Sept. 1906.] 



209 



Saps and Exudations. 



REPORT UPON A VISIT TO GREAT BRITAIN TO INVESTIGATE THE 

 INDIA RUBBER INDUSTRY IN ITS RELATION TO THE GROWTH 

 AND PREPARATION OF RAW INDIA-RUBBER IN THE 

 MALAY PENINSULA. II. 

 By P. J. Burgess. 



PREPARATION OF RAW RUBBER. 



14. I have already stated I am not at present in a position to say decisively 

 how the rubber should be best coagulated and prepared for export, but I am 

 inclined to recommend that as little as possible in the way of acids or drugs should 

 be added to the milk or latex. Where a washing machine is used, the milk might, I 

 think, with advantage be allowed to coagulate by simply standing for 24 or 26 hours 

 and allowing the natural fermentation, or souring, which takes place, to produce 

 coagulation. This, of course, will preclude any possible additions of preservative, 

 such as formalin or dilute ammonia, to the latex in the cups, and it will be desirable to 

 keep the latex as concentrated as possible. This natural method is of course only 

 possible where a washing machine is used, and it involves more time be taken in the 

 actual coagulation process. There is among the manufacturers an objection to the 

 use of any acid or addition of any drug at all to the rubber during coagulation, from 

 fear that traces of it might be left in the rubber, even after washing. If there were 

 an appreciable amount remaining, it is highly probable that it would give trouble 

 during working and vulcanisation of the rubber by acting chemically on some of the 

 ingredients with which the rubber is mixed and perhaps producing gases which 

 would form blow holes in the finished goods. These bubbles and blow holes do 

 sometimes occur after vulcanisation, and care has always to be exercised to prevent 

 their occurrence, and anything which might lead to their formation has to be 

 carefully avoided. Whether this objection to the use of a volatile acid in curing the 

 rubber is really sound, can only be decided by practical experience in working with 

 rubbers so cured, but the objection is actually held, and the fear entertained, by some 

 of the most prominent of the rubber manufacturers in England, and the knowledge 

 of the fact that acids have been used in the curing of plantation rubber makes the 

 manufacturer less inclined to use crepe or plantation washed rubber without a 

 further re-washing in the factory. Another objection to the use of acid preservative, 

 and the addition of any drug at all to the latex, lies in the possible action of such 

 drug on the rubber itself. Speaking h priori and considering the mild character 

 of acetic acid, and the preservative action of formalin, together with the singularly 

 inert nature of rubber, I should not expect any harmful action whatever to 

 occur. I have, however, seen samples of rubber made from latex to which 

 small amounts of various aniline dyes had been added. Some of the dyes (the 

 reds especially) had produced most marked effect, making the rubber hard and 

 brittle, and as readily torn as thick paper. Other dyes appeared to have had 

 little deleterious effects. This perishing of the rubber had certainly been brought 

 about by the action of quite trifling amounts of what are regarded as harmless 

 and inactive chemicals. I have already mentioned cases of plantation rubber 

 perishing utterly in a few years from unknown causes. With these instances 

 before me I feel less inclined to treat the possibility of acetic acid or formalin 

 causing rubber to perish as absurd or fanciful, and until the question has been 

 experimentally investigated I should recommend that, wherever possible, the 

 use of any chemical be avoided. The position is therefore this — some of the users of 

 rubber object to the rubber being cured with acid, and in the absence of experimental 

 evidence we are not justified in assuming acids, even vegetable ones such as acetic, to 

 be harmless. To avoid using any coagulant is only practically possible where a 

 mechanical treatment of the rubber by a washing machine is in use, and then it is a 

 matter for consideration whether the use of acid, which has been extremely con- 



