achorion 
It is the constituent of the crusts of favus (achor), and 
belongs to thi: group of fungoid plants denominated 
Oidiuni. It consists of spores, sporidia or tubes tilled 
with spores, and empty branched tubes or mycelium. 
1'Jruxinxx HYAs-K//. 
Achras (ak'ras), n. [L.,< Gr. axpaf, a kind of wild 
pear-tree.] A genus of plants consisting of a 
single species, A. tiapota, of the natural order 
Saputacetc. It is an evergreen tree, with thick shining 
leaves anil milky juice, a native of tropical America, and 
is often cultivated for its edible fruit, the sapodilla or 
sapodillaplum. Its bark (Jamaica bark) is astringent and 
is used as a febrifuge ; the seeds are aperient and diuretic. 
2. A genus of coleopterous insects. Water- 
house, 1879. 
achroiocythemia, achroiocythsemia (a-kroi"- 
o-si-the'ini-a), . [NL., prop, achrasocythaimia, 
< Gr. axi>oiu<;, same as a^poof, colorless (see 
achroous), + /cwror, a cavity (< Kcetv, contain), + 
alfia, blood.] In pathol., diminution of the nor- 
mal amount of hemoglobin in the red blood- 
corpuscles. Also called oligochromemia. 
achroite (ak'ro-it), n. [< Gr. d;rpoof, colorless, 
+ -ite 2 .] A colorless variety of tourmalin found 
on the island of Elba. 
achroma (a-kro'mii), H. [NL., < Gr. a- priv. + 
Xpupa, color : see achromatic.] In pathol., lack 
of pigment in the skin j achromasia. 
achromasia (ak-ro-ma'zi-a), n. [NL., < Gr. 
d^poi/iarop, without color : see achromatic.] In 
pathol., lack of pigment in the skin. 
achromatic (ak-ro-mat'ik), a. [< Gr. d 
without color (< a- priv., without, + 
color), + -ic : see chromatic.] Destitute of 
color ; free from coloration ; transmitting light 
without decomposing it into its constituent 
colors : as, an achromatic lens or telescope. 
The human eye is not achromatic. It suffers from chro- 
matic aberration as well as from spherical aberration. 
Tyndall, Light and Elect., p. 72. 
Achromatic condenser, an achromatic lens placed be- 
tween the mirror and the stage of a microscope to con- 
centrate the light upon the object when the 
light from the concave mirror is not sufficiently 
intense. Achromatic lens, a lens sensibly 
free from chromatic aberration. It is usually 
composed of two lenses made of glass having 
different refractive and dispersive powers (for 
example, a double convex lens of crown-glass 
[a a] and a concavo-convex lens of flint-glass 
[b &]), the forms of which are so adjusted that 
one lens very nearly corrects the dispersion of 
the other without, however, destroying its re- 
fraction. Achromatic telescope or micro- 
scope, a telescope or microscope in which the 
chromatic aberration is corrected, usually by Achromatic 
means of an achromatic object-glass. 
achromatically (ak-ro-mat'i-kal-i), adv. In an 
achromatic manner. 
achromaticity (a-kro-ma-tis'i-ti), n. [< achro- 
matic + -ity.] The state or quality of being 
achromatic ; achromatism. See equation. 
achromatin (a-kro'ma-tin), n. [< Gr. dxp&uaroc, 
not colored, + -Hi 2 .] 'In bot., that portion of the 
basic substance of the nucleus of a vegetable- 
cell which, under the action of staining agents, 
becomes less highly colored than the rest. 
achromatisation, achr omatise, etc. See achro- 
matization, achromatize, etc. 
achromatism (a-kro'ma-tizm), n. [< achromat- 
ic + -ism. Cf. F. achromatisme.] The state or 
quality of being achromatic; absence of col- 
oration : as, to secure perfect achromatism in a 
telescope. 
achromatization (a-krd"ma-ti-za'shon), n. The 
act of achromatizing or depriving of color. Also 
spelled achromatisation. 
achromatize (a-kro'ma-tiz), v. t. ; pret. and pp. 
achromatized, ppr. achromatizing. [< achromat- 
ic, as if < Gr. a- priv. + xpujiaTi&iv , to color, < 
Xpu/ia(T-), color.] To render achromatic; de- 
prive of color, or of the power of transmitting 
colored light. Also spelled aehromatise. 
