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Various materials and apparatus for special purposes sent for examination
during the year included—
(1) Gas alarm lamps, for use in the sewers, for the detection of explosive gas or
deoxygenated air. Lamps and apparatus of various designs were examined, including
(a) special types of safety lamps made to give a warning by showing, through
the operation of a bimetallic spring acting upon an electric switch, a red light when
there is an appreciable amount of inflammable gas in the air; and (b) apparatus for
showing the actual amount of these gases present. These were both found to be
very reliable and should be most useful in discovering a dangerous condition of the
sewer air.
(2) Wood, composite boards, metal sheets, etc., used as building materials, were
tested for fire resistance in accordance with the British standard me hod and for
thermal conductivity.
(3) Aluminium hot-water bottles, used in hospitals, were on occasions found to
become badly corroded under certain conditions. The cause for this was ascertained
and instructions given for treatment to prevent or reduce corrosion, such treatment
consisting of adding about ½ oz. of potassium bichromate to 100 gallons of the water
used in filling the bottles.
(4) Aluminium food containers, for use in hospital wards, were examined as to
thermal conductivity and rate of cooling, as it was alleged that the food did not
remain hot sufficiency long when brought to the wards in these containers. After
making tests it was decided that a great improvement in the heat retaining properties
of these containers could be effected by the insertion of a non-conducting
material to break the continuity of the metal between the inner and outer lining of
the container, and this was recommended.
(5) Incrustation in boiler pipes, from a boiler used for the heating installation
at a school. The incrustation had the appearance of foundry sand, but was found
to be almost entirely calcium compounds from the water, indicating that there was
a large amount of make-up water used, due either to leakage or to a large use of the
water for purposes other than heating.
(6) Collapse of ceiling.—An investigation as to the cause of the serious collapse
of a ceiling was made. The ceiling was suspended from the beams of a reinforced
concrete floor by means of galvanised staples driven into a patent composition
which formed the lower surface of the beam. It was found that the patent composition
was one of the well-known class of materials composed of a sawdustPortland-cement
concrete, containing a hygroscopic chloride, part of which was
easily soluble in water. The steel member of the concrete beams, the staples and
the expanded metal of the ceiling were all found to be corroded badly as a result
of contact with the saline constituent present in the composition, and the complete
rusting of the staples, especially at the pointed ends, rendered them incapable of
supporting the weight of the ceiling.
Compositions of this character are used to a considerable extent, but should be
employed only in dry places, and never in contact with metal.
Milk samples.
The total number of milk samples examined during the year in the laboratory
at County Hall was 312. Of this number 198 were of milk supplied to children in the
elementary and residential schools, whilst 114 were from supplies to general, special
and mental hospitals and public assistance institutions, under contracts which require
a minimum of 3.25 per cent. of fat and 8.5 per cent. of other solids, except during
the months of March and April, when the fat must not be less than 3 per cent. The
quality of the supplies generally, has been more satisfactory than in recent years,
only 4 samples (slightly over 1 per cent.) being deficient in fat.
One sample was found on analysis to give results showing the addition of
water, notwithstanding the presence of the full amount of non-fatty solids required
by the contract.
The condition of the supplies in respect of extraneous matter was again less
satisfactory, for of the 312 samples examined 27 (about 9 per cent.) were found to
contain an excessive amount.