64 
ALU 
ALU 
A M A 
outer extremity, at the base of the primary 
quill-feathers, and consists of from three to 
live small leathers of the quill kind. 
ALUM, a neutral salt, the base of which 
is alumina, argil, or clay, combined with sul- 
phuric acid. , 
Alum, ore* of , include all those minerals 
which .either contain alum ready formed, or 
are capable of yielding this salt by manufac- 
ture: they may be divided (1.) into the sa- 
line, all the species of which are almost 
wholly soluble in water; (2.) the earthy sa- 
line, the soluble particles of which are diffused 
through a large proportion of earth ; (3.) the 
earthy, which containing no alum, but the 
materials of it, are insoluble, and destitute of 
that sweetish astringent taste which charac- 
terises the two former. 
There are four varieties of alum, which are 
all triple salts ; two neutral, and two in the 
statp ot super salts. These varieties Dr. 
Thomson distinguishes by the following 
names : 
1. Sulphate of alumina and potash. 
2. Sulphate of alumina and ammonia. 
3. Supersulphate of alumina ahd potash. 
4. Supersulphate of alumina and ammo- 
nia. 
The two last of these varieties are. usually 
confounded under the name of alum; the 
two first have been called alum saturated 
ivith earths , or illuminated alum. 
We owe the discovery of alum to the 
Asiatics, and it continued to be imported 
from the East till the fifteenth century, when 
a number of alum-works were established in 
Italy! In the sixteenth century it was ma- 
nufactured in other parts of the continent ; 
and during the reign of queen Elizabeth an 
alum-work was established in England. 
The composition of alum has been but 
lately understood with accuracy. It has, in- 
deed, been Jong known that sulphuric acid 
is one of the ingredients, and it was equally 
certain that alumina is another. But these 
are incapable of forming alum. The addi- 
tion of potash, or of ammonia, or of some 
substance containing these alkalis, is .almost 
always necessary ; and where these additions 
are not wanted, the earth from which the alum 
is obtained contains already a quantity of 
potash. Hence it appears that alum is pro- 
perly a triple salt, composed of sulpTiuric 
acid, alumina, and potash or ammonia united. 
Alum crystallizes in regular octahedrons, 
consisting of two four-sided pyramids applied 
base to base, the sides are equilateral triangles. 
Its taste is sweetish, and very astringent. It 
always reddens vegetable blues : its specific 
gravity is 2.71 1 nearly. At the temperature 
of 60 degrees, it is soluble in from 15 to 20 
parts of water, and three-fourths of its weight 
in boiling water. When exposed to -the air 
it effloresces slightly. When exposed to a 
gentle heat it undergoes the watery fusion. 
A very strong heat causes it to swell and foam, 
and to lose 44 percent, o* its weight, consist- 
ing chiefly of water of crystallization ; what re- 
mains is called calcined or burnt alum, and 
is sometimes used as a corrosive. By a still 
more violent heat, the greater part of the acid 
may be driven off. 
There are three varieties of alum in com- 
mrrj|: (1.) the supersulphate of alumina 
andpotash ; (2.) supersulphate of alumina 
and ammonia; and (3.) a mixture of these 
tv/o, which contains both potash and ammonia. 
This is the most common, because the ma- 
nufacture!* of alum use both urine and mu- 
riate of potash to crystallize their alum. 
The first variety is composed of 
49 Sulphate of alumina 
7 Sulphate of potash 
44 water 
100 . 
Crystallized alum contains, 
17.66 acid 
12.00 base 
70.34 water 
100. ( , 
Burnt alum contains, 
36.25 acid . 
63.75 base 
100 . 
When an unusual quantity of potash is add- 
ed to alum liquor, the salt loses its usual form, 
and crystallizes in cubes ; this is called cubic 
alum, and contains an excess of alkali ; and 
when the potash is still farther increased, the 
salt loses the property of crystallizing, and 
falls down in Hakes : it then consists of sul- 
phate of potash combined with a small pro- 
portion of alumina. 
All the varieties of alum are capable of com- 
bining with an additional dose of alumina, 
and forming perfectly neutral compounds. 
Alum is of great importance as a mordant 
in dying ; it is used also in the manufacture 
of leather, it is employed by calico-printers, 
engravers, &c. and it is used in medicine, in 
preserving animal substances from putrefac- 
tion, and m preventing wood from taking lire. 
If three parts of alum, and one of Hour or 
sugar be melted together in an iron ladle, and 
the mixture dried till it becomes blackish 
and ceases to swell ; if it be then pounded 
small, put into a glass phial, and placed in a 
sand-bath till a blue flame issues from the 
mouth of the phial, and after burning a mi- 
nute or two be allowed to cool, a substance 
is obtained called Homberg’s phosphorus, 
which lias the property of catching /ire when 
exposed to the open air, especially if it be 
moist. — See Thomson’s Chemistry, vol. ii. 
