GUTTA PERCHA, per'ka, a substance which has been known generally and used in Western countries only since about 1845, though travelers and residents in the East were ac quainted with it long before, and had seen various articles made of it, but without knowing the nature of the material. The commercial article is made from the inspissated milky juice of several large trees belonging to the order Sapotacece, the principal being /sonandra gutta, and is obtained by felling the large and old trees, cutting off rings of bark at intervals along the stem, collecting the juice which issues, and con centrating by evaporation, if necessary. The re sult of this terribly wasteful process is, that the gutta percha tree has been exterminated from various districts in which it was formerly abundant. The tree is found in the Malayan Peninsula, and in some of the neighboring islands, in great numbers and of very large size; hut if these trees be also cut down, instead of the juice being tapped by incisions (a method which has now come into use), gutta percha will become one of the rarest of substances.
The crude substance is gray or reddish, and is mixed with fragments of bark, leaves and other impurities, from which it is separated by washing with cold and then with warm water. This softens the gutta percha, and the impurities can be easily picked out. When pure it has a brown color ; at the ordinary temperature it is hard and tough, and in not too thick pieces is flexible like leather. It is elastic only to a very slight extent, and cannot be beaten out. It has little or no adhesion for other bodies, but its own cohesiveness is remarkable, a thin strip of it hearing a very considerable weight. When warmed it gradually softens and then can be drawn into fine fibres, rolled into sheets or molded. For the latter purpose it is admirably adapted, as when warm and soft it takes the finest impressions, which it retains after it has become cold and hard. When heated to a suf ficiently high temperature in the air it catches fire, and burns with a bright flame; heated in close vessels it gives off oily hydrocarbons and an acid liquor, so that gutta percha seems to consist mainly of carbon and hydrogen, with some oxygen, while nitrogen is absent, or pres ent only in very minute quantities. Attempts
have been made to resolve gutta percha into proximate constituents, and accordingly three substances extracted from it have been de scribed. These are named respectively gutta, which is the chief constituent, and when pure is white and opaque; alban, a white oxygenated crystalline substance; and fluavil, also oxygen ated, and of a yellow color. These two are said to be formed from the first by oxidation, but there is a considerable diversity of opinion on the nature of these bodies. Ordinary gutta percha is insoluble in water, partially in alcohol and ether, readily and completely in chloroform, turpentine, benzol, bisulphide of carbon and naphtha. It is also dissolved to a slight ex tent by oils. It is not attacked by solutions of alkalis, nor by hydrofluoric acid; but it is acted on by sulphuric, nitric and hydrochloric acids—being darkened in color, oxidized, ren dered brittle or altogether disintegrated—and by chlorine, which transforms it into a white substance like ivory. It is also affected by the oxygen of the air, especially in light, becoming brittle, resinous and acid; it combines with sul phur and, like caoutchouc, can be vulcanized, being then often popularly miscalled hard rub ber. It may also be mixed with caoutchouc in a soft, elastic composition. Gutta percha is employed for a great variety of purposes, es pecially for insulating electric wires, being in valuable for submarine telegraph cables because it is not affected by water, is very pliant and forms a uniform and close-fitting coating to the wires. It is much prized for making certain kinds of surgical instruments, and in sheets for surgical dressing, and is used for making water pipes and tubes of various kinds, hose, buttons, dental plates, golf ball covers, overshoes, buckets, picture-frames and many other articles in general use. The United States importation and consumption was about 1,600 tons in 1916, and the quantity tends to increase. Consult Pearson, 'Crude Rubber and Compound In gredients' (1909) ; McIntosh, Rubber and Gutta Percha' (1910).