1 96 On the Prussic and Prussous Acids. 



at first that I had thus produced the conversion of the 

 mucous acid either into malic acid or tartarous acid ; but 

 the experiments which I made to verity this opinion, do 

 iK)i vet appear sufficient to permit me to venture an opinion 

 on the nature or' the change which takes place in the ex- 

 periment which I have described. 



XXXVI. On the Prussic and Prussous Acids. By Mr. 

 R. Porrett, Junior, of the Tower.* 



v CONSIDERABLE differences of opinion exist among the 

 most celebrated chemists respecting the composition of the 

 prussic acid; some agreeing with Fourcroy and Vauquelin, 

 that Oxygen is one of its component parts, and others with 

 Berfholletand Proust, who dispute its presence. Mr. Proust, 

 in his history of the -prussiates, asserts, "That there is no 

 fact that indicates oxygen in- make a part of this acid, and 

 that from the well-known affinities of its three elements, 

 added to the circumstances under winch it is formed, it 

 can scarcely be thought that it does.'* This difference of 

 opinion implies a want of some decisive experiments, which 

 may set the question for ever at rest ; and those which I 

 am coins; to relate I am induced to think are of that de- 

 scription. 



Some time back, F proposed to myself the discovery of 

 a method ot preparing a triple prussiate of potash, in a 

 pure state, which should be free from the objections to 

 which the processes in general use are subject. In reflect- 

 ing on the means most likely to attain this end, it occurred 

 to me, that I should succeed if I decomposed prussiate of 

 iron by double elective attraction rather than by single, 

 employing, instead of a pure potash, that alkali, in com- 

 bination with a substance uniting the properties of solu- 

 bility when combined with potash, strong attraction for 

 oxide of iron, and insolubility when unittd to that oxide. 

 The only substances I could think of possessing all these 

 requisite properties were the succinic acid and sulphur ; as 

 the high price of the former precluded its' use for ihis pur- 

 pose, I determined to employ the latter. I therefore took 

 oni- ounce of dry sulphuret of potash, and one ounce and a 

 half of the best prussian blue, previously well washed and 

 powdered, and put them into a Florence rla?k, two thirds 



* From Traxtactwn* of the Society fur the Encouragemeyit of Arts, Manv- 



s, and Commerce, vol. xxvii. The Society volcd their silver medal 



to Mr. Porrett for this communication. 



• filled 



