, methods for disposing of the lime
sludge coming from an acetylene generator, it was stated that on occasion
a use could be found for this material. If the carbide has been entirely
decomposed in an apparatus free from overheating, the waste lime is
recovered as a solid mass or as a cream of lime practically pure white in
colour. Sometimes, however, as explained in Chapter II., the lime sludge
is of a bluish grey tint, even in cases where the carbide decomposed was
of good quality and there was no overheating in the generator. Such
discoloration is of little moment for most of the uses to which the
sludge may be put. The residue withdrawn from a carbide-to-water
generator is usually quite fluid; but when allowed to rest in a suitable
pit or tank, it settles down to a semi-solid or pasty mass which contains
on a rough average 47 per cent. of water and 53 per cent. of solid
matter, the amount of lime present, calculated as calcium oxide, being
about 40 per cent. Since 64 parts by weight of pure calcium carbide yield
74 parts of dry calcium hydroxide, it may be said that 1 part of ordinary
commercial carbide should yield approximately 1.1 parts of dry residue,
or 2.
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