handled, can be employed as a substitute for iridium to harden platinum alloys.
The
essential uses of platinum metals are in the chemical and electrical
industries, and probably their use by the dental industry should also
be classed as essential. Pure platinum is required in the chemical
industry for catalyzers in the manufacture of sulphuric acid by the
contact process and in the manufacture of nitric acid from ammonia. For
the sulphuric acid industry platinum chloride is the primary material
containing platinum. In nitric acid plants very fine mesh platinum
gauze is used for the catalyzer. Pure platinum utensils of various
kinds, including crucibles, dishes, tongs, and triangles, are required
in every chemical laboratory. It is possible to substitute
palladium-gold alloys, or even gold, nickel, nichrome, and silica for
some utensils, but no substitutes have yet been found which will
entirely replace platinum in chemical ware.
Platinum-iridium
alloys have been used very extensively by the electrical industry, but
substitutes are constantly being developed. Tungsten, molybdenum, and
nickel-chromium alloys are the principal substitutes used so far, but
their use has not done away with the need for platinum in the industry.
The principal use of platinum-iridium alloys in electrical work is in
contact points, and the proportion of iridium necessary in the alloys
is directly dependent on the intensity of the current passing through
the contacts and the speed at which the contacts move. Probably the
largest consumption of platinum alloy is in the manufacture of
telephone and telegraph equipment, in eluding sending and receiving
instruments, switchboards, and relays. There is also a large
consumption of platinum for contact points in magnetos used for
various kinds of internal-combustion engines. Automobile makers are,
however, developing starting systems which do not require platinum in
their construction, so the future demand from that quarter will
probably diminish.
Platinum
has an important use in dentistry, though palladium-gold alloys are
being used as substitutes. It would appear, however, that the
substitutes are not entirely satisfactory. The principal uses are for
pins for crown work, pins for fastening artificial teeth to plates, and
foil for making molds of cavities in which to bake porcelain fillings. '
