

Energy of Chemical Combinations. 435 



. 29413 



. 14838 



. 48480 



. 35520 



. 23783 



B. The gases have less energy than their constituents, and are 

 not formed on simple heating. 



HO 



CO 



CO 2 



SO 2 



C1H 



HBr . 



. 9322 



PCI 3 . 



. 94804 



PCI 5 . 



. 100373 



As CI 3 . 



. 7183 



NO 4 



NO 2 



NH 3 . . 22728 



SH . . 2741 

 C 2 H 4 . . 22000 



C. The gases have more energy than their components. 



NO 

 CIO 

 HI 



8724 



C 2 N 



7370 



CS 2 



3606 



C 4 H 4 



38994 

 9659 

 8000 



The numbers are the heats of combination according to Favre 

 (energy of the constituents minus energy of the combination). 

 Only the gases A are all formed on being passed through a heated 

 tube : of the gases B and C only CS 2 is formed under these 

 circumstances. The action in the heated tube may be twofold. 

 Either heat becomes free in the formation of the compound, in 

 which case the action excited in portions of the mass will be pro- 

 pagated through the entire mass, and if this takes place rapidly 

 explosion will be the result ; or the action is accompanied by an 

 absorption of heat ; the action is then restricted to the place where 

 it is commenced, and the combination is then more complete. 

 In decomposition, of course the reverse takes place. When, as in 

 the case of water and carbonic acid, the compound explodes, the 

 decomposition must be incomplete ; the gases C, on the con- 

 trary, such as nitrous oxide and hypochlorous acid, must be 

 completely decomposed, sometimes explosively, as in the case of 

 hypochlorous acid. The latter depends on the temperature 

 chosen, and on the velocity with which the action is propagated 

 in the gases. 



(2) Compound gases may be formed by catalytic action. 



As the exciting body here remains unchanged, it can deve- 

 lope no energy, and can only produce changes in which no heat 

 is absorbed. The gases C can never be formed by catalytic action; 

 it is only possible in the case of the gases A and B. 



(3) Compound gases can be formed by the action of the elec- 

 trical spark. 



The action of the electrical spark is essentially thermal. By 

 sparks of adequate strength all combinations can be decomposed. 

 If the sparks are less powerful, phenomena of combination may 

 occur. At the same time the spark effects a change in the affi- 



2 F 2 



