Page:Treatise on Soap Making.djvu/37

21 salt, united with a certain quantity of fixed air. This may be increased so far as to make the vegetable alkali assume a crystalline form, and lose great part of its alkaline properties. But, as the adhesion of great part of this air is very slight, it easily separates with a gentle heat.

The only method of depriving it of its fixed air entirely, is by mixing an alkaline solution with quicklime.

The alkaline salts for the use of the soap-boiler, are produced from the following materials: The first of which to be noticed is that well-known article, the produce of our own sea-shores, &c. called kelp.

From the large quantity of alkali therein contained, it is very justly esteemed an excellent and useful material in hard soap-making. The best of this article is made from sea-ware, or weed, cut from the rocks of the shores at low water-mark, not under four