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1945 Theatre Catalog, 4th Edition, Page 161 (139)

1945 Theatre Catalog, 4th Edition
1945 Theatre Catalog
1945 Theatre Catalog, 4th Edition, Page 161
Page 161

1945 Theatre Catalog, 4th Edition, Page 161

ance may make it commercially useful in constructing compact resistors.


To see dozens of spools with thousands of yards of zirconium wire and to see beautiful sheets of zirconium metal emphasizes the recent remarkable progress made in the metallurgy of this rare element. Zirconium is very resistant to chemical attack, hydrofiuoric acid (the one that etches glass) being the only one to dissolve the metal rapidly.


Within the space of five years, columbium has passed from the rating as a very rare and precious metal to one of everyday industrial application. In the study of the intergranular corrosion of stainless steelsenotably the 18-8 varietyeit was found that the addition of small amounts of columbium effectively counteracted this corrosion.


Tantalum, as metal, is now used extensively for its outstanding chemical and physical properties. It is highly resistant to corrosion; it can be hammered, drawn, and welded. Stills and kettles are lined with tantalum sheet. It is used in making spinnerettes for rayon; grids and plates for radio tubes; and chlorineresistant needle valves. Seamless tantalum tubing is available in a wide range of sizes, down to the smaller-bore tubing used in hypodermic needles. Tantalum carbide is very hard and competes with tungsten carbide in making machining tools.


The lead industries of America have, during recent years, been promoting new fields of application for bismuth. It is now used in low-fusing alloys for a wide variety of purposes. and in special lowmelting solders.


Molybdenum, widely used both as metal and in steel alloys, should no longer be classed as a rare metal. Thinwalled, high-strength, chromium-molybdenum steel tubing has made modern high-speed airplanes possible. Added to steel, molybdenum improves its toughness and fatigue resistance. Added to cast iron, it eliminates porosity and increases the high temperature strength. Molybdenum metal, as such, is uSed extensively for parts of radio tubes.


Tungsten is no longer considered a rare metal. Its steel alloys are used for magnets and high-speed cutting tools and, as a metal, it is widely employed for the filament in electric light bulbs.


Uranium metal is malleable and ductile. Large quantities of uranium mineral are available as a forced by-product of the radium industry. In spite of several distinctive properties of uranium metal-one of which has come to public


notice in connection with the atomic-energy bombelittle commercial use has so far been found.

Serenium and Tellurium

Selenium and tellurium are both derived from by-products of electrolytic copper refineries. A few years ago both metalloids were largely discarded and wasted, but today they are carefully recovered.

The outstanding development with selenium is its application in the new photo-electric cells. These cells are not based on the old principle of a change in resistance with a change in illumination, but on the electronic emissivity of this film of selenium when exposed, to light.

Small percentages of selenium added to stainless steels make them free-machining. Similar effects on steel are obtained upon addition of tellurium. Added to lead in small percentages, tellurium makes lead more resistant to corrosion.

Tellurium has become an important reagent in the purification of electrolytic zinc solutions, to assure a more complete removal of objectionable traces of cobalt. Of interest, too, is the use of tellurium vapor in certain tube lamps.


Cobalt is rare When compared with iron and nickel. However, cobalt is a metal of very wide commercial application. Many tons of the alloy stellite (chromium, tungsten, and cobalt), one of the best alloys for cutting tools ever developed, are made. Another recent develop ment is the aluminum-nickel-cobalt-iron alloy commonly called Alnico. Cobalt is the best cement for tungsten carbide.

Very little nickel as such is plated in America today. The so-called fibright nickel" deposits are usually an alloy deposit of nickel and cobalt. A deposit composed of one part cobalt and two of nickel is the whitest deposit known, even silver due to an unavoidable tarnish film looking yellowish in comparison.


Rhodium is the most interesting from an electrochemical point of view. The metal has a high refiectivity, is relatively hard, and is very resistant to corrosion. Rhodium-plated nowadays are millions of articles, including intricately designed silver jewelry and large three-foot reflectors used in air beacons and smaller ones used in motion-picture projectors.

THE HIGH VACUUM NECESSARY for modern electronic tubes has been possible only through "getters," substances which remove whot is left of the air after the pumps have removed all they can. These Radio Corporation of America photographs show the machine which turns out the getter mounts and boats and a tube with the device in place. The getter is placed in the boat and volatilized through highvfrequency currents.

1945 Theatre Catalog, 4th Edition, Page 161