THE LATEX AND HOW IT IS COAGULATED 137 



one should say, preserves the quality of the rubber. The 

 reason of this is apparent. Any fermentations arising, however 

 slight, attack the nerve of the rubber, and if allowed to pro- 

 ceed to any length the rubber would become tacky. Sodium 

 bisulphite has antiseptic qualities and thus prevents these 

 fermentations arising or checks them promptly if they have 

 started. It is, therefore, obvious that if sodium bisulphite is 

 to be added to the latex it should be added as soon as is possible. 

 It may well be the case and it is suggested here that it 

 would be a good thing if using water in tapping operations to 

 use a very weak solution of this sort instead of ordinary water. 

 The objection to the use of water that it assists the arising 

 of ferments could not be cited, but, on the contrary, the solu- 

 tion would have the desirable effect of hindering ferments 

 arising at the first stage of the proceedings. In this way it is 

 possible that a very high grade of rubber might be produced 

 and lump rubber reduced to the vanishing point. 



Each manager should carefully experiment for himself and 

 ascertain what is the smallest quantity of sodium bisulphite 

 powder which will give him the best results in colour and 

 quality. Sodium bisulphite very readily absorbs moisture 

 and should be carefully kept in a very dry place not in the 

 factory or it will lose its qualities. After lower-grade rubbers, 

 such as scrap, bark-shaving rubber and earth rubber, have been 

 cleansed of the impurities associated with them, a wash over 

 with a weak solution of sodium bisulphite will have the effect 

 of improving their colour and their keeping qualities. The best 

 results are obtained when the solution is prepared fresh as 

 required. When smoked is manufactured instead of pale crepe, 

 there is little or no excuse to use sodium bisulphite. 



Latex will coagulate without the addition of any acid if left 

 to stand long enough, but the rubber is not so good a quality, 

 nor would this method be convenient in factory operations 

 where dispatch is of the utmost importance. 



There are many proprietary coagulants on the markets, 

 but acetic acid is generally found to be the most serviceable. 

 The scrap rubber which dries upon the trees is stronger than 

 the coagulated first-latex qualities. This fact suggests that 

 there is yet room for improvement, and that we may have yet 

 to learn the best method of preparing rubber. 



