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GUTTA PERCHA

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Originally appearing in Volume V12, Page 744 of the 1911 Encyclopedia Britannica.
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GUTTA PERCHA , the name applied to the evaporated milky fluid or latex furnished by several trees chiefly found in the islands of the See also:Malay See also:Archipelago. The name is derived from two Malay words, getah meaning See also:gum, and pertja being the name of the See also:tree—probably a Bassia—from which the gum was (erroneously) supposed to be obtained. Botanical Origin and See also:Distribution.—The actual tree is known to the See also:Malays as taban, and the product as getah taban. The best gutta percha of Malaya is chiefly derived from two trees, and is known as getah taban merah (red) or getah taban sutra (silky). The trees in question, which belong to the natural See also:order Sapotaceae, have now been definitely identified, the first as Dichopsis gutta (See also:Bentham and See also:Hooker), otherwise Isonandra gutta (Hooker) or Palaquium gutta (Burck), and the second as Dichopsis oblongifolia (Burck). Allied trees of the same genus and of .the same natural order yield similar but usually inferior products. Among them may be mentioned See also:species of Payena (getah soondie). Gutta percha trees often attain a height of 70 to See also:loo ft. and the See also:trunk has a See also:diameter of from 2 to 3 ft. They are stated to be mature when about See also:thirty years old. The leaves of Dichopsis, which are obovate-lanceolate, with a distinct pointed See also:apex, occur in clusters at the end of the branches, and are See also:bright See also:green and smooth on the upper See also:surface but on the See also:lower surface are yellowish-See also:brown and covered with silky hairs. The leaves are usually about 6 in. See also:long and about 2 in. wide at the centre. The See also:flowers are See also:white, and the seeds are contained in an ovoid See also:berry about x in. long.

The See also:

geographical distribution of the gutta percha tree is almost entirely confined to the Malay See also:Peninsula and its immediate neighbourhood. It includes a region within 6 degrees See also:north and See also:south of the See also:equator and 93°–119° See also:longitude, where the temperature ranges from 66° to 900 F. and the See also:atmosphere is exceedingly moist. The trees may be grown from seeds or from cuttings. Some planting has taken See also:place in Malaya, but little has so far 'been done to acclimatize the plant in other regions. See also:Recent See also:information seems to point to the possibility of growing the tree in See also:Ceylon and on the See also:west See also:coast of See also:Africa. Preparation of Gutla Percha.—The gutta is furnished by the greyish milky fluid known as the latex, which is chiefly secreted in cylindrical vessels or cells situated in the cortex, that is, between the bark and the See also:wood (or cambium). Latex also gutta percha of various grades of quality but also other inferior products sold under the name of gutta percha, some of which are referred to below under the See also:head of substitutes. The value of gutta percha cannot therefore be correctly gauged from the value of the imports. In the ten years 1896—1906 the best qualities of gutta percha fetched from 4s. to about 7s. per lb. Gutta percha, however, is used for few and See also:special purposes, and there is no See also:free See also:market, the See also:price being chiefly a See also:matter of arrangement between the See also:chief producers and consumers. Characters and Properties.—Gutta percha appears in See also:commerce in the See also:form of blocks or cakes of a dirty greyish See also:appearance, often exhibiting a reddish tinge, and just soft enough to be indented by the See also:nail. It is subject to considerable See also:adulteration, various materials, such as coco-See also:nut oil, being added by the Malays to improve its appearance.

The solid, which is fibrous in texture, hard and inelastic but not brittle at See also:

ordinary temperature, becomes plastic when immersed in hot See also:water or if otherwise raised to a temperature of about 65° -66° C. in the See also:case of gutta of the first quality, the temperature of softening being dependent on the quality of the gutta employed. In this See also:condition it can be See also:drawn out into threads, but is still inelastic. On cooling again the gutta resumes its hardness without becoming brittle. In this respect gutta percha differs from See also:india-See also:rubber or caoutchouc, which does not become plastic and unlike gutta percha is elastic. This See also:property of softening on See also:heating and solidifying when cooled again, without See also:change in its See also:original properties, enables gutta percha to be worked into various forms, rolled into sheets or drawn into See also:ropes. The specific gravity of the best gutta percha lies between 0.96 and 1. Gutta percha is not dissolved by most liquids, although some remove resinous constituents; the best solvents are oil of See also:turpentine, See also:coal-See also:tar oil,See also:carbon bisulphide and See also:chloroform, and See also:light See also:petroleum when hot. Gutta percha is not affected by alkaline solutions or by dilute acids. Strong sulphuric See also:acid chars it when warm, and nitric acid effects See also:complete oxidation. When exposed to See also:air and light, gutta percha rapidly deteriorates, See also:oxygen being absorbed, producing a brittle resinous material. Chemical See also:Composition.—Chemically, gutta percha is not a single substance but a mixture of several constituents. As the proportions of these constituents in the crude material are not See also:constant, the properties of gutta percha are subject to variation.

