Potash derives its name from the _pots_ in which the vegetables, from which it was obtained, used formerly to be burnt; the alkali remained mixed with the ashes at the bottom, and was thence called potash. EMILY. The ashes of a wood-fire, then, are potash, since they are vegetable ashes? MRS. B. They always contain more or less potash, but are very far from consisting of that substance alone, as they are a mixture of various earths and salts which remain after the combustion of vegetables, and from which it is not easy to separate the alkali in its pure form. The process by which potash is obtained, even in the imperfect state in which it is used in the arts, is much more complicated than simple combustion. It was once deemed impossible to separate it entirely from all foreign substances, and it is only in chemical laboratories that it is to be met with in the state of purity in which you find it in this phial. Wood-ashes are, however, valuable for the alkali which they contain, and are used for some purposes without any further preparation. Purified in a certain degree, they make what is commonly called _pearlash_, which is of great efficacy in taking out grease, in washing linen, &c.; for potash combines readily with oil or fat, with which it forms a compound well known to you under the name of _soap_. CAROLINE. Really! Then I should think it would be better to wash all linen with pearlash than with soap, as, in the latter case, the alkali being already combined with oil, must be less efficacious in extracting grease. MRS. B. Its effect would be too powerful on fine linen, and would injure its texture; pearlash is therefore only used for that which is of a strong coarse kind. For the same reason you cannot wash your hands with plain potash; but, when mixed with oil in the form of soap, it is soft as well as cleansing, and is therefore much better adapted to the purpose. Caustic potash, as we already observed, acts on the skin, and animal fibre, in virtue of its attraction for water and oil, and converts all animal matter into a kind of saponaceous jelly. EMILY. Are vegetables the only source from which potash can be derived? MRS. B. No: for though far most abundant in vegetables, it is by no means confined to that class of bodies, being found also on the surface of the earth, mixed with various minerals, especially with earths and stones, whence it is supposed to be conveyed into vegetables by the roots of the plant. It is also met with, though in very small quantities, in some animal substances. The most common state of potash is that of _carbonat_; I suppose you understand what that is? EMILY. I believe so; though I do not recollect that you ever mentioned the word before. If I am not mistaken, it must be a compound salt, formed by the union of carbonic acid with potash. MRS. B.