486 Mr. J. Napier on Copper Smelting. 



Notation. 



k, volume of unity of weight of the gas, under a pressure of 

 unity of weight on the square metre, at 0^ Centigrade. 



Kw, mechanical equivalent of the specific heat of unity of 

 weight of liquid water =1389'6 feet, or 423*54 metres 

 of fall per Centigrade degree, as determined by Joule. 

 . Kp, mechanical equivalent of the specific heat of unity of 

 weight of the gas under constant pressure. 



Kv, mechanical equivalent of the specific heat of unity of 

 weight of the gas at constant volume. 



ff, accelerating force of gravity =9*80896 metres per second 

 (at the observatory of Paris). 



u, velocity of sound in the gas at 0° Centigrade 



V. 



'"■w. 



LXXVII. On Copper Smelting. By James Napier, F.C.S.* 

 [Concluded from p. 354.] 



THE metal being brought to the state of blister copper, the 

 next operation is that of refining — bringing it into a state 

 fit for the market. The refining, furnace is similar in form to a 

 roasting-furnace, but a little smaller, and the bottom is made to 

 incline a little to the front door, where a small well is made. 

 The copper being ladled from the furnace, this well allows of the 

 ladles being dipped into the metal when the quantity in the 

 furnace is small, so that the last portions of the metal can be 

 taken out. 



About six tons of copper from the roasting-furnace are put 

 into the refining furnace,' the doors and air-holes of which are 

 closed, and the heat raised until the metal is in fusion, when the 

 air-holes are opened. A short roasting is generally required, 

 which is done in the manner we have described, and the scoria 

 which collects is carefully skimmed off". The separation of im- 

 purities is facilitated by occasionally stirring the metal with a 

 rake. Some refiners throw pieces of green wood upon the sur- 

 face, under the impression that it assists the escape of sulphur. 

 The roasting is continued until a ladleful of the metal taken out 

 sets with contraction. If the metal be very coarse, it will set 

 with a surface having a frothy appearance ; if finer, it sets with 

 expansion, first round the edge, then swelling towards the centre, 

 forming a little mound or cone, and occasionally boils over and 



♦ Communicated by the Author, who reserves to himself the copyright, 

 any infringement whereof will invoke legal proceedings. — Eds. 



