divided into cephalous and acephalous (Acephala), according
as they have or have not an organized part of their anatomy
as the seat of the brain and special senses. The Acephala,
or Lamellibranchiata (q.v.), are commonly known as bivalve
shell-fish. In botany the word is used for ovaries not
terminating in a stigma. Acephalocyst is the name given by R.
T. H. Laennec to the hydatid, immature or larval tapeworm.
ACERENZA (anc. Aceruntia), a town of the province of
Potenza, Italy, the seat of an archbishop, 15 1/2 m. N.E. of the
station of Pietragalla, which is 9 m. N.W. of Potenza by rail,
2730 ft. above sea-level. Pop. (1901) 4499. Its situation is
one of great strength, and it has only one entrance, on the
south. It was occupied as a colony at latest by the end of
the Republic, and its importance as a fortress was specially
appreciated by the Goths and Lombards in the 6th and 7th
centuries. It has a fine Norman cathedral, upon the gable of
which is one of the best extant busts of Julian the Apostate.
ACEROSE (from Lat. acus, needle, or acer, sharp),
needle-shaped, a term used in botany (since Linnaeus) as
descriptive of the leaves, e.g., of pines. From Lat. aeus,
chaff, comes also the distinct meaning of ``mixed with chaff.''
ACERRA, a town and episcopal see of Campania, Italy,
in the province of Caserta, 9 m. N.E. from Naples by
rail. Pop. (1901) 16,443. The town lies on the right
bank of the Agno, which divides the province of Naples from
that of Caserta, 90 ft. above the sea, in a fertile but
somewhat marshy district, which in the middle ages was very
malarious. The ancient name (Acerrae) was also borne
by a town in Umbria and another in Gallia Transpadana
(the latter now Pizzighettone on the Adda, 13 m. W.N.W. of
Cremona). It became a city with Latin rights in 332 B.C.
and later a municipium. It was destroyed by Hannibal in 216
B.C., but restored in 210; in 90 B.C. it served as the
Roman headquarters in the Social war, and was successfully
held against the insurgents. It received a colony under
Augustus, but appears to have suffered much from floods of
the river Clams. Under the Empire we hear no more of it,
and no traces of antiquity, beyond inscriptions, remain.
ACERRA, in Roman antiquity, a small box or pot for holding
incense, as distinct from the turibulum (thurible) or
censer in which incense was burned. The name was also
given by the Romans to a little altar placed near the
dead, on which incense was offered every day till the
burial. In ecclesiastical Latin the term acerra is still
applied to the incense boats used in the Roman ritual.
ACETABULUM, the Latin word for a vinegar cup, an ancient
Roman vessel, used as a liquid measure (equal to about
half a gill); it is also a word used technically in
zoology, by analogy for certain cup-shaped parts, e.g.
the suckers of a mollusc, the socket of the thigh-bone,
&c.; and in botany for the receptacle of Fungi.
ACETIC ACID (acidum aceticum), CH3.CO2H, one of the most
important organic acids. It occurs naturally in the juice of
1 See Gibbon, ch. xlvii. (vol. v. p. 129 in Pury's ed.).
many plants, and as the esters of n-hexyl and n-octyl
alcohols in the seeds of Heracleum giganteum, and in the
fruit of Heracleum sphondylium, but is generally obtained,
on the large scale, from the oxidation of spoiled wines, or
from the destructive distillation of wood. In the former
process it is obtained in the form of a dilute aqueous
solution, in which also the colouring matters of the wine,
salts, &c., are dissolved; and this impure acetic acid is
what we ordinarily term vinegar (q.v.). Acetic acid (in
the form of vinegar) was known to the ancients, who obtained
it by the oxidation of alcoholic liquors. Wood-vinegar was
discovered in the middle ages. Towards the close of the
18th century, A. L. Lavoisier showed that air was necessary
to the formation of vinegar from alcohol. In 1830 J. B.
A. Dumas converted acetic acid into trichloracetic acid,
and in 1842 L. H. F. Melsens reconverted this derivative
into the original acetic acid by reduction with sodium
amalgam. The synthesis of trichloracetic acid from its
elements was accomplished in 1843 by H. Kolbe; this taken
in conjunction with Melsens's observation provided the first
synthesis of acetic acid. Anhydrous acetic acid--glacial
acetic acid--is a leafy crystalline mass melting at 16.7 deg.
C., and possessing an exceedingly pungent smell. It boils
at 118 deg. , giving a vapour of abnormal specific gravity.
It dissolves in water in all proportions with at first a
contraction and afterwards an increase in volume. It is
detected by heating with ordinary alcohol and sulphuric acid,
which gives rise to acetic ester or ethyl acetate, recognized
by its fragrant odour; or by heating with arsenious oxide,
which forms the pungent and poisonous cacodyl oxide. It is
a monobasic acid, forming one normal and two acid potassium
salts, and basic salts with iron, aluminium, lead and copper.
Ferrous and ferric acetates are used as mordants; normal
lead acetate is known in commerce as sugar of lead (q.v.);
basic copper acetates are known as verdigris (q.v.).
Pharmacology and Therapeutics.---Glacial acetic acid is
occasionally used as a caustic for corns. The dilute acid,
or vinegar, may be used to bathe the skin in fever, acting
as a pleasant refrigerant. Acetic acid has no valuable
properties for internal administration. Vinegar, however,
which contains about 5% acetic acid, is frequently taken
as a cure for obesity, but there is no warrant for this
application. Its continued employment may, indeed, so injure
the mucous membrane of the stomach as to interfere with digestion
and so cause a morbid and dangerous reduction in weight.
