The thirteenth, that Silver has a greater affinity with Lead than with Copper.
The fourteenth contains the affinities of Iron. Regulus of Antimony stands immediately underneath it, as being the Metallic substance which has the greatest affinity with it. Silver, Copper, and Lead, are placed together in the next square below, because the degrees of affinity which those metals have with Iron are not exactly determined.
The same is to be said of the fifteenth column: Regulus of Antimony stands at its head; Iron is immediately below it; and below the Iron the same three metals occupy one square as before.
Lastly, the sixteenth column indicates that Water has a greater affinity with Spirit of Wine than with Salts. By this general expression must not be understood any Saline substance whatever; but only the Neutral Salts, which Spirit of Wine frees from the water that kept them in solution. Fixed Alkalis, on the contrary, as well as the Mineral Acids, have a greater affinity than Spirit of Wine with water: so that these Saline substances, being well dephlegmated, and mixed with Spirit of Wine; imbibe the water it contains and rectify it.
To these might be added another short column, having Spirit of Wine at its head: immediately below it should be the character of Water, and below that the mark of Oil. This column would shew that the Spirit of Wine has a greater affinity with Water than with Oils; because any Oily matter whatever, that is dissolved in Spirit of Wine, may be actually separated from it by the affusion of Water. This rule admits of no exception but in one case; which is when the oily substance partakes of the nature of soap, by having contracted an union with some saline matter. But as this must be imputed wholly to that adventitious saline matter being superadded to the oily substance, it is no just foundation for an exception, and the affinity in question is nevertheless general.
We have now delivered every thing material that we had to say concerning Mr. Geoffroy's Table of Affinities. It is, as we observed before, of exceeding great service, as it collects into one view the principal truths laid down in this Treatise. Indeed the most advantageous way of using it is, not to delay consulting it till you have read the book through, but to turn to it while you are reading, as oft as any affinity between bodies is treated of; which it will imprint more strongly on your mind, by representing it in a manner before your eyes.
[CHAP. XVIII.]
The Theory of Constructing the Vessels most commonly used in Chymistry.
Chymists cannot perform the operations of their art without the help of a considerable number of vessels, instruments, and furnaces, adapted to contain the bodies on which they intend to work, and to apply to them the several degrees of heat required by different processes. It is therefore proper, before we advance to the operations themselves, to consider particularly and minutely what relates to the instruments with which they are to be performed.