88 HISTORY OF CHEMISTRY. [LECTURE vi. 



if the electrical polarities are better equalised in AC and BD 

 than they were previously. In reactions of this kind, Ber- 

 zelius, like Berthollet, assumes an influence upon the resulting 

 phenomena, of the quantities of the substances present and of 

 cohesion ; but he differs from Berthollet in regarding the affinity 

 as a function of the electrical polarity, and as independent of 

 the saturating capacity of the substance. 



This theory constitutes the basis of the dualistic theory of 

 chemical composition. Berzelius establishes it as follows : 7 



" If the electro-chemical views are accurate, it follows that 

 every chemical combination depends wholly and only upon 

 two opposite forces, namely, the positive and the negative 

 electricities, and that every compound must be composed of 

 two parts, united by the effects of their electro-chemical reac- 

 tions, since there is not any third force. From this it follows 

 that every compound substance, whatever the number of its 

 constituents may be, can be divided into two parts, of which 

 the one is positively and the other is negatively electrical. 

 Thus, for example, sulphate of soda is not composed of sulphur, 

 oxygen, and sodium, but of sulphuric acid and soda, each of 

 'which can, in turn, be. separately divided into an electro- 

 positive and an electro-negative constituent. In the same way, 

 also, alum cannot be regarded as immediately composed of its 

 elementary constituents, but is to be looked upon as the pro- 

 duct of the reaction of sulphate of alumina, as negative element, 

 with sulphate of potash, as positive element; and thus the 

 electro-chemical view justifies what I have said with respect to 

 compound atoms of the first, second, third, etc., orders." 



As may be perceived from this, Berzelius had formed a 

 definite opinion as to the composition of compounds, and he 

 went so far with this opinion, that he regarded as inadmissible 

 the assumption, which lies readiest to hand, that the substance 

 is composed of its elementary constituents. He thought he 

 knew the arrangement of the atoms in compounds so minutely 

 (principally from the decompositions which they underwent 



7 Lehrbuch. 3, part I, 79-80. 



