Fresh latex as it flows from the tree consists of a fluid emulsion which closely resembles rather thin cream in general appearance. The composition is also somewhat similar, except that the fats of the cream are replaced by a different hydrocarbon. This hydrocarbon has the empyrical formula C10Hie, which is the same as that of solid rubber. In the latex, however, the rubber probably exists in a liquid form. In this case the process of coagulation is either accompanied or followed by solidification of the rubber globules. The liquid hydrocarbon existing in the latex is believed to undergo polymerisation to form true rubber by the coalescence of several comparatively simple molecules into one of a more complex character. In freshly drawn Hevea latex the rubber globules are, on the average, approximately one-thousandth of a millimetre in diameter, but many smaller globules also occur. In other latices the globules may be somewhat larger, but their size probably seldom exceeds one ten-thousandth part of an inch. The further study of such minute bodies is naturally a difficult matter, but it is believed that the rubber or simpler hydrocarbon is kept in emulsion by the existence of a thin skin surrounding each globule, and that this skin is either of a resinous or of a proteid nature.
According to various estimates the composition of the latex of Hevea is approximately as follows:
50—60 per cent
The latex from old trees usually contains a considerably larger proportion of rubber than that obtained from young trees. The composition of the latex is not much altered by moderate tapping, but if tapping is excessive the amount of rubber present may be greatly reduced.