QUARTZ, has been described in the article [Lapidary].
QUASSIA, is the wood of the root of the Quassia excelsa, a tree which grows in Surinam, the East Indies, &c. It affords to water an intensely bitter decoction, which is occasionally used in medicine, and was formerly substituted by some brewers for hops, but is now prohibited under severe penalties. It affords a safe and efficacious fly-water, or poison for flies.
QUEEN’s WARE. See [Pottery].
QUEEN’s YELLOW, is an antient name of Turbith Mineral, or yellow subsulphate of mercury.
QUERCITRON, is the bark of the Quercus nigra, or yellow oak, a tree which grows in North America, The colouring principle of this yellow dye-stuff has been called Quercitrin, by its discoverer Chevreul. It forms small pale yellow spangles, like those of Aurum musivum, has a faint acid reaction, is pretty soluble in alcohol, hardly in ether, and little in water. Solution of alum developes from it, by degrees, a beautiful yellow dye. See [Calico-printing] and [Yellow Dye].
QUICKLIME; see [Lime].
QUICKSILVER; see [Mercury].
QUILL; see [Feathers].
QUININA. This medicine is now prepared in such quantities as to constitute a chemical manufacture. Quinina and cinchonina are two vegetable alkalis, which exist in Peruvian bark or cinchona; the pale or gray bark contains most cinchonina, and the yellow bark most quinina. The methods of extracting these bases are very various. In general, water does not take them out completely, because it transforms the neutral salts in the barks into more soluble acidulous salts, and into less soluble sub-salts. To exhaust the bark completely, one or other of the following solvents is employed:
1. Alcohol.—An extract by this menstruum, is to be treated with very dilute warm muriatic acid, in order to dissolve every thing thus soluble; the acid liquor is to be saturated with magnesia, by boiling it with an excess of this earth; the precipitate is to be dried, filtered, and then exhausted by boiling-hot alcohol.