310 LECTURES TO SCIENCE TEACHERS. 



you please, this experiment, as we shall need hereafter to 

 make use of this property. 



Now I think we have got a clear idea of the general 

 nature of the manufacture. Let us next pass to consider 

 in detail the several parts of the process. First we will 

 begin with the raw materials. Up to within the last 

 thirty years all the sulphuric acid manufactured was 

 made from sulphur imported into this country from Sicily, 

 where you know it occurs in the native state amongst the 

 volcanic deposits of which that island is the seat. The 

 price of Sicilian sulphur up to the year 1838 varied from 

 Ql. to 8. per ton, but in that year the King of the Two 

 Sicilies attempted to establish a monopoly, which had the 

 effect of raising the price of sulphur to 201. per ton. This 

 senseless action, however, soon worked its own cure, for the 

 manufacturers beginning to inquire about other and cheaper 

 sources of sulphur, found that a sulphur ore known as 

 pyrites, and consisting of bi-sulphide of iron (FeS 2 ), and 

 usually containing small quantities of sulphide of copper, 

 could be obtained in large deposits in Ireland, Spain, and 

 elsewhere, and that this, when burnt in kilns, yields sul- 

 phur dioxide precisely as sulphur itself does, but at a far 

 cheaper rate, as the mineral is abundant, and is obtained 

 without much cost. 



Another great advantage possessed by this pyrites is that 

 its use as an ore of sulphur establishes a new industry, viz. , 

 the extraction of the three or four per cent, of copper which 

 the burnt ore contains. This has now become an important 

 trade, and when you learn that at least 500,000 tons of 

 pyrites containing from three to five per cent, of copper is 

 annually burnt in England, you will be able to appreciate 

 the importance of this new source of copper. 



A sectional view of a series of three sulphuric-acid 

 chambers is seen in Fig. 6. This likewise exhibits the 

 construction of the pyrites kilns; whilst in Fig. 7 the 

 detailed arrangement of such a burner is seen. The pyrites 

 burns when it is once kindled by throwing the stone into 

 a kiln previously heated to redness, and a second charge 

 is brought into the furnace and ignited whilst the first is 

 still hot, so that a constant supply of sulphurous acid to 

 the chamber is kept up by charging the burners in 

 regular order. The ordinary charge of pyrites is about five 



