172 MR. CHARLES A. BURGH ARDT ON THE 



of copper turnings, heated to redness in a well-closed cru- 

 cible, furnishes eventually a reddish-brown crystalline mass, 

 which is cuprite. 



2. A mixture of lOO parts of cupric sulphate and 57 

 parts of soda crystals is heated until all the water of crys- 

 tallization is driven out ; the residue powdered finely, 

 37 parts of copper tui*niugs are added, and the whole mix- 

 ture heated in a crucible to a Avhite 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. 



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 dissolve all the resulting precipitate, and then gently 

 heated ; cuprous oxide then separates out in the form of a 

 crystalline powder. (Mitscherlich, Journal fur practische 

 Chemie, xix. 430.) 



2. Bequerel (Compt. Rend. xliv. 308) describes a beau- 

 tiful method which is applicable for the preparation of many 

 minerals. He filled a test-tube with a neutral solution of 

 cupric nitrate, placing a little cupric oxide and a clean strip 

 of copper plate at the bottom, closed the tube air-tight and 

 left it to itself for many months. In this way he suc- 

 ceeded 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 with an alkaline carbonate, carbonic acid gas is 



