Page:Treatise on Soap Making.djvu/63

47 no such appearance ensue upon the combination of the acid and alkali, the ley is fit for immediate use, being arrived at the state of a proper caustic soap-ley.

A soap-ley, by being long exposed in open vessels, will lose the whole of its causticity, and seem entirely restored to the state of an ordinary fixed alkali. The keeping them as close as possible, therefore, appears exceedingly necessary.

By means of the acid may be discovered also the comparative strength between one ley and another, and so ascertain which of the two contains the greatest quantity of fixed alkaline salt. Thus, take a specific quantity of each; a wine glassful, for instance; drop therein a dozen drops, or so, of acid; stir with a bit stick, and apply a slip of the test-paper. If it appear green, more acid must be added, and stirred again. Applying the test a second time, if still