COPPER, SALTS OF 947 



test solution is prepared by dissolving a known weight of copper (0'5 or 1 grain) in 

 dilute nitric acid, adding ox'cess of ammonia and diluting to 10,000 grains. This 

 solution is kept in a well-stoppered, long, glass graduated vessel. Tho ammoniacal 

 solution of copper obtained by the decomposition of a given weight of the substance 

 is transferred to a graduated measure of the same shape and capacity, and water 

 added until the tint corresponds to that of the standard coloration test. The per- 

 centage of copper is calculated as follows : 10,000 grains of the standard coloration 

 test contain 0-5 grain of copper; the solution of 100 grains of the substance required 

 dilution to 8,000 grains 



10,000 : 8,000 ::0-5 : 0-4 per cent, of copper. 



b. A series of standard coloration test solutions of copper are prepared and kept 

 in a number of colourless square or round glass bottles. The bottles should be of the 

 same shape and capacity. If the series comprise ten bottles, the first bottle may con- 

 tain ith of a grain of copper, the second j^ths, and so on to the last of 1 grain. From 

 50 to 100 grains of the powdered slag or other substance are treated with nitric or 

 with nitro-hyclrochloric acid, until decomposition is effected. In some cases previous 

 fusion with carbonate of soda may be found necessary. The solution is diluted with 

 water, excess of ammonia added, and filtered, or the precipitate allowed to settle and 

 the solution decanted. If necessary, the precipitate obtained by ammonia is redis- 

 solved in acid, and reprecipitated by ammonia ; and if the filtrate has a blue tint it 

 must be added to that previously obtained. The whole of the solution is then diluted 

 with water until there is the same volume of solution as in one of the test bottles. 

 The colour is then compared with the coloration test bottles, and the one it corre- 

 sponds to represents the amount of copper present in the quantity of substance 

 operated on. From this datum the per-centage of copper is calculated. If nickel or 

 cobalt bo present the copper must first bo separated by means of sulphuretted hydrogen 

 or otherwise, and the precipitate redissolved in acid. 



COPPER ORES. See COPPER. 



COPPER, OXIDES OP. Two oxides are known : the red or suboxido (cuprous 

 oxide) Cu 2 0, and the black or protoxide (cupric oxide), CuO. Both occur native, and 

 are valuable ores. The suboxide may be prepared artificially by adding grape-sugar to 

 a solution of the blue sulphate of copper, treating the product with an excess of caustic 

 potash, and then boiling the solution. The suboxido communicates a fine ruby-rod 

 colour to glass ; this oxide is soluble to some extent in metallic copper, the metal be- 

 coming thereby ' dry ' or brittle. Protoxide of copper may be prepared by calcining 

 copper, or by igniting the nitrate or the sulphate. It communicates a green colour to 

 glass. The protoxide is employed in organic analysis for yielding oxygen during 

 combustions. 



COPPER PYRITES. See COPPER. 



COPPER, SALTS OP. COPPER, ACETATE OF. A basic acetate of copper (cupric 

 acetate) is largely used as a pigment under the name of Verdigris. The neutral 

 iicetate is also prepared commercially, and termed Distilled Verdigris. It appears that 

 the well-known pigment, Schweinfttrth or Emerald Green, is a combination of acetate 

 and arsenite of copper. See VERDIGRIS ; SCHWEIXFDRTH GREEN. 



COPPER, ARSENITE OF. The fine green pigment called Scheele's Green is an arsenite, 

 and Schweinfurth Green is an aceto-arsenito of copper. See SCHEELE'S GREEN; 



SCHWEINFURTH GREEN. 



COPPER, CARBONATES OF. Two of these occur native, forming the minerals known 

 us Malachite and Azurite. An artificial basic carbonate is prepared as a pigment under 

 the names of Brunswick and mineral-green. See AZURITE ; COPPER ; MALACHITE ; 



^ 7 'KRDITEH. 



COPPER, CHLORIDES OF. Two chlorides are known ; the subchloride (cuprous chloride) 

 Cu'Cl (Cu 2 Cl 2 ), and the protochloride (cupric chloride) CuCl (CuCl 2 ). The latter 

 is readily obtained by dissolving either oxide or carbonate of copper in hydrochloric 

 acid ; it is a deliquescent salt soluble in alcohol, the alcoholic solution burning with a 

 fine green flame. The subchlorido may be reduced from the protochloride by boiling 

 its solution with sugar. A solution of the subchloride in hydrochloric acid is used in 

 gas-analysis for the absorption of carbonic oxide. There are also several oxychlorides of 

 copper ; one of these occurs native, forming an ore known as Atacamito. See COPPER. 



COPPER, NITRATE OF. This salt is prepared by dissolving copper in moderately 

 strong nitric acid, and evaporating to crystallisation. Its formula when anhydrous 

 is CuO,NO s (Cu2M"O 8 ). This salt is used to produce a fine green in fireworks. 



COPPER, SULPHATE OF, called in commerce Blue Vitriol, Blue Stone, or Blue 

 Copperas. This salt is frequently prepared by roasting copper pyrites with free access 

 of air, but sulphate of iron is formed at the same time, and the two salts are not 

 readily separated. It is also obtained by heating old copper with sulphur, 'by which a 



3 p2 



