THE SOURCES AND USES OF IRON PYRITES. 
By J. ABTHUR PHILLIPS, F.G.S. 
[PLATES HI. & IV.] 
T HE process still generally employed for the manufacture of 
carbonate of soda from common salt was the discovery of 
the French Chemist Leblanc, and was first carried out, on a 
large scale, by him and his partners in France. Previous to the 
revolution of 1789 the only kind of soda commercially known 
was that obtained from various marine plants, the greater 
portion of the raw material having been imported from the coast 
of Spain and Portugal. 
The wars which were at that time ravaging Europe na- 
turally had the effect of putting a stop to this branch of 
industry, and although, in case of need, potash may replace 
soda in the manufacture of glass and soap, the emergency of the 
times rendered it necessary that the whole of the available 
potash should be converted into saltpetre for the preparation of 
gunpowder. 
With a view to meeting this very serious difficulty, the 
Committee of Public Safety called, by special proclamation, 
upon all citizens to place in the hands of commissioners for the 
public benefit, and without regard to private interests, whatever 
plans or methods of preparing soda might be known to any of 
them. 
In consequence of this demand numerous schemes were laid 
before the Commissioners, who eventually reported that the 
method proposed by M. Leblanc appeared to be that best 
adapted for the manufacture of soda upon an extensive scale. 
This process consists in first converting chloride of sodium into 
sulphate of soda by the addition of sulphuric acid, and the 
subsequent decomposition of sulphate of soda, at a high tempe- 
rature, by a mixture of limestone and dust coal. 
In order to convert one ton of common salt into sulphate of 
NEW SERIES, VOL. III. — NO. X. I 
