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and the faults which underlie it can be easily removed. But before 
doing this the problem to be solved and the material under treat- 
ment should be further considered, The wet slabs of freshly 
coagulated rubber are composed of the following ingredients 
Rubber, proteid, oils, and resins making up the solid matter and 
a watery liquid full of those impurities — the gum, sugar, salts and 
excess of acetic acid — which were present in solution in the latex 
during coagulation. 
While the slabs are rolled and pressed, much of the watery 
liquid is expelled, but a limit is quickly reached and when the 
slabs are set apart to drv there is usually fifty per cent or more 
of this watery liquid with the impurities dissolved in it still ad- 
herent to the rubber “sponge." On drying the water itself evapo- 
rates but leaves behind in the rubber whatever gum, sugar, salts 
or other soluble matter it previously contained. 
1'hese are impurities which can and should be removed from 
rubber— the other impurities, the oils, resins and coagulated pro- 
teid which are not soluble in water, cannot be removed and may 
be neglected. The rubber slabs in their wet condition beain to 
putrefy and become most offensive, and during the Iona- period 
of drying much attention is required to keep them moderately free 
from mould. This is entirely due to those impurities which were 
soluble in water and which are being dried up inside the rubber 
slab. The rubber itself undergoes no appreciable change and it 
is doubtful whether it is in any way eventually damaged by the 
putrefaction which occurs in drying. At the same time by spoil- 
ing the pretty appearance of the rubber sheets, the mould and 
decomposition products detract from the price the dry rubber 
commands, and it is a source of annoyance and very disagreeable 
to the rubber producer. s 
The slabs take a long time to dry because the outside film 
which quickly dries seals the inner portions, and slabs which are 
haif an inch thick are not dry at the end of many months. As 
the slabs dry the colour changes from white to grey and finally 
when dry the rubber is transparent. A sheet of rubber may be 
taken to be dry when the grey colour is no longer apparent in 
a freshly cut surface. ^ 
Ail raw rubber before -it is vulcanised by combination with sul- 
£' S V6 7 s * n f ltlve ^ heat > * temperature of i S o°F. renders para 
lubber quite sticky on the surface, and a higher temperature utterly 
s roys the nerve ol it. It is consequently very injudicious to 
use any artificial heat in hastening the drying of rubber. If some 
artificial heat were absolutely necessary a very carefully regulated 
temperature never exceeding i20°F. would probably not cause anv 
evident damage, but bearing m mind the fact that a temperature of 
150 t does produce marked damage the sound policy is, 1 feel 
sure, o avoid artificial heat altogether. I may here mention that I 
nave subsequently visited many plantations and seen rubber beino- 
dried with the aid of heat and in no case did I fail to find som? 
rubber that had been clearly overheated. Fortunately it is possible 
?/rto 
