Page 16 - My FlipBook

ver the amalgam will first expand considerably and afterward
shrink a good deal. But the amalgam we are using now will
neither shrink nor expand, and it is very different in its struc-
ture from the alloys heretofore used. It is much more diffi-
cult to amalgamate, and it requires a great deal more time.
The amalgamation should always be begun in a mortar. If
you undertake to amalgamate the mass in your hand you will
lose considerable of it before you are through. I speak under-
standingly, because I have tried it over and over myself. In
my experimental work with amalgam I always weighed it
before and after mixing, and took note of the loss in mixing,
and, no matter how we mix it, there will be a loss ; I have
never been able to mix amalgam in any way without some
loss occurring.
We have the alloy and mercury put up in separate cap-
sules, and the aim is to get just the right amount of mercury
for the alloy in each. It is difficult to get this as accurately
done as we would like. Sometimes you will find that there
is too much mercury and it will be necessary to wring it out.
I would prefer that there be a little too much mercury than
not quite enough. Place the filings and mercury in the
mortar and rub slowly. If you rub very rapidly you will
throw some of the mercury out, almost inevitably, and lose a
part. Keep up the rubbing for some little time, long enough
tor the filings and mercury to become amalgamated so that
there will be no loose filings to waste and no loose mercury
to waste. When the mercury has all been taken up by the
filings, then turn the mass out into the hand and finish the
amalgamation. The last part is much more perfectly done in
the hand than in the mortar. The hand should be dry. If
you have a moist hand it would be better to finish the amalga-
mation in a rubber finger stall ; this does very nicely for that
purpose. This mix seems to have had too much mercury ; it
is too soft (demonstrating). Now you see the mass rubs out
into a smooth layer, a little bit soft. To expel just
a little bit of the mercury you may take the mass
between the fingers, squeeze the mercury out and
then go on with the rubbing. There is a little too much
mercury yet. It doesn't seem to hurt a mix very much to
squeeze out quite a little extra mercury if the alloy has been
well made ; that is, we do not wash out one material in