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adhesives, building papers, concrete and stone water-proofers, timber-preservatives,
etc. In addition, regular examination was made on a large scale of samples of sub-soil
and soil-water to ascertain the amounts of sulphate present (high concentrations being
injurious to ordinary Portland cement) and hence to decide which type of cement
should be used. Four basically different types are available.
Many samples were examined to elucidate the causes of site trouble experienced with
various building materials. These included plasters, concretes, mortars, floorings, asphalts,
etc., and in a large number of cases investigation necessitated visiting the site. The
material itself was not always found to be responsible for the defects observed.
Remedial treatments were recommended.
The following examples of work are perhaps of special importance or interest:
A sudden increase was observed in the number of domestic baths which developed
cracks in the vitreous enamel shortly after installation at new housing sites. Despite
the strenuous denial of liability by suppliers this defect was eventually traced to the
lack of control at the manufacturers' works over the thickness of enamel build-up
and hence to strains set up in this fired glaze on cooling.
Assistance was given in efforts made to trace and account for the inleakage of
water through new foundations which were tanked in bitumen felt. The cause was
found to be damage sustained by the felt sheeting owing to insecure positioning.
British Standards Specification 476 having to be revised and re-issued, a new
apparatus was included (largely as the result of the efforts of the Deputy Chemist
on the B.S. Committee) for determining ' The preliminary surface spread of flame.'
This apparatus has now been installed in the laboratory and many materials have
already been tested on it.
Assistance was given in identification of certain stones and other materials of
historic interest.
Problems of maintenance, e.g., special cleaning difficulties, arose in various
buildings, and, after making the necessary test, it was usually possible to recommend
a suitable procedure.
In many cases of disintegration or weakness of mortars, renderings or floor screeds,
analysis showed that the mix used was not in accordance with that specified.
Many varieties of jointless flooring and of flooring tiles continue to appear on
the market. These were examined by a standardised procedure designed to give as
much useful data as possible.
In order to answer the problem of floor maintenance many products now exist
which are intended either to seal, or to yield a semi-permanent glaze coat upon, the
floor surface. Several such compounds were examined during the year.
Foodstuffs
A wide variety of food samples were examined on behalf of the Supplies Department, of
user departments, and of hospital boards. Some in the first category were examined to
ensure the acceptance of the most economical and suitable tenders, but the majority were
for the purpose of checking the quality of deliveries against that of the tender samples.
Others involved complaints from users where some deterioration had occurred or
suspicions had been aroused. In other cases an opinion was required by the Public
Control Department as to whether certain fancy preparations would come under
given definitions such as 'sugar confectionery 'or' biscuits.' Numerous loaves of
short-weight bread were examined to show that they were not 'protein-enriched' as
this would be a defence under the Bread Order. In some cases the analyst was required
to attend court to give evidence as to his findings.
A number of estimations of the fat content of tinned soups were made by different
methods, at the request of a technical sub-committee of the canned soup section of the