314 ScientifiG Proceedinqs, Royal Dublin Society. 



some reagent (usually a chloride after a preliminary roasting of 

 the ore) has been found therefore more generally satisfactory. 



Thus, if copper pyrites be mixed with a certain proportion of 

 lime ; or a calcareous or dolomitic copper ore mixed with pyrites 

 (Bischof), finely ground, moulded into bricks and roasted in a kiln, 

 the reagents react on each other, forming sulphate of copper and sul- 

 phate and sulphide of lime. Or, when burnt or roasted pyrites is 

 mixed with sulphuric acid, and after being moulded into bricks 

 roasted till sulphate of iron is decomposed, the sulphate of copper 

 formed may then be extracted with water {De la Rue and Miiller) 

 It has also been proposed to treat the ore in cast-iron pots with 

 sulphuric acid at 65° C. and to boil the liquor till ib thickens. The 

 copper may then be extracted as sulphate (Hauch). 



At the present day it is usually preferred to convert the copper 

 into chloride, which may be accomplished either by a wet or by a 

 dry process, the latter, especially in the treatment of pyrites 

 cinders, being more generally adopted. 



The ore having been ground and roasted is mixed with an 

 alkaline chloride (usually common salt, but at Ocker, potassic 

 chloride is used),and calcined, when chloride of copper and sulphate 

 of the alkali are formed, which are dissolved out with water, but 

 if gold or silver be present, a strong brine is used. Besides the 

 chlorides previously mentioned (soda, potash, ammonia and lime), 

 ferric chloride has also been proposed, as also roasting with sodic 

 chloride and digesting with sea water and sulphuric acid (Stella) ; 

 or moistening with hydrochloric acid and subsequent roasting. 



Solution of the Copper Salts. 



The solution of the copper salts is usually effected by water, 

 but acids are used for the less soluble salts, and under certain 

 conditions some other solutions. 



Generally the ores, after the preliminary treatment, are placed 

 in the lixiviating tanks, which have false bottoms, on which a 

 filter of coke or of similar material is formed. The first washings 

 are of water often heated, but sometimes the last washings of a 

 previous supply of ore are used ; when the more soluble salts are 

 removed dilute acid is added, and finally water, the last washings 

 being reserved for the first washings of the next supply, as there 

 is a great advantage in having the solutions concentrated. In the 

 accounts of the different processes, numerous appliances for 



