188 M. Dumas on tlie Law of Substitutions, and the 



without influence on chemical phaenomena? Unquestionably 

 not : only it must be agreed, that it is at the moment when the 

 combinations are made, at the moment when they are de- 

 stroyed, that the function (rule) of electricity may be observed. 



But when the elementary molecules have taken their equi- 

 librium, we know not any longer how to define the influence 

 that their electric properties may exercise, and no one has put 

 forth views on this subject which agree with experience. 



I have then been induced to declare that the facts which I 

 have just discovered were irreconcilable with the electro-che- 

 mical theory of M. Berzelius, who considers hydrogen as al- 

 ways positive and chlorine always negative, whilst we see them 

 supply each other's place, and perform the same function. 



But I am far from denying, on that account, that the che- 

 mical and electrical forces may be the same, and there is no 

 reason to take up the defence of the general function of elec- 

 tricity in chemical phenomena, when it is simply a particular 

 electro-chemical theory which is under discussion. What I 

 wished to say, what I said, is, that when we have endeavoured 

 to represent the electric state of the combined molecules, pure 

 hypotheses have been attained without any result for the sci- 

 ence. 



When, on the contrary, as has been done so happily by our 

 colleague M. Becquerel, an endeavour has been made to take 

 advantage of this electricity which shows itself at the moment 

 of chemical combinations or decompositions, results the most 

 important and the most fruitful have been obtained. 



It is in this class of facts that the beautiful discoveries of 

 Davy may be classed, those which M. Becquerel pursues with 

 so much perseverance and success ; in fact, the experimental 

 law with which Mr. Faraday himself more recently enriched 

 chemical philosophy. 



All the discoveries of these great physicists have reference 

 to the phaenomena of the chemical action, and are quite inde- 

 pendent of the views which they may have expressed on the 

 function of electricity in compound bodies. 



In the course of this memoir I have several times made use 

 of the actions (reactions] of bodies, as being the only method 

 quite proper for unfolding their real nature. There is not- 

 withstanding an objection in the experiments themselves, to 

 which I have often referred the reader, thus : 



A chemist who, without knowing the origin of it, had had 

 to study the body C 8 H 6 Ch 4 O, seeing that under the influ- 

 ence of potassa this body is changed into chloride of potassium 

 and acetic acid, would certainly have seen in it either a chlo- 



