Knight's cyclopædia of the industry of all nations, 1851 / [edited by George Dodd].

Date:
[1851]
Catalogue details

Licence: Public Domain Mark

Credit: Knight's cyclopædia of the industry of all nations, 1851 / [edited by George Dodd]. Source: Wellcome Collection.

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    85 plant by biuning which a saline mass is ob- tained containing the allvaU in question ; and in this terra are comprehended vanous other bodies possessing simUar properties. The nUcaUes are numerous, and they are aU com- pound substances; they do not result, how- ever, from the action of any specific or aUcalizing principle, being very variously con- stituted. Ail exist in nature, and some may be artificially formed. The alkaUes may be di\ided into three classes:— 1st. Ammonia, existing in the animal fluids, and composed of two gaseous bodies, viz., hydi-ogen and azote. As it readily evaporates it was formerly called the volatile alkali. 2nd. Compounds of certain metals and oxygen, among which are potash and soda, which, though long known as the fixed alkalies, and usually obtained from the ashes of plants, were discovered by Davy to be metaUic oxides. This class also comprehends the alkaliae oxides or earths, hme, magnesia, &c. No metal jdelds two alkalies by different degrees of oxidizement; nor does any one become an alkaU and an acid. 3rd. The vegeto-alkalies, produced in plants during vegetation. They are, as far as has been ascertained, quaternary compounds of oxygen, hydi-ogen, carbon, and azote. This class includes quina, an active medicinal prin- ciple of chinchona or bark, and morphia, one of the narcotic principles of opium, &c., [Alkaloids.] The chemical and distinguishing proper- ties of the alkalies are, that their aqueous solutions turn vegetable blues green, and vegetable yellows reddish-brown ; and hence infusion of red cabbage and infusion of tur- meric, or paper stained with them, are used as tests of the presence of an alkali. The alkalies restore the colour of vegetable blues which have been reddened by acids, and, on the other hand, the acids restore vegetable colours which have been altered by the alka- lies. The alkahes have great affinity for and readily combine with acids, forming salts and the power of both in altering vegetable co- lours is generally destroyed. The allcaUes are sepai-ated at the negative pole of the vol- taic trough. In odour, taste, molecular form, and uses in the arts, the alkalies difi'er con- siderably. The salts formed with alkaUes are apt to effloresce, and resolve the crystals into the state of powder, or to absorb water from the air, and deliquesce, or become liquid. The alkalies possess a power of rendering albu- men soluble: unboiled white of egg is an albuminate of soda. The albumen of the blood is rendered more fluid by alkalies; hence in excess they impair the plastic power of that fluid. The chief practical uses of tlio alkalies are noticed under the names of the principal varieties, Ammonia, Potash, Soda, &c. ALICALIMETEB. Like as acids and alco- hols call for the hse of acidimeters and alcoho- meters to measiu-e their strength, so do alkahes require the aid of analagous instru- ments, which may fittingly be called allcali- meters. Chemists are aware of many methods of effecting this ; and neat instruments have been devised for the purpose. The German . soap boilers adopt a somewhat clumsy mode of determining the strength of the alkali which they employ; they pour a quart of water on a pound of alkah, then put in a piece of Dutch soap, and add water until the soap sinks: the more water required to bring about this result, the stronger is the alkah supposed to be. But in the land of Liebig such a rough method is not likely to continue: it is being superseded by more scientific pro- cesses. ALKALOIDS, substances which modern chemistry has discovered, ai-e termed some- times vegetable alkalies as hitherto found only in vegetables, atid sometimes organic alkalies, from requiring a vital power to effect their formation ; but the name given to them above is the most appropriate. They possess allca- Hne properties in the lowest degree, and are either tasteless or have a bitter acrid taste, existing generally in a solid, mostly crystal- line form; some, however, are amorphous (Aconitinfe), occasionally in a Uquid state (Conia and Nicotina), the latter very volatile, and readily undergoing decomposition, with an evolution of ammonia, at a moderate tem- perature. The point in which they differ most from the common alkaUes (except Am- monia) is in having nitrogen in their compo- sition, one of them (Cafieina) being perhaps the most highly nitrogenized compound known. Sometimes one only exists in a plant, sometimes several in the same plant, as in opium. Generally they are combined mth an acid; most frequently it is a pecuHar acid. Many of them are with difficulty soluble in water, more so in alcohol; they seldom com- pletely neutrahze acids, but the salts which they form are more soluble than tlie bases ; hence various of their salts are used in medi- cine in preference to the primitive article. The alkaloids are less extensively used in the manufacturing arts than in medicine. ALKEEMES is the name of a favourite cordial, made in some of the northern coun- tries of Europe. It is made from bay leaves, mace, nutmegs, cinnamon, cloves, brandy, syrup of kermes, and orange-flower water.