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29
Chemical branch
The work of the chemical branch was carried on during the year at the three
laboratories, the total number of samples examined being 14,991.
A large proportion of the work during the year was again of an investigational
and advisory character, this being necessitated by requests from chief officers of
other departments for assistance on various matters in regard to which the science
of chemistrv could be of service. Examines are :—
Central
laboratory
(1) The Chief Officer, Meals Services, asked that consideration be given to the
possibility of improving the efficiency of the washing-up process in restaurants
where this is done by hand. The theoretical basis of detergency was studied and
many commercial detergents were examined, particular attention being paid to
those of the hew synthetic type. Laboratory scale tests were made, and subsequently
it was recommended that trials of three formulae should be conducted on a practical
basis, the opinion being expressed that the suggested procedure would, with due
regard to economy, improve the efficiency of the washing-up process.
(2) In view of the general use of petrol containing lead, the Chief Engineer asked
that the question of the lead content of the air of the vehicular tunnels should be
investigated having regard to the possibility of toxic effects due to lead. The
conclusion was that, while the amount of lead in the air in the tunnels was by no
means negligible in relation to the standards generally accepted, no risk to health
need be anticipated from this source. A standard of ventilation in which the limit
for carbon monoxide is 25 parts per 100,000 will also ensure that the concentration
of lead is kept within the usually accepted limit.
(3) The Architect requested that the failure of the sheet lead flashing on a large
roof should be investigated. The conclusion was that it was due to fatigue occasioned
by thermal effects causing the repeated application of alternating tensile and compressive
stresses. The suggested remedies were the use of expansion joints or alternatively
a lead alloy which had a greater resistance to such stresses.
(4) An explosive incendiary bomb having penetrated the roof and damaged the
coil of a refrigerator at a hospital, the food therein had become contaminated with
methyl chloride, and, as appeared from the observations made, the decomposition
products of this by heat. The various foods were examined and appropriate action
was recommended in each case.
(5) At the request of the Chief Officer, Public Control Department, opinions
were expressed in a number of cases as to whether various processes being carried
out in certain premises could be deemed to be " dangerous businesses " under the
terms of the London Building Act, 1930. The many factors involved in each individual
case (e.g., materials or chemicals used, method of heating or processing,
the type and arrangement of the premises) were reviewed and a considered opinion
was given.
(6) The Chemist-in-Chief being also the Official Agricultural Analyst for the
County under the Fertilisers and Feeding Stuffs Act, 1926, several samples of "unrationed"
poultry food were submitted for examination. The war-time shortage
of good feeding stuffs has encouraged vendors to offer for sale materials which are
of doubtful value. It was difficult in some instances to decide whether the potential
small feeding value outweighed the disadvantages of the material, but a considered
opinion was expressed in each case, some being definitely adverse.
(7) Samples of hair and nails from a man suspected, on clinical grounds, possibly
to be suffering from arsenical poisoning were found to contain relatively large amounts
of arsenic, and spectrographic examination also revealed the presence (subsequently
confirmed and estimated chemically) of lead. The opinion was expressed that the
patient might have been employed in an industry using lead arsenate and this, on
enquiry, proved to be the case. Subsequent periodical examination of specimens
showed a steady decline of the content of both metals.