" This acidity places the water in
the condition of a direct solvent for iron, and that dissolved iron may
cause great injury. If such water cannot be dispensed with, the best way
is to carefully neutralise it with carbonate of soda; the iron is then
precipitated as carbonate of iron, and can be removed.
_Contamination of Water by Factories._--You may have neighbours higher
up the stream than yourselves, and these firms may cast forth as waste
products substances which will cause immense waste and loss. Amongst
these waste products the worst are those coming from chemical works,
paper works, bleach works, etc. If the paper works be those working up
wood pulp, the pollutions of effluent water will be about as noxious as
they well can be. You will have gums and resins from the wood, calcium
chloride from the bleach vats, acids from the "sours"; resin, and
resin-soaps; there may also be alumina salts present. Now alumina, lime,
resin, and resin-soaps, etc., precipitate dyestuffs, and also soap; if
the water is alkaline, some of the mordants used may be precipitated and
wasted, and very considerable damage done.
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