412 ZINC, CADMIUM, LEAD, &c. 



the name of oxide of copper ; while to the red 

 oxide we shall apply the term suboxide, indicat- 

 ing that it is a compound of two atoms copper 

 and one atom oxygen. Such suboxides in gen- 

 eral are incapable of constituting permanent salts 

 with acids. 



As the black oxide of copper constitutes the 

 basis of all the cupreous salts, the knowledge of 

 its atomic weight is of most importance in a 

 chemical point of view. We may employ the 

 common sulphate of copper, as a good instru- 

 ment for determining the atomic weight of this 

 oxide ; because being manufactured to a con- 

 siderable extent, and employed both in medi- 

 cine and the arts, it may be easily procured in a 

 state of purity. It has a fine blue colour, an ex- 

 ceedingly disagreeable cupreous taste, reddens 

 vegetable blues, and crystallizes in oblique four- 

 sided prisms, the faces of which are inclined to 

 each other at angles of 124 and 56. 

 Analysis of 1. When a solution of 15*625 grains of these 

 crystals in water, is mixed with a solution of 

 13*25 grains of chloride of barium, a double de- 

 composition takes place, sulphate of barytes pre- 

 cipitates, and the supernatant liquid is neither 

 affected by sulphate of soda nor muriate of ba- 

 rytes. Hence, it follows, that 15*625 grains of 

 this salt contain just 5 grains of sulphuric acid. 



2. If the whole oxide of copper be precipita- 

 ted from 15*625 grains of blue vitriol, and col- 



