PIIRTURE, in heraldry, the color purple, expressed iu engravings by lines in bent sinister. It is of unfrequent occurrence in.British heraldry.
PURPURINE (C3,1180b = CHII5(OH)z02)"; discovered by Robiquet and Colin in 182S ; named also madder-purple, oxyalizarine, and triaryantbraguinone, Produced from a vegetable source, madder, and existing therein as a glucoside, it requires for its extraction as a separate dye the operation of mineral chemicals; it is included, in its glucoside form, in the rubian of Schnuck, an amorphous mixture of glucosideg (see RuffiAN and ALIZARINE); but it is distinctly separate from the crystalline ruberythric acid of Rothleder, which is the alizarine glucoside. It is found also in combination with umnjistine, in munjeet. The purpurine glucoside itself has not yet been isolated, being very unstable. As a dye-stuff and in calico-printing, purpurine, with alumina mordants, yields bright reds; with iron, a grayish violet. Resisting cleaning with soap and nitro mu•iatc of tin fairly well, they are yet not so permanent against washing and light as alizarine colors. When using madder, garancine, etc., on calicoes, some dyers consider the purpurine nearly useless, but others contend for its necessity to particular shades of pink and red. Robiquet and Schanck assert that the finest madder colors are due to alizarine: this is supported by Kopp, who decides the basis of Turkey-red, an important dye, to be alizarine; stating that purpurine, while dying mordanted cloth perfectly, is unstable compared with alizarine, and does not so readily "take" on oiled cloth. Optical Propertic3.—Aceording to Stokes, the spectroscope determines the existence of purpurine, from the two dark bands in the green, in its solution in alkaline carbonates; as also those in ether and alum, the last being delicately, fluorescent. The carbonate of soda solution secures enough purpurine from a square. inch of dyed cloth to exhibit its reaction. Alizarine yields different spectroscopic absorption bands, and also is known from purpurine by forming violet solutions with alkalies and alkaline carbonates, the solutions remaining unchanged in air; while purpurine would be destroyed by oxida tion. slightly soluble in boiling water, giving a rose-color solu tion, dissolves in alum, not separating even from a concentrated solution, and presents a beautiful fluorescence, and appears as a red, feathery, crystalline powder by sublima tion, and deposits in orange-red needles from boffin.. alcohol. In sulphuric acid of 400° Pahr. temperature it is unchanged, and precipitates from its solution if thrown into water. In nitric acid, if boiled. it changes to phthalic and oxalic acid. Other solvents
are ether, benzol, glycerine, acetic acid, and ammonia, in which it forms popuramide or purpurine (C.H,NII2(OH)202) on standing or on the application of heat; precipi tating then in deep violet flocks on the addition of an acid. In alkaline hydrates and carbonate its solutions are cherry or poppy red, and acids reprecipitate it in orange yellow flocks; and in alkaline hydrates it oxidizes and disappears on standing in air, so decolotizing the solution. A mixture of purpurine and caustic soda solution with some ether yields sodic purpurate in crystals. Its basic. calcic. and almninic lakes are soluble in boiling carbonate of soda solution. Heated with zinc dust, it forms anthracene (C,411,.). Bolley claims to have changed it to alizarine by a heat of 410° Kahn applied to tubes containing it. Martin of Avignon claims that it and its chief compounds are convertible into alizarine by adding zinc dust to a sulphuric acid solution, and precipi tating in water. (See Calvert's Dyeing and Calico Printing, Loud. 1876, p. 38.) Rosen stiehl, with various reducing agents, not only purpure-xanthin, not alizarine. Prepara tion.—Identical in its extraction from madder, with alizarine purpurine more easily dis solves in solution of alum, and is thus extracted. Several methods of preparation are known. Kopp's, worked commercially at Strasburg. extracts the madder with aqueous sulphuric acid, and decomposes the glucoside of purpurine; precipitating the dye free, from alizarine, by adding 3 to 5 per cent of sulphuric acid and heating to 86' to 104° Fehr.; leaving unaltered the ruberythric acid, only changeable by a higher temperature. Sehritzenberger and Schiffert found in crude purpurine about per cent pseudo, 12-i purpurine, 121 orang• matter, and one-fifth of one per cent purpuro-xanthin; Scliunck claims these to be mixtures of separate bodies, ispecially the orange; considered as close resemblance to rubhwine. Rosenstiehl confirms this. F. de Lalande changes alizarine to purpurine by treatment in sulphuric and arsenic acid or manganese dioxide; purifies its precipitate in water, with alum; claiming to have so proved, that its siugle atomic difference of oxygen from alizarine does not come from a hydroxyl group; tl.pre fore, that purpurine is oxyalizarine. The attempted artificial formation of purpurine from alizarine sulphuric acid, by its fusion with potassic hydrate, is a, failure. See MAD DER, ante.