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44
Two washing-up machines were examined and, in one case, the design, with
modifications, would be of interest but, in the other case, the efficiency was poor.
Several quaternary ammonium compounds were examined but generally, where
practicable, heat sterilisation was advised as being more positive.
Laundry
work
Considerable work was done in this field to improve the efficiency of washing in
hard water. By employing a synthetic detergent and carboxy-methyl cellulose an
appreciable improvement was attained as compared with the use of soap. Further substantial
improvement was made by introducing sodium meta-silicate instead of soda ash
as usually employed. The details of the process were worked out and a reduction of the
damage done to the fabric has been accomplished. On the results of the work so far
carried out it is considered that, in most cases, it would not be justifiable to recommend
installing water softening plant having regard to the problem of the maintenance and
also to its appreciable capital cost.
Work was also undertaken on the assessment of various laundry starches and 011 the
removal of stains from linen. The question of washing clothes by hand was investigated
and a specification was evolved for a suitable efficient powder for this purpose. There
was, in some quarters, a demand for greater foaming power and, whilst it is appreciated
that this property does not indicate detergent efficiency, some attempt to increase the
foaming power will, for psychological reasons, be made to prevent complaint.
A comprehensive report on the activities of the branch in the field of detergency
was presented to the Royal Sanitary Institute in December, the authors being Dr. S. G.
Burgess, Mr. D. Burns and Mr. C. W. Tidy.
Plastics
This type of product, which is also mentioned under surface coatings, paints, etc., is
coming increasingly into our daily life. Feeding bottles, plates and sputum jars made
of polythene, bath mats of plasticised and pigmented polyvinyl chloride and spoons of
melamine have been examined. In general, they serve their purpose and, in some cases,
possess a great advantage as regards utility. However, in other cases, special considerations
must be borne in mind ; for example, coal tar disinfectants should not be applied
to the bath mat mentioned above and scratched polythene retains fat rather tenaciously.
The spontaneous disintegration of some of the harder plastics was investigated. This is
due to injury by unsuitable treatment allowing water absorption and the eventual
expansion very occasionlly causes violent disintegration. Hypochlorites should be
avoided when urea-formaldehyde and melamine resins (or mixtures of these) are
present and, in consequence, it is necessary to establish the particular type of every
product before employing it in the Council's service. Standard tests were established to
ascertain the efficiency of curing of melamine resins. The application of dye under
specified circumstances gives an indication of the correct curing and, if treatment for
24 hours with a one per cent. solution of citric acid extracts not more than 20 parts per
million of zinc, cups, beakers and drinking utensils can be employed without the risk of
contamination of the normal liquids ingested therefrom.
Rubber-spreading and skin degreasing works
There are four works in the County using inflammable solvents for processes which
are operated in accordance with the terms of licences issued by the Council under the
Petroleum (Regulation) Acts, 1928 and 1936. Periodical visits of inspection were made
to see that the stipulated conditions were complied with and to examine air samples to
ensure that the content of petroleum vapour did not exceed the safety limits.
During the year, 10 visits of inspection were made and 37 samples were examined.
In most cases it was found that the plant was being operated in a satisfactory manner,
but there were single occasions at two different premises where the tests disclosed
defects in the systems and advice was given to rectify the position.