THE ash-colour'd Gravel is made from the Wine-Lees calcin'd dry, and that it may have the due Quality requir'd, it ought to be a Stone new made, of a greenish white Colour, and of a saltish bitter Taste. This is us'd by the Dyers and other People, that have occasion for it; and the best is that which comes from Burgundy, because it is made of the best, and therefore must needs be much better than what our Vinegar-Brewers make.
As this is Wine-Lees calcin'd, they make it by means of hot Water, which has almost the very same Virtues with Salt of Tartar, except that it is more corrosive, as well as the Oil per Deliquium that is made from it. This is also employ'd with quick Lime to make a Salt, which, after it has been fus'd in a Crucible, is cast upon a Stone, or into a Bason, and after it is cold, is cut into little Tablets, and put into a Bottle well stopp'd; and these little Stones are true Caustick Stones. They are likewise made together with Oak-Ashes, Alum, and quick Lime, by the Assistance of hot Water and Fire; and these are called Velvet Causticks, because they operate so gently.
Tartarum, or Tartar, is a hard stony or crusty Matter, which is found sticking to the Insides of Wine Casks. This Tartar is compos'd of the grossest and most saline Part of the Wine, which is separated by Fermentation, and harden'd to a stony Substance on the Sides of the Cask. There are two Sorts of Tartar, one call'd white Tartar, that is made from white Wine; and the other red Tartar, that is made from red Wine.
The white Tartar is separated in much less and thinner Pieces than the red Tartar, but is much finer, and fuller of Salt. Chuse the thickest, heaviest, and most brittle, of a greyish or ash-colour'd White, clean, crystalline, and shining within, and of a sharpish pleasant Taste.
The red Tartar is divided into large thick Pieces, being to be chose pure, dry, reddish, and weighty. This Tartar is coarser than the white, but of the same Taste, and contains the same Principles, but less of Salt. The best sort comes from Germany, Languedoc, and Provence. White Tartar is purified by boiling in Water, and straining it thro' woollen Bags, then evaporating and crystallizing the Liquor, which makes what we call Crystals of Tartar. The Scum or Cream that floats at Top during the Evaporation, is call'd Cream of Tartar. This, when dried, is confounded with the Crystals, which ought to be in little clear shining Bodies, pure, white, heavy and dry, of a sharpish agreeable Taste. It is us'd to blanch Wax, and also to clarify Whey, a Dram being sufficient for a Pint. This white Tartar yields a great deal of essential acid Salt, and some Oil.
Red Tartar yields less Salt than white, but more Oil and Earth. They both make Vinegars when dissolv'd in Wine. The Crystals differ not from the Tartar itself, but that they contain less earthy Parts in them. All the Tartars from Wine are aperitive, and something laxative, open Obstructions, and excite to Urine, allay or abate Fevers, and are proper to dissolve tough Flegm in the Glands. The Dose of Tartar depurated is from a Dram to three Drams.