The thin film of latex picked up by the belt was coagulated partly by the action of smoke constituents by evaporation due to heat. Assuming (1) that the belt was of adequate length, (2) that the rate of travel was not excessive, (3) that the latex was not too dilute, (4) that the temperature of the smoke was sufficiently high, (5) that the smoke was sufficiently dense and not too damp—then the process should be a continuous one.
It will be clear that success could only be obtained by a careful adjustment of all these factors. The latex must, necessarily, be of a fairly rich consistency (at least 21⁄2 lbs. dry rubber per gallon), but unfortunately there is considerable difficulty in maintaining such latex in a state of fluidity for the period demanded by this process, without loss of latex. Naturally, the addition of an anti-coagulant would retard the rate of output of the machine to a marked degree.
The layer of rubber thus formed on the belt was stripped off, and hung for further air-drying, as it still contained a fair percentage of moisture.
As a really practicable method for treating plantation latex, the process failed by reason of its low rate of output over a given interval. This alone was sufficient to condemn it, apart from the facts (1) that it was not shown to be a cheaper method than coagulation by acetic acid, (2) that the resulting rubber was not proved to be of superior intrinsic value to rubber prepared by ordinary methods.
Spontaneous Coagulation.—All readers will be aware of the phenomenon of the curdling or souring of milk. The behaviour of Hevea latex, under certain conditions, may be taken to be analogous. Difficulty is experienced in maintaining fluidity—a difficulty which appears to vary in great degree according to locality, nature of soil, age of trees, the relative demand made upon the trees by the system of tapping employed, etc.
It is sometimes found, before the latex reaches the store, that it may exhibit one of various stages of premature (spontaneous) coagulation:
(a) To all appearances it may be quite fluid, but a close examination shows it to consist mainly of a serum containing very minute particles of rubber in suspension (microscopic coagulation).
(b) In a later stage these particles coalesce to form larger “flocks” (macroscopic coagulation).
(c) The whole, or practically the whole, of the latex may have coagulated, forming one mass of rubber with a milky residual serum.
Passing from this aspect of the question, it may be noted as peculiar facts that: