347 



believes in the likelihood of the production of substitute for the real 

 article, or has seen a sample of it, and at the lower range of prices for 

 all kinds of rubber and the increasing supplies the danger now from 

 this source is more remote than ever.' " 



Queensland Agricultural Journal, June 1908. 



TREATMENT OF LATEX IN THE 

 PREPARATION OF RUBBER. 



M. KELWAY Bamber, The Laboratory, Colombo, Ceylon. 



A point of considerable importance in the manufacture of Planta- 

 tion rubber is to obtain, not only purity, but constant uniformity in 

 the finished product. 



At present there are almost daily variations in appearance, due to 

 causes which cannot easily be overcome, such as weather, age of trees 

 being tapped, and the bringing of new trees into bearing, all of which 

 affect the colour and clearness of the dried rubber. 



The discolouration is due to oxidation of soluble organic bodies 

 allied to tannin in the latex water, by means of an oxidising enzyme, 

 and is intensified by a warm temperature and exposure to the air. 



Thorough washing of the freshly coagulated caoutchouc will re- 

 move'much of the soluble matter with the enzyme, but it is difficult or 

 impossible to remove it all, and other means have to be adopted to 

 prevent the darkening on drying which almost invariably occurs. 



This is done by destroying the enzyme by means of heat before 

 oxidation occurs, with the result that the rubber dries of a clear pale 

 yellow colour, and of perfect uniformity from day to day. 



The heating can be done in different ways before or after coagula- 

 tion. 



1st. By passing steam into the bulked latex until the temperature 

 reaches 80° C or 167° F, and maintaining this temperature for 15 

 minutes or longer, according to the thickness of the rubber. 



2nd. By immersing the biscuits or sheets etc., in water of the 

 temperature for some minutes immediately after passing through the 

 above rolling machine ; then re-rolling to the requisite thinness, and im- 

 mersing again for a shorter time to ensure destruction of the enzyme. 



3rd. Hot w r ater can be employed in the washing machine, and if 

 necessary steam heated rollers as well. 



Heating while coagulating most nearly resembles the method of 

 making hard para, but the other method gives excellent results. 



To insure the best product cleanliness in all stages of collection 

 and manufacture is absolutely essential, and if the loss in value from 

 want of simple precautions in the preparation was more fully realised 

 on the estates, much greater care would be exercised. Many samples 

 of excellent rubber appear on the London market, but from want of 

 uniformity, and perhaps the presence of some slight impurity, they do 

 not realise by some pence per lb., the value they otherwise would. 



Rubber made by this process, has already been sold on the market, 

 and realised a premium of up to about 4d. per lb., over ordinary good 

 biscuits which indicates that the process can be successfully applied on 



