704 CAOUTCHOUC 



to be worthy of much notice. He soon made other trials, the India-rubber always 

 charring and hardening. 



As ordinary India-rubber is always tending to adhere, many plans had been tried 

 to prevent this. Chalk, magnesia, and sulphur had been patented in England and 

 America, but no one seems to have supposed any other change would be produced by 

 heat Mr. Goodyear proceeded to try experiments, and produced remarkable results : 

 samples of goods were shown about and sent to Europe. 



The late Mr. Brockedon, so well known for his talents and love of scientific inves- 

 tigations, had long pursued means to obtain a substitute for corks, and, after much 

 ingenuity, had devised India-rubber stoppers. As soon as all mechanical difficulties 

 were over, objections were taken to the colour of the substance. Some samples of a 

 changed rubber came into his possession, of which it was declared they would keep 

 flexible in the cold, and were found not to have an adhesive surface. These caused 

 numerous experiments, as it was recognised that a change had been effected, and 

 although Mr. Brockedon failed, yet Mr. Hancock kept on working, combining sulphur, 

 with every effect, but that of vulcanisation, as he was ignorant of the power of heat to 

 effect this change. He used melted sulphur, and produced proof of absorption, for 

 the pieces of caoutchouc were made yellow throughout ; by elevating the temperature 

 he found they became changed, the lower end of slips 'nearest the fire turning 

 black, and becoming hard and horny' (the sulphur was melted in an iron pot). 

 By these simple observations, as they now seem, Mr. Goodyear in America and Mr. 

 Hancock in England were induced to take out patents, and commence that series of 

 manufacturing applications to which there seemed no limit. The first English patent 

 was by Mr. Hancock. The general method is to incorporate sulphur with caoutchouc, 

 and submit it to heat ; if any particular form is required, the mixture is placed in 

 moulds, and takes off any delicate design that may be upon the metal mould, 

 and if these are submitted to higher degrees of heat, the substance and evolved gases 

 expand, and thus a very hard, horny, or light but very strong substance is produced, 

 called hard India-rubber, or 'vulcanite.' Mouldings, gun-stocks, combs, cabinet- 

 work, and hundreds of forms may be obtained by these curious means. The term 

 ' vulcanisation ' was given by Mr. Brockedon to this process, which seemed by the em- 

 ployment of heat and sulphur to partake of the attributes of the Vulcan of mythology. 

 For the ' change ' or ' vulcanising ' to get a yielding but permanently elastic substance, 

 steam heat is usually employed in England, but in America, ovens, with various plans 

 for producing dry heat, are generally employed. 



The articles thus made being more elastic, unaffected by heat, cold, or solvents, 

 attracted much attention, and Mr. Parkes was engaged to find out a method of pro- 

 ducing the same effects now secured by patent : all ordinary means were used and 

 given up, but he finally succeeded. The process of cold sulphuring of Mr. Parkes 

 consists in plunging the sheets or tubes of caoutchouc into a mixture of 100 parts of 

 sulphuret of carbon and 2 J parts of protochloride of sulphur, for a minute or two, and 

 then immersing them in cold water. Thus supersulphuration is prevented in conse- 

 quence of decomposing the chloride of sulphur on the surface by this immersion, 

 while the rest of the sulphur passes into the interior by absorption. Mr. Parkes pre- 

 scribes another, and perhaps a preferable process, which consists in immersing the 

 caoutchouc in a closed vessel for 3 hours, containing a solution of polysulphuret of 

 potassium indicating a density of 25 Beaume, at the temperature of 248 Fahr., then 

 washing in an alkaline solution, and lastly in pure water. A uniform impregnation 

 is thus obtained. 



In the first instance sulphur, caoutchouc, and heat were alone employed ; the tem- 

 perature and the time to which the mixtures are subjected to heat being determined 

 by practical experiments. Vulcanised rubber is not only the changed substance, 

 as produced by sulphur, but it contains metallic oxides, &c., metallic and mineral 

 substances ; and these compounds, are perhaps much better fitted for their respec- 

 tive uses than the pure sulphur and India-rubber. White lead, sulphide of 

 antimony, black lead, and other substances enter into these combinations. After 

 the early experiments with vulcanised rubber there seemed reason to believe 

 that changes slowly took place. The rubber was found to become brittle, and 

 bands stretched out broke immediately. To a great extent this has been remedied by 

 the use of lead, which seems to combine with the sulphur, for changes are believed by 

 practical men to take place with pure elastic vulcanised caoutchouc which do not 

 occur when metallic matters are duly mixed. This is a trade statement, which may 

 be true for some special uses. The brittleness may perhaps more fairly be admitted 

 to be due to inexperience, and the difficulties to meet the demands of the public for a 

 new article ; but to those whom it may most concern, we have raised this question so 

 far as to obtain the conscientious opinion of Mr. Thomas Hancock (now retired from 

 business), who considers that by the peculiar plan of vulcanising by a bath of sulphur t 



