Source, Etc

Guttapercha is obtained from the latex of several species of Palaquium and Payena (N.O. Sapotaceoe), the principal being P. oblongifolium, Burck, P. borneense, Burck, P. Leerii, Burck, and P. Treubii, Burck, all of which are stately trees indigenous to the Malay Archipelago. They contain in the bast, as well as in the cortical parenchyma of the stem, extending into the mesophyll of the leaves, numerous superposed, elongated laticiferous cells which are filled with a granular latex. It is this latex that forms, when properly prepared, guttapercha. To that end the trees with a trunk about 30 cm. in diameter are felled, the branches stripped off, and transverse or oblique channels cut in the bark. Into these the latex is discharged, and in them it coagulates. This coagulation is apparently due to the coagulation of an albumin in the latex by which the separate particles of guttapercha are entangled and retained. The coagulated latex is then scraped from the incision, kneaded under hot water to free it from accidental impurities, beaten with mallets, and finally made into cakes which are bought up by Chinese merchants.

At present Sumatra yields the bulk of commercial guttapercha, but the destructive and wasteful method of collection has led to numerous endeavours to cultivate the trees and obtain from them the guttapercha by a more rational method. These endeavours have met with some success. Burck has shown that by making V-shaped incisions in the living tree large quantities of guttapercha can be obtained, and that the tapping can be continued for three or four years without apparent injury to the tree. It has also been found that the leaves contain more guttapercha than the stem-bark, and that it can be extracted by boiling the dried and crushed leaves with a suitable solvent, such as toluene or petroleum spirit; from the latter solution the pure guttapercha is deposited on cooling (Obach's process). Not only could the trees be preserved by this means, but the stools of trees that have already been felled send up shoots, the leaves of which could be utilised, although the stems are too young to fell. The guttapercha obtained by this means is, however, not equal to that produced by incision, and the process has not yet established itself.

The yield by felling has been variously computed at about 300 to 600 gm. from each tree, whereas by tapping 1,400 gm. has been obtained annually; the leaves are said to yield 10 per cent, of their weight.

Description

Crude guttapercha occurs in commerce in lumps or blocks of very variable, often large size, of a brown or a greyish brown colour externally, reddish yellow or reddish grey internally, and of laminated or fibrous nature. It has (especially when rubbed), an odour that is not disagreeable and it is flexible though scarcely elastic. It often contains mechanical impurities, from which it is freed by slicing and washing it and pressing it whilst plastic through wire gauze, or by softening in hot water and rolling into strips; these are then torn by machinery into shreds and the shreds kneaded into dark-brown lumps (purified guttapercha).

White guttapercha is prepared by dissolving purified guttapercha in chloroform, decolorising the solution with charcoal, filtering, and precipitating with alcohol.

Purified guttapercha is firm, tough, and flexible, but scarcely elastic; it can be cut easily with a knife, and at a temperature of 45°-60° it softens and can be rolled or drawn. It is soluble in chloroform and carbon disulphide in the cold; turpentine and benzene dissolve it when warmed, alcohol and ether only partially, whilst caustic alkalies and dilute acids have no action upon it. It is a very bad conductor of heat and electricity, and upon the latter fact depends its extensive use as an insulator.

Constituents

The principal constituent of guttapercha is a hydrocarbon, gutta, C30H48; with this are associated several crystalline substances which have been grouped into three series, viz. albans, fluavils, and albanans. Guttapercha also contains tannin, salts, substances resembling sugar, and an unstable substance, guttan.

Gutta is white when pure, and has been obtained in minute crystals; on exposure to the air it gradually assumes a reddish colour.

The albans are soluble in boiling alcohol, but not in cold; they are crystalline and are distinguished by the prefixes α,β,γ, etc.; they yield by hydrolysis with alcoholic potash the corresponding alcohol, albaresinol, together with cinnamic acid.

The fluavils are soluble in cold alcohol; they are also crystalline, are similarly distinguished, and yield an alcohol and cinnamic acid when saponified.

The albanans are insoluble both in cold and hot alcohol.

As the albans, etc, from different varieties of guttapercha are not identical, these substances are further distinguished by a prefix indicating their source; thus those obtained from commercial (Sumatra) guttapercha are termed ' sum-albans,' ' sumafluavils,' etc.

The quality of commercial guttapercha is judged by exhausting with ether or petroleum spirit and determining the resins (albans, fluavils, etc.) which dissolve, then removing the gutta with chloroform, and weighing the insoluble residue.

Uses

Apart from the varied technical uses of guttapercha a solution of that substance in chloroform is used to form a protective covering on the skin or as a means of applying various remedies.

Allied Drug

Balata is a similar substance obtained from Mimusops globosa, Gaertner, by tapping and coagulating the latex either by standing (sheet balata) or by boiling (block balata); it closely resembles guttapercha both in physical characters and chemical composition.