176 Mr. J. Napier on Copper Smelting. 



The following analyses give a fair average of the results of 

 calcining coarse metal : — 



Metal put 

 into calciner. 

 Copper . . . . *32 



Iron 36 



Sulphur .... 25 

 Insoluble matter . 7 



100 



100 



The following is given by Le Play as the composition of cal- 

 cined coarse metal, which differs but little from the average of 

 our experience : — 



99-6 1000 1000 



The interference, arising from the solid character of the gra- 

 nules, with the full development of the chemical reactions in the 

 calcination, is completely got over by obtaining the coarse metal 

 in the state of a powder, either by crushing it mechanically, or by 

 the process referred to in the last article, namely, fusing with 

 sulphate of soda and coals, and immersion in water. In calcining 

 such powders, the reaction between the metal and the air or 

 gases in the chamber or hearth go on without interruption, and 

 enable us to define it experimentally. It is with powder pro- 

 duced by the last process to which our investigations have been 

 mostly directed ; but the results we find applicable not only to 

 crushed powder, but to the granulated coarse metal, so far as 

 the action can be developed consistent with their solid state. 



The first series of experiments with the powder were made in 

 a two-bedded calciner. The powder was obtained from a poor 

 Cornish ore, and was not thoroughly washed. A sample was 

 taken from the furnace every four hours ; 100 grains were boiled 

 in distilled water, and the quantity of sulphates ascertained; 

 another portion was digested in nitromuriatic acid, and the 

 copper, iron, sulphur, and insoluble matters determined; the 

 sulphur in the sulphates being deducted from the whole to deter- 

 mine what was combined with the metal as sulphuret. The 

 following table gives the results : — 



