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APPENDIX
NOTE BY PROFESSOR SMITHELLS
ox determining the specific gravity of gold
fillings
The Yorkshire College, Leeds.
We have found it impossible to make any accurate
and useful determinations of the " dental " specific
gravity of your plugs by simply weighing in air and
then in water. The plugs are more or less porous,
and as the water gradually enters the pores the
apparent weight alters. After a number of different
trials, we settled on the following method, which has
given satisfactory results :
The fillings were first made impenetrable to water
by heating in vaseline to 100° C. for ten minutes.
When the vaseline had cooled to the temperature of
the room, the fillings were removed and thoroughly
polished with fine linen. The volume of each im-
penetrable filling was calculated from the difference
APPENDIX
NOTE BY PROFESSOR SMITHELLS
ox determining the specific gravity of gold
fillings
The Yorkshire College, Leeds.
We have found it impossible to make any accurate
and useful determinations of the " dental " specific
gravity of your plugs by simply weighing in air and
then in water. The plugs are more or less porous,
and as the water gradually enters the pores the
apparent weight alters. After a number of different
trials, we settled on the following method, which has
given satisfactory results :
The fillings were first made impenetrable to water
by heating in vaseline to 100° C. for ten minutes.
When the vaseline had cooled to the temperature of
the room, the fillings were removed and thoroughly
polished with fine linen. The volume of each im-
penetrable filling was calculated from the difference
