350 



ON THE PRUSSrC AND PRUSSOUS ACIDS. 



and also when we compare the effects of the metallic solu- 

 tions in Table II with those which would ensue with liquids 

 containing sulpar. But, if any doubt should still be enter- 

 tained on this subject, the following experiment 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 oxirauriatic 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 hy the contact of the atmos- 

 phere. In confirmation of this question, it may likewise be 

 asserted, that the long boiling with the hidroguretted sul- 

 phuret is a powerful deoxidating process. But it will be 

 said to me, if it is really true, that the prussic acid has 

 be«n deoxidated by this process, you ought to be able to 

 recompose that acid from the solution B by oxidation, 

 and may be re. This struck me very forcibly; and being anxious to give 

 wEon.'''' this last proof oft the truth of my deductions, I attempted 

 the rccomposition of this acid by several oxidating pro- 

 cesses for some time without success. I had at last, how- 

 ever, the particular satisfaction of succeeding completely 

 by the agency of nascent hyperoximuriatic acid. The 

 method I employed was the following. 



A litde hyperoximuriate of potash was put into the bot- 

 tom of a glass tube. Over this some of the liquid B, mixed 

 with a few drops of diluted sulphuric acid, was poured. 

 The heat of a candle was then applied r« the bottom of the 



*ube. 



Question 5 

 answered. 



Theprussic 

 acid is deoxi- 



lVo<;es« . 



