ca., V 2 0 7 , and 

 Ba 2 V 2 0 7 , are white precipitates obtained by adding the chlorides to a 



