CAOUTCHOUC 695 



Indies, spots are frequently found of a viscid tarry-looking matter, which, when ex- 

 posed to the air, act in some manner as a ferment, and decompose the whole mass into 

 a soft substance, which is good for nothing. Were the plan of boiling the fresh juice 

 along with its own bulk of water, or a little more, adopted, a much purer article would 

 be obtained, and with incomparably less trouble and delay, than has been hitherto 

 brought into the market. 



' I find that neither of the above two samples of caoutchouc juice affords any appear- 

 ance of coagulum when mixed in any proportions with alcohol of 0-825 specific 

 gravity ; and, therefore, I infer that albumen is not a necessary constituent of the 

 juice, as Dr. Faraday inferred from his experiments published in the 21st vol. of the 

 Journal of the Eoyal Institution. 



' The odour of Mr. Sievier's sample is slightly acescent, that of Mr. Beales, which 

 is by far the richer and purer, has no disagreeable smell whatever. The taste of the 

 latter is at first bland and very slight, but eventually very bitter, from the aloetic 

 impression upon the tongue. The taste of the former is bitter from the first, in con- 

 sequence of the great excess of aloes which it contains. When the brown solution, 

 which remains in the capsule after the caoutchouc har; been separated in a spongy 

 state by ebullition from 100 grains of the richer juice, is passed through a filter and 

 evaporated, it leaves 4 grains of concrete aloes. 



' Both of these emulsive juices mix readily with water, alcohol, and pyroxylic spirit, 

 though they do not become at all clearer ; they will not mix with caoutchoucine (the 

 distilled spirit of caoutchouc), or with petroleum-naphtha, but remain at the bottom of 

 these liquids as distinct as mercury does from water. Soda caustic lye does not 

 dissolve the juice ; nitric acid (double aquafortis) converts it into a red curdy magma. 

 The filtered aloetic liquid is not affected by the nitrates of baryta and silver ; it affords 

 with oxalate of ammonia minute traces of lime.' 



The best solvent is a mixture of 100 parts of bisulphide of carbon with from 6 to 8 

 parts of anhydrous alcohol. If the alcohol be mixed with a little water a dough is 

 obtained, from which the caoutchouc may be drawn out into threads and spun. By 

 Gerard's process, gutta-percha is also soluble in the above mixtures of bisulphide of 

 carbon and alcohoL 



The sulphuration of caoutchouc, a valuable invention, is due to Mr. Charles Goodyear 

 of New York. 



Caoutchouc, according to the experiments of Dr Ure, which have been confirmed by 

 those of Dr. Faraday, contains no oxygen, as almost all other solid vegetable products 

 do, but is a compound of merely carbon and hydrogen, in the proportion, by these 

 results, of 90 carbon to 10 hydrogen, being three atoms of the former to two of the 

 latter. Dr. Faraday obtained only 87'2 per cent, of carbon. Melted caoutchouc forms 

 a very excellent chemical lute, as it adheres very readily to glass vessels, and withstands 

 the corrosive action of acid vapours. Caoutchouc is much used for effacing the traces of 

 plumbago pencils, whence it derived the name of India-rubber. It has been em- 

 ployed very extensively for making elastic bands or braces. The caoutchouc bottles 

 are skilfully cut into long spiral slips, which are stretched, and kept extended till 

 nearly deprived of their elasticity, and till they form a thread of moderate fineness. 

 This thread is put into a braid machine, and covered with a sheath of cotton, silk, 

 linen, or worsted. The clothed caoutchouc is then laid as warp in a loom, and woven 

 into an elegant riband. When woven, it is exposed upon a table to the action of a 

 hot smoothing iron, which, restoring to the caoutchouc all its primitive elasticity, the 

 riband retracts considerably in length, and the braiding corrugates equally upon the 

 caoutchouc cores. Such bands possess a remarkable elasticity, combined with any 

 desired degree of softness. Sometimes cloth is made of these braided strands of 

 caoutchouc used both as warp and as weft, which is therefore elastic in all directions. 

 When a light fabric is required, the strands of caoutchouc, either naked or braided, 

 are alternated with common warp yarns. For this mixed fabric a patent has been 

 obtained. The original manufacturer of these elastic webs was a major in the Austrian 

 service who erected a factory for them at St. Denys, near Paris. 



I. CAOUTCHOUC MANUFACTURES. 



But before entering upon these special divisions we may advert to some of the 

 steps that have created this new employment for capital, commerce, and skill, es- 

 pecially as Mr. Hancock conceives it but just to the memory of the late Mr. Macintosh, 

 to record the circumstances which led to his invention of the ' Waterproof double 

 textures,' that have been so long celebrated through the world by the name of 

 ' Macintoshes.' 



It will be recollected that on the introduction of coal-gas, the difficulties were very 

 great to purify it from matters that gave a most disagreeable odour to the gas and 



