PHILOSOPHICAL TRANSACTIONS. 
VIII. On Circumstances modifying the Action of Chemical Affinity. 
By J. H. Gladstone, Ph.D., F.R.S. 
Received February 1, — Read March 8, 1855. 
It is among the facts in chemical science which admit of no dispute, that a substance 
frequently shows a greater tendency to combine with one body than with another. 
This has usually received the appellation “ elective attraction,” or “ elective affinity.” 
It is also perhaps universally allowed that the manifestations of this elective affinity 
are greatly influenced by the insolubility, or the volatility of the original substances, 
or of the resulting compounds. The degree of temperature, the respective masses of 
the different substances, the presence of other bodies, and many circumstances beside 
these, are supposed to modify the result. 
The attempt has frequently been made to construct tables showing the relative 
strength of affinity of different substances for some particular body, and Guyton de 
Morveau even endeavoured to give a numerical expression to them. In treating of 
this subject the elaborate disquisition of Bergman, ‘ De Attractionibus Electivis,’ must 
be referred to ; in which he illustrates at once the chemical fact, and the meaning of 
the term, by supposing A to be a substance united to c, and that on the addition of b, 
the c is excluded, and the union of the latter substance with A is brought about ; in 
which case he says b has a stronger elective attraction for A than c has*. He, in 
common with most chemists both of his own and of later times, takes it for granted 
that if b decomposes Ac, it does so completely. The Swedish chemist gives the results 
of nearly 2000 reactions in one table, the first column of which exhibits the following 
substances arranged according to their affinity for sulphuric acid, commencing with 
what he conceived the most powerful: — baryta, potash, soda, lime, magnesia, am- 
* The whole passage runs thus : — “ Sit A materies, quam aliae heterogeneae a, b, c, &c. adpetunt : ponatur 
ulterius K no c unitum ad saturationem (quod per Ac in sequentibus indicamus), addito b, ejusdem ambire 
unionem cum exclusione tov c, A dicitur fortius adtrahere b, quam c, vel etiam b gaudere attractione electiva 
fortiori, quam c ; tandem Ab, addito a, priora vincula laxet, b respuat, et ejus loco a eligat, hinc intelligitur a no 
b vi attractiva prsepollere, et ratione efficaciae seriem quamdam constituere a, b, et c.” 
MDCCCLV. 2 C 