Alum, native, or fossile Alum, that 
formed by nature, v itliout the assistance of 
art. 
There are still mines of native alum in the 
island of ChiQ, consisting of a kind of vaults, 
or apartments, crusted over with alum, which 
may be regarded as exfoliations from the 
rocks. 
Alum, plumose, or plume Alum, a kind 
of natural alum, composed of a sort of threads, 
or fibres, resembling feathers ; whence it has 
its name. 
Alum, prepared, or purified Alum, that 
which is dissolved in hot rain-water, and after- 
wards made to crystallize, by evaporating 
the water. 
Alum, Roman, a sort of rock alum, of a 
reddish colour, made in the country near 
Rome. 
Alum, saccharine, is a composition of com- 
mon alum with rose-water, and clarified by 
the whites of eggs, which being boiled to 
the consistence of a paste, is formed in the 
shape of a sugarloaf ; hence it obtained its 
name : it is used as a cosmetic. 
ALUMINA, derives its name from alum, 
of which it is the base. It is the argillaceous 
part of common clay, or, in other words, 
pure argil or clay, free from all impurities. 
It is smooth and unctuous to the touch, 
when pure, diffusible in water, and adhering 
to the tongue. • Its specific gravity is 20m 
Us bulk is diminished by great heat, and its 
hardness may he so increased by baking 
as to enable it to strike lire with steel, it 
forms a difficult combination with the acids. 
With the sulphuric it makes sulphate of alu- 
mina ; but its crystallization is difficult, both 
with the nitre and muriatic. It has a power- 
ful attraction tor lime. The most intense 
heat is not able to melt it alone, but it is 
easily fusible when lime or an alkali is added 
to it. By its mixture with water andsilex it 
acquires great solidity. 
ALUMINOUS waters, those impreg- 
nated, either naturally or artificially, with the 
virtues of alum. 
Of the former kind is the spa at Scar- 
borough represented to be ; and of the latter, 
the aqua aluminosa of the shops. 
ALUNGU is a name given by the people 
ot Malabar to an animal resembling a large 
lizard, except as to head and tail, which 
are both pointed. It is of the species of the 
manis of Linnaeus, and belongs to the family 
ot ant-eaters ; w hie!) have no teeth, but a round 
tongue, with which they catch ants. 
ALURNUS, a genus of insects of. the 
order of coleoptera, with filiform antennae, six 
short feelers, and a horny arched jaw. Three 
species of them are found at the Cape of Good 
Hope, viz. a. grossus, femoratus, and dentipes. 
See Plate Nat. Hist. fig. 13. 
ALWAIDI D, a sect of Mahometans, who 
believe ail great crimes to be unpardonable. 
ALYSSUM, or Ai.yssoxq madnort, in- 
botany, a genus of the tetrady n-amia siliculosa 
class and order, of the naturad order of sill- 
quosae and crucifers) of Jussieu. The flower 
is of tlie cruciform kind, and consists of four 
petals ; the fruit is a small roundish capsule, 
divided into two cells, in which are contained 
a, number of small roundish seeds. The es- 
sential character is, the shorter filaments 
marked with a toothlet ; the silicic emargi- 
nate. 
There are 17 species. The A. palimifo- 
lium, or sweet •alysum, is an annual plant, 
chiefly cultivated in gardens for its fragrance,. 
1 he yellow alysson is also very ornamental, 
and is perennial. 
AMA, among ecclesiastical writers, de- 
notes a vessel in which wine or water were 
kept tor the service of the eucharist. 
uma is sometimes also used for a wine 
measure, as a pipe, See. 
AMABYR, or Amvabyr, a barbarous 
custom which formerly prevailed in \\ ales 
and some other parts of the kingdom ; being 
a certain fine, or sum of money, paid to the 
lord, upon marrying a maid within ins 
manor. 
AMADOVV, a kind of black match, tin- 
der, or touchwood, which comes from Ger- 
many. It is made from spungy excrescences, 
which often grow on old trees, especially 
oaks, ash, or firs. This substance being 
boiled in common water, and afterwards 
dried and well beaten, is then put into a 
strong ley prepared with salt-petre, after 
which it Is again put to dry in an oven, when 
it is fit for use. 
AM A DO WRY, a kind of cotton, which 
comes from Alexandria, by way of Mar- 
seilles. 
AMAIN, or Amayne, in the sea lan- 
guage, a term importing to lower something 
