o24 Scientific Proceedings, Royal Dublin Society. 



reduction of these salts have been ah-eady mentioned, but in 

 addition it may be suggested that the siftings referred to at 

 page 306 might be utilized for this purpose, as both the copper 

 and iron fragments would assist in reducing the solution, accord- 

 ing to the reactions just given, the copper at the same time being 

 extracted from the siftings. 



For the complete extraction of the copper from the solutions it 

 appears that either the excess of iron salts must be first got rid of, or 

 that these salts must be completely reduced to the ferrous state. 



Eespecting the waste of the sulphate of iron this not only 

 represents a loss, but is also a source of injuiious impurity to the 

 river into which it falls, and which is polluted to such an extent 

 as to be poisonous, so that no fish of any kind can live in this 

 portion of it, consequently in the head-waters only, non- 

 migratory fish (as brown trout, char, &c.), are now to be found. 



The more usual method for the recovery of the sulphate of iron 

 is evaporation and crystallization of the salts, here, however, this 

 seems inapplicable on account of the scarcity of fuel and the large 

 volume of weak liquors to be treated. Some precipitant should 

 therefore be adopted, and the most advantageous would probably 

 be either lime or limestone, the precipitate obtained by the first 

 would be an ochre largely contaminated with sulphate of lime, 

 but if the latter were used, it is probable the method of working 

 oould be so adapted as to separate the ochre in a great measure 

 from the sulphate of lime. 



As to enriching the solutions ; " Kernal roasting " as adopted 

 at Agordo, or as formerly practised at some of these mines during 

 Weaver's management (1787-1811) appears to be preferable, but 

 some other system of roasting might be attempted, or, as many 

 of the ores here contain much pyrites they undergo weathering 

 or natural oxidation most -rapidly (especially the soft and friable 

 ores) and this decomposition might be greatly accellerated by 

 employing some of the reagents mentioned at page 313. 



At Agordo (Venetian Alps); Rammelsberg (Hartz); Schmollnitz 

 (Hungary) ; and at Fahlun (Sweden) ; where there are deposits 

 apparently very similar, and containing similarly mixed ores ; 

 peculiar modifications are adopted for working up these ores, and 

 it appears very possible that some peculiar method might be 

 adopted profitably at the Ovoca mines. 



