436 M. Schroder Van der Kolk on Chemical Combinations. 



nity of the components. The gases A are formed by a single 

 spark. If only a few atoms of the components are united by the 

 electric spark, the heat which thereby becomes free is sufficient 

 to propagate the action throughout the entire mass, and no ex- 

 plosion can in this case occur. The gases B can only be formed 

 gradually by repeated passage of the spark, and only along its 

 path. It here acts especially by alterations of affinity; the heat 

 which becomes free in the action cannot form the compound. 

 The gases C can also only be formed in the path of the spark ; 

 for here, besides the affinity, this must also furnish the necessary 

 heat. Of course, in the decomposition of the gases by the elec- 

 trical spark the inverse phenomena are observed. The gases 

 which the spark can form with explosion are slowly decomposed 

 by the electrical spark, and conversely. 



(4) Compound gases can be formed by combustion. 



Combustion is a chemical action which takes place with the 

 development of heat; and this action itself developes an amount 

 of heat sufficient to keep it up when once started. The gases C 

 can therefore never be formed by combustion ; and as, moreover, 

 the gases B cannot be formed by simple heating, they can never 

 result from combustion. The gases A alone can be formed by 

 combustion, and even here those only in which the heat developed 

 is adequate for further combustion. The same phenomena occur 

 in the combustion of compound gases. These also can only burn 

 with other gases, provided the heat developed is sufficient for the 

 further combustion. The following gases containing hydrogen 

 develope the corresponding quantities of heat for 1 equiv. H = 1 

 grm., where heat absorbed is designated as negative. The second 

 series refers to one equivalent of oxygen, or 8 grms: — 



OH . 



. 29413 



HO . 



29413 



C1H . 



. 23783 



i(C0 2 ) . 



24240 



BrH . 



. 9322 



i(S0 2 ) . 



17760 



J-(NH 3 ) . 



. 7573 



CO . 



14838 



|(C 2 H 4 ). 



. 5500 



CIO . 



-7370 



SH . 



. 2741 



NO 



-8724 



i(C 4 H 4 ). 



. -2000 







IH . 



. —3606 







Each succeeding gas cannot possibly be formed by combustion 

 from a preceding one. Of the preceding gases, only the gases A 

 can be formed by combustion; that is, only HO, CO, CO 2 , SO 2 , 

 C1H, BrH : water is formed by the action of on all the above 

 hydrogen compounds, HC1 by heating CI with the following hy- 

 drogen compounds, &c. In like manner HO is formed by heat- 

 ing H with all the above-named oxygen compounds ; CO 2 results 

 from heating C with SO 2 , CO, NO, &c. In this connexion some 

 interesting cases occur: thus the reaction 2CO + S = S0 2 -fC 



