DECOMPOSITION OF MERCURIC CYANIDE 311 



mass to the final state of carbonic acid (in solution), ammonium 

 chloride (in solution), potassium chloride, and mercuric chloride 

 (in solution). We thus get 



KCNO (diluted) + HC1 (diluted) + H 2 O = C0 2 (in solution) 

 + NH 3 (diluted) -f KC1 (diluted). 



We measure the total heat disengaged in this series of re- 

 actions; the whole series occupying a period not exceeding 

 from twenty to twenty-five minutes. Then we make sure that 

 there is no cyanogen compound remaining in solution ; this is 

 confirmed by the quantitative estimation of the ammonia, made 

 in the cold by the Schloesing process. 



The total heat disengaged by this series of reactions being 

 known, the following data are brought into the calculation the 

 heats of combustion of carbon and hydrogen, the heat of oxida- 

 tion of mercury, the heat of chlorination of hydrogen, the 

 heat of formation of ammonia, the heats of combination of 

 mercuric oxide with hydrochloric and hydrocyanic acids, and 

 lastly, the heats of combination of diluted potash and dis- 

 solved ammonia with hydrochloric acid ; making in all, nine 

 auxiliary data. 



In short, we proceed from the initial state, which is 



i[C 2 + N 2 + 4H 2 + Hg + 2C1 2 + 20 2 + 2K 2 (diluted) 

 -I- 4HC1 (diluted)], 



to the final state 



J[2C0 2 (in solution) + 2NH 4 C1 (diluted) + 2H 2 + 4KC1 

 (diluted) + HgCl 2 (diluted)]. 



By one mode of procedure, the compounds of the final state 

 may be formed directly ; the heat of formation of mercuric 

 chloride in particular being determined from the heats of forma- 

 tion of water, mercuric oxide, and hydrochloric acid, together 

 with the heat disengaged by the solution of the oxide in this 

 acid. 



By a second method, the diluted hydrocyanic acid and mer- 

 curic oxide are formed first, and then combine. 



H + C + N (liquid) disengages ... ......... x 



HCN (liquid) and water ............... + 0-4 



i[H 

 J[H 



] ............... 4-15-5 



di 



HgO + 2HCN (diluted) = Hg (CN) 2 (diluted) + H 2 0] + 15.46 



We then add to this sum the total amount of heat disengaged 

 in the calorimeter during the course of the operations, without 

 troubling about the chemical nature of the intermediate 

 reactions. 



The details of the experiments will not be given here, as 

 they will be found further on, under cyanogen chloride. It 

 will merely be remarked that the quantity, x, calculated from 



