PREMATURE COAGULATION.--Other opinion to the contrary it is now generally acknowledged that the possibility of premature coagulation in the cup or bucket is at least not diminished by the addition of even clean water. The use of water often obtained from estate drains clearly led to increased trouble. The extent to which such premature coagulation takes place varies greatly under the influence of many factors--_e.g._:
(_a_) Cleanliness of cups and spouts (the latter an important item often overlooked, and involving the presence of certain organisms which effect coagulation).
(_d_) Size of tappers' tasks (involving the length of interval between tapping, and the collection of latex).
(_e_) Distance to be traversed between the site of the task and the store.
(_f_) Care in collecting, to exclude extraneous matter.
(_g_) Nature of transport; agitation of the latex to be reduced to a minimum.
(_h_) Nature of the soil, and situation of the estate.
The last mentioned factor is of great importance. As a general rule it is noted that premature coagulation is less marked on estates situated on comparatively hilly land. The greatest effect is remarked on estates situated on the flat lands of the coastal area where peaty soils are a feature. On many such estates, in spite of the observance of all ordinary precautions, it is not possible to receive the latex at the factory without a large percentage of prematurely coagulated rubber being found in the transport vessels.
ANTI-COAGULANTS.--For this reason on these (and other) estates, the use of small quantities of anti-coagulants is common. The effect of these is to keep the latex liquid and thus render possible the preparation of a higher percentage of first-grade rubber than would be otherwise obtained.
Among the better known agents which have such an effect upon latex, formalin and sodium sulphite (not bisulphite) are the chief. The latter is the more popular as it is slightly cheaper and much more stable. As now used, it is in the form of an easily soluble powder (anhydrous sodium sulphite). The ordinary crystalline form of sodium sulphite as used in photography is not recommended, on account of its comparative lack of power and its poor keeping qualities.