COPPER. 
extracted from its ores, and not difficult to 
work. The Egyptians applied it to a great 
variety of uses, as it appears from the earli- 
est period of their history. The Greeks 
vyere acquainted with the mode of working 
copper, and employed it in many of the 
ai ts. It was the basis of the celebrated 
Corinthian metal. The Romans knew the 
uses of this metal, and it is generally sup- 
posed that of it they fabricated the greatest 
number of their utensils. The alloys which 
they made with copper, after the example 
of the Egyptians and Greeks, were very 
numerous, and applied to a great variety of 
uses. Copper exists in considerable abun- 
dance in nature ; it is found native, alloyed 
with other metals, combined with sulphur, 
in the state of oxide, and in that of salt. It 
is not unfrequently met with in the native 
state, sometimes crystallized in an arbores- 
cent form, and sometimes in more regular 
figures. Copper exists native, alloyed with 
gold and silver. Tlie most abundant ores 
of copper are the sulphurets, and of these 
there is a considerable variety, exhibiting 
various colours and various forms of crys- 
tals. In the state of oxide, it has been found 
1n Peru, of a greenish colour, mixed with 
white sand. In the state of salt, copper is 
combined with the sulphuric and carbonic 
acids, forming native sulphates and carbo- 
nates of copper. The latter present many 
varieties, but may chiefly be referred to the 
blue and green carbonates. Tlie extraction 
of the ores of copper is to be conducted 
according to the nature of the combination 
in which they exist. The following process 
is recommended for the treatment of the 
sulphurets of copper. The ore is first re- 
duced to powder, and then boiled with five 
parts of concentrated sulphuric acid. The 
solution is evaporated to dryness, and the 
residuum well washed with warm water, to 
remove all soluble matters. The solution 
being sufficiently diluted, a plate of copper 
is immersed in it, which precipitates the 
silver, and afterwards a plate of iron to 
precipitate the copper. It is boiled with 
the plate of iron till no farther precipitate 
takes place. The copper which is thus ob- 
tained is dried with a gentle lieat, so that it 
may not undergo oxidation. It is supposed 
that the copper is mixed witlx iron; the 
whole may be dissolved in nitric acid ; and 
the process is again repeated by introduc- 
ing the plate of iron. In this way it is easy 
to discover the quantity of copper in the 
sulphurets of this metal. 
Copper is a very brilliant metal, of a fine 
red colour, differing from every other me- 
tallic substance. The specific gravity of 
copper is 8.58. When it is hammered it 
acquires a greater density. It possesses a 
considerable degree of hardness, and some 
elasticity. It is extremely malleable, and 
may be reduced to leaves so fine, tliat they 
may be carried about by the wind. It has 
also a considerable degree of ductility, in- 
termediate, according to Guyton, between 
tin and lead. The tenacity of copper is also 
very great. A wire .078 of an inch in dia- 
meter will support a weight without break- 
ing equal to more than 300 Ihs. avoirdupois. 
Copper has a peculiarly astringent and dis- 
agreeable taste. It is extremely deleteri- 
ous, when taken internally, to the animal 
economy, and indeed may be considered as 
a poison. It is distinguished by a peculiarly 
disagreeable odour, which it communicates 
to the hands by the slightest friction. Cop- 
per does not melt till the temperature is 
elevated to a red heat, which is about 27“ 
Wedgwood, or by estimation 1450“ Fahren-: 
heit. When it Ls rapidly cooled after fusion, 
it assumes a granulated and porous texture ; 
but if it be cooled slowly, it affords crystals 
in quadrangular pyramids, or in octahe- 
drons, which proceed from the cube, its 
primitive form. When the temperature is 
raised beyond what is necessary for its fu- 
sion, it is sublimed in the form of visible 
fumes. When copper is exposed to the air, 
especially if it be humid, it is soon depri'^ed 
of its lustre. It tarnishes, becomes of a 
dull brown colour, which gi'adually deepens 
till it is converted into that of the antique 
bronze, and at last is covered with a shining 
green crust, which is well known under 
the name of verdigris. This process is the 
oxidation of the metal by the absorption of 
oxygen from the atmosphere ; and it is pro- 
moted and accelerated, either by being 
moistened with water, or by the water 
which exists in the atmosphere. As this 
oxide is formed, the carbonic acid of the 
atmosphere combines with it, so that it is to 
be considered as a mixture of oxide and 
carbonate of copper. Rut when copper is 
subjected to a strong heat, the oxidation 
proceeds more rapidiy. If a plate of cop- 
per be made red-hot in the open air, it loses 
its brilliancy, becomes of a deep brown co- 
lour, and the external layer, which is of this 
colour, may be detached from the metal. 
This is the brown oxide of a copper. This 
oxide nray be obtained by immersing a 
plate of red-hot copper into cold water. 
The scales which are formed on the surface 
