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type and those based on selective diffusion is made to ensure that all lamps are in good
order and advice is given as required on the use of self-contained oxygen respirators.
Experiments have continued on methods of improving sewer ventilation.
River Thames
The work on the assessment of pollution of the River Thames continued ; weekly
samples were analysed from 26 points between Teddington Weir and the Black Deep
(the sludge dumping area) and in addition the water off the two outfalls is sampled
daily at both high and low tides.
The condition of the river is obviously worst in the summer ; in 1954, the average
daily fresh water flow over Teddington Weir was 502 million gallons for the July—
September quarter which was more than double that of the previous year. The effect of
this increased flow, coupled with the recorded lower average air and water temperatures,
produced an improvement in general river conditions. The dissolved oxygen level
improved and the area where sulphide was detected was smaller and of shorter duration
and the actual concentrations were much reduced.
The necessity for the reduction of the pollution load on the river is apparent and
the Council's additional treatment works now under construction or being planned
will, when in operation, make a substantial contribution to this end. It should be
emphasised in this connection that there are many sources of pollution gaining access
to the river, as well as the effluent from the Council's works ; for example, other
sewage effluents, trade waste discharges, water from impure tributaries and contamination
from shipping.
The Scientific Adviser continued to be a member of the Thames Committee of the
Department of Scientific and Industrial Research and also of the Heated and Other
Effluents Committee of the Ministry of Housing and Local Government. Both Committees
deal with aspects of the condition of the water of the river and are to report,
in due course, their recommendations for its improvement.
Mention should be made of research work done at the Southern Outfall works
laboratory on the iron salts in the river water. The amount varies from 0.4 p.p.m. to
2.5 p.p.m. (average 1.4 p.p.m). Normally they are present in the ferric state but when
sulphides become established they are reduced partially or wholly to the ferrous state.
Throughout 1954 a regular examination of high and low tide samples was made to
determine the changes of the ferrous and ferric balance.
Housing
The work done by the Scientific Branch for this service covers a very wide field. The
largest section, that concerned with paints and other surface coatings, is of considerable
economic importance, since the total expenditure of the Council on these products and
their application is round about £4 million. The Inter-departmental Paint Committee
and Sub-Committee continued their regular meetings and played an important part by
ensuring that good-quality products only were used and by taking all possible steps to
avoid site difficulties. The approved paint lists comprised hard gloss, semi-gloss, flat, oil
and emulsion paints and chlorinated rubber and black protective bitumen. In this range,
61 new brands were approved during the year and 87 were found not to be of the
quality required.
The faults to which a paint is prone are many and varied but several exterior hard
gloss paints were rejected because their pigments contained excessive quantities of
calcium carbonate or lithopone, sometimes as much as 50 per cent. In one case, a pigment
for a paint recommendecf for Grade A exterior contained 63 per cent. of china clay.
A common fault found on the site was the inadequate sealing of porous surfaces and,
in some instances, complaint was made of slow drying and the difficulty of application.
Special laboratory investigations were necessary in connection with some site troubles
and advice notes were sent to user departments on—
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