Amalgam game
Mercury, we recognise, is an element to be treated
with respect and handled as little as possible. In the history of science
are many instances of unwary alchemists searching for the secret of turning
base metals into gold, and evil plotters wishing to produce a lethal poison,
whose careless management of mercury has brought disastrous consequences.
Gold miners trying to concentrate mineral deposits, and ignorant of the
perils of inhaled vapour, have also succumbed. Industrial wastes containing
mercury and turned loose into seas and rivers have led to methylation
of the element and the serious poisoning of people consuming local fish,
as in the notorious Minamata affair. Yet, I think, we are mistaken in
taking too strong a nanny attitude to mercury with all its interesting
applications.
A question and answer page in New Scientist
for 11 May raises the question of the effect of contact with mercury on
articles of jewellery. The query concerned a woman wearing gold rings
who came into contact with mercury and discovered that her rings had turned
silver. Such a mishap was not uncommon in hospitals where I worked and
mercury was present in clinical thermometers and sphygmomanometers. These
articles were always subject to spillage or breakage, and in dental units
the exposure was relatively great, since amalgams were made.
We were also frequently asked for help by distressed
nurses who found that their rings had discoloured. Our solution was to
heat the ring for some time in our hot-air oven at 300-400 degrees, when
the colour was effectively restored. I must admit we were not unduly perturbed
by the possibility that, unless ventilation was good, we may have been
at some risk of poisoning.
In these days of the nanny-state, when any kind
of laboratory chemistry is regarded with suspicion, and when protective
clothing and special facilities are considered essential before any student
handles a flask or a test-tube, we have become sensitive to mercury in
all its shapes and sizes. I must admit that, in practising hospital pharmacy,
I have handled many substances that with the light of later knowledge
I might have avoided had I been aware of the hazards at the time — several
nasty carcinogens, for example.
In those days we relied upon common sense and good
hygiene, and I can recollect few of my colleagues who suffered serious
reactions later in life. Regarding mercury, however, I look back with
some misgivings to some events of my grammar school days, when I remember
we regaled visitors to our parents' evening with a grand exhibition of
our prowess in the chemistry laboratory.
Apart from the pyrotechnics, including a model of
erupting Vesuvius, one popular exhibit was the so-called "beating heart"
display. This involved placing an evaporating basin half full of mercury
(into which dipped a copper rod to produce an impressive periodic surface-tension
effect) on an open bench, unprotected even by a bell jar. Today a school
governor would turn pale at the mere idea. The fact that the exhibition
was in midwinter, in a hot and close laboratory, was an additional factor.
Then there was always the matter of spillage. Inevitably,
mercury found its way into the cracks of the floorboards in our laboratory.
We were instructed to sprinkle sulphur over the area and sweep it up later,
to overcome the volatility problem. So far as I know, this was effective,
and we certainly encountered no toxic reactions, though what happened
to the sweepings I cannot recollect.
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