M. Berzelius on the Theory of Substltuiiofis ofM. Dumas. 3 



of substitution harmonizes with electro-chemical opinions, and 

 as these latter have not, according to him, the property of 

 yielding to facts or of explaining or predicting them, he dis- 

 patches the electro-chemical theory by saying, " It must be 

 admitted there is nothing in it." 



This is certainly a complete revolution in the state of che- 

 mistry. 



When questions of such importance to science are treated 

 of, the love of truth should ensure a mature examination of 

 the propositions of the author of such a I'evolution, for the 

 purpose of engaging us on his side if be is right, and of op- 

 posing him if he is v^'rong. 



One of the great advantages of the theory of substitutions 

 over electro-chemical opinions seems to be, that the type of 

 composition preserves the same properties after the exchange 

 of hydrogen for chlorine. 



Let us then examine the few properties of chloracetic acid 

 which M. Dumas has described, and compare them with those 

 of acetic acid. It will be seen that these two acids differ infi- 

 nitely more from each other than do formic acid and acetic acid. 



ACETIC ACID. 



Smell strong and pungent. 



Liquid at common tempera- 

 tures. 



Solidifies at about 50° Fahr., 

 boils at about 212°. 



Specific gravity 1'06. 



Potash salt deliquescent. 



^ther very fluid, odour sethe- 

 real ; floats on water. 



CHLOROACETIC ACID. 



Scarcely any smell. 

 Solid at common tempera- 

 tures. 

 Solidifies at about 187° Fahr. 

 Boils at about 392°. 

 Specific gravity 1*617. 

 Potash salt unalterable in 



the air. 

 ^ther oleaginous, odour like 

 mint; sinks in water. 

 These two acids, therefore, have no other resemblance than 

 that which belongs to acids in general, and it might be stated 

 that chloracetic acid resembles sulphuric acid as much as it 

 does acetic acid. Thus the type does not lead to an antici- 

 pation of the particular properties of an acid in which hy- 

 drogen is replaced by* chlorine. 



With respect to the composition of chloracetic acid, M. 

 Dumas is of opinion that it is formed of three atoms of oxy- 

 gen and of one atom of a radical composed of four atoms of 

 carbon and of six atoms of chlorine. In examining into 

 this composition, it is natural to inquire if other bodies which 

 have an analogous composition are not known, and whether 

 M. Dumas's opinion is not equally applicable to them, for 

 it is evident that any explanation not applicable to similar 

 cases ought to be rejected. 



* " reviplacf par." See preceding notes. — R. T, 



B 2 



