82 



The analysis of the latex oft Hevea brasiliensis shows that it con- 

 tains : — 



Rubber \\i per cent. 



Proteid matter l?> „ 



Calcium and sodium salts 9*7 „ „ 



Resin traces 

 Water 55 to 56 per cent. 



It is slightly alkaline to litmus paper, f 



The presence of albumin, globulin, and other proteids, has been de- 

 monstrated by Green * in some other rubber-yielding latices. 



As a general rule all these substances are to be found in rubber as 

 it is at present prepared, often with others added to bring about coagu- 

 lation of the latex, and accidentally or intentionally added impurities 

 such as bark and clay. In all cases the percentage of impurities is large, 

 how large we shall see later, and when it is remembered that some 

 cause a rapid deterioration of the rubber, it is obviously much to the 

 interest of those connected with the industry that a method of prepara- 

 tion should be adopted which would minimize them or ensure their 

 absence. 



1 propose now to consider a few of the better known varieties of 

 rubber. 



Para Rubber is the product of Hevea brasiliensis, a tree which 

 thrives in many parts of the Amazon valley, British Guiana, etc. As 

 pointed out by ( 'hurchill** in his consular report, there is no danger of this 

 source of supply becoming exhausted, though this is the frequent cry of 

 companies formed for rubber-planting, usually fated for an ephemeral 

 existence. The tapping is done with considerable care by the natives, and 

 even should a district become exhausted, in a few years a fresh supply 

 of trees springs up. From the planters' point of view Brazil is hardly 

 a suitable country, for the climate is bad, it is difficult to obtain labour, 

 and the exchange is liable to endless variations. The trees have, how- 

 ever, been introduced into Ceylon, where small plantations exist, and 

 into other coloniesj. 



The method ol preparing the rubber has been so frequently des- 

 cribed that repetition is needless ; but a " translation of a valuable 

 article on rubber of the Orinoco " || has received so much atten- 

 tion of late that it requires some examination. One of its most 

 striking errors is the following : — " As the juice contains a considerable 

 quantity of water, the preparation of rubber consists essentially in 

 separating the former from the latter, which is performed by evaporat- 

 ing the water by means of a heating process or obtaining its coagula- 

 tion by certain chemical processes. Although the last system is more 

 rapid, they prefer the former, as they pretend that the rubber thus ob- 

 tained is of a superior quality — a supposition devoid of all reason." 



f " Le Caoutchouc." etc., p. 94. 



* Green, " Proc. Roy. Soc," 1886. p. 28. 



** " Kew Bulletin." 1898, p. 242. . 



t " Kew Bulletin, " 1893, p. 159. 



f| " Trinidad Bulletin, " 1893, No. 18, and 1897, p. ft 



