qida23

By subjecting different vegetable substances to ultimate analysis, it has been ascertained that the products which result from the different combinations of oxygen and hydrogen, are as follows :
A vegetable substance is always acid where the oxygen which it contains is to the hydrogen in a proportion greater than is necessary to form water, or where there is excess of ,oxygen.
A vegetable substance is resinous, oily, or alcoholic, where the oxygen is to the hydrogen, in a less proportion than in water, or where there is excess of hydrogen.
A vegetable substance is neither acid nor resinons, but saccharine, mucilaginous, &c. where the oxygen and hydrogen are in the same relative proportion as in water, or where there is no excess of either.
Obs. In addition to the oxygen and hydrogen, there is in resin, oil, alcohol, sugar, and mucilage, a quantity of carbon.
OF THE INGREDIENTS OF PLANTS.
530. jThe ingredients of plants are distinct substances, formed by their secreting organs, and separable from each other without destructive distillation.
531. They are separated by certain solvents which have the power of dissolving some, but not the others. Thus water dissolves gum, but not resin ; while alcohol will take up the resin and leave the gu.-u, &c.
Obs. The solvents made use of for separating the ingredients of vegetables, are hot aud cold water, alcohol, ether, and some of the acids.
2. The following are the principal ingredients, or what are called the proximate principles of vegetables. Some account of the most important among them will be given.
1. Gum. 9. Fixed oil.
2. Sugar. ,10. VolatUe oil.
3. Starch. 11. Camphor.
4. Gluten. 12. Resins.
5 Extractive and Lignin 13. Narcotic principle.
6. Tannin. 14. Bituminous substances.
7. Colouring matter, 15. Vegetable acids.
8. Wax.
532. Gum. Gum Arabic may be taken as a specimen of pure gum. It dissolves in water forming a viscid solution, or mucilage from which it may be obtained in its original state by evaporation. It is insoluble in alcohol, which therefore causes a white precipitate in its aqueous solution.
Obs. 1. Gum is decomposed by sulphuric and nitric acids : the former produces water, acetous acid, and charcoal; tbe latter among other products converts a portion of the gum into a white acid substance, called mucous acid.
2. When gum is submitted to destructive distillation it affords carbonic acid, and carburetted hydrogen, empyreumatic oil, water, and a quantity of impure acetic acid.)