206 Prof. Clausius on the Internal Work 



however, is not usually the case under the circumstances which 

 accompany our chemical operations. Nevertheless cases do 

 occur in which this condition is fulfilled, especially in the chemi- 

 cal changes brought about by the action of electric force. The 

 galvanic current affords us a simple means of causing combina- 

 tion or decomposition ; and in this case the cell in which the 

 chemical change takes place itself forms a galvanic element, the 

 electromotive force of which either contributes to intensify the 

 current, or has to be overcome by other electromotive force ; so 

 that in the one case there is a production, and in the other a 

 consumption of work. 



Similarly, I believe that we could in all cases, by producing 

 or expending work, cause the combination or separation of sub- 

 stances at pleasure, provided we possessed the means of acting 

 at will on the individual atoms, and of bringing them into what- 

 ever position we pleased. At the same time I am of opinion 

 that heat, leaving out of view its secondary effects, tends in a 

 definite manner, in all cases of chemical change, to render the 

 combination of atoms more difficult, and to facilitate their sepa- 

 ration, and that the energy of its action is likewise regulated by 

 the general law above given. 



Supposing this to be the case, the theorem which we have 

 deduced from this law must also be applicable here, and a che- 

 mical compound must contain exactly the same quantity of heat 

 as its constituents would contain at the same temperature in the 

 uncombined state. Hence it follows that the true specific heat 

 of every compound must admit of being simply calculated from 

 the specific heats of the simple bodies. If we further take into 

 consideration the well-known relation between the specific heats 

 of the simple bodies and their atomic weights (a relation which 

 I believe not only to be nearly, but, in the case of the true spe- 

 cific heats, absolutely exact), it is apparent what enormous sim- 

 plifications the law which we have established is capable, suppo- 

 sing it to be true, of introducing into the doctrine of heat. 



§ 10. After these expository remarks, I can now cite the more 

 extended form of the theorem of the equivalence of transforma- 

 tions. 



In § 1 I have mentioned two kinds of transformations : first, 

 the transformation of work into heat, and vice versa; and secondly, 

 the transference of heat between bodies of different temperatures. 

 In addition to these, we will now take, as a third kind of trans- 

 formation, the alteration of the disgregation of a body, assuming 

 the increase of disgregation as a positive, and the diminution of 

 it as a negative, transformation. 



We will now, in the first place, bring the first and last trans- 

 formation into relation with each other; and here the same 



