the Constitution of the Pnissic and other Acids, ^c. SG7 



feeing the quantity contained in 25 grains of corrosive subli- 

 mate. 

 Then as 21-5 : 19-94: :37-2 : 84-48 the quantity of red oxide 



in 40 prussiate of mercuvv, 

 And as 21-5 : 19-9J : : 9-3 :3-62 the quantity of ditto in 10 of 



ditto, 

 100 grains of prussiate of mercury are therefore composed of 



Prussic acid, Experiment C. .. .. .. !3-8 



Red oxide of mercury. Experiment B. C. and D. 86-2 



100-0 



Analysis of Prussic Acid. 

 Being very desirous of accomplishing the analysis of this acid 

 if possible, I considered very attentively the nature of the diffi- 

 culties to be surmounted in order to effect it. The principal 

 ones ajipeared to me to be the following. 



1st. Tliat of always ascertaining with precision the quantity 

 which is the subject of analysis. 



2d. That of effecting its combustion with oxvgen in such a 

 manner, that while, on the one hand, tlie whole of its carbon 

 and hydrogen should be oxygenated; so, on the other, that none 

 of its azote should undergo tTiis process. 



3d. That of determining with great acairacy the quantity of 

 oxygen which combines with the elements of the prussic acid 

 during its combustion, so as, after allowing for what has been 

 expended in the formation of carbonic acid, to be able to infer 

 with confidence, from the disappearance of the rest, the quantity 

 of hydrogen which was ccmtained in the acid. 



The property which the prussic acid possesses of assuming the 

 liquid form at a low temperature, and that of a gas or vapour 

 at common temperatures, the volume of which is materially in- 

 fluenced bv mixture with other gases, and by slight alterations 

 of temperature and pressure, did not appear to me to be favour- 

 able to the employment of it in an uncombined form for the 

 purpose of its analysis. 



1 therefore determined upon employing it in the state of con- 

 densation in which it exists in prussiate of mercury, and this 

 determination made me undertake the analysis I have just de- 

 scribed of that salt ; of the correctness of which having satis- 

 fied myself, I conceived that 1 had overcome the first difriculty. 



The second and third difficulties 1 thought would be best sur- 

 mounted by cmplwing, for the combustion of the prussic acid, 

 the same oxide witii whi<}h it is united in the prussiate of mer- 

 cury, namely, the red oxide of that metal ; increasing the quan- 

 tity of it by multiples of that which the salt contains, until I found 

 that the whole of the prussic acid was dccompo-^cd. 



I meula 



