than does copper, and for that reason is preferred in railway signal lenses. It has been found that addition of an extremely small amount of tellurium increases the depth of chill in cast iron. Both selenium and tellurium may be added to copperbase electrical contact alloys to help prevent sticking. Tunesten. New deoosits of scheelite. calcium tunestate. . have been discovered in Ontario through the use of short wave ultraviolet mercury vapor lamps. To the prospector, "lamping" a t night has become as important as "panning." I n d i m . Indium plating on such metals as cadmium, tin, lead, and copper results in an alloy surface which is more corrosion resistant than the base metal and has superior hardness or wearing characteristics. Indium diffused into silver or silverlead hearings enhances antifriction properties and resistance t o erosion and corrosion. Precious Metals. Palladium hardened with five per cent ruthenium is now being employed for jewelry. Gold has received an unusual industrial demand because of its corrosion resistance, and a satisfactory electrolytic gold surface can he applied a t a cost of one-half cent a square foot. Soft solder, containing two and a half per cent silver, the rest lead, is used in soldering the side seam of tin cans in place of the tin-lead solder previously used. Joints made by silver alloy brazing of 18-8 stainless steel sections are frequently stronger than the metals jointed. Silver bearings, used for the main motor bearings in aircraft, are produced by electroplating the casting. Platinum clad steel, with a platinum layer irom 0.002 t o 0.005 in. thick, is now used for corrosion resistance. Platinum alloy electrodes are used in spark plugs. Alkoliand Alkaline Earth Metals. A solution of lithium chloride is used in air-conditioning systems in public buildings and in certain types of naval vessels. The demand is so great that no lithium remains available for ceramics. Production of lithium salts from North Carolina spodumene has been started. Strontium peroxide is an important chemical for making tracer bullets. This demand has stimulated experimental work on the recovery of strontium sulfate from the low grade celestite ores in Texas. Barium cements containing as much as 50 per cent barium oxide have high specific gravity and have been suggested for making concrete blocks to be substituted for pig iron for ships ballasts. These cements have greater mechanical strength than ordinary Portland cement and their relative impermeability to x-rays permits them to be substituted for lead for protection from such radiations. Cesium, rubidium, and potassium can be used as well as selenium for cathodes in light-sensitive cells. Radium. The Eldorada Mine a t Great Bear Lake, Canada, has heen reopened after two years of idleness and has resumed production of pitchblende concentrates as a source of radium and uranium compounds. Tantalum. Tantalum is being used in relatively large quantities for making tantalum carbide machine tools and for fabricated tantalum equipment for the chemical industry. . production of pure ductile zirroniurn Ztrroniuw. Sn~all-,~alr ha$ hcen j r a r r d in [hi; ruunlry. Ry reducing r h e cotnple gall, potassium zirconium fluoride, by means of potassium, or by reducing zirconium oxide by means of calcium, 99.7 per cent pure zirconium is obtained. Mica. Mica is so essential for certain types of military equipment that sales of the better grades are rigidly controlled. Mica spark plugs are superior t o all others for combat planes. A deposit of high quality muscovite was discovered in Ontario from which sound sheets up t o two by three feet may be ohAbstracted from Annual Review Issue of Mining and Metal- tained. L. S. FOSTER lurgy, February, 1943.
Magnesium. In 1939 the production of magnesium was 3350 tons. During the past year several new plants have been erected which have increased production 100-fold. The Permanente Corporation has a plant which uses the Hansgirg process, in which calcined magnesite is reduced with carbon a t high temperatures (2000aC.). This temperature is reached by use of a. 3-phase electric arc furnace. If the products were allowed to c w l together the reaction would be reversed; so the magnesium vapor is diluted with a cold inert gas, in this instance natural gas. The magesium is recovered as a fine powder which must be consolidated before fabrication. The waste natural gas is used for fuel in the cement kilns adjacent to the magnesium plant. Several plants are operating which have adopted the Pidgeon ferrosilicon process. I n this method dead-burnt dolomite is briquetted with ground ferrosilicon (75 per cent silicon or higher) and heated in alloy steel retorts t o about 1150°C. The magnesium is removed by vacuum distillation and is aystallizd in stainless steel tubes from which i t is readily removed. The calcium is not removed under the conditions of operation. One of the problems presented by this process is the selection of the best and most economical type of retort, since the temperature of maximum efficiency is only slightly below the softening point of the special stainless steel used. The companies which use the method a t present are the New England Lime Co., The Ford Motor Company, the Permanente Corp., and the Magnesium Reduction Company, with plants spread from coast t o coast. Basic Magnesium, Inc., the world's largest magnesium plant. began operation in the middle of last year and in November was placed under the management of the Anaconda Copper Mining Comoanv. This ~ l a nuses t as raw material mamesite (MECOZI. . which is mined, concentrated, and calcined s t the site of the ore deposit. The oxide is converted to anhydrous magnesium chloride, which is melted and electrolyzed. At the Freeport plant of the Dow Chemical Company. 85 per cent magnesium chloride, MgCl2.H2O, is used as feed in the electrolytic cell and is procured from sea-water. The magnesium in the raw water is precipitated as Mg(OHh by means of lime and is then converted to the chloride. The Permanente Corporation is also turning to oceanic magnesium as a source. Procurement of magnesium has not been the sole problem faced in this development; i t has been necessary t o erect fabrication plants, t o train labor, and to provide adequate housing, often in remote sites, for the large number of workers required. In addition, i t has been necessary to procure adequate electrical power for those plants which are based upon the electrochemical reduction methods. Despite this, progress has been so great that there will be enough magnesium produced this year for the very large estimated requirements. Beryllium. Approximately twice as much beryllium is being produced as a t the beginning of 1942, amounting to about seven tens a month. Much of this is used in beryllium-copper alloys for heavy bushings, instrument parts, springs, and diaphragms. Important new beryllium ores have been discovered in New Mexico and Illinois. Beryllium can he purified by melting it in bervllium oxide or maohite crucibles and distillinp off the mames i u k Addition of%.& per cent of beryllium t o piatinurn, foruse as resistance windings in furnaces, increases the life of the coil from four to six times. Selainnz and Tellurium. The use of selenium in photoelectric cells is rapidly expanding; 100,000 pounds of selenium are also used annually in the praduction of pink and ruby glass. Selenium permits better transmission in the red part of the spectrum
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