VOL. LXXIII.] PHILOSOPHICAL TRANSACTIONS. 335 



3dly. This degree of precision must tend considerably to the improvement of 

 the arts of dying and enamelling, the processes by which many of their ingre- 

 dients are procured being at present much too vague. 



4thly. The uses of this knowledge in the examination of mineral waters, and 

 in essaying of ores, have been amply proved in the elaborate treatises which the 

 celebrated Bergman has lately given us on these subjects. And I may further 

 add, that the knowledge of the quantity of acid requisite for the solution of dif- 

 ferent metallic substances may also furnish us with a new criterion for distin- 

 guishing them from each other, and the purer from their alloys, and in some 

 cases inform us of the quantity and quality of the alloy. 



But the end which of late I had principally in view, was to ascertain and mea- 

 sure the degrees of affinity or attraction that subsist between the mineral acids, 

 and the various bases with which they may be combined, a subject of "the greatest 

 importance, as it is on this foundation that chemistry, considered as a science, 

 must finally rest. Chemical affinity or attraction is that power by which the in- 

 visible particles of different bodies intermix and unite with each other so inti- 

 mately as to be inseparable by mere mechanical means. In this respect it differs 

 from magnetic and electrical attraction. It also differs from attraction of cohe- 

 sion in this, that the latter takes place between particles of almost all sorts of 

 bodies whose surfaces are brought into immediate contact with each other; for 

 chemical attraction does not act with that degree of indifference, but causes a 

 body already united to another to quit that other and unite with a third, and 

 hence it is called elective attraction. Hence attraction of cohesion often takes 

 place between bodies that have no chemical attraction to each other; thus regulus 

 of cobalt and bismuth have no chemical attraction to each other, for they will 

 not unite in fusion, yet they cohere to each other so strongly, that they can be 

 separated only by a stroke of a hammer. 



Hence bodies, which refuse to unite to each other chemically when they are 

 most minutely divided, as when both are in a vaporous or aerial state, or when 

 both are in a liquid state, may be judged, in the first case, to have none; or in 

 the second case to have at best but a very small affinity to each other. But those 

 that unite, when one of them only is in a liquid state, may be said to have a 

 strong affinity to each other, and it is thus that acids unite to alkalis, earths, and 

 metals, for the most part. 



The discovery of the quantity of real acid in each of the mineral acid liquors, 

 and the proportion of real acid taken up by a given quantity of each basis at the 

 point of saturation, led me unexpectedly to what seems to be the true method of 

 investigating the quantity of attraction which each acid bears to the several bases 

 to which it is capable of uniting; for it was impossible not to perceive, 1st, That 

 the quantity of real acid, necessary to saturate a given weight of each basis, is 



