oz. of alum; and a similar quantity of sal ammoniac. These ingredients must now be exposed, in an open crucible, to a moderate heat for some hours; after which, the fire ought to be increased for a short time; and, at length the mixture should continue for three hours, in a degree of heat sufficiently powerful to keep the crucible red hot. At the expiration of that term, it will acquire a beautiful yellow colour; which may be rendered of a brighter golden shade, by augmenting the proportions of antimony and sal ammoniac.
Yellow pigments of various shades may also be obtained, by triturating flowers of sulphur, or yellow ochre, in different proportions, with a solution of gum in water: and, lastly, the calx of iron, when precipitated by quick-lime, from a solution of green vitriol, has been recommended as a substitute for yellow ochre, in house-painting.—Another method of preparing the celebrated Naples yellow, is that of M. Passery, who makes use of the following ingredients, namely: antimony, 1lb.; lead 112lb.; alum and common salt, of each 1 oz.—We have inserted this recipe, on the authority of Wiegleb; who simply enumerates the articles here stated, without communicating the process of compounding them.
Yellow Ink may be prepared, by previously dissolving a small portion of alum aud gum-arabic in pure water, and then infusing a few grains of dry saffron in the same solution.—It may, likewise, be obtained by slowly boiling 2 oz. of Avignon or French berries in one quart of water, with half an ounce of alum, till one-third of the fluid be evaporated; when 2 drams of gum-arabic, 1 dram of sugar, and a similar quantity of pulverized alum, are to be dissolved in this liquid: the mixture should then be filtred, and preserved in bottles.
Sympathetic Yellow Ink, is directed, by Wiegleb, to be prepared in the following manner:—Take a handful of the leaves of common marigold (Calendula officinalis, L.), and macerate them for eight days, or longer, in half a pint of the best distilled vinegar; when the liquid must be separated from the leaves, by expressing them through white linen or cotton, and preserved in a glass bottle carefully stopped. If the desired colour is to be of a pale shade, an additional quantity of water may be added.—Invisible characters may be formed with this liquor on white substances, such as linen, silk or paper; and the yellow tint will appear on immersing them in the following liquor:—Take a sufficient quantify of violet or daisy flowers; bruise them in a marble mortar; add a small portion of water; express the liquid through white linen, and also preserve it in a glass bottle.—An infusion of turnsol will answer the same purpose.
YELLOW FEVER, is one of the most fatal epidemics to which the inhabitants of warm climates are subject.
As the opinions of physicians, concerning the nature and treatment of the Yellow Fever, are various and contradictory, we shall avail ourselves of the clear and satisfactory view of this malignant disease, lately given by Dr. Thomas Dancer, in his excellent work, entitled "The Medical Assistant, or Jamaica Practice of Physic," (4to. Kingston, Jamaica; and Lond. Murray and Highley, pp.384,
