Table II.—Alkalimetrical Equivalents.
| Grains. | are equivalent to | Grains. |
| 22 Carbonic anhydride (dry). | 17 Ammonia (pure or gaseous). | |
| 63 Oxalic acid (crystallised). | 431⁄2 Carbonate of ammonia (neutral, hydrated). | |
| 49 Sulphuric acid (liquid, monohydrated, sp. gr. 1·8485). | 59 Sesquicarbonate of ammonia (Ph. L.; translucent, hydrated). | |
| 75 Tartaric acid (crystallised). | 79 Bicarbonate of ammonia (crystallised). | |
| 1000 Dilute sulphuric acid (sp. gr. 1·033). | 47 Potassa (anhydrous). | |
| 56 Hydrate of potassa (pure caustic potassa). | ||
| Water—gr. measure. | 69 Carbonate of potassa (anhydrous). | |
| 1000 Dilute sulphuric acid (sp. gr. 1·032). | 83 Carbonate of potassa (granulated, commercial). | |
| 87 Carbonate of potassa (crystallised). | ||
| 100 Bicarbonate of potassa (crystallised). | ||
| 31 Soda (anhydrous). | ||
| 40 Hydrate of soda (pure caustic soda). | ||
| 53 Carbonate of soda (anhydrous). | ||
| 143 Carbonate of soda (crystallised). | ||
| 84 Bicarbonate of soda (crystallised). | ||
| 831⁄2 Sesquicarbonate of soda (average commercial). | ||
| 84 Bicarbonate of soda (crystals, or cryst. powder, free from moisture). | ||
| 15 Lithia. | ||
| 24 Hydrate of lithia. | ||
| 37 Carbonate of lithia. | ||
| 761⁄2 Baryta (pure, caustic). | ||
| 851⁄2 Hydrate of baryta. | ||
| 981⁄2 Carbonate of baryta. | ||
| 28 Lime (pure, caustic; i. e. quick-lime). | ||
| 37 Hydrate of lime (slaked lime). | ||
| 50 Carbonate of lime (chalk; marble). | ||
| 20 Magnesia (pure, calcined). | ||
| 42 Carbonate of magnesia (dry, neutral). | ||
| 481⁄2 Carbonate of magnesia (ordinary commercial). | ||
| 52 Stronia (pure, caustic). | ||
| 61 Hydrate of strontia. | ||
| 74 Carbonate of strontia. |
ALKALOID. Syn. Vegetable Alkali, Organic Base; Alkaloïdes (pl., -IDES, or -IDÆ), L.; Alcaloïde, Alcali organique, Fr. In chemistry, a name commonly given to any proximate principle of vegetable origin possessing alkaline or basic properties, however feeble. In its most extended sense the term embraces all organic bases, whether obtained from the animal or vegetable kingdom, or produced artificially. The alkaloids form a numerous and important class of bodies. They exist in nature nearly always in the form of salts, the acid being often, like themselves, peculiar to the plant, or class of plants, in which they are found; whilst the medicinal activity of the latter, in most cases, almost entirely depends on their presence.
Prep. The following general methods of procuring the alkaloids will be found applicable to such as full directions are not given for under their respective heads:—
1. (When the base is insoluble in water, non-volatile, and existing in the plant in an insoluble form.) The bruised plant is boiled or macerated in water acidulated with hydrochloric or acetic acid, and the liquor, after filtration, is neutralised with an alkali (ammonia, potassa, lime, or magnesia); the resulting precipitate is purified by re-solution in dilute acid, digestion with a little animal charcoal, and subsequent crystallisation, or re-precipitation with an alkali; or the first precipitate is purified by dissolving it once, or, if necessary, several times, in boiling alcohol, which yields the pure alkaloid either on cooling or by evaporation.
2. (When the base is insoluble in water, and non-volatile, but existing in the plant as a soluble salt.) The bruised or sliced plant is boiled or macerated in water, and the filtered liquor precipitated and otherwise treated as before.
3. (When the base is soluble in water, and non-volatile.) An infusion made with very dilute acid, hydrochloric or acetic, is concentrated by a gentle heat; and the residual liquor treated with potassa (or concentrated solution of ammonia) and ether conjointly; after repose, the ethereal solution is decanted and evaporated. For those alkaloids which are insoluble in ether (as morphia and cinchonia), the previous process may be adopted.
4. (When the base is both soluble in water and volatile.) The vegetable, in a bruised or divided state, or its extract, is alkalised with potassa and distilled; the distillate is neutralised
with dilute oxalic or sulphuric acid, and carefully evaporated to dryness; the residuum is next digested in alcohol, and the resulting tincture agitated with potassa and ether, the former being in quantity just sufficient to seize on all the acid; lastly, the ethereal solution thus formed, on careful evaporation, leaves the alkaloid nearly pure. It may be further purified by cautious distillation.
As some of the alkaloids are soluble in excess of the alkaline precipitant, over-saturation should be carefully avoided; or the precipitant may be used under the form of carbonate or bicarbonate. When lime and magnesia are employed, they are boiled for a few minutes with the solution.