29 
Wet Methods of Preparation of Cuprite. 
1. A solution of equal parts of cupric sulphate and grape 
sugar is mixed with sufficient caustic soda solution to dis- 
solve all the resulting precipitate and then gently heated, 
cuprous oxide then separates out in the form of a crystalline 
powder. (Mitscherlich Journal Pract. Chem. XIX. 430.) 
2. Bequerel (Compt. Rend. XLIY. 308) describes a beau- 
tiful method which is applicable for the preparation of 
many minerals. He filled a test tube with a neutral solu- 
tion of cupric nitrate, placing a little cupric oxide and a 
clean strip of copper plate at the bottom, closed the tube 
airtight and left it to itself for many months. In this way 
he succeeded in obtaining small shining cubes of cuprite. 
3. A. Knop (Jahrb. f. Min. 1861, 508) states that if a 
mixture of solutions of cupric sulphate and ferrous sulphate 
be treated by an alkaline carbonate, carbonic acid gas is 
evolved and a mixture of ferric hydrate and hydrated 
cuprous oxide is precipitated, the latter becoming crystal- 
line after the expiration of some time. 
Of the three methods given above that of Knop undoubt- 
edly furnishes one of the most probable processes by which 
many large deposits of the so-called tile ore and copper 
pitchblende have arisen ; but there are again many other 
deposits of cuprite which may easily have been formed in 
other ways. I will not discuss at the present time the 
various opinions upon the formation of copper ores ex- 
pressed by some very eminent and competent authorities, 
but I may mention that Dr. Ferdinand Wiebel, in a lengthy 
and exhaustive treatise (Das Gediegen Kupfer und Roth 
Kupfererz, Hamburg, 1864) concludes that the native metal 
and cuprite have in all cases been formed from a cupric 
sulphate solution (obtained by the oxidation of copper 
pyrites) through its reduction by a solution of ferrous 
sulphate (also derived from the oxidation of copper pyrites). 
This statement is doubtless correct in the case of some 
