212 Mr. J. Prideaux's Experiments on Vanadiate of Ammonia^ 



more water were added, by which it was dissolved; and after 

 the subsidence of a yellow sediment the solution was pale 

 blue and strongly acidulous. The yellow sediment dissolved 

 in liquid ammonia, and was vanadic acid. 



Carbonate oi'barytes in fine powder was added to the solu- 

 tion, to get rid of the excess of sulphuric acid. It produced little 

 effect, till heat was applied; when effervescence took place, 

 the liquid became pistachio-green, and a flocculent dark olive 

 precipitate appeared; which gradually subsided, leaving the 

 liquor still blue and acidulous. Liquid ammonia did not 

 render it neutral, until a nearly black precipitate had fallen in 

 considerable quantity; almost the whole of which was taken 

 up again by ammonia in excess. 



In the second attempt the precaution was taken to add car- 

 bonate of ammonia in decomposing the salt, that the first 

 impression of heat might fill the crucible with an atmosphere 

 of that substance. I'he remaining oxide, however, still con- 

 tained vanadic acid. 



The solution in muriatic acid was blue, and could not be 

 neutralized without precipitation. Before neutralization took 

 place, liquid ammonia threw down an olive precipitate, and 

 made the liquor green, as above. The green liquid, poured 

 off, and gradually neutralized with ammonia, gave a dark- 

 brown precipitate. The olive precipitate dissolved green, the 

 brown one blue, in muriatic acid. 



After various experiments, in none of which did the oxide 

 of vanadium neutralize the acid employed, or yield with it 

 a crystallized salt, the solutions were mixed together, and 

 thrown into an excess of caustic potass, largely diluted. A 

 deep brown light precipitate fell, doubtless hydrate of the 

 oxide (most probably of the protoxide), leaving the liquor of 

 the same colour but transparent. A portion of this liquor was 

 withdrawn, and mixed with bi-carbonaie of potash, when it 

 bleached, but without precipitating. The remainder was then 

 poured off and tried with muriatic acid, in slight excess, which 

 produced the green colour mentioned before, but without 

 disturbing the transparency. Caustic potash was then slowly 

 added, and whilst still acidulous, an inky precipitate fell; after 

 which a reddish brown one followed, when the liquor became 

 neutral. 



The reddish-brown and purple precipitates were both solu- 

 ble in acids, alkalies, and distilled water, and were therefore 

 difficult to wash ; both also reddened litmus paper. The brown 

 pi-ecipitate became piu'ple on the surface, when no great depth 

 of water lay on it, and at the same time square plates formed 

 iu it, very small and thin, iridescent by reflected, but deep 



yellow 



