ALKALI. A term originally applied to the ashes of plants. The term is now generally used to designate potash, soda, and ammonia. Lime and magnesia are alkali-earths. Potassium, so dium, lithium and, rubidium are alkali metals. The alkali-earths, lime and magnesia, are formed by the union of calcium and magnesium with oxygen. According to Heyne and Lenk, the functions of alkalies and alkali-earth is as fol lows: The organic 'acids, viz. : oxalic, malic, tartaric, citric, etc.:require alkalies and alkali earths to form the salts which exist in plants, as bitartrate of potash in the grape, oxalate of lime in beet-leaves, malate of lime in tobacco; and without these bases it is, perhaps, in most cases impossible for the acids to be formed, though in the orange and lemon citric acid exists in the uncombined or free state, and in various plants, as Somervivum arboreum, and Cacalia ficoicles, acids are formed during the.night which disappear in the day. The leaves of these plants are sour in the morning,, tasteless at noon, and bitter at night Alkaloids are a class of bodies very numerous in poisonous and medicinal plants, of which they constitute the active prin ciple. Nicotine, caffein and theo-bromin are the three having an agricultural interest, and are described by Johnston in How Crops Grow, as follows, the figures attached to the letters C, H, N, 0, designating the relative proportion con tained of carbon, hydrogen, nitrogen and oxy gen: Nicotine, C10, N2, is the narcotic and extremely poisonous principle in tobacco, where it exists in combination with malic and citric acids. In the pure state it is a colorless,
oily liquid, having the odor of tobacco in an extreme degree. It is inflammable and volatile, and so deadly that a single drop will kill a large dog. French tobacco contains 7 or 8 per cent., Virginia 6 or 7 per cent., and Maryland and Ha vana about 2 per cent. of nicotine. Nicotine contains 17.3 per cent, of nitrogen, but no oxygen. Caffein, Cs, HIO, N4, 02, exists in coffee and tea, combined with tannic acid. In the pure state it forms white, silky, fibrous crys tals, and has a bitter taste. In coffee, it is found to the. extent of one-half per cent. ; in tea it oc curs in much larger quantity, sometimes as high as 6 per cent. Theo-bromin, 118, Na, resembles caffein in its characters, and is closely related to it in chemical composition. It is found in the cocoa bean, froth which chocolate is manufactured. The alkaloids are remarkble as containing nitrogen, and from having strongly basic characters. They derive their designation, alkaloid, from their likeness to the alkalies.