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GOLD. — 203
Required Fineness of Gold Plate. —Alloys of gold to
^
be permanently worn in the mouth should be of such purity
as will most certainly, luider all the conting-encies of health
and disease, resist any chemical changes that would tend
to compromise either the comfort or health of the patient.
It should not, therefore, as a general thing, be of a less
standard of fineness than from eighteen to twenty carats.
It may exceed this degree of purity in some cases (as for
lower dentures), but will rarely or never, unless alloyed
with platinum, admit of being used of a higher carat than
the present .American coin, which is 21.6 carats fine.
Formulas for Gold Plate used as a Base for Artificial
Dentures.—Any of the following formulas may be em-
ployed in the formation of gold plate to be used as a base
or support for artificial dentures. The relative proportions
of the alloying components may be varied to suit the
peculiar views or necessities of the manipulator :

GOLD PLATE EIGHTEEN CARATS FINE.
Formula No. i. Formula No. 2.
18 dwts. pure gold, 20 dwts. gold coin,
4 dwts. fine copper, 2 dwts. fine copper,
2 dwts. fine silver. 2 dwts. fine silver.
GOLD PLATE NINETEEN CARATS FINE.
Formula No. 3. Formula No. 4.
19 dwts. pure gold, 20 dwts. gold coin,
3 dwts. copper, 25 grs. copper,
2 dwts. silver. 40 -|- grs. silver.
GOLD PLATE TWENTY CARATS FINE.
Formula No. 5. Formula No. 6.
20 dwts. pure gold, 20 dwts. gold coin,
2 dwts. copper, 18 grs. copper,
2 dwts. silver. 20 -j- grs. silver.
GOLD PLATE TWENTY-TWO CARATS FINE.
For Crozvn- and Bridge-Work.
Formula No. 7.
22 dwts. pure gold,
I dwt. fine copper,
18 grs. silver,
6 grs. platinum.