Imagens da página
PDF
ePub
[merged small][merged small][ocr errors]

Class IV. TETRANDRIA.—Order I. MONOGYNIA.
NATURAL ORDER, STELLATÆ.-T HE MADDER TRIBE.

Fig. (a), the flower magnified; (b), the calyx; (c), the pistillum ; (d), the anther; (e), the fruit.

This species of Rubia is the Epey@o@avoy of Dioscorides. It is a perennial plant, a native of the South of Europe, the Levant, and Africa, flowering in June. It was first cultivated in this country by Gerarde, since which period its cultivation has become an object of national importance, from the immense consumption of the roots as a dye-stuff, by the calico printers and dyers.

The root of this plant is long, round, jointed, composed of succulent fibres, from which proceed numerous small thready side roots, which extend a considerable distance under the ground, and throw up many shoots, from which the plant may be propagated; the stems are procumbent, quadrangular, jointed, four or five feet in length, and covered with short hooked points, by which they adhere to the neighbouring plants for support, and subdivide into numerous branches, proceeding from the articulations; the leaves are placed in whorls, from four to six together, elliptical, pointed, rough, ciliated, and arise from the joints of the stems and branches; the flowers are small and terminal; the calyx is divided into four teeth; the corolla is of a yellow colour, campanulate, and cut at the brim into four ovate segments; the four filaments are short, and support simple erect anthers; the germen is inferior, double, supporting a slender style, dividing at the top into two globular stigmata; the germen becomes two round black berries, each containing an ovate seed.

The madder imported from Smyrna is more esteemed than the best Dutch madder, which ranks the first of that grown in Europe. The madder produced in the lower part of the Rhine is considered by Berthollet as not inferior to that of Zealand.

This is an adjective dye, but affords a permanent colour to cloth which a few days previously has been boiled for two or three hours in a solution of alum and tartar. Linen takes this dye with more difficulty than cotton. It is seldom used for silk, but is one of the most valuable dyeing drugs for a variety of purposes. It is an agent for dyeing many colours, and is therefore peculiarly adapted to the process of calico-printing, since by the use of different mordants, a variety of hues may be produced by immersion in the madder bath. One mordant in combining with it precipitates the colouring matter red, another purple, another black, and so of every possible shade from lilac to black, and from pink to deep red. If a portion of weld or quercitron be added to the madder, every shade from brown to orange inay be produced. Tin, iron, and aluminous bases, as well as other mordants, are used for this purpose, dependant on the colour required. It is a matter of doubt and speculation with chemists whether these various colours are produced by the combination of the colouring principle of madder with the different mordants, by which a chemical change takes place, or whether several colouring matters are not really contained in the substance itself, and severally precipitated or retained by the varying action of the different agents to which it may be subjected. It is, however, certain that it contains at least two distinct colouring matters, a fawn and a red, and that the admixture of the former with the latter very much injures its clearness and beauty. In consequence of this, two kinds of red are obtained from madder. The first is simply called madder red, which contains the whole of the colouring matter. The other possesses far more lustre, and is much more valued; it is called Turkey red, because first obtained from the Levant. Its superior brilliancy is imparted in consequence of the red colouring matter being alone preserved; and while the tint communicated excels in brightness, it has the additional and great advantage of extreme durability.

The manner of producing this desirable effect was for a long period of time a subject of much interest and inquiry, the process used in Turkey being enveloped in mystery. The industry of the French artisans was stimulated by the interest which their government took in the discovery. Yet attempts at imitating this beautiful dye were long fruitless, and when at length they proved successful, this success was limited to one or two dye-houses. It was only by very slow degrees that it became more diffused, and then each individual who acquired the knowledge jealously guarded his own peculiar secrets which he had introduced in the process.

In 1804 the gold medal of the Society for the encouragement of Arts, &c. was voted to Sir H. C. Englefield, for his discovery of a pigment prepared from madder. He obtained a fine lake by many different processes, and found that the colour produced from the Smyrna was of a deeper and richer tint than any prepared from the Dutch madder. In pursuing his experiments he discovered that the colouring matter might be extracted from fresh madder, and thus not only all the expenses and difficulty attendant on the process for prepared madder might be avoided, but the cost of carriage would be one fourth less than for the roots; while separated from these the colouring matter might be kept for any length of time without danger of being spoiled. A further advantage would also arise in the quantity obtained, as all the colouring matter could be extracted; while in the manner which the dyers use the roots, a very considerable part of the colour is left in the refuse matter, and consequently wasted.

Mr. Field, in his valuable work “Chromatography,” (page 179,) says-Superior red lakes are prepared from cochineal, lac, and kermes; but the best of all are those prepared from the root of the rubia tinctoria, or madder plant. Of the various red lakes the following are the principal:

1. RUBRIC, or MADDER, LAKES. These pigments are of various colours, of which we shall speak at present of the red or rose colours only; which have obtained, from their material, their hues, or their inventor, the various names of rose rubiate, rose madder, pink madder, and Field's lakes.

