Experiments, notes, &c. about the mechanical origine or production of divers particular qualities among which is inferred a discourse of the imperfection of the chymist's doctrine of qualities : together with some reflections upon the hypothesis of alcali and acidum / by the Honourable Robert Boyle ...

CHAP. III.

AND this leads me to another Exception against the Hypothe∣sis of the Duellists, which is, that the Framers of it seem arbitrarily to have assigned Provinces or Offices to each of their two Principles, as the Chy∣mists do to each of their tria prima, and the Peripateticks to each of their Four Elements. For 'tis not enough to Say, that an Acid, for instance, as such, performs these things, and an Alkali so many others, that they di∣vide the Operations and Phaenomena of nature, or at least (as some, more cautious, are content to say) of mixt bodies between them; since Asserti∣ons of such great moment ought not to be advanc'd or received without

sufficient Proof. And perhaps the very distribution of Salts into Acids and Alcalies hath somewhat of arbi∣trary in it, since others may, without assuming much more, take the free∣dom to distribute them otherwise, there being not only several things wherein Acids and Alcalies agree, but also several things wherein Salts of the same denomination widely differ. As, for Instance, some Alkalies, accord∣ing to those I reason with, are, like salt of Tartar, fixt, and will endure the violence of the fire; others, like salt of Urin or Harts-horn, are exceed∣ingly fugitive, and will be driven up with a scarce sensible degree of Heat; some, as salt of Tartar, will precipitate the solution of Sublimate into an Orange-tawny; others, as spirit of Blood and Harts-horn, precipitate such a solution into a milky substance. Oil of Tartar will very slowly ope∣rate upon filings of Copper, which Spirit of Urin and Harts-horn will readily dissolve in the Fire.

And among Acids themselves the difference is no less if not much greater. Some of them will dissolve bodies that others will not, as Aqua fortis will dissolve Silver and Mercu∣ry, but leave Gold untouched; or as Aqua Regis, though made without Sal Armoniac that dissolves Gold readily, will dissolve Mercury but scurvily, and Silver not at all. And this may happen, when the Menstruum that will not dissolve the body is reputed much stronger than that which does; as dephlegm'd spirit of Vinegar will dissolve Lead, reduc'd to minute parts in the cold; which is an effect that Chymists are not wont to expect from Spirit of Salt. Nay, which is more, one Acid will precipitate what another has dissolved, and contrarily; as spirit of Salt will precipitate Silver out of spirit of Nitre. And I found oil of Vitriol to precipitate bodies of divers kinds, Minerals and others, out of some acid Menstruums, particularly spirit of Vinegar.

To this might be added the Pro∣perties, peculiar to some particular Acids, as that Spirit of Nitre or Aqua fortis will dissolve Camphire into an Oil, and coagulate common oil into a consistent and brittle substance like Tallow; and, though it will both corrode Silver, Copper, Lead, and Mercury, and keep them dissolved, it will quickly let fall almost the whole body of Tin, very soon after it has corroded as much as it can of it. By all which, and some other like Instan∣ces, I am induc'd to question, whether the Acidum and Alkali, we are speak∣ing of, have the simplicity that Philo∣sophy requires in Principles; and shall be kept from wondering, if others shall think it as free for them to constitute other Principles, as 'tis for the Learned men I reason with, to pitch upon Acidum and Alkali.

And some perhaps will be bold to say, that, since the former of those Principles comprehend such a number of bodies, that are, many of them, very differing, and some of them directly

contrary in their operations, it seems a slight and not Philosophical Ac∣count of their Nature, to define an Acid by its Hostility to an Alcali, which (they will say) is almost as if one should define a Man by saying, that he is an Animal that is at enmity with the Serpent; or a Lyon, that he is a fourfooted beast that flies from a Crowing Cock.