RUBBER MANUFACTURE. IO5 



barrel is completely rilled, about eight ounces of formaldehyde 

 are added, the whole well stirred, and allowed to stand for 

 twenty-four hours. The action of the formaldehyde appears to 

 be twofold. In the first instance, it effectually prevents any 

 tendency of the albumen to coagulate in the hot solution, and 

 thereby to cause mischief. But, as comparative experiments 

 showed beyond any doubt, it also has a most distinct effect upon 

 the india-rubber, which collects on the top of the wash-water in 

 the form of a snow-white cake of rubber of such strength and 

 toughness that it can in one mass be lifted out from the barrel. 

 On cutting this cake open, it will be found that it is rather 

 spongy, being full of little holes which are still filled with some 

 of the albuminous though very dilute mother liquor. If, there- 

 fore, the rubber were dried in this state it is obvious that it 

 would still contain a small quantity of the objectionable albumin- 

 ous matter. For this reason the rubber contained should at once 

 be taken, cut into strips, and subjected to a thorough washing 

 upon an ordinary rubber washing machine." 



I made several attempts, when in the Gold Coast, to separate 

 rubber from Para latex in the manner above suggested, but 

 failed in each instance, although the latex stood, in one or two 

 instances, for nearly three weeks without the rubber separating out. 



The following method was suggested by the same author, and 

 he states * that it produces similar results to that previously 

 mentioned : 



" To every gallon of the rubber latex, from |- oz. to I oz. of 

 formaldehyde (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 I Ib. of sodium sulphate 

 (commercial) in one pint of boiling water is added while still 

 hot, and the mixture stirred for some time. Coagulation may 

 take place immediately or after several hours' standing, according 

 to the condition (age) of the latex. Great care must be taken 

 to use a sodium sulphate of entirely neutral (not acid) reaction. 



" Rubber prepared in this manner will be found free from 

 every trace of albuminous matter. It is of a degree of purity 

 greatly surpassing the finest Para rubber ever produced, and 



India-rubber Journal, i5th Feb. 1904. 