For two kinds of light a flint-glass prism may be achro- 
matized by a second prism of crown-glass. 
A. Daniell, Prin. of Physics, p. 480. 
achromatopsia (a-kro-ma-top'si-a), n. [<Gr. 
a- priv. + ^pu//a(r-), color, + 6i/f, sight, < 6i//, 
the eye, face : see optic.] Color-blindness, or 
inability to see or distinguish colors. Also 
called acritochromacy. 
achromatopsy (a-kr'o'ma-top-si), n. Same as 
achron/a topsia. 
achromatosis (a-kro-ma-to'sis), n. [NL., < Gr. 
axpufiaro/;, without color, + -usi.f.] A name 
applied to diseases characterized by a lack of 
pigment in integumental structures, as albi- 
nism, vitiligo, or canities. 
achromatOUS (a-kro'ma-tus), a. [<Gr. axpufia- 
rof, without color : see 'achromatic.] Without 
color; of a lighter color than normal : as, achro- 
matous spots. 
47 
achromophilous (a-kro-mof 'i-lus), a. [< Gr. d- 
priv. (fl-I8) + chromophilous.] In embryo!., not 
chromophilous (which see). See extract. 
The substance of the ovum [of Ascariv] is also remark- 
ably differentiated, that of the ''polar disk" alone ex- 
hibiting a vertical striation, and differentiating into two 
layers, supertteial and subjacent (termed aclii-<i>uoi>lii{i>ii* 
and chromophilous respectively). Em-tic. /J/-i(.,XX. 417. 
achromous (a-kro'inus), a. [< Gr. d- priv. + 
Xpufia, color.] Colorless; without coloring 
matter. 
achronic, achronical (a-kron'ik, -i-kal), a. An 
eiToueous spelling of acronych, acronychal. 
achroodextrine (ak"ro-6-deks'trin), . [< Gr. 
axpoof, colorless (see achroous), + E. dextrine.] 
Dextrine which is not colored by iodine : con- 
trasted with erythrodextrine. 
ach-root (ach'rot), n. [< ach% + root.] The 
root of Morinda tinctoria, used in India as a 
dye. See ach 2 . 
achroous (ak'ro-us), a. [< Gr. axpoof, also d^powc , 
colorless, < d- priv. + %p6a, xP L "-> color. Cf . 
achromatic.] Colorless; achromatic. 
achylous (a-ki'lus), a. [<Gr. d^vAor, < d- priv. 
+ ^ti?.(!f, chyle.] Without chyle. Sijd. Soc. 
Lex. 
Achyrodon (a-ki'ro-don), n. [NL., < Gr. d^jjpov, 
pi. axvpa, chaff, bran, husks, + bdo'vf (bdovr-) = 
E. tooth.] A genus of fossil mammals from the 
Purbeck beds of England, having teeth of the 
insectivorous type, and more than eight molars 
and premolars. Owen, 1877. 
acicle (as'i-kl), n. Same as acicula, 2. Dana, 
Crustacea, I. 434. 
acicula (a-sik'u-la), n. ; pi. acicula; (-le). [L., 
a needle, a small pin, dim. of acus, a needle, 
from same root as acer, sharp, acies, an edge, 
acutus, sharp, etc.: see acid, acute, acerb.] 1. 
A needle, pin, or bodkin, of wood or bone, 
used by Roman women as a hair-pin. It was 
not smaller than an acus (which see), but of in- 
ferior material. 2. A spine or prickle of an 
animal or plant. Also called acicle. 3. [cop.] 
A name applied to several genera of gastropods, 
and retained for the representative genus of the 
family Aciculida;, inhabiting Europe. A.fusca 
is the best-known form. 4. [cap.] A genus of 
worms. 
acicula, n. Plural of aciculum. 
