(_b_) The efficiency of the apparatus. (_c_) Condition of the timber as to moisture. (_d_) The temperature employed, and rate of working. (_e_) The point at which distillation ceases (_i.e._, the duration of interval between commencement of heating and cessation of collection). Samples received from estates for testing purposes were found to contain equivalents varying from 2 per cent. to 10 per cent. of acetic acid. They were all suitable coagulants when used in quantity calculated from the discovered acidity, but produced rubber darker than ordinary when air-dried. This effect was not of much importance in the preparation of smoked sheets, but to produce a pale crepe it was necessary to employ sodium bisulphite as an anti-oxidant. This darkening in colour is to be ascribed to the presence of traces of phenols,[24] which are stated to exert an effect upon the rubber during and after vulcanisation.[25] This subject will be discussed in another section. [24] Whitby, _Journal Soc. Chem. Industry_, vol. xxxv., No. 9, 1916. [25] See also "Preparation and Vulcanisation of Plantation Rubber" (Eaton, Grantham, and Day), Bulletin No. 27, F.M.S. Department of Agriculture, April, 1918. With this provision the crude pyroligneous acid which can be produced on estates, could be employed as a coagulant until such time as the price of glacial acetic acid was so low as to make the production of the crude acid non-profitable. This point would be determined from a knowledge of the cost of production per gallon, and the percentage of acetic acid per unit. For example, if the cost of production (including cost of timber for distillation, cost of fuel for heating the retort, cost of labour, etc.) was 60 cents per gallon of crude acid containing 9 per cent. of acetic acid, that would be equivalent approximately to buying glacial acetic acid at $30 per demijohn of 44 lbs. SMOKED WATER.--A weak solution of pyroligneous acid may also be obtained by passing smoke through water. With this object in view, a machine was designed by the Federated Engineering Company of Kuala Lumpur. In this the principle of retorting was not employed. Smoke was produced by ordinary combustion in a compartment of the apparatus, and was drawn through water by the action of a high-speed fan worked by hand. A solution, equivalent in effect to a 2 per cent. solution of acetic acid, could be obtained at a comparatively cheaper cost than crude pyroligneous acid produced by dry distillation as it was then being practised. This was chiefly because of the wasteful methods of fuel combustion, in the latter process, in the heating of the retort. CHINESE VINEGAR.--This agent was found to be a satisfactory coagulant, and, _a priori_, there is no reason why it should not be suitable, as it is essentially a dilute solution of acetic acid. The qualities sold were generally colourless, and were probably the result of acetic fermentation of rice.