PEOFESSOE EOSCOE’S EESEAECHES ON VANADIUM. 
327 
decomposed into sodium carbonate, which crystallizes out, and sodium metavanadate, 
which, being the more soluble salt, remains in solution ; thus : — 
Na 4 V, 0 7 + C0 2 =2Na V0 3 +Na 2 C0 3 . 
The insoluble pyrovanadates precipitated in solutions of the various metals possess 
properties generally similar to those of the corresponding tribasic vanadates. 
Calcium Vanadates. 
If to a freshly prepared solution of trisodium vanadate a solution of chloride of calcium 
be added, a white precipitate falls down, whilst the liquid possesses a strongly alkaline 
reaction and absorbs carbonic acid from the air. The precipitate is a mixture of 
calcium pyrovanadate and calcium hydroxide ; the tribasic calcium salt, therefore, 
cannot thus be obtained, as it at once decomposes as follows : — 
Ca 3 V, 0 8 + H 2 O = Ca 2 V 2 0 7 + Ca H 2 0 2 . 
Calcium Pyrovanadate , Ca 2 V 2 () 7 +2-bII 2 O. — This compound is precipitated as a 
white amorphous powder when a solution of chloride of calcium is added to one of the 
tetrabasic sodium salt. The salt was dried at 100° C., and of this dry salt 0T32 grm. 
lost on ignition 0-0270 grin., corresponding to 12-63 per cent, of water. For the calcium 
determination 0-3366 grm. was dissolved in acetic acid and precipitated by oxalic acid, 
the liquid being warmed until all the vanaclic acid was reduced ; the precipitation of the 
oxalate had to be twice repeated in order to free the precipitate completely from vana- 
dium. 0-1956 grm. CaC0 3 was thus obtained, corresponding to 23-23 per cent, of 
calcium, and the filtrate yielded on evaporation 0-1802 grm. V 2 0 5 , or the salt contained 
30-16 per cent, of vanadium. 
These numbers correspond to the formula 
Ca 2 
V 2 . 
0 7 . 
Ca 2 V 2 0 7 + 2iH,0. 
Calculated. 
r 
A 
Found. 
80-0 
23-56 
23-23 
102-6 
30-21 
30-16 
112-0 
32-98 
45-0 
13-25 
12-63 
339-6 
100-00 
Barium Pyrovanadate , Ba 2 V 2 0 7 . — The dibasic barium salt is anhydrous, but other- 
wise it closely resembles the corresponding calcium compound. It is slightly soluble in 
water. For analysis it was dried at 100° C. 0-438 grm. dissolved in hydrochloric acid 
and precipitated with sulphuric acid yielded 0-4097 grm. Ba$0 4 , corresponding to 54*69 
per cent, of barium. The filtrate from the barium precipitate left on evaporation 0-1678 
grm. V 2 O s , corresponding to 215 per cent, of vanadium. 
