GUTTA PERCHA, the name applied to the evaporated milky fluid or latex furnished by several trees chiefly found in the islands of the Malay Archipelago.
The best gutta percha of Malaya was chiefly derived from two trees belonging to the family Sapotaceae. They are Palaquium Gutta, now no longer cultivated and P. oblongi f olio. Allied trees of the same genus and of the same family yield similar but usually inferior products. Among them may be mentioned species of Payena.
Gutta percha trees often attain a height of 7o to Iooft. and the trunk has a diameter of from 2 to 3 feet. They are stated to be mature when about thirty years old. The leaves of Palaquium, which are obovate-lanceolate, with a distinct pointed apex, occur in clusters at the end of the branches, and are bright green and smooth on the upper surface but on the lower surface are yellow ish-brown and covered with silky hairs. The leaves are usually about 6in. long and about sin. wide at the centre. The flowers are white, and the seeds are contained in an ovoid berry about tin. long.
The gutta percha tree is almost entirely confined to the Malay Peninsula and its immediate neighbourhood. It includes a region within 6 degrees north and south of the equator and 93°-119° longitude, where the temperature ranges from 66° to 9o° F and the atmosphere is exceedingly moist. The trees may be grown from seeds or from cuttings.
The gutta is furnished by the greyish milky fluid, the latex, chiefly secreted in cylindrical vessels or cells in the cortex. Latex also occurs in the leaves of the tree and may be removed from the powdered leaves by the use of appropriate solvents, but the process is not practicable commer cially. The latex flows slowly where an incision is made through the bark, but not nearly so freely as the india-rubber latex. On this account the Malays usually fell the tree to collect the latex, which is done by chopping off the branches and removing circles of the bark, forming cylindrical channels about an inch wide at various points about a foot apart down the trunk. The latex ex udes and fills these channels, from which it is removed and con verted into gutta by boiling in open vessels over wood fires. The work is usually carried on in the wet season when the latex is more fluid and more abundant. Sometimes when the latex is thick water is added before boiling. The best results are said to be ob tained from mature trees which furnish about 2 to 31b. of gutta.
The Chinese and Malays appear to have been acquainted with the characteristic property of gutta percha of softening in warm water and of regaining its hardness when cold, but this plastic property seems to have been utilized only for ornamental pur poses, the construction of walking-sticks, of knife handles and whips, etc. The brothers Tradescant brought samples of the curious material to Europe about the middle of the 17th century.
Gutta percha appears in com merce in the form of blocks or cakes of a dirty greyish appear ance, often exhibiting a reddish tinge, and just soft enough to be indented by the nail. It is subject to considerable adulteration. It is solid, fibrous in texture, hard and inelastic, but not brittle at ordinary temperature, becomes plastic when immersed in hot water or otherwise raised to a temperature of about 65°-66° C — in the case of gutta of the first quality, the temperature of soften ing being dependent on the quality of the gutta employed. In this condition it can be 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 india-rubber or caoutchouc, which does not become plastic and unlike gutta percha is elastic. This property of softening on heating and solidifying when cooled again, without change in its original properties, enables gutta percha to be worked into various forms, rolled into sheets or drawn into ropes. The specific gravity of the best gutta percha lies between 0.96 and 1. Gutta percha is dissolved by the liquids which dissolve rubber such as carbon disulphide and chloroform, and light petroleum when hot. Gutta percha is not affected by alkaline solutions or by dilute acids. Strong sulphuric acid chars it when warm, and nitric acid effects complete oxidation. When exposed to air and light, gutta percha rapidly deteriorates, oxygen being absorbed, producing a brittle resinous material.
Chemically, gutta percha is a mix ture of several constituents. The proportions in the crude material are not constant. For electrical purposes it should have a high insulating power and dielectric strength and a low inductive capacity; the possession of these properties is influenced by the resinous constituents present.
The principal constituent of the crude material is a hydro carbon of the empirical formula
It is therefore isomeric with the hydrocarbon of caoutchouc. Accompanying this are at least two oxygenated resinous constituents—albanes and fluavils which can be separated from the gutta by solvents. Pure gutta is not dissolved by ether and light petroleum in the 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 percha. When distilled at a high temperature, gutta percha like india-rubber is resolved into a mixture of simpler hydro carbons, isoprene
and hydrocarbons of higher boiling point containing C10H16 and C30H48. Alban has been described as a mixture of resins, white in colour and soluble in hot alcohol. Fluavil is a yellow amorphous resin which dissolves in cold alcohol.
The imports of gutta percha and balata into the United Kingdom for home consumption in recent years have been in centals of 100 lb., as follows: 1925 . . 96,300 1926 . . 74,700 1927 . . 42,000 The fall in imports shown in these figures was continued in 1928.