Aciculacea (a-sik-u-la'se-a), n. pi. [NL., (Aci- 
cula + -acea.] A synonym of Aciculida! (which 
see). 
acicular (a-sik'u-lar), a. [< NL. acicularis, < L. 
acicula, a needle : see acicula.] Having the 
shape of a slender needle or stout bristle ; hav- 
Acicular Crystals, Stibnite. 
ing a sharp point like a needle : as, an acicular 
prism, like those of stibnite ; an acicular bill, 
as that of a humming-bird. Other forms are 
aciculate, aciculated, aciculiform, and aciculine. 
The silver salt crystallizes from its aqueous solution in 
small acicular prisms. 
E. Frankland, Exper. in Chem., p. 30. 
Acicular bismuth. See aikinite. 
acicularly (a-sik'u-lar-li), adv. In an acicu- 
lar manner; in the manner of needles or 
prickles. 
aciculate, aciculated (a-sik'u-lat, -la-ted), p. a. 
[< NL. aciculatus, < L. acicula: see acicula.] 
Needle-shaped; acicular; aciculiform. 
aciculi, n. Plural of aciculus. 
aciculid (a-sik'u-lid), n. A gastropod of the 
family Aciculida!. 
Aciculidse (as-i-ku'li-de), . pi. [NL., < Acicula, 
q. v., + -idee.] A family of operculate pulmonif- 
erous mollusks, represented by the European 
genus Acicula (which see) and the West Indian 
Geomelania. They have very small turreted shells with 
few whorls and a thin opereulum, the outer lip plain or 
produced into a tongue, and the eyes on the back of the 
head. 
aciculiform (a-sik'u-li-form), a. [< L. acicula, 
needle, + -formis, < forma, form.] Same as 
acicular. 
aciculine (a-sik'u-lin), a. [< NL. adculinus, 
< L. acicula: see acicula.] Same as acicular. 
aciculum (a-sik'u-lum), n. ; pi. acicula (-la). 
[NL., a neut. form to acicida, q. v.] In tool., 
one of the slender sharp stylets which are em- 
acidify 
bedded in the parapodia of some annelids, as 
the l'ol>Jch(Kta. The notopodial and the neuropodial 
divisions of the paraimdia each carry one of these acicuhi. 
aciculus (a-sik'ii-lus), n. ; pi. ncteuli (-11). [NL., 
a masc. form of acicula, q. v.] In hot., a strong 
bristle. 
acid (as'id), a. and n. [=F. <zcirfe = Sp. Pg. 
It. acido, < L. acidus, sour, < acere, be sour 
(>acetum, q. v.), akin to acer, sharp, acies, 
edge, Gr. iiK.pi, E. acme, edge, etc., all from -^"ak, 
be sharp, pierce.] I. a. Sour, sharp, or biting 
to the taste ; tasting like vinegar : as, acid fruits 
or liquors. - Acid rock. See acidic. 
II. n. [< NL. aciditm, neut. of L. acidus, a.] 
Originally, a substance possessing a sour taste 
like that of vinegar ; in modern chemical use, a 
name given to a large number of compounds 
which do not necessarily possess this property. 
It does not appear that very great importance was at any 
time attached to sourness as a characteristic of acids from 
a chemical point of view. The following properties are 
common to most acids: 1st, solubility in water; 2d, a 
sour taste (in some acids, on account of their corrosive- 
ness, this property ean be perceived only after dilution 
with a large quantity of water); 3d, the power of turning 
vegetable blues to red ; 4th, the power of decomposing 
most carbonates, and displacing the carbonic acid with 
effervescence ; 5th, the power of destroying more or less 
completely the characteristic properties of alkalis, at the 
same time losing their own distinguishing characters, form- 
ing salts. In modern chemistry an acid may be termed 
a salt of hydrogen, or it may be defined as a compound 
containing one or more atoms of hydrogen which become 
displaced by a metal, or by a radical possessing to a cer- 
tain extent metallic functions. An acid containing one 
such atom of hydrogen is said to be monobasic, one con- 
taining two such atoms bibasic, etc. Acids of a greater 
basicity than unity are frequently termed polybasic acids. 