The acetates constitute a valuable group of medicinal agents,
the potassium salt being most frequently employed. After
absorption into the blood, the acetates are oxidized to
carbonates, and therefore are remote alkalies, and are
administered whenever it is desired to increase the alkalinity
of the blood or to reduce the acidity of the urine, without
exerting the disturbing influence of alkanes upon the digestive
tract. The citrates act in precisely similar fashion, and may be
substituted. They are somewhat more pleasant but more expensive.
ACETO-ACETIC ESTER, C6H10O3 or CH3.CO.CH2.COOC2H5,
a chemical substance discovered in 1863 by A. Geuther, who
showed that the chief product of the action of sodium on ethyl
acetate was a sodium compound of composition C6H9O3Na,
which on treatment with acids gave a colourless, somewhat
oily liquid of composition C6H10O3. E. Frankland and
B. F. Duppa in 1865 examined the reaction and concluded that
Geuther's sodium salt was a derivative of the ethyl ester
of acetone carboxylic acid and possessed the constitution
CH6CO.CHNa.COOC2H5. This view was not accepted by
Geuther, who looked upon his compound C6H10O3 as being
an acid. J. Wislicenus also investigated the reaction
very thoroughly and accepted the Frankland-Duppa formula
(Annalen, 1877, 186, p. 163; 1877, 190, p. 257).
The substance is best prepared by drying ethyl acetate over
calcium chloride and treating it with sodium wire, which
is best introduced in one operation; the liquid boils and
is then heated on a water bath for some hours, until the
sodium all dissolves. After the reaction is completed,
the liquid is acidified with dilute sulphuric acid (1:5)
and then shaken with salt solution, separated from the salt
solution, washed, dried and fractionated. The portion
boiling betbeen 175 deg. and 185 deg. C. is redistilled. The
yield amounts to about 30% of that required by theory.
A. Ladenburg and J. A. Wanklyn have shown that pure ethyl
acetate free from alcohol will not react with sodium to produce
aceto-acetic ester. L. Claisen, whose views are now accepted,
studied the reactions of sodium ethylate and showed that
if sodium ethylate be used in place of sodium in the above
reaction the same result is obtained. He explains the reactions
/ONa
CH3.C==O + NaOC2H5 = CH3.C-OC2H5,
\ OC2H5 \OC2H5
this reaction being followed by
/ONa H\
CH3.C-OC2H5 + CH.COOC2H5 = 2 C2 H5OH +
\OC2H5 H/ CH3.C(ONa):CH.COOC2H5;
and on acidification this last substance gives aceto-acetic
ester. Aceto-acetic ester is a colourless liquid boiling at
181 deg. C.; it is slightly soluble in water, and when distilled
undergoes some decomposition forming dehydracetic acid
C8H8O4. It undoubtedly contains a keto-group, for it
reacts with hydrocyanic acid, hydroxylamine, phenylhydrazine
and ammonia; sodium bisulphite also combines with it to
form a crystalline compound, hence it contains the grouping
CH 3/0.CO-. J. Wislicenus found that only one hydrogen atom
in the--CH2- group is directly replaceable by sodium, and
that if the sodium be then replaced by an alkyl group, the
second hydrogen atom in the group can be replaced in the same
manner. These alkyl substitution products are important,
for they lead to the synthesis of many organic compounds,
on account of the fact that they can be hydrolysed in
two different ways, barium hydroxide or dilute sodium
hydroxide solution giving the so-called ketone hydrolysis,
whilst concentrated sodium hydroxide gives the acid
Ketone hydrolysis:-
CH3.CO.C(XY).CO2C2H5 -> CH3.CO.CH(XY) +
C2H5OH + CO2;
Acid hydrolysis:-
CH3.CO.C(XY).CO2C2H5 -> CH3.CO2H + C2H5OH +
CH(XY).COOH;
(where X and Y = alkyl groups).
Both reactions occur to some extent simultaneously. Acetoacetic
ester is a most important synthetic reagent, having been
used in the production of pyridines (q.v.), quinolines
(q.v.), pyrazolones, furfurane (q.v.), pyrrols (q.v.),
uric acid (q.v.), and many complex acids and ketones.
For a discussion as to the composition, and whether
it is to be regarded as possessing the ``keto', form
CH3.CO.CH2.COOC2H6 or the ``enol'' form CH3.C(OH):
CH.COOC2H5, see ISOMERISM, and also papers by J. Wislicenus
(Ann., 1877, 186, p. 163; 1877, 190, p. 257), A. Michael
(Journ. Prak. Chem., 1887, [2] 37, p. 473), L. Knorr
(Ann., 1886, 238, p. 147), W. H. Perkin, senr. (Journ. of
Chem. Soc., 1892, 61, p. 800) and J. U. Nef (Ann., 1891,
266, p. 70; 1892, 270, pp. 289, 333; 1893, 276, p. 212).
ACETONE, or DIMETHYL KETONE, CH3.CO.CH3, in chemistry,
the simplest representative of the aliphatic ketones. It
is present in very small quantity in normal urine, in the
blood, and in larger quantities in diabetic patients.
It is found among the products formed in the destructive
distillation of wood, sugar, cellulose, &c., and for this
reason it is always present in crude wood spirit, from which
the greater portion of it may be re-covered by fractional
distillation. On the large scale it is prepared by the dry
distillation of calcium acetate (CH3CO2)2Ca = CaCO3 +
CH3COCH3. E. R. Squibb (Journ. Amer. Chem. Soc., 1895,
17, p. 187) manufactures it by passing the vapour of acetic
acid through a rotating iron cylinder containing a mixture
of pumice and precipitated barium carbonate, and kept at a
temperature of from 500 deg. C. to 600 deg. C. The mixed vapours
of acetone, acetic acid and water are then led through a
condensing apparatus so that the acetic acid and water are
first condensed, and then the acetone is condensed in a second
