PROGRESS IN CHEMISTRY. 245 



elcM'tro-neg-ativo. This idea was the result of experiineiits on the 

 behavior of substances such, for example, as coY)per and sulphur. If 

 portions of those elements be insulated and then brought into contact, 

 they become oppositely electrified. The degree of electrification is 

 intensified by rise of temperature until, when combination ensues, the 

 electrification a anishes. Combination, therefore, according to Davy, 

 is concurrent with the equalization of potentials. In 1812 Berzelius 

 brought forward an electro-chemical theory, which for the following 

 twenty years was generally accepted. His primary assumption was 

 that the atoms of elements or, in certain cases, groups of atoms are 

 themselves electrified; that each atom or group of atoms possesses two 

 poles — one positive, the other negative; that the electrification of one 

 of these poles predominates over that of the other, so that the atom or 

 group is itself, as a whole, electro-positive or electro-negative; that 

 combination ensued between such oppositely electrified bodies by the 

 neutralization, partial or complete, of their electric charges; and, 

 lastl}^ that the polarity of a*n element or group could ])e determined 

 by noting whether the element or group separated at the positive or 

 the negative pole of the galvanic battery or electrolysis. For Berzelius, 

 oxygen was the most electro-negative and potassium the most electro- 

 positive of the elements, the bridge between the "nonmetals'' and the 

 "metals" being hydrogen, wdiich, with nitrogen, forms a basic or 

 electro -positive group, while with chlorine, etc.. it forms electro- 

 negative groups. The fact that an electric current splits compounds 

 in solution into two portions led Berzelius to devise his "dualistic" 

 svstem, which involved the assumption that all compounds consist of 

 two portions, one electro-positive, the other electro-negative. Thus, 

 sulphate of magnesium and potassium was to be regarded as composed 

 of electro-positive potassimn sulphate in combination with electro- 

 negative magnesium sulphate; the former in its turn consisted of 

 electro-negative sulphur trioxide (SO3) in combination with electro- 

 positive oxide of potassium (KgO), while each of these proximate 

 constituents of potassium sulphate were themselves composed of the 

 electro- negative oxygen in combination w4th electro-positive sulphur 

 or potassium. On contrasting sulphur with potassium, however, the 

 former was considered more electro-negative than the latter; so that 

 the group SO3 as a whole was electro-negative, while K2O was electro- 

 positive. The symbols given above, which are still in universal use, 

 were also devised by Berzelius for the purpose of illustrating and 

 emphasizing his views. These views, however, met with little accept- 

 ance at the time in England. 



OLD THEORIES LOSE GROUND. 



Lavoisier's idea that oxygen was the necessary constituent of all 

 acids began about this time to lose ground; for Davy had proved 

 the elementary nature of chlorine, and hydrochloric acid, one of the^ 



