On analysis the liquid was found to consist mainly of sulphuric acid, against the indiscriminate use of which warnings have been given. Thus it was a dangerous substance for common use.
Furthermore, comparing the value with its sulphuric acid content, it was found that the price required for “Coagulatex” was roughly four times the contemporary cost of commercial sulphuric acid in the Federated Malay States.
Those in charge of estates should realise, therefore, that no proprietary coagulants should be adopted until a proper report of tests, and a comparative valuation, has been obtained from one of the research laboratories.
Carbonic Acid Gas, Carbon Dioxide.—Now of only scientific interest, it may be noted that some years ago great claims were made for the use of carbon dioxide gas as a coagulant. In actual practice we were unable to effect coagulation by passing the dry gas into latex. It was suggested that the original investigators were misled by failure to secure a dry and clean gas. It would appear that probably the gas was prepared by the action of hydrochloric acid upon marble or limestone. Unless intervening “washers” and “driers” were used, the liberated gas, when passed into latex, would carry with it traces of hydrochloric acid, which would effect coagulation.
Alcohol.—In the cheap form of methylated spirit, alcohol has been employed by us as a speedy coagulant for many years. Latex run slowly into alcohol coagulates instantaneously. The method has been in common laboratory use.
The employment of alcohol has also been made the part-subject of a patent process of coagulation, to which reference will be made in the [succeeding chapter].
Vegetable Extracts.—At various times experimental work has been directed towards the use of liquids of purely vegetable origin, such as the juices of tropical fruits, and of a waste product of tropical industry—the so-called “milk” (or water) of ripe coconuts.
In the former class there is usually a natural acidity, but in coconut water the acidity is chiefly the result of fermentation of the carbohydrate (sugar) constituents.
These substances were all found to effect a more or less satisfactory coagulation, but it is unlikely that they would be suitable for practical application on a large scale.
As being more directly related to the subject of coagulation in general than to coagulants in particular, a discussion of several special processes will be relegated to the [ensuing chapter].