278 Klaproth on the Cheinicai Knowledge 



nected with the pneumatic apparatus, afforded about 35 cubical 

 inches of carbonic acid gas : the intermediate recipient con- 

 tained several drops of pure water. The ignited residue was 

 black and shining, and weighed 70 grains. As this residue has 

 already been shown to consist of pure oxide of copper, of which 

 the oxygen constitutes a fifth part, the above 70 grains are 

 obviously composed of 56 grains of copper and 14 of oxygen. 

 Hence the following are the constituents of the ore : 

 Copper ..... 56 

 Oxygen ..... 14 



Carbonic acid . . . , 24 

 Water 6 



100 

 Contrasting these results with those afforded by the analysis 

 of malachite*, it appears that the blue carbonate of copper 

 differs from malachite in containing more carbonic acid and 

 less water. 



Analysis of a Green Copper Ore from Siberia. 



This ore occurs in the Turjin mines ; it is massive, has little 

 lustre, is translucent in thin fragments, brittle, and of a verdi- 

 gris green colour inclining to sky-blue. 



A. a. 100 parts heated to redness, lose 24 parts, and ac- 

 quire a black colour. 



b. It is slowly acted upon by nitric acid, evolving air-bubbles 

 and leaving a residue of pure silica. The weight of the car- 

 bonic acid is 7 per cent., which, deducted from the 24 per cent. 

 lost during ignition, gives 17 per cent, as the weight of the water. 



B. a. 100 grains digested in nitric acid leave 26 grains of 

 silica. 



b. The nitric solution, of a pure blue colour, was super- 

 saturated by ammonia ; the precipitate at first thrown down 

 was perfectly redissolved, and a deep blue solution was 

 obtained. 



c. This solution, supersaturated with sulphuric acid and pre- 



• Beitrdge, 2 B. s. 290. 



