4 M. Berzelius on the Theory of Substitutions ofM. Dumas. 



Chloracetic acid is composed of carbon combined with 

 chlorine and oxygen. There exists a numerous class of similar 

 combinations; it is divided into three subdivisions according 

 to the radicals combined with the chlorine and with the oxy- 

 gen; these shall be considered in rotation. 



1. Simple electro-positive radicals. — This subdivision is 

 very numerous and well known : it consists of the basic mu- 

 riates of the ancient theory of the nature of hydrochloric acid. 

 The general opinion, which has not been contested, is that 

 these bodies are composed of a chloride and an oxide. They 

 are readily decomposed and recomposed. 



In applying the new theory of M. Dumas to the compound 



Pb CI + 3 Pb, it should be expressed by Pb* Cl^ + 3 O, in 



which Pb* Cl^ is a radical composed of lead and chlorine. 



I am persuaded that M. Dumas would protest against this 

 extension of his views; but if they are true, however, it is re- 

 quisite to do so, and to be consistent, we must go still further, 

 and consider the salts of the oxacids as oxides of a radical 

 composed of that of the acid and also of the base, sulphate 

 of potash, for example, as KS + 4< O. 



2. Simple electro-negative radicals. — The number of com- 

 binations known of this class is very limited. They are to be 

 considered under two different points of view. M. Henry 

 Rose, who discovered the combination of chromium belong- 

 ing to this class, considers it as composed of Cr CF + 2 Cr, 

 and this manner of viewing it has been generally adopted. 

 It has since been proposed to consider it as chromic acid in 

 which an equivalent of chlorine is substituted for an equiva- 

 lent of oxygen. This manner of viewing it is more simple, 

 but it is easy to prove that it is not correct, for the chloride 

 of chromium may be replaced by other chlorides*, and we 

 have several examples of salts formed of an atom of a chloride 

 and of two atoms of chromic acid ; but the preceding hypo- 

 thesis admits only a single relative number of atoms of chlo- 

 rine and of oxygen, although several are known to exist. 

 Consequently, the only admissible explanation in this class of 

 bodies, is that of considering them as composed of a chloride 

 and of an oxide. i 



The following are the only combinations of this species 

 hitherto discovered : — 



Radicals. Formula. Authors. 



Sulphur S C13 + S Regnault. 



Do S_Cl3 +5S 



* " se laisse remplacer par d'autres chlorures.'* 



