NUMERICAL TABLE OF ELECTIVE ATTRACTIONS. 355 



tual attractive forces of the component parts of different 

 salts; but these attempts have hitherto been confined within 

 narrow limits, and have indeed been so hastily abandoned, 

 that some very important consequences, which necessarily 

 follow from the general principle of a numerical represen- 

 tation, appear to have been entirely overlooked, ft is not 

 impossible, that then* m;iy be some cases, in which the pre- 

 sence of a fourth substance, beside the two ingredients of 

 the salt, and the medium in which they are dissolved, may 

 influence the precise force of their mutual attraction, either 

 by affecting the solubility of the salt, or by some other un- 

 known means, so that the number, naturally appropriate 

 to the combination, may no longer correspond to its affec- 

 tions ; but there is reason to think, that such cases are 

 rare; and when they occur, they may easily be noticed as 

 exceptions to the general r. les. It appears therefore, that 

 nearly all the phenomena of the mutual actions of a hundred 

 different salts may be correctly represented by a hundred 

 numbers, while, in the usual manner of relating every case as 

 a different experiment, above two thousand separate articles 

 would be required. 



Having been engaged in the collection of a few of the prin- Asetiesof num- 

 cipal facts relating to chemistry and pharmacy, I was induced s ^ r e s ri „g v e 'rj n " 

 to attempt the investigation of a series of N these numbers; generally. 

 and I have succeeded, not without some difficulty, in obtain- 

 ing such as appear to agree sufficiently well with all the cases 

 of double decompositions which are fully established, the 

 exceptions not exceeding twenty, out of about twelve hun- 

 dred cases enumerated by Fourcroy. The same numbers 

 agree in general with the order of simple elective attrac- 

 tions, as usually laid down by chemical authors; but it was 

 of so much less importance to accommodate them to these, 

 that I have not been very solicitous to avoid a few inconsis- 

 tencies in this respect; especially as many of the bases of Common tables 

 .1 . , ,. i i - i x. , • of simp'e elefl- 



the calculation remain uncertain, and as the common tables t ive attractions 



of simple elective attractions are certainly imperfect, if they imperfect. 

 are considered as indicating the order of the independ nt 

 attractive forces of the substances concerned. Although it 

 cannot be expected, that these numbers should be accurate 

 measures of the forces which they represent, yet they may 

 2A2 be 



