Lead poisoning and lead absorption : $b The symptoms, pathology and prevention, with special reference to their industrial origin, and an account of the principal processes involving riskLegge, Thomas Morison, Sir
Science
Lead poisoning and lead absorption : $b The symptoms, pathology and prevention, with special reference to their industrial origin, and an account of the principal processes involving risk
Legge, Thomas Morison, Sir
Lead poisoning
Red lead can be, and is, now made on an extensive scale in such a way
that all operations, from commencement with pig-lead to the final
packing, are carried out by mechanical means so entirely closed in that
the worker does not come into contact with the material. The person
who then may be affected is the fitter attending to repairs of the
machinery. The pig-lead is melted, stirred, and mixed in a covered-in
melting-pot. The massicot which is formed is drawn off by an exhaust
into a hopper, from the bottom of which it is fed mechanically on to
the floor of the furnace. Mechanical rabbles stir it from the centre
to the outside of the furnace floor, from where it is conveyed, under
negative pressure, to the hopper of a grinding mill. From here it is
again similarly fed into another furnace. The exhaust pipe from this
furnace collects the finished product, carrying it mechanically to a
hopper which automatically feeds the red lead into casks. Negative
pressure throughout prevents escape of dust.
=Manufacture of Litharge.=--Pig-lead is placed in a cupellation
furnace, and constantly stirred and raked over to cause entire
oxidation, and then is either raked out or run out from the furnace
hearth into moulds, and allowed to cool in the form of large balls.
These balls, of a roughly crystalline nature, are deposited on the
floor, where they are exposed to the air. Disintegration is accelerated
by breaking up the large fragments by hand. Subsequently the material
is placed in a disintegrator for fine division and packed.
_Dangers and Prevention._--Manufacture of litharge may cause a greater
amount of dust than any other process with which we are familiar. The
nature of the operations is such that it is impossible at all stages
to control this dust. Danger is greatest in the early operations of
shovelling up the disintegrated powdery material from the floors into
receptacles, and in discharging the contents into the disintegrating
machine. The work is heavy, and a respirator is with difficulty worn.
A movable hood attached to a flexible duct in connection with an
exhaust which could be moved from place to place on the floor suggests
itself, but when tried it has not effectively controlled the dust,
owing to both the trouble involved and the difficulty of bringing
the exhaust near enough to the work. When once the material reaches
the disintegrator, exhaust over the hopper, and in connection with
the enclosed sifter and grinder and packing machine, can readily be
secured. Bins should be provided for the litharge lumps, so as to
avoid trampling the powder underfoot, and covered barrows for removing
the semi-powdered material. Alternation of employment lessens risk,
and should be always arranged. In any new plant the possibility of
automatic methods of carrying out the process as far as possible should
be considered.
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