Because in many cases it produced confusion. In which class, for instance, would you place carbonic acid? CAROLINE. Now I see the difficulty. I should be at a loss where to place it, as you have told us that it exists in the animal, vegetable, and mineral kingdoms. EMILY. There would be the same objection with respect to phosphoric acid, which, though obtained chiefly from bones, can also, you said, be found in small quantities in stones, and likewise in some plants. MRS. B. You see, therefore, the propriety of changing this mode of classification. These objections do not exist in the present nomenclature; for the composition and nature of each individual acid is in some degree pointed out, instead of the class of bodies from which it is extracted; and, with regard to the more general division of acids, they are classed under these three heads: First, Acids of known or supposed simple bases, which are formed by the union of these bases with oxygen. They are the following: The _Sulphuric_ _Carbonic_ _Nitric_ _Phosphoric_ _Arsenical_ Acids, of known and simple bases. _Tungstenic_ _Molybdenic_ _Boracic_ _Fluoric_ _Muriatic_ This class comprehends the most anciently known and most important acids. The sulphuric, nitric, and muriatic were formerly, and are still frequently, called _mineral acids_. 2dly, Acids that have double or binary radicals, and which consequently consist of triple combinations. These are the vegetable acids, whose common radical is a compound of hydrogen and carbon. CAROLINE. But if the basis of all the vegetable acids be the same, it should form but one acid; it may indeed combine with different proportions of oxygen, but the nature of the acid must be the same. MRS. B. The only difference that exists in the basis of vegetable acids, is the various proportions of hydrogen and carbon from which they are severally composed. But this is enough to produce a number of acids apparently very dissimilar. That they do not, however, differ essentially, is proved by their susceptibility of being converted into each other, by the addition or subtraction of a portion of hydrogen or of carbon. The names of these acids are, The _Acetic_ _Oxalic_ _Tartarous_ _Citric_ _Malic_ Acids, of double bases, being of vegetable origin. _Gallic_ _Mucous_ _Benzoic_ _Succinic_ _Camphoric_ _Suberic_ The 3d class of acids consists of those which have triple radicals, and are therefore of a still more compound nature. This class comprehends the animal acids, which are, The _Lactic_ _Prussic_ _Formic_ Acids, of triple bases, or animal acids. _Bombic_ _Sebacic_ _Zoonic_ _Lithic_