56 
It is obvious, to begin with, that the value of a crude rubber to 
the manufacturer will to a large extent depend upon the proportion of 
actual rubber substance or caoutchouc it contains ( see Heil and Esch 
Handbuch der Gummiwaren-fabrikaton , p. 40). A crude rubber, 
such as hard cty-e Para, will contain certain substances normally 
present in the latex from which it was obtained ; of these the most 
important are resin and protein or nitrogenous bodies. It may also 
contain extraneous substances, such as sand and dirt of all kinds, 
and finally it will always contain more or less water. It is usual to 
determine these constituents and by difference to calculate the 
amount of caoutchouc, there being no agreed satisfactory method of 
directly estimating the latter. It has been suggested that a further 
examination should be made of the resin and protein bodies with a 
view to characterising them more exactly ; but, quite apart from the 
large amount of research work which will be necessary before this can 
be done, it is difficult to see what advantage will be gained except for 
the purpose of distinguishing the source of the rubber; in any case it 
is doubtful if the results would justify the additional work entailed in 
the analysis. 
Table I gives the analysis of a typical hard cure Para and that of 
a plantation “block”; the latter represents the mean of numerous 
analysis we have made from time to time on good qualities of this 
product. 
Table I. 
Hard cure Plantation “block,” 
Para. as imported. 
127 0-4 
3-1 4*0 
2-9 2*8 
0*3 0*1 
Caoutchouc (by difference) ... 81 *o 927 
It will be seen that the figures are distinctly in favour of the 
plantation product; the moisture is particularly low in the latter 
owing to its having undergone a systematic drying process. This has 
the great advantage that the rubber is much less likely to undergo 
putrefactive change during transport through hot climate — as every- 
one knows— moulds and bacteria must have moisture for their growth 
and development. The samples we have examined of properly pre- 
pared wild rubber all contained large quantities of water, such as form 
10 or 12 per cent. Of course, plantation rubber which is merely air- 
dried, as in the form of biscuits, may contain more than one-half per 
cent, moisture, but the amount will not be excessive. 
Moisture ... 
Resins 
Protein ... 
Ash 
2 
