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Building
materials.
Various materials intended for partitions, doors, etc., have been examined for
fire-resisting properties by the methods to which reference has been made in previous
reports. The general question of standardisation of such materials and tests is
now under consideration by a committee of the British Engineering Standards
Association, on which the chemist, with other officers, represents the Council.
Testing of
reflectors.
Some chromium-plated reflectors for use in directing longitudinally the light
of the lamps in the Thames subway tunnels were submitted for examination. When
exposed for 1,000 hours to a moist atmosphere artificially polluted with carbon
dioxide and sulphur dioxide in amounts vastly greater than would occur in any
tunnel, very little discolouration was observed, but it was found that the surface
layer was lifted in places from the copper beneath, which was corroded. These
failures were associated with faults in the surface due to no visible lack of continuity
of the film, but to variations of thickness of the deposited layer and of the consolidation
produced, it was presumed, by burnishing.
It does not appear that any other material, except, perhaps, a rustless steel,
would behave better than or as well as chromium-plated metal, which seems to
stand well the ordinary laboratory atmosphere and cleans up well with a damp
cloth. A more drastic treatment seems likely to scratch the surface.
Water
softening.
An interesting problem in water softening has been successfully dealt with
at one of the Council's pumping stations where it is necessary to use river water for
"make-up" for boilers. The dry weather led to very great variations in salinity
(and incidentally in hardness) from about 23 parts per 100,000, due to normal Thames
water up to as much as 134 parts due mainly to about 18 per cent. of sea water,
which introduces large quantities of magnesium and calcium salts. By systematic
examination of raw water as impounded and the recommendation of mixtures of
softening reagents adapted to the varying nature of the water, an average reduction
of hardness throughout the year of 78 per cent. was effected.
A water of varying hardness would seem specially appropriate for softening by
the base-exchange process at least as a finishing treatment after chemical softening.
The great sodium content of tidal waters, however, seems to militate against the
successful use of this process. The chemist has discussed this matter with the
Director of Chemical Research Laboratory of the Department of Scientific and
Industrial Research, who is conducting an investigation on the base-exchange
process.