The pigments formerly called madder Jakes were brick-reds of dull ochrous hues; but for many years past these lakes have been prepared perfectly transparent, and literally as beautiful and pure in colour as the rose; qualities in which they are unrivalled by the lakes and carmine of cochineal. The rose colours of madder have justly been considered as supplying a desideratum, and as the most valuable acquisition of the palette in modern times, since perfectly permanent transparent reds and rose colours were previously unknown to the art of painting.

These pigments are of hues warm or cool, from pure pink to the deepest rose colour;—they afford the purest and truest carnation colours known;—from permanent tints with white lead; and their transparency renders them perfect glazing or finishing colours. They are not liable to change by the action of either light or impure air, or by mixture with other pigments; but when not thoroughly edulcorated they are, in common with all lakes, tardy dryers in oil, the best remedy for which is the addition of a small portion of japanner's gold-size; or, as they are too beautiful and require saddening for the general uses of the painter, the addition of manganese brown, cappagh brown, or of burnt umber, as was the practice of the Venetian painters in the using of lake, adds to their powers and improves their drying in oils.

Notwithstanding they are equally beautiful and durable as water-colours, they do not work therein with the entire fulness and facility of cochineal lakes: when, therefore, permanence is of no consideration, the latter may still be preferred; but in those works in which the hues and tints of nature are to be imitated with pure effect and permanence, the rose colours of madder are become indispensable, and their powers in these respects have been established by experience from the palettes of our first masters during upwards of a quarter of a century. With respect to the future, too, there is this advantage attending these pigments, that they liave naturally the peculiar quality of ultramarine, of improving in hue by time—their tendency being to their own specific prismatic red colour.

These pigments have been imitated on the Continent with various success, and in many instances by the lakes of lac, cochineal, and carthamus. The best we have seen is the laque de garance, the brightest of which was evidently tinged by the rouge of safflower, and proved inferior in durability to the genuine lake of madder. As, however, the colours of safflower, cochineal, and lac, are soluble in liquid ammonia and alkalies in general, which the true madder lakes or rubiates are not, the latter may be as easily tested by an alkali as ultramarine is by an acid; and if pure ammonia do not extract colour from a lake so tested, we may with general certainty pronounce it to be a true madder lake.

2. LIQUID RUBIATE, or Liquid Madder Lake, is a concentrated tincture of madder of the most beautiful and perfect rose colour and transparency. It is used as a water-colour only in its simple state diluted with pure water, with or without gum; it dries in oil by acting as a dryer to the oil. Mixed or ground with all other madder colours with or without gum, it forms combinations which work freely in simple water, and produce the most beautiful and permanent effects. The red of the definitive scale is of the pigments 1 and 2 combined. Liquid rubiate affords also a fine red ink, and is a durable stain which bears washing, for marking, painting, or printing on cotton or linen cloth, &c., and is peculiarly suited to the tinting of maps and charts permanently.

SENSIBLE AND CHEMICAL PROPERTIES, &c.—The roots of madder have a bitter and somewhat austere taste; the odour is not strong, but rather unpleasant; the infusion made with boiling water is of a deep reddish brown; to cold water, alcohol, and the essential oils, the roots impart a bright red colour. Both the taste and odour of madder is imparted to the watery and alcoholic infusions. The colouring matter of madder is precipitated of a brownish red, by a solution of alum; of a deep lake or blood red colour, by lime water and the alkaline carbonates; and brown, by acetate of lead. The colouring matter of madder roots appear to differ from most other substances used for the purpose of dyeing, in having the peculiar property of tinging with a red colour the milk and bones of those animals which have fed upon it; a circumstance which was first noticed by Antoninus Mizaldus, and subsequently by Mr. Belchier, who published an account of a pig and a cock, whose bones became red by eating madder mixed with their food; since which time (from various experiments that have been made) it has been ascertained, that the colouring matter affects the bones in a very short time, and that the most solid part of the bones first receives the red colour, which gradually extends through the whole osseous substance.

MEDICAL PROPERTIES AND USES.—Madder has been long regarded as a deobstruent, detergent, and diuretic, and more latterly as an emmenagogue. It has been chiefly used in jaundice, dropsy, and diseases proceeding from obstructions, particularly those of the liver and kidneys; but its efficacy in any disease scarcely warrants the encomiums that were formerly bestowed upon it. Its diuretic effects do not appear to be constant, and as an emmenagogue, its powers are neither uniform nor powerful. The roots of madder, when powdered, may be given in substance, in doses of from twenty to thirty grains three or four times a day; or in decoction, two ounces to a pint and a half of water, of which from one to three ounces may be taken three times a day.

Off. The Roots.

« AnteriorContinuar »