PARA RUBBER. 115 



These analyses show a relationship between the degree of tack- 

 iness and the percentage of proteids and resins; the latter mi\ 7 be 

 due to oxidation. Too rapid drying is said to induce softening and 

 tackiness in raw rubber. 



Keeping the Proteid Inactive. 



If the local conditions are such that the rubber cannot be prepared 

 by any method other than coagulation, and the proteid and other 

 materials must be included, it will be necessary to take steps to keep 

 the obnoxious ingredients in a quiescent state. This can be done by 

 treating the latex with some reagent which has antiseptic properties, 

 such as creosote or corrosive sublimate, and quickly drying the rub- 

 ber after effectively washing and pressing the freshly-coagulated 

 material. 



In some cases it is doubtful whether it is even necessary to add 

 antiseptic reagents if the rubber is thoroughly dried, as the decom- 

 position of the proteids is dependent upon a supply of water being 

 present. A communication from Messrs. Lewis and Peat on this 

 subject is given in the chapter dealing with plantation and fine 

 Para rubber. 



No matter whether the latex has been treated with antiseptics or 

 not, the coagulated substance should be very well washed; too 

 much water cannot be used. In the washing processes the water 

 may carry away a considerable portion of the soluble proteid or 

 that precipitated on the surface, and thus minimise the danger. 



The use of washing machinery or antiseptics or both is almost cer- 

 tain to become a necessity in the near future, judging by the 

 reports of European firms on the condition of various packages of 

 plantation rubber which they have received. Dilution of the latex 

 before coagulation might also reduce the proportion of proteid in the 

 prepared rubber. The quicker and more effectively the rubber 

 is dried, the less likelihood there is of putrefaction or tackiness 

 setting in. 



The Removal of the Proteid from the Latex. 



But it is not beyond the ingenuity of the chemist or planter to 

 treat the latex with some reagent which will keep the proteids in 

 solution while the caoutchouc globules are segregating, and ensure 

 their expulsion by subsequent pressing and washing. 



Weber, as the result of experiments mainly with Castilloa latex, 

 suggested that the treatment of dilute hot solutions of latex with 

 formaldehyde (Formalin), or the use of the latter with sodium 

 sulphate, may be effective in reducing the amount of proteid matter 

 in prepared rubber: — 



" To every gallon of the rubber latex, from J oz. to 1 oz. of formalde- 

 hyde (formalin 40 per cent, solution) is added, the latex well stirred 

 and allowed to stand for one hour. Then to each gallon of latex a 

 solution of 1 lb. of sodium sulphate (commercial) in one pint of boil- 

 ing water is added while still hot, and the mixture stirred for some 



