Page:Collier's New Encyclopedia v. 01.djvu/160

ALKALI ALKALI, a strong base, capable of neutralizing acids, so that the salts formed are either completely neutral, or, if the acid is weak, give alkaline reactions. It was formerly restricted to the hydrates of potassium, sodium, lithium, and ammonium, but now includes the hydrates of alkaline earths (baryta, strontia, and lime) and many organic substances. The term alkali usually means, in commerce, caustic soda or potash, impure, NaHO or KHO; both are used in the arts for the manufacture of glass and soap, and for many other purposes. Caustic potash is used in surgery as a cautery.

ALKALIMETRY, the process of determining the purity of alkalies. Commercial potash and soda contain foreign substances, which diminish the percentage of real alkali. The alkalimeter furnishes a simple and ready means of determining the proportion of pure carbonate of potash or soda contained in any sample. It consists of a graduated glass tube, filled with diluted sulphuric acid, and containing as much absolute sulphuric acid as would neutralize a given weight, say 100 grains, of carbonate of potash. One hundred grains of the article to be judged of is then dissolved in water, and as much acid is gradually added to it from the tube as to neutralize the solution, that is, take up all the alkali. The point at which neutralization is complete is determined by means of colored tests. Formerly, the two vegetable colors, litmus and turmeric, were alone used for this purpose. It is not, however, always easy to recognize the neutral point, and other indicators (as these coloring matters are called) have come into use. The chief of these are methyl-orange and phenolphthalein. A mixture of the alcoholic solutions of these substances imparts a pale yellow color to strictly neutral liquids, which is changed to deep red by the least trace of alkali, and to pink by a trace of acid.

This method of determining the strength of alkalies is called the alkali-metric process.

ALKALOID, a substance resembling an alkali in properties. Alkaloids are natural organic bases containing nitrogen, and having high molecular weights. They occur in many plants, and some in animal tissues; they have not, except conine, been formed by synthesis. They are substitution compounds of ammonia; most are tertiary amines. They have mostly a bitter taste, act powerfully on the animal system, and are used in medicine as quinine, morphine, and strychnine; they are frequently violent poisons.

ALLAH (compounded of the article al and ilâh—i. e., "the god," a word cognate with the Hebrew Eloah), the Arabic name of the supreme god among the heathen Arabs, adopted by Mohammed for the one true God. See MOHAMMED and MOHAMMEDANISM.

ALLAHABAD. (1) A division of British India; has an area of 17,264 square miles, is one of the most fertile and populous portions of India. (2) A district of the above division, lying around the junction of the Jumna and Ganges. Area 2,852 square miles. (3) The capital of the division of Allahabad; at the confluence of the Ganges and Jumna; seat of government of the Northwestern provinces; 72 miles W. of Benares. It carries on a large trade, especially in sugar, cotton, indigo, gold and silver ornaments, and furniture. It is a resort of Hindu pilgrims and the seat of an annual fair, usually attended by about 250,000 persons. Among the principal buildings are the fort founded by Akbar Khan in 1575, the Juma Masjid mosque. Sultan Khusru's caravansary, and the Muir Central College (1874). The town was taken by the British in 1765, and assigned by them to the titular Emperor of Delhi, but transferred to the Nawab of Oudh in 1771, who restored it to the British in 1801. It suffered severely during the mutiny of 1857. Pop. about 170,000.

ALLAN, DAVID, an eminent painter known as "the Scotch Hogarth," born in 1744. He studied art for 16 years in Rome, gaining a gold medal for historical composition in 1773. In 1777 he began to paint portraits in London. Among his most celebrated pictures are "The Origin of Portraiture" and the illustrations for Allan Ramsay's "Gentle Shepherd." He died in 1796.

ALLEGHENIES, a word used as synonymous with the APPALACHIAN MOUNTAINS (q. v.), sometimes applied only to that portion of the system which extends from Pennsylvania to North Carolina, and which forms the watershed between the Atlantic and the Mississippi. The ridges, 2,000 to 2,400 feet high, are remarkable for their parallelism and regularity, all the main valleys being longitudinal. They are rich in coal, iron, and limestone, and their forests supply valuable timber.

ALLEGHENY, a former city in Allegheny co., Pa., now consolidated with PITTSBURGH (q. v.).