The tree is reckoned to be of proper age when its trunk is about a foot in diameter. It is then cut down, and the whole of the woody part, with the exception of the smaller branches and the bark, is chopped into chips. Some accounts state that only the darker heartwood is thus used. The chips are then placed with water in earthen jars, a series of which is arranged over a mud-built fireplace, usually in the open air. Here the water is made to boil, the liquor as it becomes thick and strong being decanted into another vessel, in which the evaporation is continued until the extract is sufficiently inspissated, when it is poured into moulds made of clay, or of leaves pinned together in the shape of cups, or in some districts on to a mat covered with the ashes of cow-dung, the drying in each case being completed by exposure to the sun and air. The product is a dark brown extract, which is the usual form in which cutch is known in Europe.
In Kumaon in the north of India,[934] a slight modification of the process affords a drug of very different appearance. Instead of evaporating the decoction to the condition of an extract, the inspissation is stopped at a certain point and the liquor allowed to cool, “coagulate,” and crystallize over twigs and leaves thrown into the pots for the purpose. How this drug is finished off we do not exactly know, but we are told that by this process there is obtained from each pot about 2 lb. of “Kath” or catechu, of an ashy whitish appearance, which is quite in accordance with the specimens we have received and of which we shall speak further on.
In Burma the manufacture and export of cutch form, next to the sale of timber, the most important item of forest revenue. According to a report by the Commissioner of the Prome Division, the trade returns of 1869-70 show that the quantity of cutch exported from the province during the year was 10,782 tons, valued at £193,602, of which nearly one-half was the produce of manufactories situated in the British territory. Vast quantities of the wood are consumed as fuel, especially for the steamers on the Irrawadi.[935]
Description—Cutch is imported in mats, bags, or boxes. It is a dark brown, extractiform substance, hard and brittle on the surface of the mass, but soft and tenacious within, at least when newly imported. The large leaf of Dipterocarpus tuberculatus Roxb., the Ein or Engben of the Burmese, is often placed outside the blocks of extract.
Cutch when dry breaks easily, showing a shining but bubbly and slightly granular fracture. When it is soft and is pulled out into a thin film, it is seen to be translucent, granular and of a bright orange-brown. When further moistened and examined under the microscope, it exhibits an abundance of minute acicular crystals, precisely as seen in gambier. We have observed the same in numerous samples of the dry drug when rendered pulpy by the addition of water, or moistened with glycerin and viewed by polarized light.
The pale cutch referred to as manufactured in the north of India, is in the form of irregular fragments of a cake an inch or more thick, which has a laminated structure and appears to have been deposited in a round-bottomed vessel. It is a porous, opaque, earthly-looking substance of a pale pinkish-brown, light, and easily broken. Under the microscope it is seen to be a mass of needle-shaped crystals exactly like gambier, with which in all essential points it corresponds. We have received from India the same kind of cutch made into little round cakes like lozenges, with apparently no addition. The taste of cutch is astringent, followed by a sensation of sweetness by no means disagreeable.
Chemical Composition—Extractiform cutch, such as that of Pegu, which is the only sort common in Europe, when immersed in cold water turns whitish, softens and disintegrates, a small proportion of it dissolving and forming a deep brown solution. The insoluble part is Catechin in minute acicular crystals. If a little of the thick chocolate-like liquid made by macerating cutch in water, is heated to the boiling point, it is rendered quite transparent (mechanical impurities being absent), but becomes turbid on cooling. Ferric chloride forms with this solution a dark green precipitate, immediately changing to purple if common water or a trace of free alkali be used.
Ether extracts from cutch, catechin. This substance has been investigated by many chemists, but as yet with discrepant results. It agrees, according to Etti (1877), with the formula C₁₉H₁₈O₈, when dried at 80° C. By gently heating catechin, Catechu-tannic acid, C₃₈H₃₄O₁₅, is produced:
2(C₁₉H₁₈O₈)-OH₂ = C₃₆H₃₄O₁₅.
This is an undoubted acid, readily soluble in water, of decidedly tanning properties, precipitating also the alkaloids and albumin. Catechu-tannic acid being the first anhydride of catechin, there are several more substances of that class; one of them is called Catechuretin. This blackish brown almost insoluble substance is obtained by heating catechin with concentrated hydrochloric acid at 180°: