ACCUM ACETIC ACID 61 m. Friedrlch, a German chemist, born in Buckeburg, March 29, 1769, died in Berlin, June 28, 1838. In 1793 he went to London, where he was appointed in 1801 professor of chemistry and mineralogy in the Surrey insti- tute. Being accused of purloining books and engravings from the library of the royal insti- tution, he returned to Germany, and in 1822 was appointed professor in the school of indus- try and the academy of architecture in Berlin. He is known in connection with the introduc- tion of gas lights in London. He wrote "A System of Chemistry " (2 vols., London, 1803), "A Practical Treatise on Gas Lights" (1815), and " On the Adulteration of Food." ACELDAMA (Chaldaic, 'hakal dema, field of blood), the name given to the potter's field which was purchased with the money for which Judas betrayed Christ. It was after- ward used as a place of burial for strangers. ACEPHALOCYST (Gr. a privative, /ce^a^, head, and /cwmc, bladder ; literally, a cyst without a head), a vesicular or hydatid growth, some- times found in the substance of the liver, kid- ney, or other of the abdominal organs, in man and some of the lower animals. It is a globu- lar bag or sac, having its walls composed of a condensed albuminous substance, of a lami- nated texture, and containing in its cavity a clear, colorless fluid, with albuminous or gelat- inous ingredients. The main cyst produces smaller secondary cysts by a process of bud- ding or outgrowth from its walls, and these secondary cysts are sometimes very numerous. They are developed between the layers of the principal cyst wall, and project sometimes in- ternally and sometimes externally. Those species in which the young cysts project in- ternally, and are thrown off into the central cavity, are called endogenous, and are found principally in the human subject; those in which they project externally are called ex- ogenous, and are found in the ox and other ruminating animals. Acephalocysts are usu- ally regarded as of a parasitic nature, and be- longing to the class of cestoid worms, of which the ordinary tapeworm is the familiar repre- sentative. The embryo of these cestoid worms .presents at one period a globular body armed with six calcareous hooks, which afterward becomes developed into a tapeworm head, enclosed in an inverted globular membrane. When one of these partially developed tape- worm heads is found by itself, surrounded by a cyst and imbedded in one of the internal organs, it is called a cysticercus. When the principal cyst enlarges and throws off a number of secondary cysts containing tapeworm heads, it is called an echinococcus. The acephalocyst is believed to be a growth having the same ori- gin as the above, but in which for some reason the tapeworm heads either have not been de- veloped at all, or have become disintegrated and disappeared. Hence its name, indicating the absence of the head, which, if present, would be decisive proof of its parasitic origin. ACETATES, compounds of which acetic acid is one of the principal constituents. They are generally soluble in water and alcohol, and some of them are deliquescent ; those that are least soluble are acetates of mercury, silver, molybdenum, and tungsten. There are three classes of salts, neutral, acid, and basic, all of them destroyed at a red heat or by sulphuric acid, which latter liberates acetic acid, easily recognized by its pungent odor. Heated with a mixture of sulphuric acid and alcohol, they give rise to acetic ether ; with lime they fur- nish acetone, which has a peculiar character- istic odor; and distilled with caustic potash, they yield marsh gas. Their solutions yield a deep yellow color with ferric chloride (ses- quichloride of iron), not given by free acetic acid. There are numerous acetates, some largely used in medicine and others in the arts. Among the former may be mentioned the fol- lowing: potassic acetate, employed as a diu- retic ; ammoniac acetate, used as a diaphoretic ; plumbic acetate (sugar of lead), used as an .astringent. Of the acetates employed in the arts the most important are: acetates of alumina, manganese, iron, and zinc, largely used as mordants in calico printing; acetate of copper, verdigris, and a mixture of acetate and arsenite of copper called Schweinfurt green, employed hi paints and for wall paper ; acetate of lime, prepared as a crude material in the manufacture of acetic acid from the distilla- tion of wood. Many modern chemists divide the acetates into two classes: 1. Metallic ace- tates, in which the basic hydrogen of the acetic acid is replaced by a metal or group ; 2. Acetic ethers or organic acetates, in which the hydrogen is replaced by an alcoholic radical. ACETIC ACID (Lat. acetum, vinegar, of which it constitutes about 6 per cent.) has been known in a dilute form from the remotest antiquity. It' can be prepared in two conditions : acetic anhydride, or anhydrous acetic acid, and acetic acid. Anhydrous acetic acid, as obtained by Gerhardt, is a colorless, very mobile liquid, of high refracting power, having a very pungent smell and emitting a vapor which is extremely irritating to the eyes. It gradually absorbs moisture from the air, and becomes converted into the common acid. Acetic acid can be made in a great number of ways : by treating aldehyde, alcohol, and ethylic ethers with oxi- dizing agents ; by fusing sugar, starch, oxalic acid, tartaric acid, or citric acid with potash ; by submitting wood, sugar, and gums to dry distillation; by distilling gelatine, caseine, 01 fibrine with a mixture of sulphuric acid and manganese dioxide. It has been made syn- thetically by Wanklyn, by passing a current of carbonic acid into a solution of sodium methyl, and appears to exist ready formed in the juices of certain plants, such as the sap of the oak, and in some animal fluids. The pro- duct of the fermentation of wine and other spirituous liquids is vinegar, formed essentially of acetic acid diluted with water. (See VINE-
