44-5 
and the Theory of Chemical Types. 
Now let us go further : let us suppose that the marsh gas 
be subjected to the action of chlorine ; very different actions 
might be produced, if we only consult the general forces of 
chemistry. 
Viewed precisely by the theory of organic types, if the 
marsh gas corresponds to chloroform, to methylic mther, &c., 
it realizes the carburet of hydrogen, which constitutes the 
starting point of this series, and by means of chlorine it should 
give : 
C4 
Ch2 / hydrochlorate of methylene. 
C4 PJ4 ^ 
^1^4 > monochloridated hydrochlorate. 
Ch^ chloroform. 
Ch® chloride of carbon. 
We know, by the experiments which I recently made known 
to the Academy, that marsh gas obtained from the acetates 
changes under the influence of chlorine into this chloride of 
carbon Ch®, which the theory of types had predicted as the 
necessary product of the action. 
Let me add too, that before giving this chloride of carbon, 
it also produces some chloroform. But if marsh gas [gas des 
inarais) corresponds to the chloroform as the acetic acid does 
to chloracetic acid, the conversion of marsh gas into chloro- 
form is as necessary a fact as the conversion of the acetic 
acid into marsh gas. 
If when these necessary facts have been recognized as true 
be experience, it be then proved that they were possible, that 
they did not disagree with the general laws of chemistry, I 
contend that the difficulty has not been met. What ought to 
be done in such a case, is to show how the general theory 
allows us to foresee that acetic acid should give marsh gas, 
and that marsh gas should give chloroform. 
Far from thinking that I have gone too far in establishing, 
as I have done, genera for uniting acetic acid and chloracetic 
acid, marsh gas, and chloroform, I have on the contrary been 
too cautious. 
I therefore persist in my opinion as to the propriety of 
uniting into one genus those bodies which contain the same 
number of equivalents united in the same manner.^ and which are 
endowed with the same fundame^ital che^nical properties. 
In this discussion of the characters of chemical types and 
of the true accej)tation of the fundamental properties of 
bodies, I have said nothing of the identical function attributed 
