465 
These bubbles and blow holes do sometimes occur after vulcanisa- 
tion, and care has always to be exercised to prevent their occurrence, 
and anything which might lead to their formation has to be care- 
fully 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 enterfi ined, by some of the most pro- 
minent 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 plan- 
tation 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 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 whatever 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 convenient in assisting 
and controlling coagulation, should be discontinued from fear that 
such use will produce a rubber which will not stand the test of 
time, and which wall perhaps injure in the future the reputation of 
plantation grown and cured rubber. 
DRYING RUBBER. 
15. Until the introduction of mechanical washing of coagulated 
rubber and the formation of crepe, drying had been a troublesome 
operation in the preparation of rubber for export. Artificial heat 
almost alw r ays led to the softening of the rubber, and often through 
inefficient control of the temperature caused it to become distinctly 
tacky. Crepe rubber dries easily and w^ell if simply hung up in a 
dark but airy shed, and the preparation of rubber in this form 
