133 
1880.J New Scientific Processes and Inventions. 
It is obvious that “ lead houses ” and other ordinary sulphuric 
acid plant maybe added to this, in order to utilise the 14 or 
1 r per cent of sulphurous acid that otherwise escapes by the 
chimney, this sulphurous acid being identical with that produced 
in the kilns of the vitriol-makers by roasting pyrites. 
