460 



Mr. J. Napier on Copier Smelting. 



tion of these fumes will cause an immediate decrease in the quan- 

 tity of sulphur in the portion of ore then tested; the gases 

 ahove the ore being principally composed of sublimed sulphur, 

 the admission of cold air, which always follows a rapid evolution 

 of gas, probably the result of a reacting condensation, causes a 

 portion of the sulphur to be deposited and absorbed again by 

 the ore, so that the next quantity tried contains more sulphur. 

 Regularity in the draught and heat of a calcincr ought to be 

 strictly attended to. 



Another trial was made with an ordinaiy mixture of ores, every 

 door of the calciner being clayed up air-tight, and allowing no 

 air to be admitted except through the bridge under the fire, 

 by which it was partially heated. A sample of ore taken out 

 every hour for six hours and tested for sulphur gave as follows : — 



Here we have the same intermitting action after a few hours. 



In the next experiment the calcination was continued as long 

 as sulphur was present ; or, as expressed practically, the ore 

 was calcined dead. The quantity of sulphur was determined every 

 four hours ; the ore was turned over every two hours ; the sam- 

 ples were taken out as the stirring commenced, and always from 

 one part of the hearth. 



Sulphur 25-9 



Given off every \ 

 4 hours ... J 



24-8 

 11 



207 

 41 



147 12 

 60 27 



The intermittent action is not so fully developed in four-hour 

 trials; but looking at the rate of loss each four hours, there is 

 no doubt that it existed. It must be remembered in judging of 

 the rate at which the sulphur passes oif from the ore, that in the 

 above and all calcinations the heat of the furnace is gradually 

 increasing ; showing the strong affinity the last portions of sul- 

 phui- have for the metal. 



In the above ex])eriment the quantity of sulphates formed was 

 also tested ; the following are the results : — 



After 4 hours a little sulphuric acid, no copper or iron in 

 solution. 



After 8 hours a little more acid, no metals. 



After 12 hours both sulphate of copper and ii'on. 



After 16 hours a mere trace of acid. 



