Action of Oil of Vitriol on Ferrocyanide of Potassium. 21 



present, we propose for the body we have examined the name 

 of Pseudo-cera'itie, until by further experiments we shall have 

 removed the discrepancies which at present appear to exist 

 between its characters and those ascribed by Ettling to ce- 

 raine. 



IV. On the Action of Oil of Vitriol upon Ferrocyanide of 

 Potassium. By G. Fownes, Ph.D.* 



\\THEN finely powdered ferrocyanide of potassium is heated 

 in a capacious flask or retort with eight or ten times its 

 weight of concentrated sulphuric acid, the white pasty mass 

 first produced by the action of the acid upon the salt, gra- 

 dually dissolves and disappears, its solution being accompa- 

 nied by the disengagement of a prodigious quantity of perma- 

 nent gas. This gas when collected over water is colourless 

 and transparent ; it has a very faint garlic odour, does not 

 render lime-water turbid, takes fire on the approach of a ta- 

 per, and burns with a bright blue flame, generating carbonic 

 acid. When mixed with half its bulk of pure oxygen, intro- 

 duced into the siphon-eudiometer and fired by the electric 

 spark, a contraction occurs amounting to one-third part of 

 the whole, and the residual gas becomes almost entirely ab- 

 sorbable by caustic potash. These characters are sufficient 

 to prove that the gas in question is pure carbonic oxide. 



When the oil of vitriol is first poured upon the ferrocyanide, 

 a good deal of heat is produced, and the odour of hydrocyanic 

 acid is for a moment perceptible ; this disappears, however, 

 as soon as the effervescence commences, and is replaced by a 

 trace of formic acid vapour, which may be remarked during 

 the whole period of the experiment. At the close of the re- 

 action a little sulphurous acid also may be recognised ; the 

 cause of this will become immediately apparent. 



If, the disengagement of carbonic acid having ceased, heat 

 be still applied to the now fluid contents of the vessel, the 

 escape of sulphurous acid becomes more and more marked, 

 while at the same time a number of little white pearly cry- 

 stalline plates may be observed floating about in the boiling 

 liquid. These scales rapidly increase in number until, after 

 the lapse of fifteen or twenty minutes from the time the first 

 were seen, they cover the bottom of the flask to a consider- 

 able depth, glittering, when agitated, like new-formed crystals 

 of thionurate of ammonia. 



When the whole has cooled, the acid may be poured from 



Communicated by the Chemical Society ; having been read March 21, 

 843. 



