THE ANTISEPTICISATION OF RUBBER. I2Q 



CREOSOTING THE LATEX. 



It is considered that the valuable physical properties of 

 South American Para rubber are largely due to the antisepticis- 

 ing method employed in coagulating the latex. The collector 

 takes a paddle or some similar article, dips it in the freshly 

 collected latex, and holds it in the smoke of a fire fed with wood 

 and palm nuts. 



The smoke given off by the palm nuts is reputed to contain 

 creosote and acetic acid, the former antisepticising the putrescible 

 nitrogenous substances in the latex, while the latter causes 

 coagulation. As the paddle is alternately dipped in the latex 

 and held in the smoke, it will be seen that the resulting product 

 consists of thin antisepticised films of rubber closely packed one 

 upon the other. A minimum surface is exposed to light and 

 atmospheric influences. The outside of each block or cake is 

 blackened, but the interior remains a pale grey colour until the 

 block is cut up, and it is exposed to oxidising influences. 



The bulk of cultivated Para latex is either allowed to 

 coagulate naturally or this process is effected by the addition of 

 chemical reagents. 



Natural coagulation occurs through the action of the proteid 

 or albuminous matter which becomes insoluble or, as is more 

 generally stated, coagulates. In the coagulum are included the 

 caoutchouc globules and various other matters in the latex. 

 Whilst the putrescible substances are present in the rubber, 

 fermentation and putrefaction is always liable to occur providing 

 moisture be present. However well the rubber may be dried 

 during preparation, it is obviously impossible to protect it from 

 the moisture present in the atmosphere, unless it be kept in 

 specially prepared chambers. Too rapid drying encourages 

 "tackiness." But this form of "tackiness" is fundamentally 

 different from that caused by the action of bacteria on the 

 albuminous matters in the latex, which does not occur in rubber 

 from which they have been eliminated. 



The commonest reagent employed to coagulate Para latex 

 is acetic acid. The amount of acid required to bring about 

 coagulation is usually about two or three drops to a gallon of 

 diluted latex. The exact amount required must obviously 



