COB 
named zaffre. The zaffre of commerce is 
always mixed with silicious earth ; hence, 
if exposed to a strong heat, it vitrifies ; a 
glass of a dai'k blue colour is thus formed, 
named smalt, which is used on account of 
its colour in various arts. It is from the 
zaflre of commerce that the chemist ob- 
tains cobalt; to obtain it pure, however, 
is extremely difficult. The common pro- 
cess is to mix the zaffre with three times 
its weight of black flux, a small quantity 
of oil, and a little sea salt, and expose' the 
mixture in a crucible to a strong white heat 
for some hours. A metallic button is thus 
obtained, on cooling, at the bottom of 
the crucible; but the cobalt procured is 
generally alloyed with arsenic and nickel, 
and sometimes with other metals, particu- 
larly iron. 
A number of the acids oxydize cobalt, 
and combine with its oxyde. The concen- 
trated sulphuric acid scarcely acts on it in 
the cold, but, wlien boiled on tire metal, 
sulphurous acid gas is disengaged, and a 
saline matter is obtained, which, when lix- 
iviated, forms a solution of sulphate of co- 
balt. Nitric acid is decomposed by cobalt, 
and the metal is oxydized and dissolved. 
The solution is of a red colour, and by 
gentle evaporation affords minute prismatic 
crystals of the same colour, which are de- 
liquescent and decomposed by heat. Mu- 
riatic acid does not act on cobalt, but with 
the assistance of heat ; a small portion of 
the metal is then dissolved. The solution of 
muriate of cobalt affords a celebrated sym- 
pathetic ink. When much diluted, if letters 
are traced with it on paper, and allowed to 
dry, they are invisible ; but when the paper is 
exposed to a moderate heat, they appear of 
a lively green : tliey disappear again when 
cold, and the experiment may be repeated 
for any number of times, taking xare only 
to avoid too strong a heat, by which tljey 
are rendered permanent. Tiie cause of 
this phenomenon has been ascribed to the 
muriate of cobalt fixed upon the paper 
attracting, when cold, moisture from tlie 
atmosphere, by which it is, as it were, dis- 
solved and rendered invisible; when heated, 
this moisture is evaporated, and the green 
colour of the salt appears. This explana- 
tion appears to be confirmed by tlie fact, 
that the characters are rendered visible by 
confining the paper in a vessel with quick 
lime, or sulphuric acid, either of which 
attracts humidity powert’ully. The green 
colour cannot, however, be ascribed en- 
tirely to the concentration, but is owing to 
coc 
the temperature ; for the solution itself be- 
comes green when moderately heated in a 
close phial, and loses this green colour as it 
cools ; nor is it easy to explain how tlie tem- 
perature does produce this change of colour. 
Cobalt combines with many of the me- 
tals. Its alloys are generally brittle, and 
none of them has been applied to any use ; 
nor have they been much examined. The 
principal, or, indeed, almost the sole use 
of cobalt, is in communicating a blue- co- 
lour to glass, enamel, and porcelain. 
COliBING, in sea language, a punish- 
ment sometimes inflicted on a sailor ; it is 
performed by striking him a certain number 
of blows on the breech with a flat piece of 
wood, called the cobbing-board. 
COBITIS, the loche, in natural history, a 
genus of fishes of the order Abdominales. 
Generic character : eyes in the upper part 
of the head ; mouth in the greater number 
of species bearded ; body almost equally 
thick throughout, and covered with easily 
deciduous and small scales ; tail rounded ; 
air bladder hail’d or osseous. There are five 
species, of which we shall notice: — C. bar- 
batula, or bearded loche. This is an inha- 
bitant of the streams of Europe and Asia, 
and lives upon worms and insects, which it 
finds on the gravel at the bottom of the 
water, from which it rarely ascends near the 
surface. It is extremely prolific, and most 
highly valued for the table in several places 
in Europe, where it is cultivated with ex- 
treme attention. It dies almost immedi- 
ately on being taken from the water. To 
preserve the exquisite flavour of it, it is 
considered by the dealers in this fish as of 
great importance frequently to shake tlie 
vessel of water in which it is placed. C. 
fossilis, or yellow-brown loche. This inlia- 
bits the stagnant and muddy waters of the 
midland parts of Europe, and in w inter 
completely shelters itself in mud. It is 
restless before storms, quitting its retreat, 
and ranging about in various directihns near 
the surface. When preserved in a vessel of 
water, with some earth at the bottom, it 
invariably indicates the, approach of storms 
by peculiar agitation, and is on this account 
not uufrequently kept to answer the pur- 
pose of a barometer. 
COCCINELLA, in natural history, a ge- 
nus of insects of the order Coleoptera. Ge- 
neric character ; antennae subclavated and 
truncated; feelers with senii-cordated tip ; 
body hemispheric, with the abdomen flat 
beneath. This genus is easily distinguished 
by its hemispheric form, having the upper 
