SODIUM SULPHITE.--It would not be amiss to insist upon the point that while the nature of sodium _bisulphite_, as employed in the preparation of rubber, is anti-oxidant, sodium sulphite is employed chiefly for its anti-coagulant property. It is not used, therefore, in the making of crepe rubber, but is of service in the preparation of sheet rubber, where the aim is to keep the latex in good fluid condition as long as is necessary, and to retard coagulation slightly so that enclosed bubbles of gas or air may escape. Formulæ have been given for its use in the field when required. On some estates this practice is not found necessary, but a quantity of solution is always placed in the bottom of the reception vessels prior to the straining of latex into them. Only a small quantity is used, and as a working basis the following formula may be adopted: _Sodium Sulphite: For Use in the Factory._ (_a_) Dissolve 2 ozs. of anhydrous sodium sulphite in a gallon of water. (_b_) The gallon of solution, placed in the bottom of the reception jar or tank, is sufficient for the treatment of 40 gallons of standardised latex (1-1/2 lbs. dry rubber per gallon). The warning previously given regarding the necessity for thoroughness in the preparation of solutions is here reiterated. Stirring should be thorough, say for five minutes, and if there is any sediment or undissolved matter the solution should be strained through cloth before using. Where uniform jars or tanks are in use, the majority of which will contain uniform quantities of latex daily, the practice of using the chemical can be made almost fool-proof even in the hands of coolies. A calculation is made of the quantity of powder required for each vessel daily. The necessary number of lots is weighed out each morning and each placed in an envelope. The process is thus simplified by the fact that the contents of an envelope, neither more nor less, are required for each unit reception vessel. Even the weighing can be done by a coolie if he is given a counterpoise (of lead, for example) equivalent to the required weight. It will not be found necessary to do any vigorous stirring of the solution with the latex, as the latter is strained into the solution and the continued addition of successive quantities is sufficient to give a good mixture. USE OF FORMALIN.--Few estates now use formalin (formaldehyde) as an anti-coagulant. It must be acknowledged that when not abused there are points in favour of its employment in preference to sodium sulphite, but these are outbalanced by certain disadvantages. The argument may be stated thus: _Points for_: (1) If made up freshly it is an effective anti-coagulant. (2) Formalin being the solution of a gas in water, there is no residual substance left in the rubber to delay drying. (3) Its use gives a bright clear rubber. _Points against_: (1) Its cost at all times is greater than that of sodium sulphite.