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).
It is to be noted also that the addition of small quantities of soluble calcium (lime) salts to latex has much the same effect as the employment of sugars. Recent investigations[30] showed that the addition of 0·5 to 1 gramme of calcium chloride per litre of latex caused complete coagulation in closed vessels within twenty-four hours, a result agreeing with the findings of Barrowcliff.
[30] "Archief voor de Rubbercultuur," Nederlands Indies, 1920, 4, 273.
On page 308 of the same publication, experiments on the effect of sugars are described, in connection with _aerobic_ coagulation. Observations from a further set of experiments tended to indicate a direct connection between the effects of tapping and spontaneous coagulation. It is suggested that heavy tapping causes a diminution in the latex of those substances which act in some way as accelerating agents in coagulation--_e.g._, sugars. The smaller the proportion of these substances, the slower and less complete is natural (spontaneous) coagulation.