200 On the Prussic and Prussous Acids. 



the other salts with which it was contaminated, I asked 

 myself to what were its formation and the simultaneous dis- 

 appearance of the prussic acid, during the second ebullition, 

 owing? I could imagine but five causes for this that were 

 likely to have been efficient, concerning each of which I 

 made a question to be resolved by experiment, viz. 



Ouestion I. Was it owing to the complete separation of 

 the oxide of iron from the triple of prussiate by the sul- 

 phur, and the subsequent decomposition of the simple prus- 

 siate by the heat of ebullition long continued ? 



Question IT. Was it owing to the action of the sul- 

 phurous acid produced ? v 



Ouestion TIT. Was it owing to the action of the sulphu- 

 retted hydrogen ? 



Ouestion IV. Was it owing to a combination of the 

 prussiate of potash and sulphur? 



Question V. Was it owing to the de-oxidation of the 

 prussic acid, by the hydroguretted sulphuret? 



To answer jhe first question, it is only necessary to at- 

 tend to the results afforded by long-continued boiling of 

 the simple prussiate of potash. I shall state these results 

 as I find them recorded by professor Proust. 



They are carbonate of ammonia, carbonate of potash, 

 and some simple prussiate that escapes decomposition, even 

 after four or five successive distillations : there is, therefore, 

 no analogy between the products of this experiment and 

 the liquid A; for, had the latter contained carbonate of 

 potash, it must have changed turmeric paper brown ; had 

 it contained carbonate of ammonia, it must have done the 

 same, and likewise have given out ammoniacal gas when 

 potash and lime were added ; it must also have turned blue 

 the solution of copper; 'and had it contained prussiate of 

 potash,, it must have produced prussiate of iron when added 

 to the green sulphate of that metal : it will be seen by re- 

 ferring to Table T. that none of these effects were produced. 

 Were further evidence necessary of the dissimilarity of the 

 two liquids, it might he mentioned that professor Proust 

 poured alcohol on the saline residuum of his distillation of 

 the prussiate, which took up a part that he found to be 

 prussiate of potash : had any of the tingeing salt B been 

 present, the alcohol must have dissolved that likewise, and 

 it could not have escaped his observation. We have, there- 

 fore, ample grounds for negativing the first question. 



In order to answer the second question, I passed sul- 

 phurous acid gas for a long time through a solution of tri- 

 ple prussiate of potash; the prussic acid was expelled, and 



sulphite 