When an acid contains oxygen, its name is generally 
formed by adding the terminal -ic either to the name of 
the element with which the oxygen is united or to an ab- 
breviation of that name. Thus, sulphurforms with oxygen 
sulphuric acid; nitrogen, nitric acid; and phosphorus, 
phosphoric acid. But it frequently happens that the same 
element forms two acids with oxygen ; and in this case 
the acid that contains the larger amount of oxygen re- 
ceives the terminal syllable -/e, while that containing less 
oxygen is made to end in -ous. Thus, we have sulphurous, 
nitrous, and phosphorous acid, each containing a smaller 
proportion of oxygen than that necessary to form respec- 
tively sulphuric, nitric, and phosphoric acid. In some 
instances, however, the same element forms more than 
two acids with oxygen, in which case the two Greek words 
VJTO (hypo-), under, and inrtp (hyper-), over, are prefixed to 
the name of the acid. Thus, an acid of sulphur contain- 
ing less oxygen than sulphurous acid is termed hyposul- 
phurous acid ; and another acid of the same element con- 
taining, in proportion to sulphur, more oxygen than sul- 
phurous acid and less than sulphuric, might be named 
either hypersulphurous or hyposulphuric acid ; but the 
latter term has been adopted. The prefix per- is frequently 
substituted for hyper-. Acetic acid, fatty acid, nitric 
acid, etc. See these adjectives. Nordnausen acid, 
brown fuming sulphuric acid, a solution of sulphur trioxid 
in sulphuric acid, used as a solvent of indigo, and at pres- 
ent in the manufacture of artificial alizarin. It is named 
from the place where it was first manufactured. 
acid-green (as'id-gren'), ii. A coloring mat- 
ter, a sulphonic acid of various sorts of benzal- 
dehyde-greens. It is one of the coal-tar colors. It 
dyes a brighter color than the so-called solid green. It is 
also called Helvetia green, and light green S. Benedikt 
and Knecht, Chem. of Coal-tar Colors, p. 84. 
acidic (a-sid'ik), a. 1. Acid: in chem., applied 
to the acid element, as silicon, in certain salts: 
opposed to basic. 2. Containing a large amount 
of the acid element: as, the acidic feldspars, 
which contain 60 per cent, or more of silica. 
Acidic (or acid) rock, a crystalline rock which contains a 
relatively large amount of silica, through the presence of 
an acidic feldspar, and sometimes also of free quartz, as a 
prominent constituent. For example, trachyte is an acid 
or acidic rock ; basalt, a 6ac rock. 
acidiferous (as-i-dif'e-rus), a. [<NL. acidum, 
acid, + ii.ferre =E. bear 1 , + -ous.] Bearing, pro- 
ducing, or containing acids, or an acid Aci- 
diferous mineral, a mineral which consists of an earth 
combined with an acid, as calcium carbonate, aluminite, 
etc. 
acidifiable (a-sid'i-fl-a-bl), a. [< acidify + 
-able; = F. acidifiable.] Capable of being acidi- 
fied, or of being converted into an acid. 
acidific (as-i-dif'ik), a. Producing acidity or 
an acid ; acidifying. Said of the element (oxygen, 
sulphur, etc.) which in a ternary compound is considered 
as uniting the basic and acidic elements. Thus, in cal- 
cium silicate, calcium is called the basic, silicon the acidic, 
and oxygen the acidific element. Dana. 
acidification (a-sid"i-fi-ka'shon), n. [< acidify; 
= P. acidification = Sp. acidification = Pg. aci- 
dificaqao.] The act or process of acidifying, or 
of changing into an acid. 
Acidification ... is intended to break up, corrode, or 
carbonize the albuminiferous matters. 
W. L. Carpenter, Soap, etc., p. 264, 
acidifier (a-sid'i-fi-er), n. One who or that 
which acidifies ; specifically, in chem., that which 
has the property of imparting an acid quality. 
acidify (a-sid'i-fl), v. ; pret. and pp. acidified, 
ppr. acidifying. [< acid + -fy ; = F. acidifier = 
Pg. addificar.] I. trans. To make acid ; con- 
