A MODERN INSTALLATION.--In the most recent scheme for dealing with the reception of latex, its standardisation, and conveyance to the coagulating tank, the main principle of the first system outlined is retained; but the receptacles are not mobile. Glazed-tile tanks are employed, the capacity of each being approximately equivalent to that of each unit coagulating tank.
The accompanying illustrations show the general arrangement and some details of the system of reception tanks employed on the well-known Pataling Estate.
Whether it is necessary to employ any coagulant, or whether latex should be allowed to coagulate naturally, will not be discussed at this stage. Neither will mention be made of any patent processes of coagulation which employ other than acid mediums. These subjects will be treated in a subsequent section of the book.
CHOICE OF COAGULANTS.--It is not proposed here to enter into a discussion as to the merits of the dozens of known coagulants. Suffice it to state that acetic acid, although the oldest general coagulant, still remains the best and safest at the present time. There is a deal to be said in favour of the use of another organic acid, formic acid. It is equally as safe as acetic acid, and quite efficacious; the only drawback is that, taking all things into consideration, it is very slightly more expensive. Acetic acid, therefore, will always be implied in this chapter when the word "acid" is used.
STRENGTH OF ACID SOLUTION.--In the old days it was the rule rather than the exception to find pure, undiluted acid used in coagulation. In many cases no harm resulted, for the simple reason that, owing to the large proportion of water in the latex, the acid was thereby very much diluted. The estates had to thank the over-dilution of the latex for the non-injury of the resulting rubber.
Some estates make up a stock solution of 1 part acid to 20 of water, and use this with success because of the fair amount of added water present in the latex.
It must be understood that what is being referred to now is not the absolute quantity necessary for coagulation, but the proportions--_i.e._, the respective volumes of acid and water in the solution of acid made up every day. That the strength of the acid solution, as well as the quantity used, has an effect upon coagulation can be easily demonstrated in the following way: