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GOLD. 20
GOLD.
Symbol, Au (Aunim). .Itoiiiic z<.'ci^lit. 196.2.
Occurrence.— (loUl is one of the few metals found in the
metallic state, the native metal being found in some of the
oldest rock, and usually contains more or less silver, and
sometimes associated with it in small quantities. The
purest specimens of native gold contain from 95 to 99 per
cent, of gold.
Physical Properties.—The individuality of gold among
metals is strongly marked, owing to its color, orange-red
or yellow, its extreme malleability and ductility (surpassing
all other metals), its perfect resistance to the action of the
air (non-oxidizable), conducting power for heat and elec-
tricity, hig'h fusing point, resistance to simple acids (soluble
only in aqua regia), its rarity and consecjuent intrinsic
value.
The fusing point of gold is 2016° F. It fuses with con-
siderable expansion and on cooling contracts more than
any other metal.
Properties of Particular Alloys of Gold.—In the dental
laboratory gold is liable to become contaminated with other
metals which are highly destructive in their influence to
the properties which adapt gold to the various needs of the
mechanical operator. Care should be taken to prevent
their admixture with the gold scraps or filings that are to
be reconverted into proper form for use. The effect of
alloying certain metals with gold is as follows :
Zinc with gold forms a brittle alloy, and wdien combined
in equal proportions is exceedingly hard, wdiite, and brittle.
Lead renders gold intractable (refractory; not easily
managed )
Tin, bismuth, and arsenic also render gold intractable.
Copper hardens and toughens gold without practically
GOLD. 20
GOLD.
Symbol, Au (Aunim). .Itoiiiic z<.'ci^lit. 196.2.
Occurrence.— (loUl is one of the few metals found in the
metallic state, the native metal being found in some of the
oldest rock, and usually contains more or less silver, and
sometimes associated with it in small quantities. The
purest specimens of native gold contain from 95 to 99 per
cent, of gold.
Physical Properties.—The individuality of gold among
metals is strongly marked, owing to its color, orange-red
or yellow, its extreme malleability and ductility (surpassing
all other metals), its perfect resistance to the action of the
air (non-oxidizable), conducting power for heat and elec-
tricity, hig'h fusing point, resistance to simple acids (soluble
only in aqua regia), its rarity and consecjuent intrinsic
value.
The fusing point of gold is 2016° F. It fuses with con-
siderable expansion and on cooling contracts more than
any other metal.
Properties of Particular Alloys of Gold.—In the dental
laboratory gold is liable to become contaminated with other
metals which are highly destructive in their influence to
the properties which adapt gold to the various needs of the
mechanical operator. Care should be taken to prevent
their admixture with the gold scraps or filings that are to
be reconverted into proper form for use. The effect of
alloying certain metals with gold is as follows :
Zinc with gold forms a brittle alloy, and wdien combined
in equal proportions is exceedingly hard, wdiite, and brittle.
Lead renders gold intractable (refractory; not easily
managed )
Tin, bismuth, and arsenic also render gold intractable.
Copper hardens and toughens gold without practically
