443 



COPPER. 



copper, 64, and one of oxygen, 8, = 72. The sulphu- 

 ric, muriatic, and probably several other acids, form 

 with it salts, which, for the most part are colourless. 

 On exposure to the air, they attract oxygen, and are 

 rapidly converted into per-salts. The peroxide of 

 copper is also found native, and may be prepared 

 artificially by calcining metallic copper, by precipita- 

 tion from the per-salts of copper, by means of pure 

 potash, or by heating the nitrate of copper to redness. 

 It is composed of one atom of copper, 64, and two of 

 oxygen, 16, = 80. It varies in colour from a dark- 

 brown to a bluish-black, is insoluble in water, and 

 does not affect the vegetable blue colours. It un- 

 dergoes no change by heat alone, but is readily 

 reduced to the metallic state by heat and combustible 

 matter. It combines with nearly all the acids, and 

 most of its salts have a green or blue tint. It is so- 

 luble, likewise, in ammonia, forming with it a deep 

 blue solution a property by which the peroxide of 

 copper is distinguishable from all other substances. 



Metallic copper is oxidated and dissolved by the 

 greater numbe'r of the acids, and forms with them, in 

 general, soluble, and crystallizable salts. 



Sulphuric acid, either concentrated or diluted, oxi- 

 dates it, and combines with the peroxide, especially 

 when assisted by heat. The solution is of a blue co 

 lour, and, when evaporated, affords crystals in the 

 form of rhomboidal prisms. This salt is the Hue vit- 

 riol of commerce, and is usually obtained, either by 

 evaporation of the solution of it, formed by the infil- 

 tration of water through copper mines, or by expo- 

 sure of sulphuret of copper to the action of air and 

 humidity, until the sulphur is converted into sulphu- 

 ric acid, and the metal is oxidated and combined with 

 it. Nitric acid acts on copper with great energy, the 

 metal attracting a portion of its oxygen, nitric oxide 

 gas being disengaged, and the oxide combining with 

 the remaining acid. The solution, when evaporated, 

 affords prismatic crystals, of a deep-green colour, de- 

 liquescent, and easily soluble in water. From the 

 facility with which it parts with oxygen, it acts with 

 energy on several substances. Thus it detonates 

 when struck with phosphorus, and it burns several of 

 the metals. If wrapped in tmfoil, the tin is oxidated 

 with such rapidity as to be attended with inflamma- 

 tion. 



Muriatic acid dissolves copper slowly, when the 

 air is admitted : if it is excluded, the action is very 

 inconsiderable, unless heat is applied. The solution 

 is of a fine green colour, and, by evaporation, slender 

 prismatic crystals are obtained, which are deliques- 

 cent, and very soluble in water. 



The combinations of peroxide of copper with phos- 

 phoric, carbonic, and other acids, are effected by add- 

 ing to a solution of nitrate or sulphate of copper a 

 solution of a neutral salt, containing the acid with 

 which the copper is designed to be combined. Cop- 

 per is slowly oxidated by a number of weaker acids, 

 as by some vegetable juices, when acted on by them 

 with the admission of air. Acetic acid, or vinegar, 

 in particular, forms an important compound with the 

 oxide of copper. To obtain it, copper plates are ex- 

 posed to the fumes of vinegar. A crust is soon 

 formed of a green colour, which is the verdigris of 

 commerce. 



All the salts of copper are decomposed by the al- 

 kalies and earths. Potash, soda, and the alkaline 

 earths, throw down precipitates, which are of various 

 shades of green or blue, according to the quantity of 

 alkali added, the colour being green, if a small quan- 

 tity is added, and becoming blue from a larger quan- 

 tity. These precipitates are sub-salts, the alkali 

 attracting the greater portion of the acid, but the 

 oxide precipitated still retaining a portion of the acid 

 combined with it. 



The action of ammonia upon the salts of copper a 

 more remarkable. It first abstracts a portion of the 

 acid, anil throws down a green or blue precipitate, 

 which is a sub-salt ; but, when added in larger quan- 

 tity, it redissolves this precipitate, and forms a trans- 

 parent solution, of a very deep-blue colour, which, 

 when evaporated, affords fine blue crystals. A triple 

 compound, used in medicine under the name of am- 

 moniuret of copper, is prepared by triturating toge- 

 ther two parts of sulphate of copper with one part of 

 carbonate of ammonia, thfe mass becoming soft from 

 the mutual action of the two salts, the carbonic ;ici<l 

 being disengaged with effervescence, and the triple 

 compound of sulphuric acid, oxide of copper, and am- 

 monia, being obtained of a deep violet-blue colour. 



Copper is precipitated in its metallic state, from 

 its saline solutions, by zinc and iron ; either of these 

 metals attracting the oxygen which serves as the 

 medium of its union with the acid of the solution. 

 Its oxide is precipitated by albumen, and the precipi- 

 tate is almost inert ; hence the whites of eggs have 

 been recommended as an antidote to the poisonous 

 salts of copper. 



The best mode of detecting copper, when sus- 

 pected to be present in mixed fluids, is by sulphureted 

 hydrogen. The sulphuret, after being collected, 

 should be placed on a piece of porcelain, and digest 

 ed in a few drops of nitric acid. A sulphate of cop- 

 per is formed, which, when evaporated to dryness, 

 strikes the characteristic deep blue, on the addition 

 of a drop of ammonia. 



Copper and sulphur unite by fusion, the combina- 

 tion being attended with the evolution of heat and 

 light. A bi-sulphuret of copper also exists in copper 

 pyrites. 



Copper combines with a great number of the me- 

 tals by fusion. It communicates hardness to gold and 

 silver, without much impairing their ductility, or de- 

 basing their colour, when in small proportion ; hence 

 it is employed in the standard alloys of these metals, 

 that of gold containing one-twelfth, that of silver one- 

 sixteenth, of the mass. With platina, it forms an 

 alloy, ductile, and susceptible of a fine polish. With 

 tin, it forms several valuable alloys, which are cha- 

 racterized by their sonorousness. 



Bronze is an alloy of copper, with about eight or 

 ten per cent, of tin, together with small quantities of 

 other metals, which are not essential to the compound. 

 Cannons are cast with an alloy of a similar kind, and 

 the ancient bronze statues were of nearly the same 

 composition. See Bronzes. 



Bell-Metal is composed of eighty parts of copper 

 and twenty of tin. The Indian gong, so much cele- 

 brated for the richness of its tones, contains copper 

 and tin in this proportion. The proportion of tin in 

 bell-metal varies, however, from one-third to one- 

 fifth of the weight of the copper, according to the 

 sound required, the size of the bell, and the impulse 

 to be given. M. d'Arcet has discovered that bell- 

 metal, formed in the proportion of seventy-eight parts 

 of copper, united with twenty-two of tin, is, indeed, 

 nearly as brittle as glass, when cast in a thin plate, 

 or gong ; yet, if it be heated to a cherry red, and 

 plunged into cold water, being held between two 

 plates of iron, that the plate may not bend, it becomes 

 malleable. Gongs, cymbals, and tamtams have been 

 manufactured with this compound. 



Brass. Copper and zinc unite in several propor- 

 tions, forming alloys of great importance in the arts. 

 The best brass consists of four parts of copper to one 

 of zinc ; and, when the latter is in greater propor- 

 tion, compounds are formed called tombac, Dutch, 

 gold, and pinchbeck. An alloy called Bath metal is 

 made by adding nine pounds of zinc to thirty-two of 

 brass ; and an extremely pale, nearly white me tal, 



