78. Turmeric is enumerated by Dr Bancroft among the vegetable colouring matters which he calls substan tive; though the little durability which it possesses, as a dye, scarcely entitles it to that epithet. Turmeric is the root of the curcuma, of which there are two species, the rotunda and the Tonga. The former is chiefly culti vated for the use of the dyer. Turmeric is of a very rich colour, and surpasses every other yellow colouring matter in beauty ; but it has a very slight attraction either to stuffs, or the mordants which are usually em ployed to give fixity to colours. The root must he re duced to powder to be fit for use. It is sometimes em ployed to give the yellows made with weld a golden cast, and to communicate an orange tint to scarlet ; but its effects soon disappear.
79. Mr Bayley, who, in 1793, was extensively en gaged in dyeing silk handkerchiefs to imitate those of India, informed Dr Bancroft that the yellow spots were produced solely by a tincture of turmeric, made by di gesting six pounds of the powder of turmeric in a gallon of malt spirits, and afterwards by a press separating three quarts of a rich tincture, which cost about four shillings the quart. The tincture was applied topically, and with out thickening, to the spots of the silk handkerchiefs, which in the dyeing had been reserved white by the usual means. Dr Bancroft found that a tincture of tur meric so obtained, and gummed, when applied topically to calico, produced a beautiful yellow, which, by wash ing with soap, became red ; but being well tinted, and exposed to the atmosphere, it recovered its former co lour, and retained it after several washings. See Ban croft, vol. i. p. 278.
80. The seeds of the bixa orellana, which grows spon taneously in different parts of Guiana, are covered with a reddish pulp, which is collected and exported to dif ferent parts of Europe under the names of annotta, ar notta, and roucon. This substance is sometimes em ployed for dyeing silk, and occasionally for cotton ; but in either cast it adheres but slightly to the stuff. It par takes so much of a resinous nature, that it is very im perfectly dissolved in water. It is therefore usual to employ at least its own weight of potash to increase its solubility, and afterwards to immerse, in the solution, the ilk or tton to be dyed, w ithout any mordant. °lout of the annutta thus dissol%ed may be rendered of arams shades of I dim., by destroying, by means of chile acid, the eflects of the In dye-houses, w here mu h annetta is conginied, it is put into a copper c ullruder, having veiy small holes, (being pi cviously reduetd to a state of minute v ision,) and the whole immersed in a copper filled w ith tepid water. The an
notta is stilled and diffused by a stick in the form of a pestle, and passes into the bath through the holes of the cullendt r. strainer is then filled with ashes from the dregs of wine, I% hich is treated in the same man ner; after Which the bath is well stirred, and made to boil up two or three times, w hen the boiling is stopped by throwing in cold water. When the bath is not suffi ciently alkalized, it produces a brick or tile colour; in which case an additional quantity is applied, it is made to boil up. and the boiling stopped as before with cold water. (Chuptal.) In Britain, annotta is scarcely em ployed for any other purpose than in giving a yellowish orange tint to cheese.
81. Carthamus, or bastard saffron, (carthanius audio rius,)of which the flower only is useful in dyeing, is an annual plant, cultivated in the southern parts of Europe, Egypt, and the Levant. The dower of carthamus af fords two colouring matters, one of which is soluble in water, and yields an inferior yellow ; the other is resin ous, and obtained by the action of the fixed alkalies. The latter alone is valuable, as it furnishes a red of greater delicacy and beauty than can be procured from any other colouring matter, though of but little dura bility.
82. The colour is obtained by tying up the flowers in a linen bag, and then subjecting them to maceration and pressure,in clear running water, until all the yellow co louring matter which they contain is dissolved, and wash ed away. After this has been done, the flowers are again macerated in a solution of pure soda, just sufficient to dissolve aml extract the resinous colouring matter, which is separated by draining, and the repeated effusion of portions of water, until it is wholly dissolved and carried off. A solution of the colouring matter being thus ob tained, the soda is neutralized by an acid; the citric is usually preferred, and it is thought to answer the pur best, when it is in the state in which it exists in lemons, or limes beginning to spoil. Next to the citric acid, some have recommended that of tamarinds and tar tar; though Bergman prefers the sulphuric, if it be not used in excess. Scheirer affirms that the acid juice of the mountain ash produces a better, and more durable colour than even the citric acid. The expressed juice, after being allowed to ferment, is bottled up, and be comes fitter for use the longer it is kept.