31. The same solution, being mixed with syrup of violets, became of a reddish colour. 32. Saccharum Saturni being added to the solution, precipitated a thick lactescent cloud. 33. Ol. tart. p.d. being also added to this solution, it caused no visible effervescence, yet raised some bubbles of air, and caused a coagulation of many small brown terrene nubeculæ in the water; which, after standing some time, subsided to the bottom, and left the water clear. These experiments do plainly evince, that this water contains an aluminous salt, conjoined with a fine terrene substance, which is probably a part of the matrix, from whence the salt has been formed. This salt gives no signs of any alkaline principle; but, on the contrary, of an acidity, as its solution reddens with syrup of violets. With this salt there are also intimately conjoined some very subtile chalybeat parts, which are not separable from it by elixation or evaporation. Alum is distinguishable from all other mineral salts, by liquifying and bubbling upon a red-hot iron, and turning into a white calx. But this could not be well expected from this aluminous salt, which we had extracted from the water, because it was extremely foul, by being combined with so large a proportion of earth; which earthy parts were the occasion of turning the salt of a blackish colour upon the iron. However, we see it turns white by a further degree of heat. But if the salt had been dissolved, filtrated, and crystallized, till it had been purified and freed from this terrene matter, it would then certainly have had the same appearance upon the red-hot iron, as a pure aluminous salt. Again, as it is peculiar to an aluminous salt to liquify in some degree with fire, so we see, that this was evidently the case of this salt. Its eliquation indeed could not be so remarkable, as in pure alum, because of its being mixed with so much earth; but that it did liquify in some degree is plain, because the whole mass of salt and earth, even when reduced to a powder, ran all together like a cinder. The experiment upon the solution of this salt with ol. tart. p.d. is also a further proof of what we have already asserted: for tho’ there was no visible effervescence, yet the bubbles of air shew, that there was an intestine conflict of the oil with the acid principle in the solution; which being absorbed by the alkali, the earth was precipitated, to which it formerly adhered. The two next experiments were made in order to discover, whether an acid or alkaline principle prevailed in the water. _Exp._ 34. Forty gutts of the syrup of violets being added to an ounce of the water, the mixture became of a bright sea-green colour. 35. A quantity of water being kept boiling for five minutes, and afterwards allowed to stand till it became clear, was carefully filtrated from its ochrous sediment: after which, upon its mixture with syrup of violets, it turned of a faint reddish colour.