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ACEPHALI. Monophysite Controversy. (3) To clergy belonging to no diocese. (4) To the Flagellants (q.v.).

ACEPH'ALOCYST (literally, a cyst with- out a head; Gk. a, a, priv. + Keipalri, kephale, head + nvart^, kystis, a bladder, bag). A hydatid growth found in the liver, kidneys, or other glandular organs of man, and sometimes of lower animals. It is a globular sac with walls of condensed albuminous substance of laminated composition. In its cavity is a col- orless fluid of albuminous and gelatinous compo- sition. Sometimes many secondary cysts occur. They are of parasitic origin, being produced by the larvae of a species of tapeworm (Toenia echi- nococcus).

A'CER. See.

ACERBI, a-cher'be, (1773-1846). An Italian naturalist, born at Castel Goffredo. He studied at Mantua and became proficient in natural science. He was the first Italian to reach North Cape (1798). In 1816 he founded the Biblioteca Italiana, a literary review published at Milan, and from 1826 to 1836 was Austrian consul-general in Egypt, where he made important archæological collections for the museums of Vienna, Padua, Milan, and Pavia. He published (in English) ''Travels Through Sweden, Finland. Lapland,'' [2 volumes, London, 1802).

ACERRA, a-eher'ra, the ancient An episcopal city in south Italy, nine miles northeast of Naples and opposite Mount Somma, from which there is an excellent view of Vesuvius. It has a cathedral and a seminary. The country is fertile, but until recently, when the marshes were drained, was extremely unhealthful, owing to the inundations of the Agno, which is the Clanius non æquus Acerris of Vergil. Pop., 1901, 16,443.

ACET. A combining form used in various chemical terms, and ultimately 'derived from Lat. acetum, vinegar; as in acetal, acetanilid, etc.

ACETAL, as'e-tal, CH,CH(OC,H:,),. A color- less liquid of agreeable odor and taste. It is readily obtained" by heating a mixture of alde- hyde and ordinary alcohol. It has been used to improve the flavor of wine.

ACETANILID, as'et-an'ihid. A crystal- line powder made by the action of acetic acid on aniline. It is odorless, slightly bitter, spar- ingly soUible in water, but freely so in alcohol, ether, and chloroform. Chemically, it is phenyl- acetamide, CHjCONHCoHb. It is known also by the trade naiue antifebrin. Its action resembles that of antipyrine ( q.v. ), but is less likely to cause eruptions, respiratory disturbance, cyanosis, and collapse, and its administration is followed by less sweating. In health it does not affect the temperature to any extent. Its uses are similar to those of antipyrine. but being insoluble it cannot be used hypodermatically, and is gener- ally given in tablet, capsule or wafer. The dose required is much smaller than that of antipyrine.

ACETATES, as'e-tSts. The salts of acetic acid, which are generally prepared by the action of acetic acid on metallic carbonates or hydrox- ides. Most acetates are soluble in water. To prove the presence of an acetate in a solution, the analytical chemist adds to the solution some strong sulphuric acid and a little alcohol and heats the mixture for a few seconds; by this treatment, of an acetate solution ethyl acetic

ester is produced, which is readily recognized by its pleasant and characteristic odor. Some of the acetates are: (1) Aluminium acetate. This has been obtained only in its aqueous solution, which is used as a mordant under the name of "red liquor." (2) The acetate of iron, known as "black liquor," is likewise used as a mordant in dyeing and printing cotton. The acetates of (3) lead, (4) ammonium, and (5) potassium are much used in medicine. Lead acetate, commonly known as "sugar of lead," is used for external applications as an astringent. Ammonium acetate is used to promote perspiration; it is prepared best by passing an excess of gaseous ammonia into strong acetic acid. Potassium acetate is very largely used as a diuretic. Other metallic acetates are mentioned under the names of the metals (qq.v.).

ACE'TIC ACID, CH.COOH. The sour prin- ciple of vinegar, an acid composed chemically of carbon, hydrogen, and oxygen. The commer- cial acid is largely used in the manufacture of acetates, dye-stuffs, etc. Concentrated acetic acid burns the skin, and is therefore applied as a caustic to remove small warts and corns. Like any other acid, if taken internally for any length of time, dilute acetic acid impairs the digestion and absorption of food.

Acetic acid occurs here and there in the organic world. It is found ready formed in sweat and other animal secretions, as well as in the juices of various plants. It is manufactured either by the oxidation of ordinary alcohol through fermentation (see ), or by the destructive distillation of wood. The aqueous product obtained in the latter process is subjected to fractional distillation, and the fraction constituting impure acetic acid (called pyroligneous acid) is neutralized with soda or lime. In this manner a solution of sodium or calcium acetate is obtained; this solution is evaporated to dryness, and the remaining salt is freed from water and organic impurities by heating above 400° F. Pure acetic acid is prepared by distilling the acetates thus obtained with strong sulphuric acid. The pure anhydrous acid is known as glacial acetic acid; at temperatures below 62° F. it is solid and crystalline; above that temperature it forms a colorless liquid readily known by its pungent, penetrating odor. Since carbon is one of its constituent elements, it is, of course, classed with the compounds of organic chemistry. It is a comparatively weak acid, its salts being broken up not only by the strong mineral acids, but even by many organic acids. Besides the methods just mentioned, acetic acid can be made by synthesis from the constituent elements. When electric sparks are passed between carbon poles in an atmosphere of hydrogen, acetylene gas is produced; and when oxygen (furnished, say, by chromic acid) is made to act upon acetylene in the presence of water, the acetylene combines with oxygen and water, and, as a result, acetic acid is formed according to the following chemical equation:

C,H, + O + H,0 = C:HA Acetylene Acetic acid

It would not pay, however, to use this method in manufacturing acetic acid for practical purposes.

ACETO-ACETIC (ris'e-tu-a-se'tik) ES'TER, ClI,('0('tI.('00(',H,. A colorless liquid organic substance obtained by the action of metallic