On the Prussic and Pr us sous Acids. 201 



su.pbite of potash formed ; but this sulphite was not mixed 

 with any tingeing salt. On the supposition that the disap- 

 pearance of the prussic acid, in the liquid A. might have 

 been owing to its having been expelled entirely by the sul- 

 phurous acid, and that the tingeing liquid resulted from the 

 mutual action of the other principles, namely, the oxide of 

 iron and hydroguretted sulphuret of potash; I subjected a 

 mixture of these materials to long boiling, but could not by 

 this means produce a liquid that tinted oxy-sulphateof iron 

 red. Sulphurous acid gas, passed through water in which 

 prussjan blue was diffused, did not in the least affect that 

 compound. These experiments completely refute the opi- 

 nioiton which the second question was grounded. 



To enable me to replv to the third question, I passed sul- 

 phuretted hydrogen gas for several hours through a solu- 

 tion of triple prussiate of potash, on which it was found to 

 have no effect. 



We shall be little disposed to allow that there is any 

 foundation for the fourth question, when we consider the 

 circumstances of the last -mentioned experiment, In which 

 sulphur in the state of the most minute division was of- 

 fered to the triple prussiate, without any combination en- 

 suing; and also when we compare the effects of the me- 

 tallic soluhons in Table II. with those which 'would ensue 

 with liquids containing sulphur. But, if any doubt should 

 still be entertained on this subject, the following experi- 

 ment will perhaps remove it: Into a solution of prussiate 

 of mercury throw some pieces of phosphuret of lime, the 

 oxide of mercury of this prussiate will thus be reduced and 

 separated from the liquid which is to be filtered ; some of 

 this liquid poured into carbonate of iron turns it red, the 

 red colour soon disappears, and a white precipitate begins 

 to form ; this white precipitate soon changes to green, 

 and if a little nitric or oxy-muriatic acid be now poured 

 upon it, it becomes a perfect blue prussiate of iron. This 

 experiment, in which a liquid turning a solution of iron 

 red was produced without the employment of a particle of 

 sulphur, goes very far to negative our fourth question; 

 and when considered in conjunction with the preceding 

 ones, we can hardly do otherwise than dissent from the 

 supposition which gave rise to that question. 



But if the experiment last adduced tends to refute the 

 fourth question, it very strongly supports the fifth ; for the 

 changes of colour observable were undoubtedly owing to 

 successive stages of oxidation by the contact of the atmo- 

 sphere. In confirmation of this question, it may likewise 



be 



