TURPENTINE, MANUFACTURE OF. The common turpentine used in the arts is mostly imported from America, in barrels and casks. [TURPENTINE.] It is used for very few purposes in the state in which it is imported. The process of distillation is in most cases reserted'to, as a means of separating it into solid resin and liquid oil or essence of turpentine. Turpentine-works, where this distillation is carried on, are managed with much caution on itecount of the inflammable nature of the substance operated on. The viscid turpentine is put into a still and exposed to heat ; it melts into a liquid, gives off its essential or oily portion in the form of a vapour, and there remains a liquid resin iu the still. The vapour, on leaving the still, passes through a refrige rator or cooling vessel, and is collected as a clear and limpid oil or spirit of turpentine. The residue is taken from the still as resin, black or yellow according to the kind of turpentine which has been employed.
A patent was taken out in America a few years ago, for making soap at the same time as distilling turpentine. Itaw turpentine and alkali were put into the still ; the spirit of turpentine passed off into a con denser, while the resin became partially saponified by combining with the alkali, and prepared to enter into the composition of soap.
Considered as an ingredient in house-painters' colours, spirit of turpentine, or turps, is an important substance. Chevreuil has pointed out three kinds of service which turpentine renders to oil-eolours, It facilitates the application, by diminishing the viscidity of the oily mixture ; it allows the painter greatly to modify the appearance of his work, by varying the degree of gloss or of dullness; and it prevents the appearance of cracks which would otherwise be visible when the work is varnished. As, however, the durability of the work de pends chiefly on the oil, the best mode is found to be to use as little turpentine as possible when the work is neither to be dead nor var nished.
Common or crude turpentine is imported to the extent of about a quarter of a million cwts. annually (246,458 cwts. in 1858, and 256,663 in 1859). A small import duty, imposed many years ago, has been since repealed.