106 PARA RUBBER. 



may be obtained fairly pure by making a benzene solution, allowing 

 the insoluble matter to settle out, and subsequently precipitating the 

 rubber from the clear solution by the addition of alcohol. 



Resinous and Sugary Substances. 



The resins, gums, and oily substances are present in varying quan- 

 tities. Generally the latex from young trees, branches, and twigs 

 contains a large proportion of these substances ; they may occur as 

 globules suspended in the latex or in solution. In the ordinary pro- 

 cesses of coagulation the greater part of the resin becomes part and 

 parcel of the rubber, and the extraction from the latter by the manu- 

 facturers in Europe is a difficult and tedious task. 



The sugars are rarely present in large proportions, and a maximum 

 of 0"5 per cent, may be taken as correct. The yare known as inosite.* 

 bornesite, matezite, and dambinite, and are dissolved in the liquid in 

 which the globules of caoutchouc and resins are suspended, and in the 

 washing of the freshly- coagulated rubber are generally removed. 



The Proteids. 



The proteid or albuminous matter, about which more will be said, 

 varies from 19 to 2" 7 per cent, of the fresh latex, or approximately 3 

 to 4 per cent, of the dried coagulated product. This is a very high 

 proportion, but from the analyses quoted above no other con- 

 clusion can be drawn. It is believed that this proteid matter is of a 

 complex nature, and, alone or with the gums and sugars, is respons- 

 ible for the development of bacteria on the finished product, which 

 lead to putrefaction or " tackiness. " The use of formaldehyde in 

 connection with the elimination of the proteid matter has been con- 

 sidered when dealing with coagulation. 



When the rubber is prepared by simple coagulation the insoluble 

 proteids become a part of the rubber, but if a centrifugal method is 

 adopted, and the freshly-coagulated material frequently and well 

 washed, pressed and dried quickly, a considerable amount may be 

 removed or rendered less harmful. In the purification of rubber this 

 subject will be dealt with. It is believed that the removal of the pro- 

 teids from the commercial rubber, though so much desired, is almost 

 impossible, and in the perfecting of mechanical processes and the use 

 of antiseptic reagents for dealing with the proteids in the latex as it 

 comes from the tree lies a considerable amount of important profit- 

 able work for the planters in the Tropics. 



The mineral matter occurring in suspension and solution in the 

 latex and the various insoluble compounds indicated in the analyses 

 previously quoted, may be regarded as impurities of minor import- 

 ance , and can be better dealt with in the sections concerned with the 

 components of commercial rubber and the purification processes. 



Webor, /. c, p. 2. 



