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(2) School meals.—In connection with the provision of meals for necessitous
children, 103 samples were examined during the year, representing 51 complete
two course meals. The standard adopted is that each meal shall contain not less
than 25 grammes protein and have a heat value of not less than 750 calories. The
average of the samples examined was 33 grammes protein and 810 calories, which
indicates that the meals were generally well balanced as well as being satisfactory
in quality and quantity. In several cases, where the requirements were not fulfilled,
suggestions were made to remedy the deficiencies.
(3) Food poisoning.—Seven samples were submitted during the year for chemical
examination in connection with three cases of suspected food poisoning. The
results were all negative but in one instance were interesting, this being in connection
with the supply of boned and rolled cooked herrings in open metal containers. As
regards the particular case of suspected poisoning, the amounts of poisonous metals
found in the herrings were so small as to have no significance, particularly in view
of the amounts which have been found to be naturally associated with certain
varieties of fish. Analysis of the tinned coating, however, led to a recommendation
that tinplate used for cooking purposes should be in conformity with the official
government specification, which requires pure tin (99.5 per cent. tin) to be used
for this purpose.
(4) Ancesthetic ether.—A systematic investigation into the question of the
decomposition of ether was begun during the year. Preliminary experiments confirmed
the results of previous workers, and emphasised the fact that ether used for
anaesthetic purposes should be stored in the dark, that only small bottles filled
almost to the stopper should be used and that these should be wrapped in black
paper not reaching all round, thus leaving a vertical slit through which the level
of the ether can be observed. The necessity for the production of a very pure
ether has for long been generally recognised, especially with regard to the absence
of even extremely small amounts of peroxides, and there is no doubt that autoxidation
of ether is closely related to its initial purity. The question of peroxide contamination
seemed, therefore of primary importance and this aspect of the matter
was first studied. Experiments were carried out in several ways, some of which
involved imitating the use of the "open mask" method of anaesthesia, and others
the use of a Boyle's apparatus. The results showed conclusively that ether peroxide
was much less volatile than ether itself, and that, on bubbling air through ether
the peroxide was not volatilised in appreciable amount even in the case of ethers
so badly contaminated that they would in no case be used for anaesthetic purposes;
also that, under normal conditions of use, the time is too short for the original ether
to deteriorate to any great extent. It was finally concluded that, although it is
unquestionable that anaesthetic ether should be as pure as possible, peroxides
themselves are not the cause of the after-effects which may be produced by impure
ether.
(5) Enamelware.—There has again been a marked improvement in the quality
of the samples examined. In all 221 samples were tested and only six were rejected
(2.7 per cent. compared with 4.7 per cent. in 1935), 4 for failing to comply with
the Council's acid resistance test and 2 for containing antimony.
(6) Special investigations have been made in connection with efflorescence on
plaster and brickwork ; failure of cement concrete ; corrosion of iron water pipes
by softened water ; leakage of methyl chloride from a refrigerating plant; the
chlorination of sewage ; the abnormal reading of an automatic water level recorder,
which was found to be due to the diffusion of carbon dioxide gas from the liquid
through the rubber diaphragm of the instrument; the disturbance of earth level
in the vicinity of a school, found to be due to the character of the waste material
which had been used for making up the ground.
Milk samples.
The total number of milk samples examined during the year in the laboratory
at County Hall was 160. Of this number 46 were of milk supplied to children in
residential schools and educational institutions, whilst 110 were from supplies to