﻿M. Dumas's Remarks on Affinity. 89 



of decomposition furnished by the battery, all bodies might be 

 analyzed. Increasing, therefore, the voltaic power at his disposal, 

 he succeeded in isolating the metals of the alkalies, those of the 

 earths, boron, and silicon. 



Since this great event electrochemical theories have taught 

 nothing which could at all guide chemists either as to the nature 

 of affinity, or the laws which regulate its influence in the forma- 

 tion or in the destruction of bodies. 



It has been simply proved that every chemical action is ac- 

 companied by a movement of electricity, and that every con- 

 ducting chemical compound may be disjoined when it is placed 

 between the two poles of a battery. The metals are always libe- 

 rated at the negative, and the oxygen at the positive pole, and 

 other substances at one or the other pole, according to the nature 

 of the compounds in which they are engaged. 



When two bodies combine, electricity is disengaged ; and when 

 two bodies separate, electricity is absorbed. 



How much electricity is produced when two bodies combine ? 

 How much is consumed in the separation of the same bodies? 

 These two questions have been attentively examined ; the disco- 

 veries of Faraday and of M. Edmond Becquerel on this important 

 point, as well as Favie's researches in the same direction, have 

 thrown a new light on them by denning in a precise manner 

 electrical equivalents, but they have not furnished chemists with 

 a doctrine of affinity. 



Having perceived that the hope of representing affinity in 

 its cause and in its effects as a purely electrical action was not 

 realized, and led to no practical conception, I returned, in the 

 last course which I had the honour of giving at the Faculty of 

 Sciences, to the following point of view. 



Accepting affinity as a fact, I proved: — (1) that combination 

 seemed possible only in case the bodies placed in juxtaposition 

 would disengage heat in acting on each other, but that in pro- 

 portion as the combination became more complicated the heat 

 disengaged became less; (2) that in order to separate com- 

 bined substances, the heat must be restored which they had lost 

 in combining. 



Thus, taking as an example the formation and destruction of 

 alum, I compared the following facts : — 



Potassium and oxygen = potash < r\. ( 



Brisk heat and 



;ht light. 



j Brisk heat and 

 Aluminium and oxygen = aluminas , . ,. v ,. 

 JQ {_ bright light. 



Sulphur and oxygen = sulphurous") R d ,. , 



or sulphuric acid .... J ° 



