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50
with the Department of Scientific and Industrial Research.
Such co-operating bodies are entitled to appoint representatives
to the Standing Conference.
"At their last meeting the Standing Conference considered
that an extension of the investigation was highly desirable,
and they decided to call the attention of all Local Authorities
to the work that is being done, and to invite further cooperation."
This letter was submitted to the Public Health Committee,
and the Senior Sanitary Inspector reported thereon. He recommended,
as an experiment, the purchase of a set of apparatus to
enable daily measurements to be taken of the concentration of
atmospheric smoke and sulphur dioxide, the apparatus to be
installed at the Public Health Department, Sidmouth Road, Leyton.
This recommendation was adopted, and the Chairman and Senior
Sanitary Inspector were nominated as the Council's representatives
on the Standing Conference. The Superintendent of Observations,
of the Department of Scientific and Industrial Research, was
consulted as to the siting and equipment of the station, and observations
were begun on 1st March, 1950.
Daily measurements of the average concentration of smoke
and sulphur dioxide in the air during the preceding 24 hours are
made by the "volumetric" method—one of the standard methods
recommended by the Department of Scientific and Industrial
Research.
The outside air is drawn in at a steady rate of about 60 cubic
feet per day, the actual volume being measured with a gas meter.
The air is first passed through a white filter paper in such a way
that the suspended solid impurities (chiefly consisting of smoke)
remain in the filter paper as a greyish or brownish stain. An
estimate of the intensity of this stain is made by visual comparison
with a calibrated scale of shades, and from this the concentration
of smoke is calculated. After passing through the smoke filter,
the air is bubbled through a dilute solution of hydrogen peroxide
where the sulphur dioxide is removed from the air and combines
with the hydrogen peroxide to form sulphuric acid. At the end
of a day's run, the volume of standard alkali needed to neutralise
the sulphuric acid is measured and the average concentration of
sulphur dioxide is then calculated.