For See also:

electrical purposes it should havea high insulating See also:power and See also:dielectric strength and a See also:low inductive capacity; the See also:possession of these properties is influenced by the resinous constituents See also:present. The See also:principal constituent of the crude material is the pure gutta, a See also:hydrocarbon of the empirical See also:formula CioH16• It is therefore isomeric with the hydrocarbon of caoutchouc and with that of oil of turpentine. Accompanying this are at least two oxygenated resinous constituents—albane C1oH16O and fluavil C2oH320—which can be separated from the pure gutta by the use of solvents. Pure gutta is not dissolved by See also:ether and light petroleum in the See also:cold, whereas the resinous constituents are removed by these liquids. The true gutta exhibits in an enhanced degree the valuable properties of gutta percha, and the commercial value of the raw material is frequently determined by ascertaining the proportion of true gutta present, the higher the proportion of this the more valuable is the gutta percha. The following are the results of analyses of gutta percha from trees of the genus Dichopsis or Palaquium: Gutta See also:Resin per cent. per cent. Dichopsis (or Palaquium) oblongifolia 88.8 11.2 „ gutta 82.0 18•o „ polyantha 49.3 50'7 pustulata . 47'8 52.2 Maingayi . 24.4 75.6 The hydrocarbon of gutta percha, gutta, is closely related in chemical constitution to caoutchouc. When distilled at a high temperature both are resolved into a mixture of two simpler hydro-carbons, isoprene (Colds) and caoutchoucine or dipentene (Cloths), and the latter by further heating can be resolved into isoprene, a hydrocarbon of known constitution which has been produced synthetically and spontaneously reverts to caoutchouc. The precise relationship of isoprene to gutta has not been ascertained, but recently Harries has further elucidated the connexion between gutta and caoutchouc by showing that under the See also:action of See also:ozone both break up into laevulinic aldehyde and See also:hydrogen peroxide, but differ in the proportions of these products they furnish. The two materials must therefore be regarded as very closely related in chemical constitution.

Like caoutchouc, gutta percha is able to combine with See also:

sulphur, and this vulcanized product has found some commercial applications. Manufacture of Gutta Percha.—Among the earliest See also:patents taken out for the manufacture of gutta percha were those of See also:Charles See also:Hancock, the first of which is dated 1843. Before being used for technical purposes the raw gutta percha is cleaned by machinery whilst in the plastic See also:state. The chopped orsliced material is washed by See also:mechanical means in hot water and forced through a'See also:sieve or strainer of See also:fine See also:wire See also:gauze to remove dirt. It is then kneaded or " masticated " by machinery to remove the enclosed water, and is finally transferred whilst still hot and plastic to the See also:rolling-See also:machine, from which it emerges in sheets of different thickness. Sometimes chemical treatment of the crude gutta percha is resorted to for the purpose of removing the resinous constituents by the action of alkaline solutions or of light petroleum. Substitutes for Gutta Percha.—For some purposes natural and artificial substitutes for gutta percha have been employed. The similar products furnished by other See also:plants than those which yield gutta percha are among the more important of the natural substitutes, of which the material known as "balata " or " Surinam gutta percha," is the most valuable. This is derived from a tree, Mimusops balata (See also:bullet tree), belonging to the same natural order as gutta percha trees, viz. Sapotaceae. It is a large tree, growing to a height of 8o to 10o ft. or more, which occurs in the West Indies, in South See also:America, and is especially abundant in Dutch and See also:British See also:Guiana. The latex which furnishes balata is secreted in the cortex between the bark and wood of the tree.

As the latex flows freely the trees are tapped by making incisions in the same See also:

fashion as in india-rubber trees, and the balata is obtained by evaporating the milky fluid. Crude balata varies in composition. It usually contains nearly equal proportions of resin and true gutta. The latter appears to be identical with the chief constituent of gutta percha. The properties of balata correspond with its composition, and it may therefore be classed as an inferior gutta percha. Galata fetches from Is. 6d. to 2s. 8d. per lb. Among the inferior substitutes for gutta percha may be mentioned the evaporated latices derived from Butyrospermum See also:Park ii (sheabutter tree of West Africa or karite of the See also:Sudan), Calotropis gigantea (Madar tree of India), and Dyera costulata of Malaya and See also:Borneo, which furnishes the material known as " Pontianac.” All these contain a small amount of gutta-like material associated with large quantities of resinous and other constituents. They fetch only a few pence per lb, and are utilized for waterproofing purposes. Various artificial substitutes for gutta percha have been invented chiefly for use as insulating materials. These often consist of mixtures of See also:bitumen with See also:linseed and other See also:oils, resins, &c., in some cases incorporated with inferior grades of gutta percha.

For further information respecting gutta percha, and for figures of the trees, the following See also:

works may be consulted: Jumelle, See also:Les Plantes a caoutchouc et a gutta (See also:Paris, See also:Challamel, 1903) ; Obach, " Cantor Lectures on Gutta Percha,” See also:Journal of the Society of Arts, 1898. (W. R.

End of Article: GUTTA PERCHA

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