however, so many substances possessing this property, that it must either be limited more exactly than has yet been done, or else given up as a distinguishing property.
All the soluble salts of iron that I have tried, except the acetate, brown turmeric paper. Weak solutions of the green and red muriate seem very alkaline indeed, and even common green vitriol strongly so. They do not, however, produce the same effect on rhubarb paper, but the persalts give it an olive-green tint, whilst the protosalts produce no change at first, but gradually give green tints, apparently from becoming persalts.
If a strong solution of muriate of zinc be boiled on zinc, it gradually oxidizes the metal and dissolves it; and a concentrated solution is obtained, which, when diluted, deposits either an oxide or a submuriate of zinc. This strong solution is apparently alkaline to turmeric paper. If it be diluted with about its bulk of water, and filtered, it will still redden turmeric paper, though it proves slightly acid by litmus paper. If further diluted, more precipitate will fall, and the solution will appear alkaline or not, according as the dilution has been small or great. This substance has the same effect on rhubarb paper, and the tint is very like that of a true alkali.
The acid nitrate of bismuth appears alkaline to turmeric; if diluted till a little oxide becomes deposited, it is more so:—the common solution of chloride of antimony in muriatic acid added to water till a precipitate falls, appears alkaline:—permuriate of tin produces a strong change; protomuriate of tin a very decided reddening; sulphate of tin, slight only. When the acid nitrate of bismuth, and the three salts of tin mentioned, are applied to rhubarb paper, they produce but little effect at first, but if dried by the fire, it becomes quite brown.
A strong solution of chloride of manganese seems feebly but evidently alkaline to turmeric paper.
It may be supposed, that with many of these substances the effect is produced principally by the acid present, inasmuch as they were all more or less acid to litmus, and it has been shown that these bodies, especially nitric acid, have this power. But the very slight excess in some of them, as in the salts of iron, zinc, manganese, &c., and the greater effect produced by further dilution, as with bismuth and antimony, show that the whole substance must act; for if it be considered due to the acid
