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NOTES ON THE EXPERIMENTS OF 

 COAGULATING AND CURING RUBBER. 



Several experiments were made in curing latex by smoking as is 

 done in Brazil, the aim being to test whether the coagulated latex from 

 plantation trees would be improved or deteriorated by such process. 



The process consists of coagulating latex in the shape of spindles, 

 or bottles, or balls, by exposure in smoke. An ordinary-sized stick 

 (about 2" diameter) is suspended at one end over a volume of smoke 

 and slowly turned by an operator holding the stick in one hand un- 

 til a film of smoke has adhered to the stick. The stick is then 

 switched over an empty vessel while another operator carefully pours 

 some latex all over the smoked v area ; this is continued as fast as film 

 on film of latex coagulates and continued daily until the spindle 

 becomes unwieldy. 



In this process all the latex is coagulated although the latex may 

 contain 50 to 60 % of water per se and from young trees, or on wet 

 days, even more. During the process of smoking — and storing while 

 curing — there is a gradual exudation of water, but the rubber is always 

 very wet. The samples we submitted for analysis exhibited 17-25 % 

 of moisture against 15-18 % from Brazil. This higher percentage of 

 moisture is most probably explained by the shorter time our smoked 

 rubber was stored, whereas Brazilian smoked balls are sometimes 12 

 months old by the time they reach their market. This higher per- 

 centage of moisture too, very probably also explains the execss of 

 resin as the resin in plantation rubber as ordinarily coagulated is 

 about 2 % only. 



Due allowance must be made for the inexperience of the operators 

 which is pointed out in the following reports on samples submitted 

 for analysis and it should be observed that of the two samples re- 

 ported on, sample I was prepared from the latex of trees 25 years old 

 and not 12 years old as stated in the reports. 



Reports on two samples of smoked rubber : — 



Imperial Institute of the United Kingdom, The Colonies 



and India. 



1st November, igog. 



Dear Sir, — With further reference to your letter of the 2nd 

 ultimo, I now forward the results of the examination of the two small 

 samples of smoked Para rubber. The specimens were labelled No. I 

 and No. 2. 



The rubber was moist and had a strong odour of creosote; 

 physical properties appeared to be very satisfactory. 



