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 

 Handhuch der Gummiwaren-fabrikaton, p. 40). A crude rubber, 

 such as hard cure 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. 



Moisture... 



127 



0-4 



Resins 





4-0 



Protein ... 



2*9 



2*8 



Ash 



0-3 



O'l 



Caoutchouc (by difference) 



8ro 



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. 



2 



