bleaching powder, cannot, so far, be produced at all by the
ammonia-soda works. The bleaching powder trade has thus remained in
the hands of the workers of the Leblanc process, and its sale has
enabled them to cover much of the loss which they are suffering on the
manufacture of soda ash and caustic soda.

In brief outline, the old Leblanc process consists in the following
operations: Salt is decomposed and boiled down with sulphuric acid.
Sulphate of sodium is formed, and a large amount of hydrochloric acid
is given off. This is condensed, and is utilized in the manufacture of
the bleaching powder mentioned above. The sulphate of sodium, known as
"salt cake," is mixed with certain proportions of small coal and
limestone, and subjected to a further treatment in a furnace, by which
a set of reactions take place, causing the conversion of the sulphate
of sodium of the "salt cake" into carbonate of sodium, a quantity of
sulphide of calcium being produced at the same time. The mass
resulting from this process is known as "black ash." It is extracted
with water, which dissolves out the carbonate of sodium, which is sold
as such or worked into "caustic" soda, as may be required. The
insoluble residue is the "alkali waste," which forms the vast piles,
so hideous to look at and so dreadful to smell, which surround our
large alkali works.

The sulphuric acid required for the conversion of the salt into "salt
cake" is made by the alkali manufacturer himself, this manufacture
necessitating a large plant of "lead chambers" and accessories, and
keeping up an immense trade in pyrites from Spain and Portugal. The
development of the alkali trade in this country has been something
colossal, and the interests involved in it and connected with it are
so great that anything affecting it may safely be said to be of truly