198 



Cnmpnunds 

 tHar have I he 

 grfa;est affi'ii 

 ty least, suiu- 

 bla. 



Sulphafes of 

 h;ii-vtfs and 



Tables rep-©- 

 sent the rc4l 

 affinities of 



ON CHEMICAL ATTRACTION. 



tuents of which have the gieatept affinity, will have the most 

 cohesion ; they will be the leayi soluble, and the tirst to crys- 

 tallize on evaporation. 2diy. Bergman's Tables may still be 

 considered as representing, in «orne degree at least, the af- 

 finities of bodies. 3diy. Berthoilei's opinion, that, when 

 two binary compounds are dissolveo together, a quaternary 

 compound is always formed by their union, will be in 

 great measure invalidated. These consequences we shall 

 endeavour to trace; so that, if the opinion we have stated 

 be just, it may receive due confirmation, from the observa- 

 tion of the phenomena presented by chemical attraction. 



The first proposition is abundantly proved by the follow- 

 ing observations of Berthollet, which deserve io be quoted 

 a second time. *' If all the decompositions ascribed to com- 

 ♦* plex affinities be investigated, it will be found, that the 

 ♦' prevailing affinity has been always ascribed to those siib- 

 '* stances, which have the property oF precipitating, or of 

 ** forming a salt, which can be separated by crystallization. 

 ** For this reason it may be inferred a priori, from a know- 

 ♦' ledge of the salubility of salts which may be formed in a 

 *' liquid, that those substances, which are least soluble, and 

 *' most apt therefore to p;ecipitate, will be found to be the 

 •* same as tho^e t9 which Bergman and other learned che- 

 *' mists have attributed the strongest affinity in their tables," 

 &c.-^See Keiearches, p. 106 «t seq, 



Barytes has a stronger affinity for sulphuric acid than any 

 other base; it therefore decomposes all ihe sulphates. From 

 thesaine energetic attraction the particles of sulphate of ba- 

 rytes cohere with more force, and it is found to be less solu- 

 ble than the other sulphates. Thus we consider the forcible 

 attr'action, which subsists between sul|:)huric acid and barytes, 

 as at once the cause of the decomposition of the sulphate of 

 potash, and of the strong cohesion, and of the little solu- 

 bility of the new sulphate. This account of the matter I 

 think is perfectly just and reasonable, whereas we have shown 

 the incQugruity of the opposite opinion. 



We are now naturally led to consider our second proposi* 

 tion ; that Bergman's Tables may still be considered as re- 

 presenting the real affinities of bodies. If Berthollet's opi- 

 iiion, that the decomposition and separation of salts arise 



frpra 



