On a method of treating Mineral Sulphurets, 309 



the pipe h, (fig. 4,) towards the leaden chamber / ; but 

 on its way it passes over a quantity of saltpetre placed in 

 the recess i, absorbs oxygen therefrom, becomes sulphu- 

 ric acid, is condensed in the leaden chamber I, and after- 

 wards evaporated to the proper strength ; k is an aper- 

 ture for the purpose of supplying saltpetre to the receptacle 

 i. Thus far for the manufacture of sulphuric acid. I was 

 informed, that when the furnaces were supplied with fresh 

 ore every three hours, and the well-burnt ore extracted 

 every 24 hours, the calculation was, that every three hours 

 you charge these furnaces with 1201bs. of metal, and every 

 24 hours extract 8001bs. of roasted ore. 



This roasted ore is then placed on a platform of masonry, 

 m, fig. 5, and is kept continually soaked with water aci- 

 dulated with sulphuric acid. This platform should have a 

 tilt down towards one corner, so as to permit the water to 

 percolate, and to pass charged with the sulphates through 

 one angle into the reservoir n. In proportion to the heat 

 of the weather will be the rapidity with which the diluted 

 sulphuric acid will take up the soluble matter in the ore — a 

 mixture of alumina, peroxide of iron, and silica, &c. will re- 

 main behind, and the water will pass overcharged with the 

 sulphates as of copper, iron, arsenic, &c. according to the 

 composition of the mineral. When arrived in the reser- 

 voir n, it is pumped up into another reservoir o, from 

 whence it is allowed to descend unto the baths p f p, p ; 

 in these baths are placed pieces of iron, and as the water 

 charged with acidulated sulphate of copper passes over 

 this iron, the coppper will be precipitated ; these baths empty 

 into one another by the assistance of syphons q, q, q t so 

 arranged, that they may play of themselves. Fig. 6 is a 

 bird's eye view of fig. 5, shewing the arrangement of the 

 baths, the same letters correspond to those in fig. 5. These 

 baths may be as numerous as necessary, the water with the 

 sulphate of copper being kept continually running over these 



