IN D IA RUBBER MANUFACTURES. A description of this singular substance, and of the mode in which it is obtained in the East, will be found under CAOUTCHOUC. 'When the gum became known in England, its elasti city and its imperviousness to water pointed it out as a valuable material for manufactures ; and it has gradually come into very extensive use.
Before Caoutchouc can be practically ap plied, it requires to be brought from its first crude state to that of a cake, a thread, or a liquid, according to its mode of application. The crude substance is cut into shreds,washed, heated, and kneaded byrollers until it assumes a homogeneous consistency; it is then pressed into moulds, which bring it to the form of large rectangular masses. From these masses sheets are cut by machinery to any required thickness; and from these sheets threads or any of the other countless forms of the mate rial are prepared. By the use of petroleum, naphtha, oil of turpentine, or a few other liquids, caoutchouc may be dissolved ; and in that dissolved state is an admirable varnish for rendering porous substances water-proof.
As a solid substance, as a woven material (with or without any fibrous ingredient), and as a varnish, caoutchouc is now applied to countless purposes, in dress, in machinery, and in other ways. Every reader will be able to verify this assertion.
Mr. Hancock, who has probably done more than any other person to vary the modes in which caoutchouc may be employed in manu factures, took out a patent in 1845 for remov ing three inconveniences which are often pre. sented by this substance. These inconveniences are, a clammy adhesiveness ; a tendency to stiffen and harden by cold ; and a tendency to become softened or even decomposed by heat or by oil. To remove the clammy adhesive ness, Mr. Hancock brings the caoutchouc to the state of a sheet by the pressure of iron rollers, and forces into this sheet twice its weight of powdered French chalk, or silicate of magnesia, by repeated pressure. Other processes then incorporate the two substances completely; and the compound is ready to be applied to varied purposes. For some pur poses powdered black lead, or powdered dry asphalte, are used instead of the silicate.
To enable caoutehouc to resist heat, cold, air, grease, oil, and various solvents, is the purport of Mr. Hancock's Vulcanized India Rubber. This is a compound of caoutchouc and sulphur. The sulphur is either pounded and pressed into the sheets of caoutchouc in the same manner as the silicate ; or the sheets are steeped in melted sulphur until they be come thoroughly impregnated with it. The compound is then made into is or a so lutio», or thin sheets or threads, or any of the numerous forms in which it is employed. The
caoutchouc loses some of its extent of elasti city, but acquires more perfect elasticity, the longer it remains in the melted sulphur ; that is, it becomes less easily stretched, on account of its increasing toughness, but its elasticity is more intense so far as it goes. Some of the 'Vulcanised India Rubber now used is wonderfully elastic.
In 1840 Mr. Parkes patented many improve ments in the caoutchouc manufacture. One of these is a new kind of vulcanised India rubber. The change which has obtained this name is produced, according to this patent, by immersing thin sheets of caoutchouc in a so lution of chloride of sulphur or bisulphinet of carbon, heating them to a temperature of 80 Fehr., boiling them in a caustic ley, and drying. Vulcanising in the dry way, Mr. Parkes effects by kneading or pressing fine chloride of sulphur into the substance of the soft caoutchouc. Another part of the patent relates to the dyeing of caoutchouc. The fol lowing are the ingredients named, for forming the various dyeing liquids :—For black ; sul phate of copper and caustic ammonia. For green; sulphate Of copper, muriate of ammo nia, and caustic lime. For purple ; sulphates of copper and of potash, and sulphate of in digo. For merely colouring the surface, without dyeing the substance, many ingre dients may be employed, and many tints pro duced.
It would carry its beyond our limits even to name the various patents which have beet: brought out for india rubber manufactures, and the improvements suggested therein. We May however briefly glance at a few.
Mr. Lorimer, in 1848, among other novelties patented a waterproofing material, made of caoutchouc combined with oxide of copper and slaked lime acidulated with oxalic acid. Another patent in the same year was for im parting certain qualities to caoutchouc by com bining it with carbonate of magnesia. Mr. Nickells in 1840 introduced a mode of corn. bining sulphur with caoutchouc. The caout chouc is placed in what is called a masticating machine, flowers of sulphur are added, heat is applied, and a roller passes to and fro over these substances, until they are kneaded into a uniform mass. Simpson and Foster's pa tent, in the same year, was for a mode of dis solving caoutchouc by the use of bisulphuret of carbon combined with pentachloride of anti mony. Binke's patent, about the same time, was for giving permanent elasticity to caout chouc by the application of antimony and car bonate of soda. Newton's patent, in 1850, is for combining caoutchouc with gum lac, as a means of removing its odour. Notwithstanding the large use of caoutchouc, it must be admitted that Gude, Percha has lately been outstripping it in public favour.