A certain given quantity of water ought always to be allotted for trying this; say, one or two pints; and by weighing one pint thereof afterwards, when the experiment is finished, the quantity of alkaline salt may also be discovered which one pint of said ley contains; thus, an English pint of spring water weighs 15 oz. 3 drs. 12 gr., so that all above that weight in the rubbing water, or ley, must be supposed alkaline salt. The price of the article ought to be regulated according as the experiment turns out.
From these ashes already mentioned, the strongest and purest vegetable alkali is obtained. From other vegetables, as fern, broom, bean-stalks, &c. an alkaline salt is produced, but so impure, and in such small quantities, that no soap-manufacturer in this country can use them, with any reasonable expectation of profit.