large spoonfuls, to be repeated every three hours: in some cases, this has been sufficient; but, in others, it was necessary to administer the Peruvian bark, between each dose. in a few instances, indeed, emetics and laxatives were given previously to taking the yeast; but, in general, this simple remedy seldom failed to effect a cure; provided due attention was bestowed on the diet and regimen of the patient.
YELLOW, is one of the seven primitive colours.
The principal article affording a yellow dye, is the Weld, or Dyer's Green-weed; of the culture of which, the reader will find an account in that article.—See also vol. ii. p. 205.
An excellent yellow dye may likewise be prepared from the flowers of the acacia. These must be gathered, before they be fully blown, and dried in an earthen vessel over a moderate fire, till they crisp, or curl up, in the same manner as tea-leaves. The ripe seeds of the same tree are then added in the necessary proportions; and the whole, when boiled in river-water, with the addition of alum, will impart a yellow colour of any shade required.
In the 61st vol. of the "Philosophical Transactions of the Royal Society," for 1771, the following receipt for preparing a beautiful yellow dye, is communicated by Mr. Peter Woulfe: Take half an ounce of pulverized indigo, and mix it in a deep glass vessel, with 2 oz. of strong spirit of nitre, previously diluted with 8 oz. of water, to prevent the indigo from taking fire. Let this mixture stand for a week, and then digest it in a sand-heat, for one or two hours; adding 4 oz. of water. The solution is now to be filtred: when mixed with water, in the proportion of one part of the former to 4 or 5 of the latter; and, on adding a little alum, it communicates a durable yellow colour. Mr. Woulfe remarks, that none of the tinging matter separates from the water, during the operation of dyeing, except the portion adhering to the cloth; so that this preparation promises to be of essential service to dyers. He farther states, that cochineal, cudbear, or orchal, and similar colouring substances, when treated in this manner, will also impart a yellow tinge to silk and wool.
The chief yellows used in painting, are Dutch pink, Turbith-mineral, King's and Naples yellow: of these we have given a concise account, vol. ii. p. 37; but, as the preparation of the two last-mentioned pigments has not been accurately stated; we shall subjoin, by way of supplement, a few hints respecting the manner in which they are compounded, for the use of artists.
King's-yellow:—Mix 20 parts of pulverized arsenic with one part of the flowers of sulphur: let them be sublimed in a proper vessel, in a sand-heat. When the sublimation is effected, the colour will be found in the upper part of the glass, whence it must be carefully removed, and levigated till it become a fine powder.—This pigment may also be obtained, by subliming orpiment in a similar manner; and it may be rendered of a deeper or lighter colour, by increasing or diminishing the proportion of sulphur.
Naples yellow is prepared by levigating, on a dry stone, 12 oz. of white lead; 3 oz. of antimony; 1
