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Lampitt discovered that the tin-coated
grills, on which the fish were steam
cooked, were actually coated with a
lead-tin solder instead of pure tin and
that the solder was being attacked by the
salted fish and lead absorbed. Once the
cause was traced it was a simple matter
to replace the offending grills by new
ones tested and found free from lead.
Since then the lead content of Portuguese
sardines has given no further
cause for anxiety and much credit is due
to Messrs. J. Lyons & Co., Ltd., for
conducting this investigation in the
interests of public health and for publishing
their findings.
One Millionth of an Ounce
A final point in connection with lead
analyses arises from the comment that
" different analysts using the official
method often obtain varying results
from samples drawn from the same
chest." If the lead is in the form of
separate particles varying results are
unfortunately inevitable, for it is hardly
likely that any two small portions
weighed out for analysis would each
contain a particle or particles of exactly
the same weight. One has to bear in
mind that the actual weight of lead to be
determined by the analyst in the case of
a tea containing 10 parts per million of
lead is of the order of a millionth of an
ounce. Apart from the particle variations,
such determinations require
considerable skill and experience. The
best method is rather lengthy and, if
results are found to vary the only
course open to the Analyst, after
checking the accuracy of the method, is
to carry out several determinations and
find the mean. In the case of the
Formosa tea referred to, however, the
lead does not appear to be present in
the form of separate, detached particles,
but to be intimately mixed with the tea,
and duplicate analyses have in the
writer's experience agreed quite closely.
It was because of the possibility of
variations in different parts of the same
chest that the advice was given above to
avoid as far as practicable any teas
yielding lead figures over 6 parts per
million.