and the Theory of Chemical Types. 325 



from possessing a special character, from constituting a case 

 of chemical action so particular, that it was absolutely neces- 

 sary to distinguish it from every other, as I have done. 



To be convinced that the theory of substitutions is not ge- 

 neral, there is no need of new facts; it will suffice to read my 

 memoir on chloracetic acid, which has been so often quoted 

 for some time. We there see that besides the chloracetic 

 acid produced by substitution by means of the action of 

 chlorine on acetic acid, oxalic acid and carbonic acid are de- 

 veloped, the production of which by substitution we may be 

 at a loss how to explain, at least for the present. 



And better still, it suffices to glance at my memoir relative 

 to indigo : we there see that the white indigo, under the in- 

 fluence of oxygen, loses an equivalent of hydrogen without 

 gaining anything. In this case then there is no substitution ; 

 I convinced myself of it. At a later period MM. Liebig 

 and Woehler observed facts of the same nature in their admi- 

 rable researches upon uric acid. Quite recently, Mr. Kane 

 observed similar facts in the colouring matter of Heliotrope. 



Thus, the phaenomenon of substitutions is not general; still 

 more, this is one of its most essential characters, as we shall 

 presently see. 



Not only it is not general, because a body may, under the 

 influence of oxygen, lose hydrogen without gaining anything, 

 but it is not general also for the contrary reason. Olefiant 

 gas, for example, may lose 4 equivalents of hydrogen and 

 take 6 of chlorine; every one knows this. Any one who had 

 not analysed all the intermediate degrees of this action, as 

 M. Regnault has done, would, in comparing the first and 

 last term, have found the law of substitutions defective. 



At present it may be explained and understood without 

 difficulty, when we say that if white indigo loses hydrogen 

 without gaining anything, it passes into a new molecular 

 type ; when we know that olefiant gas may produce a chlo- 

 ride of carbon of the same type as itself, and, by a fresh 

 addition of chlorine, a new chloride of a different type. 

 Thus, the law of substitutions prevails when the bodies pre- 

 serve their initial type; it is no longer applicable in the con- 

 trary case ; and, by this very means, it serves to distinguish 

 the bodies which have preserved their molecular type from 

 those which have lost it. 



But there is no occasion to return to this explanation, which 

 my wish to express myself clearly has induced me to give 

 €71 passant, to justify the necessity of distinguishing the law of 

 substitutions from other chemical actions {reactions.). 



The law of substitutions expresses, that in an organic body, 



