Page:Treatise on Soap Making.djvu/64

48 green, a few more drops must be added; and so continue, until you find the paper is by no means altered in the colour, neither green nor red. The ley is then neither an acid nor an alkali, but neutral, or a combination of both, brought to the point of saturation. A few drops more of the acid, would occasion the test-paper to take a red, instead of a green colour, which would distinctly show the power of the acid to prevail.

Treating in this manner the different leys, then counting the number of drops taken to neutralize them, the strongest ley will be discovered to be that which have required the greatest quantity of acid, to overcome the power of the alkali.

Soap-leys are also judged of by their specific gravity, or weight, comparative to water.