CAOUTCHOUC. This curious sub stance is the inspissated juice or sap of several plants ; the principal supplies are from South America and Java, and are derived from the Siphouia elastiCa (Berea caoutchoue), and probably from other Eu phorbiaceous plants. It is often termed gum elastic and India-rubber. Its gen eral properties and uses are well known. Among its more recent applications are those of elastic wove fabrics, formed of caoutchouc stretched into threads and covered with cotton ; and various water proof clothing, which is made by inter posing a layer of caoutchouc between two folds of the cloth, and then forcibly unit ing them by pressure. For tins purpose the caoutchone is dissolved by coal naph tha, and in that state brushed over the surfaces which are to be united.
Caoutchoric is a compound of carbon and hydrogen; when heated it fuses, and afterwards remains viscid. When sub jected to destructive distillation at a high temperature, it yields 4-5ths of its weight of a highly inflammable and very light volatile oily liquid (hydrocarbon), which has been called camtchoueine, and which is a good solvent of the unaltered caout chouc. 'Washed sulphuric ether dissolver
eaoutchouc, and it is also soluble in sev eral essential oils ; but of these latter so lutions the greater number leave it in a sticky state on evaporation.
The trees have incisions made into them through the bark ; the milky juice exudes, is collected on clay moulds, dried in the sun, or with the smoke of a fire, which blackens it. The juice itself is a pale yellow, creamy liquid, which is mis cible in water ; it diies off into caontchoue, and loses 55 per cent. Caoutchoue is in soluble in alcohol, but is soluble (besides ether), in naphtha from coal, oils of sassa fras and lavender, and linseed oil. It melts at 248°, and burns with a bright flame and much smoke. It is not acted on by caustic potass, cold sulphuric acid, nor nitric acid, unless very concentrated. From its great elasticity it has been used in articles of dress and machinery. (See