CYANOGEN IODIDE. 339 



liquid cyanogen chloride, together with mercuric chloride, gives 

 off -f- 7 '3 more ; or, altogether, -f- 29'6. If we suppose the 

 mercuric cyanide to be in solution, as well as the cyanogen 

 chloride, these figures do not vary to any appreciable extent. The 

 number -f 27*5, instead of + 29*6, was found by experiment. 



7. We must also note the action of water on cyanogen chloride. 

 Water first dissolves it, and then slowly converts it into car- 

 bonic acid and ammonium chloride ; a reaction similar to that 

 in the case of amides. According to calculation 



CNC1 (liquid) + 2H 2 (liquid) = C0 2 (gas) + NH 4 C1 (in solu- 

 tion) + 55*9. 

 CNCl(gas) + 2H 2 0.(solid) = C0 2 (gas) + NH 4 C1 (solid) + 65-4. 



8. The heat of combustion of cyanogen chloride would be as 

 follows : 



CNC1 (gas) + 2 = C0 2 + N + Cl + 1297. 



We know that this combustion does not take place directly. 



11. CYANOGEN IODIDE. 



1. This substance was synthetically prepared from pure 

 potassium cyanide in aqueous solution (1 eq. = 6*5 litres) 

 and solid iodine. The reaction is easy and rapid. In a first 

 experiment, potassium cyanide was used, which had been pre- 

 pared beforehand and proved to be pure. It was found that 



KCN (1 eq. = 6-5 litres) + I 2 (solid) = CNI (in solution) + KI 

 (in solution) + 6'36 Cal. 



In a second experiment, pure hydrocyanic acid was used, of 

 which a certain weight was dissolved in a diluted equivalent of 

 potash, so as to give a solution containing KCN (1 eq. = 2 litres). 

 On the addition of a corresponding quantity of solid iodine, the 

 value, + 6*21 Cal., was obtained. We will adopt the average, 

 + 6-3. 



2. Solution in water. The solution in water of crystallised 

 cyanogen iodide (6*3 grms. to 500 cc. of water) absorbs, at 20, 

 - 2-78. 



3. Formation from the elements. 



Initial system : K 4- C (diamond) + N + I 2 (solid) 4- water. 

 Final system : CNI (in solution) + KI (in solution). 



FIRST STEP. 



K 4 C (diamond) + N = KCN (solid) +30-3 



Solution - 2-9 



Keaction of I 2 (solid) ... + 6- 3 



Sum +33-7 



z2 



