COP 
COP 
extremities. The outside of the staves, 
across the wood, must be wrought into the 
segment of a circle ; and it must be thickest 
near the middle, growing gradually thinner 
towards the ends. After the staves are 
dressed and ready to be arranged, the 
cooper without attempting any great nicety 
in sloping them, so that tlie whole surface 
of the edge may touch in every point, 
brings tlie contiguous staves into contact 
only at the inner surface ; and in this way, 
by driving the hoops hard, he can make a 
closer joint than could be done by sloping 
them from the outer to the inner side. 
Cooper, on board a ship, he that looks 
to the casks and all other vessels for beer, 
water, or any other liquor. He has a mate 
under him. 
COPAIFERA, in botany, a genus of the 
Decandria Monogynia class and order. 
•Natural order of Leguminosffi, Jussieu. Es- 
sential character : calyx none ; petals five ; 
legume ovate; seed one, with a berried 
aril. There is but one species, viz. C. of- 
ficinalis, balsam of capevi tree. This is a 
lofty elegant tree, with a handsome head, 
the extreme branches at the axils are flex- 
nose, with a brownish ash-coloured hark; 
leaves alternate, round, four inches long ; 
racemes axillary, solitary, loosely divided 
into eight alternate, lateral common pedun- 
cles, an inch and half in length, with white 
flowers sitting closely on them. Native of 
South America, from this tree is obtained 
in very considerable quantities, by perfo- 
rating the trunk, fluid balsam or resin, 
which thickens by degrees ; and which is 
known in medicine by the title of balsam 
of copaiva. See. Balsam. 
COPAL. This substance which deserves 
particular attention from its importance as 
a varnish, and which at first sight seems 
to belong to a distinct class from the resins, 
is obtained from the rhus copallinum, a tree 
which is a native of North America; but 
the best sort of copal is said to come from 
Spanish America, and to be the produce of 
different trees. 
Copal is a beautiful white resinous sub- 
stance, with a slight tint of brown. It is 
sometimes opaque, and sometimes almost 
perfectly transparent. When heated it melts 
like otlier resins ; but it differs from them 
in not being soluble in alcohol, nor in oil 
of turpentine without peculiar manage- 
ment. Neither does it dissolve in the fixed 
oils with the same ease as the other resins. 
It resembles gum anim6 a little in appear- 
jince, but is easily distinguished by the 
solubility of this last in alcohol, and by its 
being brittle between tlie teeth, whereas 
aniin6 softens in the mouth. The specific 
gravity of copal varies from 1.045 to 1.139. 
Mr. Hatchett found it soluble in alkalies 
and nitric acid with the usual phenomena, 
so that in this respect it agrees with the 
other resins. 
When copal is dissolved in any volatile li- 
quid, and spread thin upon wood, metal, 
paper, &c. so that the volatile menstruum 
may evaporate, the copal remains perfectly 
transparent, and forms one of the most 
beautiful and perfect varnishes that can 
well be conceived. The varnish thus formed 
is called copal varnish, from the chief in- 
gredient in it. Copal vai'nish used by the 
English japanners is made as follows. Four 
parts by weight of copal in powder are put 
into a glass matrass and melted. The li- 
quid is kept boiling till the fumes, con- 
densed upon the point of a tube thrust into 
the matrass, drop to the bottom of the li- 
quid without occasioning any hissing noise 
as water does. This is a proof that all the 
water is dissipated, and the copal has been 
long enough melted. One part of boiling 
hot linseed oil (previously boiled in a retort 
without any litharge) is now poured into it, 
and well mixed. The matrass is then taken 
off the fire, and the liquid, while still hot, is 
mixed with about its own weight of oil of 
turpentine. The varnish thus made is 
transparent, but it has a tint of yellow, 
which the japanners endeavour to conceal 
by giving the white ground on which they 
apply it a shade of blue. It is with tliis 
varnish that the dial plates of clocks are co- 
vered after having been painted white. 
Mr. Sheldrake has lately favoured the 
public with another and easier method of 
dissolving copal. This method is as follows : 
“ Provide a strong vessel made of tin or 
other metal ; it should be shaped like a wine 
bottle, and capable of holding two quarts ; 
it will be convenient to have a handle 
strongly rivetted to the neck; the neck 
should be long and have a cork fitted 
to the mouth, but a notch or small hole 
should be made in the cork, that, when the 
spirit is expanded hy heat, a small portion 
may force its way through the hole, and 
thus prevent the vessel from bursting. Dis- 
solve half an ounce of camphor in a quart of 
spirit of turpentine, and put it into the ves- 
sel ; take a piece of copal the size of a large 
walnut, reduce it to a coarse powder or 
very small pieces, put tliem into the tin 
bottle, fasten the cork down with a wire. 
