Gums, Resins, 



360 



" I propose to endeavour to find out in Singapore, and on the plantations 

 themselves the actual reasons of this inferiority by experimental work ; and to 

 this end I have had made in Manchester, by a firm of manufacturers of rubber 

 machinery, at the expense of the Colonial Government, machines for practically 

 working up and vulcanising rubber, and I intend with the aid of these 

 machines to manufacture test pieces of vulcanised rubber from raw rubber 

 taken from trees grown in various localities of different age and cured 

 in different ways. With these samples of vulcanised rubber physical tests 

 of elasticity and tensile strength will be carried out, and a just comparison 

 of the samples among themselves, and with true South American Para, can be 

 made. There are special difficulties in carrying out physical tests on india-rubber, 

 and there is at present no uniform method of stating results ; comparisons between 

 tests made at different places are therefore of little value ; and it is essential that 

 all the work be done in the same manner on the same type of apparatus, to eliminate 

 the personal equation and correctly ascribe to each variant factor in the production 

 of the raw rubber its consequent variation in the quality of the product. When 

 this is done I shall be able to say with certainty which method of preparation 

 gives the best results, and to ascribe correctly to each and every one of the variable 

 conditions under which the rubber is jjroduced its true influence on the quality 

 of the rubber. This work I look upon as being important, and it will, I trust, settle 

 decisively many of the problems which now are controversial. To see clearly the 

 necessity for the work, and to have gained the insight into the methods of treating 

 and vulcanising rubber necessary for carrying it out, are the direct results of my 

 visit to England and the time spent in the works of the rubber manufacturers there. 



THE USE OP ACIDS TO ASSIST COAGULATION. 



" 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 a priori and considering the mild chemical 

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

 singularly inert nature of rubber, I should not except 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 effect. 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 



