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LI V. Memoir on the Lww of Substitutions^ and the Theory 
of Chemical Types, By M. Dumas.* 
TN 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 supplied, 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. 
Law 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 Comptcs Rendus de V Academic des Sciences, 1840, prem. 
semest. No. 5, Feb. 3. 
