\IAKCI1. 1912. 



KNO\VLi:i)GE. 



Its polymerisation into dipentene (a 

 Indrocarhon present in Russian and 



A Rubber Tree, Government Plantation. Kiial 

 Lumpur. 



Swedish turpentine) is shown by tlie 

 CH;i ,XH,+CH,, 



resemblance to rubber, whereas by "synthetic rubber" 

 is meant a body chemically and physically identical w ith the 

 natural product, though prepared by artificial means. The 

 most important rtibber substitutes are obtained b\' boiling 

 linseed or other oils with sulphur, or acting on them with 

 disui[)hur dichloride, when chemical combination takes place. 

 They are used commercially for mixing with certain low 

 grade rubbers. 



The synthesis of rubber dixitles itself into two processes, 

 (ji the production of isoprcne. (ii) the polvmerisation of 

 isoprene to caoutchouc. 



.\s we have already noted, tiie second of these processes 

 takes place spontaneously, but it ma\- be facilitated by 

 means of concentrated hydrochloric acid, or by saturation 

 ot the isoprene with oxygen or ozone. The latter process 

 is as follows* : — The isoprene is saturated with o.wgen or 

 ozone, allowing twenty volumes of oxvgen to one volume 

 of the hvdrocarbon. and spreading the treatment over about 

 six hours. The liquid must be kept cool during the process. 

 It is then placed in an autoclave and heated to 100"C, 

 until it is converted into a viscous mass. The resulting 

 caoutchouc is dried by evaporation, or precipitated by means 

 of alcohol. A solution of isoprene in benzene may be 

 used instead of the pure substance. The heating is not 

 alisoluteh' necessary, though advisable. 



.■\nother method is to act on the iso])rene with one of 

 the alkali metals, (e-jt,'.. sodium or potassium) or an allo\- of 

 one of these metals. + 



To turn to the preparation of isoprene. The following 

 method^ is interesting scientificalK", because it is a true 

 s\'nthesis of isoprene. in whicli it is built up from simpler 



wing equation — 



CH/ 



X-CH 



CH,= 

 2 molecules 



C-CH:, 



CH, 



soprene. 

 •CH.. 



CH,^ 



CH.. 

 X-CH X 



~"CHo-CH 



1 molecule Dipentene. 



and it is presumably by some similar, thou 

 cated, reaction (that is, involving mot 

 isoprene) that it is changed into rubber. 



CH:, 



more compli- 

 molecules of 



II. Synthetic Rrr.iuiK. 



Some of the greatest achievements of chemical science 

 in recent times have been in the direction of the synthesis 

 from inorganic materials of \arious important products of 

 the vegetable and animal world. Since the day in \H2S 

 when Wohler performed the first synthesis of this nature — 

 the preparation of urea from ammonium cyanate — an 

 inmiensc number of animal and vegetable products havi 

 been artificial!}- prepared in the chemical laboratory, amongst 

 which caoutchouc must now be included. 



Synthetic rubber must not be confused with the various 

 rubber substitutes and imitations of rubber wliicli ha\e from 

 time to time been placed upon the market. Such rubber 

 substitutes and imitations are bodies with merely a superficial 



Trees, Govcrm 

 Kuala. Lumpur. 



English Patent, 1910, Xo. 14.041. A. Heiuemann. liiiprovciiiciils relating to the Polymerisation of Isoprene. 



i English Patent, 1910. No. 24,790. F. K. Matthews and E. H. Strange. Synthetic Caoutchouc. 

 English Patent, 1907, No. 21.772. .\. Ileinemaim. A Process for the Synthetic Production of India-rubber. 



