Coagulation, in fact, can be effected thus in any kind of air-tight receptacle; and experimentally the reader can obtain a satisfactory result by filling completely with latex the bottle which has a loose stopper.
Under the patent held the coagulum may be prepared either for crepe-making, or for sheets by a modification of the tank.
The crepe when dry does not have the bright appearance of the ordinary “Fine Pale” standard prepared with the aid of the anti-oxidant sodium bisulphite.
Unfortunately the addition of this substance to the latex in normal proportions is not possible under anaerobic conditions, as it is found to prevent coagulation, probably owing to its sterilising effect upon the anaerobic organisms.
To prevent the oxidation of the rubber in actual practice, the freshly prepared crepe is soaked in a solution of sodium bisulphite before hanging to dry. The resulting colour of the rubber is quite good.
It was shown by Eaton and Grantham that anaerobic coagulation is slightly uncertain in action. Owing probably to variations in the composition of the latices, or to the extent of infection by organisms, coagulation may one day be complete and on other days less satisfactory.
They found further that, by the addition of small quantities of sugars, coagulation under both aerobic and anaerobic conditions was improved. The conclusion formed was that the addition of sugars created a medium favourable to the development of anaerobic organisms and unfavourable to those which cause decomposition of the natural nitrogenous constituents of latex.
This work was confirmed by Gorter and Swart,[29] who attributed the action to the conversion of sugar to lactic, acetic, and succinic acids by fermentation.
[29] Gorter and Swart, Bulletin No. 6, West Java Station.
Denier and Vernet, whose work has already been mentioned, studied the presence of the organisms in latex, and succeeded in isolating one which, under anaerobic conditions, effects coagulation within twenty-four hours. Sometimes to produce complete coagulation it was found necessary to employ small quantities of sugars—e.g., 1 gramme per litre of latex (1:1,000).