of Mineral Substances. 279 



cipitated by zinc, afforded 40 graias of copper, which are equi- 

 valent to 50 grains of peroxide of copper. The following, 

 therefore, are the components of this ore : 



Copper 40 



Oxygen 

 Carbonic acid 

 Silica 

 Water . 



10 



7 



2G 



17 



100 

 The silica in the above mineral is not merely mechanically 

 blended, but forms one of its chemical components. 



Analysis of the Copper Glance of Rothenburg. 



The compact variety of the above ore, of a greyish black 

 colour, soft, giving a dull black streak, and of a specific gravity 

 of 4.685, was employed in the following experiments ; it also 

 occurs at Rothenburg in hexaedral prisms. 



A. a. Having ascertained the absence of silver, lead, anti- 

 mony, 8^c. ; and that copper and sulphur are the components of 

 this ore, 100 grains were digested in muriatic acid, the action 

 of which was aided by the occasional addition of some drops of 

 nitric acid, till the ore appeared decomposed. The liquid was 

 then poured off, and the remaining sulphur having been di- 

 gested in a fresh portion of muriatic acid, was washed and 

 dried : it weighed 22 grains, and burned away without any 

 appretiable residuum. 



b. The colour of the solution, at first brown, became green 

 and blue by dilution ; the addition of ammonia occasioned a 

 precipitate perfectly redissoluble in excess of the alcali, with 

 the exception of some brown flocculi of oxide of iron, which 

 were found equal to one-half grain of metallic iron. The 

 ammoniacal liquor supersaturated by sulphuric acid, and de- 

 compoaed whilst warm by the insertion of a plate of iron, gave 

 76J grains of metallic copper. 



B. 100 grains of the same ore were reduced to powder, and 

 distilled to dryacss with six parts of dilute sulphuric acid (com- 

 U2 



