62 



Table IV. — Tests on Vulcanised Rubbers, prepared from " Block " 

 containing Mineral Matter. 



Tensile 

 strengths, 

 in grms. 



4746 

 3915 



Vulcanisation 

 reference 

 number. 



58 

 54 



Mixing. 



M 

 J 



Elongation 

 at rupture 

 when original = 



9*9 



117 



Elongation 

 under a strain 

 of 1500 grms., 



6-o 

 6-i 



The addition of mineral matter has had the effect of increasing 

 the tensile strength while reducing the elongation. This effect is 

 quite general within certain limits, and further tests are being carried 

 out in which we are investigating the influence of definite quantities 

 of mineral matters on mixings containing plantation block on the one 

 hand and hard cure Para on the other. 



Plantation Rubber by Figgis & Co. 



Messrs. S. Figgis and Co., in their annual review of the India- 

 rubber market, give the following re plantation rubber, which we 

 extract verbatim : — 



Manufacturers have shewn a decided preference for sheet, biscuit 

 and crepe ; the latter should not be drawn out too thin or have visible 

 air or steam bubbles in it, and some lots of thick crepe, nice strong" 

 rubber about J of an inch thick, were much appreciated and sold well. 



We think it has been profitable to planters to wash and clean the 

 rubber thoroughly, and to prepare as large a proportion as possible of 

 good colour — also not to send many qualities or very small lots. Block 

 has not been in favour generally, and unless clean, resilient, hard quality 

 can be sent, it may be better to ship as crepe. 



We report our recommendations of a year ago : — 



Pack it in good dry condition (excess of resin much objected to). 



Into strong cases of 1 cwt. to 2 cwt. each. No paper, fullers earth, 

 etc., to be used. 



To keep different qualities and colours separate, and not to mix 

 immature rubber with older; to send separately dirty barky pieces, 

 and to wash out all the bark in crepe, block, and sheet. 



All fine qualities should be loose crepe, sheet, or biscuit — not run 

 into a mass. 



To smoke the rubber when convenient, because " smoking M 

 appears to increase its resiliency, but keep it as clear and yellow as 

 possible. 



Smoked rubber appears to have greater resiliency and to be more 

 suitable for many purposes than unsmoked. "Smoking" prevents the 

 "proteins" in rubber from decomposition, and generally from 

 " tackiness." All fine rubber from Para is smoked. 



