﻿M. Damasks Remarks on Affinity. 87 



baryta as regards their combinations with sulphuric acid, we find 

 that the condensation of the elements increases from sulphate of 

 magnesia to sulphate of baryta. It is least in sulphate of mag- 

 nesia, that of these four sulphates which water dissolves easily; it 

 is greatest in sulphate of baryta, which is quite insoluble. 



In this respect all soluble sulphates are comparable to sul- 

 phate of magnesia ; sulphate of lead, which is insoluble, resem- 

 bles, on the contrary, sulphate of baryta. 



The same relation is observed between chloride of silver, calo- 

 mel, chloride of lead, and corrosive sublimate. The condensa- 

 tion of the elements is greatest in the first of these bodies, which 

 is the most insoluble, and least in the last, which is most soluble. 



Iodide of silver is more condensed than bromide, and this, 

 again, than the chloride of the same metal — which agrees with 

 their respective solubilities in liquid ammonia. 



In the case of an acid soluble in water, the salts which it 

 forms with bases, for the same state of saturation, are the more 

 soluble the less the acid is removed from its primordial condition 

 — that is, the weaker the condensation; and they are less so- 

 luble the stronger it is. 



The phenomena of double decomposition are always deter- 

 mined by the production of the most condensed compound and 

 by its precipitation. 



Thus a greater force of union between the parts, the measure 

 of which is their approximation (that is, their condensation), is 

 a sign of insolubility, as Newton foresaw, a proof of increase in 

 cohesion and a cause of double decomposition, as Berthollet 

 taught. 



But why is this condensation greater in the sulphates of baryta 

 and lead, and less in the sulphates of magnesia and of copper ? 

 Why are the phosphates generally insoluble, while all the ni- 

 trates and all the acetates are soluble ? We do not know ; and 

 if, to answer such questions, it is not, perhaps, necessary to arrive 

 at an absolute knowledge of the nature of affinity, we must at 

 any rate penetrate more deeply into its laws. 



Lavoisier never stated fully his opinion on the subject of affi- 

 nity. Newton wished, before investigating its nature, to make 

 a thorough investigation of the laws which it obeys. But the 

 restricted point of view chosen by these two great men gave place 

 at the beginning of this century to a new point of view. They 

 each of them compared chemical or molecular attraction to ge- 

 neral attraction; Davy, (Ersted, Ampere, Berzelius, our col- 

 league M. Becquerel, and their imitators endeavoured to connect 

 it specially with electrical attractions, or even to identify it with 

 these forces. 



An electrochemical theory which could account for the effects 



