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50
seed oil was added to facilitate the removal of the excess of mixture by shampooing
with soap mixture. Experiments on individual hairs showed that borax was effective
in loosening nits from hair so that they could easily be removed by combing or
even by sliding down the hair between the fingers. Determination of the breaking
strain of several treated and untreated hairs showed that borax did not weaken
the hair or seriously affect its elasticitv.
Specifications
for the
cleansing
mixture.
The tar oil cleansing fluid now in use and the borax soft soap mixture for the
subsequent shampoo are prepared as follows :-
Cleansing fluid Borax shampoo.
*Paraffin oil 74 volumes. Soft soap 2 pounds.
Cotton-seed oil 20 volumes. Borax 4 ounces.
Oil of lemon grass 1 volume. Water to make up to one gallon.
†Tar oil 5 volumes.
Concrete.
Linear
expansion.
A long series of experiments on the expansion after setting of concrete has
been carried out at the request of the Council's architect. Measurements made
on bars of concrete, made with clinker as an aggregate, some of which were kept
under observation for more than a year, showed that both calcium sulphide and
unburnt coal had a very marked effect in causing expansion or even disintegration.
It did not appear that iron sulphide in any form contributed materially to the
expansibility or disruption of concrete. Expansions of the order of 1 to 2 per
cent. of the length of the bar were obtained with concretes containing calcium
sulphide or coal, whilst the greatest expansion obtained with iron pyrites was about
¼ per cent.
Greenwich
Generating
Station
Laboratory.
The work of the laboratory at the Greenwich generating station comprises :—
(1) The daily examination of samples and materials for controlling the operation
of the water-softening plant, the blowing down of boilers, condenser leakage, and
the purity of condensed water supplied to the Station batteries ; (ii.) the sampling,
preparation and examination of fuel (coal); (iii.) the preparation and examination
of fuel ashes, the analysis of flue gases, boiler scales, stores, etc., and investigations
connected with corrosion and other troubles incidental to the operation of the Station
plant.
Outfalls.
At the Outfall Laboratories, the systematic daily examination of sewage treated
and the resulting effluent and sludge, as well as the water of the river Thames at
both high and low tides, has been continued, in addition to the other work which
is carried out in connection with these laboratories.
Biological
treatment of
sewage.
During 1922 the plant erected by the Activated Sludge Company has been in
more or less continuous action. Stoppage has on several occasions been necessitated
by defects arising in the sewage pumping or air compression plant. It has been
found generally, that a clear but not colourless effluent, containing relatively little
oxidisable organic matter, can be obtained by the aeration of a continuously
flowing mixture of sewage and activated sludge in certain ascertained proportions,
the mean period of stay in the aerating tanks being about 7 to 8 hours
and the period for settlement being 2 hours, making the whole period from
entry of sewage to escape of effluent over the measuring notch about ten hours.
The production of nitrates which occurs if for any reason the flow of sewage is
interrupted for a prolonged period almost entirely ceases when continuous flow
is again started. Experimental work has been started and is in progress on the
actual sequence of changes occurring in mixtures of activated sludge and sewage.
* The paraffin oil should flash at well above 73° F. There is no difficulty in obtaining oil of
fairly high flash point now that the lower boiling fractions of petroleum are in demand for motor
spirit.
† A yellow to reddish-brown liquid with characteristic smoky-acid odour, specific gravity 0.93
to l.00 at 15.5º C. One hundred cubic centimetres on distillation shall yield not less than 90 c.c. of a
distillate containing from 16 to 20 per cent. of tar acids and from 1 to 6 per cent. of acetic acid, at a
temperature not exceeding 300° C.