ACE 



ACH 



a pharynx, or beginning of the oesophagus 

 without jaws, tongue, or mouth properly 

 so called, as in the oyster. According to 

 Cuvier, this class of molluscous animals 

 comprehends many genera with bivalve 

 shells, or acephala testacea ; and a few 

 which are devoid of shells, or acephala 

 nuda. 



ACEPHALO'PHORA (a, priv., k6- 

 <pa\r], the head, ^e'pco, to bear). A term 

 applied by Blainville to a class of mollus- 

 cous animals corresponding with the 

 acephala and the brachiopoda of Cuvier. 



ACERA'CE^. The Sycamore tribe of 

 Dicotyledonous plants, named from the 

 genus Acer. Trees, with leaves opposite ; 

 petals generally 5 ; stamens usually 8, in- 

 serted with the petals on a hypogynous 

 disk ; fruit dicarpellary, samaroid ; seeds 

 exalbuminous. 



ACERA'LES. An alliance of Dicoty- 

 ledonous plants. Stamens definite in 

 number. Flowers usually un symmetri- 

 cal in their parts, or, if symmetrical, 

 more or less irregular ; in the majority, 

 small, and disposed in a compound inflo- 

 rescence. 



A'CERIC ACID. A peculiar acid said 

 to exist in the sap of the acer, or maple 

 tree. 



A'CEROSE {acerosus, chaffy). Sharp- 

 pointed ; tapering to a fine point, as the 

 leaves of juniper. 



ACE'SCENT (acesco, to become sour). 

 A term applied to substances which be- 

 come sour spontaneously, as vegetable 

 and animal juices, or infusions. 



ACETA'BULUM {acetum, vinegar). A 

 vinegar-cruet ; and hence a cup-like ca- 

 vity, as the suckers on the arms of the 

 cuttle-fish, the cavity of the hip-joint, 

 the socket on the trunk of insects which 

 receives the leg. Also, a Roman mea- 

 sure containing two ounces and a half. 



ACE'TAL. A compound of aldehyde 

 with ether, formed by the action of plati- 

 num black on the vapour of alcohol with 

 the presence of oxygen. The term is 

 derived from acetum, vinegar, and the 

 first syllable of alcohol. 



A'CETATE {acetum, vinegar). A salt 

 formed by the union of acetic acid with 

 an alkaline, an earthy or a metallic 

 base. 



ACE'TIC ACID {acetum, vinegar). The 

 pure acid of vinegar. It occurs, ready 

 formed, in several products of the vege- 

 table kingdom, and is generated during 

 the spontaneous fermentation of many 

 vegetable and animal juices. By real 

 acetic acid is meant such an acid as 

 5 



occurs in a dry acetate: it cannot exist in 

 an uncombined state. 



ACETO'METER {acetum, vinegar, 

 fxtrpov, a measure). An instrument for 

 ascertaining the strength of vinegars. 

 It consists of a globe of glass about three 

 inches in diameter, having a little ballast 

 ball drawn out beneath, and a stem above 

 of about three inches long, containing a 

 slip of paper, with a transverse line in 

 the middle, and surmounted with a little 

 cup for receiving weights or poises. 



ACETONE. The new chemical name 

 for pyro-acetic spirit; allmpid colourless 

 liquid, prepared by distilling a mixture 

 of two parts of crystallized acetate of lead 

 and one part of quicklime in a salt-glaze 

 jar. The names of such pyrogen bodies 

 terminate in one, as contain one atom of 

 oxygen and are neutral. 



ACE'TYL. A hypothetical radical, 

 pervading a series of compounds, includ- 

 ing acetic acid, and prepared by abstract- 

 ing two atoms of oxygen from ethyl. 

 The term is derived from acetum, vine- 

 gar, and v\r\, matter. 



ACHiE'NIUM{a,priv., xaiVo), toopen). 

 An indehiscent fruit ; one-celled, one- 

 seeded, superior, hard, and dry, with the 

 integuments of the seed distinct from it. 

 It occurs in the Labiatae and the Bora- 

 gin eae. 



ACHA'TINyE. Spiral snails; a sub- 

 family of the Helicidce, named from the 

 genus Achatina : the spire of their shelly 

 is elongated and conical. 



ACHE'RNAR. A star of the first mag- 

 nitude in the southern constellation Eri- 

 danus. 



ACHE'TIDiE. A group of Orthopte- 

 rous insects, belonging to the family Sal- 

 tatoria, and including the species known 

 as crickets. Many of them burrow in the 

 ground, and most of them, like the house- 

 cricket, are nocturnal. Few have an}' 

 power of active flight. 



A'CHIRITE. Emerald malachite; a 

 mineral consisting of oxide of copper, 

 carbonate of lime, silica, and water. 



ACHLAMY'DEOUS (a, priv., x^^Mi-?, 

 a cloak). The general name of all those 

 plants from which the floral envelopes — 

 the calyx and the corolla — are both ab- 

 sent. 



A'CHMIT. A mineral, supposed to be 

 a bisilicate of soda, combined with a 

 bisilicate of iron. 



ACHROMATIC (a, priv., xp^/xa. co- 

 lour). An optical terra signifying colour- 

 less as applied to a lens, in which the 

 primary colours which usually accompany 

 B3 



