398 SALTS.

but is to be separated by art, and by a very careful management brought from its hid-den state into the form of other Salts.

The waters which principally afford it are the Chalybeat ones, and I believe all of thesehave it in some degree; but none seems to contain so large a quantity of it as the Pyr -mont, to procure it in its own form and pure state from thence, a large quantity of thiswater must be gently evaporated in a broad glass, or glaz’d earthen vessel, over a smallfire in a sand heat; when this is reduc’d to dryness, there is found left a mix’d matter,compos’d of a Spar, a white marley earth, a small quantity of a pale yellow ochre, anda bitterish brackish, and somewhat pungent Salt; the eye discovers the three first sub-stances, the last is only to be found by the taste, the quantity of the earths varies fromdifferent waters, and even in the different operations on the fame, whether from thewater at times containing different quantities, or what is much more probable, fromthe different degree of fire; for it would be easy to raise almost the whole in vapour intoo great a fire ; and too much caution can never be us’d in moderating it towhrd theend of the process, to prevent the loss of part of the small remainder ; the Spar seemshowever much the same in quantity in different careful tryals, and the saline matterwholly the same.

The Residuum being taken out of the vessel, must be ground to a fine powder in aglass mortar, and mix’d by degrees with a small quantity of distilTd common water;the whole, tho’ before suspended in a pellucid water, will now no longer mix with thatmenstruum, but is a thick turbid yellowish white mixture, which must be filtratedthe clear liquor being now evaporated to a dryness, affords a brownish white Salt, verymuch resembling Salt of Tartar, but instead of this it should be evaporated only to apellicle, and then being set by for a few hours, the sides of the glass will be foundencrusted with a fort of ring of a whitish matter, marking the surface of the liquor;this is of a very pungent taste, and being examin’d by the Microscope, shews manyperfect and pure crystals of a regular figure, being all quadrilateral columns terminatedby short quadrilateral pyramids; but few of these are quite perfect, most being muti-lated or blended in their concretions among one another at the sides of the glass, andlower down, there are usually found some crystals of common marine Salt, of theirusual forms, but very small.

The Halcryptium thus separated has all the properties of the common alkaline Salts;mix’d with an acid, it effervesces and produces a neutral Salt; it turns syrup of violetsgreen, and precipitates a yellow powder from a solution of corrosive sublimate in water,and mix’d with a solution of Sal Armoniac a urinous smell is produc’d.

This Salt seems of the utmost importance to the water from which it is obtain’d,since it can be suppos’d to contain no other alkali, and without an alkali it is not easyto account for its properties; and by means of common alkali of Tartar, and a solutionof the Pyrites, or even of iron in an acid mix’d with common water, a liquor may b emade very much resembling the natural Pyrmont water.

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