28 
cuprite (Cu 2 0) either independently, or more often asso- 
ciated with malachite, azurite, brown iron ore, and native 
copper. Scarcely a specimen of copper ore can be obtained 
(with the exception of the sulphides) which does not ex- 
hibit more or less cuprite in intimate intermixture with the 
other ore ; whence it must be inferred that all, or almost all 
the ores of copper have been formed by aqueous and not by 
plutonic action, as cuprous oxide is undoubtedly prepared 
with greater facility by the wet method (that is from 
cuprous or cupric solutions) at a comparatively low tempe- 
rature than by the dry method at a very high temperature. 
I will briefly state in which way cuprite (that is the crystal- 
lised cuprous oxide) has been obtained by different authors, 
firstly by the dry method and secondly by the wet method. 
Preparation of Cuprite. 
Dry Methods of Preparation of Cuprite. 
1. A mixture of 24 parts of cupric sulphate and 29 parts 
of copper turnings heated to redness in a well closed 
crucible furnishes eventually a reddish-brown crystalline 
mass which is cuprite. 
2. A mixture of 100 parts of cupric sulphate and 57 
parts of soda crystals is heated until all the water of 
crystallisation is driven out, the residue powdered finely, 
and 37 parts of copper turnings are added, and the whole 
mixture heated in a crucible to a white heat for half an 
hour. On washing out the cooled mass with water, cuprite 
of a very fine colour is obtained. (Wohler and Liebig, 
Pogg. Ann. XXI. 581.) 
3. Crystals of this substance are often observed in the 
slags obtained in the smelting of copper ores. 
It will readily be observed from the above that an intense 
heat is requisite for the formation of cuprite by the dry 
method. 
