154 



PARA RUBBER. 



The following are analyses of two samples of tacky rubber by 

 Mr. M. Kelway Bamber : — 



Analysis of Black and Yellow Tacky Rubber. 



Black. Yellow. 



per cent. per cent. 



0-64 

 3-02 



Moisture . . 

 Resin 

 Proteids . . 

 Ash 

 Caoutchouc 



0-64 

 4-00 

 2-19 

 2-02 

 91-15 



2-19 



1-26 



92-89 



100-00 



100 00 



Nitrogen .. . . 0-34 



Resin by Alcoholic ex- 

 traction . . 0-68 



0-34 



0-72 



The first rubber obtained from old trees or that from young trees 

 seems very liable to undergo putrefactive changes. It has been 

 suggested that these decomposition processes may be due to mole- 

 cuar changes of one or more of the constituents of prepared rubber, 

 in lwhich case it would be very difficult to adopt measures to prevent 

 the undesirable result. It has also been pointed out that the pre- 

 sence of large quantities of oily and resinous substances having a low 

 melting point may be the cause of much liquefaction and subsequent 

 decomposition. The chemical analyses of rubber showing varying 

 degrees of tackiness have already been given. They appear to in- 

 dicate some relationship between the high percentage of resins and 

 proteids and the degree of stickiness and liquefaction. For the sake 

 of comparison the analyses of sound and very tacky rubber are here 

 reproduced : — 



100-00 



100-00 



The development of bacteria, which has been shown to be asso- 

 ciated with putrefactive changes of rubber, can. however, be over- 

 come either by inoculation, effective drying, or the use of 

 antiseptics. 



