PURL. Prep. To ale or beer, 1⁄2 pint, gently warmed, add of bitters, 1 wine-glassful, or q. s. Some add a little spirit. A favourite beverage with hard drinkers early in the morning.
PUR′PLE. A rich compound colour, produced by the admixture of pure blue and pure red. This colour has always been the distinguishing badge of royalty and distinction. The celebrated Tyrian purple was produced from a shell-fish called murex.
Purple An′iline. Syn. Perkin’s purple, Mauve. This valuable dye-stuff is prepared under W. H. Perkin’s patent, by mixing solutions of sulphate of aniline and bichromate of potassa in equivalent proportions, and, after some hours, washing the black precipitate with water, drying it, digesting it repeatedly in coal-tar naphtha, and, finally, dissolving it in boiling alcohol. It may be further purified by evaporating the alcoholic solution to dryness, dissolving the residue in a large quantity of boiling water, reprecipitating by caustic soda, washing with water, dissolving in alcohol, filtering, and evaporating to dryness. Thus purified, mauve forms a brittle substance, having a bronze-coloured surface. It imparts a deep purple colour to cold water, though dissolving sparingly in that liquid; it is more soluble in hot water, and very soluble in
alcohol. See Purple dye (below), and Tar colours.
Purple of Cassius. Syn. Purple precipitate of Cassius, Gold purple, Gold prepared with tin; Aurum stanno paratum, Purpura mineralis Casii, L. Prep. 1. Crystallised protochloride of tin, 1 part; crystallised perchloride of tin, 2 parts; dissolve each separately, mix the solutions, and add of crystallised terchloride of gold (in solution), 1 part; carefully wash, and dry the precipitate. Very fine.
2. (Frick.) Dissolve pure grain tin in cold dilute aqua regia until the fluid becomes faintly opalescent, then take the metal out and weigh it; next, dilute the solution largely with water, and add, simultaneously, a dilute solution of gold and dilute sulphuric acid in such proportion that the tin in the one shall be to the gold in the other in the ratio of 10 to 36.
3. (P. Cod.) Terchloride of gold, 1 part, is dissolved in distilled water, 200 parts; another solution is made by dissolving in the cold, pure tin, 1 part, in a mixture of nitric acid, 1 part, and hydrochloric acid, 2 parts; this last solution is diluted with distilled water, 100 parts, and is then added to the solution of terchloride of gold until precipitation ceases to take place; the powder is, lastly, washed by decantation, and dried by a very gentle heat.
4. Silver, 150 parts; gold, 20 parts; pure grain tin, 35 parts; fuse them together under charcoal and borax, cool, laminate, and dissolve out the silver with nitric acid.
Obs. Purple of Cassius is generally supposed to be a combination of oxide of gold and sesquioxide of tin, in which the latter acts as an acid. Heat resolves it into a mixture of metallic gold and binoxide of tin. It is used as a purple in porcelain painting, and to communicate a ruby-red colour to glass, when melted in open vessels.
PURPLE DYE. The purples now in vogue are the numerous shades of ‘mauve’ and ‘magenta’ obtained by the ‘aniline colours.’ (See above, also Red.) For silk and woollen goods no mordant is required. The proper proportion of the clear alcoholic solution is mixed with water slightly warm, any scum that may form is cleared off, and the goods are entered and worked until the required shade is obtained; a small quantity of acetic or tartaric acid is recommended to be added in some cases. For dyeing on cotton with the aniline colours, the cloth or yarn is steeped in sumac or tannic acid, dyed in the colour, and then fixed by tin; or it may be steeped in sumac and mordanted with tin, and then dyed. Purples were formerly, and are still occasionally, produced by first dyeing a blue in the ‘indigo vat,’ and then dyeing a cochineal or lac scarlet upon the top. See Violet dye.