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LIV. Memoir on the Lmo of Substitutions, and the Theory 

 of Chemical Types. By M. Dumas.* 



¥N this memoir, I propose explaining and discussing dif- 

 ■^ ferent rules and their consequences which have so often 

 been the subject of important communications to the Academy, 

 for I should think it useless to call upon its kind attention, if 

 the developments, into which I have been obliged to enter, 

 had not given it an unusual length. But the Academy will 

 pardon me, when it knows the importance and the variety of 

 the questions which I have been forced to unite in it, and 

 which are the following : 



"1. In every combination, can the elements have their 

 place suppUed, equivalent for equivalent, by simple bodies or 

 by compound bodies, which act their part ? 



" 2. Are not these substitutions often effected, without the 

 general nature of the compound being altered by it; the 

 bodies thus produced belonging to the same chemical type as 

 those from which they are derived ? 



" 3. In other cases, can these substitutions furnish products 

 entirely distinct in their actions {reactions) from those which 

 gave them birth, and is it then right to consider them not- 

 withstanding as belonging to the same molecular type? 



" 4'. Can the nomenclature of organic substances be re- 

 modeled, from the present time, in such a manner that the 

 name of each body shall express the chemical type, or even 

 the molecular type to which it belongs ? 



" 5. Do the phenomena of substitution oblige us to modify 

 profoundly the value affixed until lately to the organic ra- 

 dicals ? 



" 6. Is not the electric function [role) attributed to the ele- 

 ments of compounds by the electro-chemical theory, in com- 

 plete contradiction to the phaenomena of substitutions? " 



I shall subject each of these questions in succession to an 

 attentive examination, applying myself to what is general and 

 elevated, without entering into technical details, which will 

 take their place in special memoirs. 



La-iZi of Substitutions. 

 Some years ago, M. Gay-Lussac mentioned a very simple 

 experiment in his lectures, which has become a point of de- 

 parture for an immense succession of inquiries and disco- 

 veries. In treating wax by chlorine, said the illustrious 

 professor, I saw this substance lose some of its hydrogen, 



* From the Comptes Rendus de I'Academie des Sciences, 1840, prem. 

 seraest. No. 5, Feb. 3. 



