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Calcium
134
CURRENT
TOPICS.
[7. F. I.
the viscosity of the oil used, enough pressure can be applied to break it up into fine vapor through ten-thousandth-inch holes. C.
Mercury Pressure Lamps.--Characteristics of the high pressure mercury lamp are quite different from the lamps that have heretofore used mercury vapor, because the higher temperature of operation and high mercury pressure give the light a color more like that of the blue sky. In addition, these new lamps produce almost twice as much light for the same power consumption. They operate at an efficiency of 35 to 45 lumens per watt as compared to an efficiency of 15 to 2o lumens per watt for present mercury lamps. C. Calcium.--(C. L. M A N T E L L AND CHARLES HARDY,Chem. IndusCalcium, an uncommon metal, is produced by the electrolysis of fused calcium chloride. The commercial method uses a vertical contact cathode upon which the calcium is deposited as the electrode is continuously moved upward. The electrolyte is pure calcium chloride kept at 780 ° to 8oo ° C. Once in operation, the cathode is effectively one of calcium metal. Thin layers of calcium chloride protect the metal from the air. Laboratory applications of calcium metal are well known. It is used in freeing absolute alcohol from the last traces of water, by first digesting with calcium turnings then distilling. Calcium also is useful in the production of high vacua. If the metal be heated in a tube connected with a vessel at low pressure, it takes up the last traces of air, forming oxides and nitrides, thereby reducing the pressure in the system to very low values. Calcium does not react with that rare gas, argon, and therefore is employed to separate it from nitrogen. The number of industrial applications for calcium has increased rapidly in recent years. Three to four-hundredths per cent. added to lead greatly increases the latter's tensile strength and resistance to deformation. Lead so treated should be well suited for sheathing electric cables. Calcium's value as a deoxidizer for copper is now well established. It is preferred to silicon in that it alters the conductivity very little, while silicon affects it markedly. Highcalcium copper alloys are now commercially available, usually in powder form. Calcium added to cast iron to the extent of 0. 5 per cent. produces a casting that is denser and more uniform in grain structure. Good results have been obtained with steel. It has the advantages
tries, 35, 403.)
Jan., 1935.]
CURRENT TOPICS.
135
over other deoxidizers that practically none of the reagent is left in the metal. Methods had to be developed for introducing the calcium metal into the steel. Mechanisms are now used by means of which slugs or piecesof calcium are shot into the ladle of molten metal through an air-pressure gun. There is sufficient force to shoot the calcium projectile deep into the metal where it disintegrates, does its deoxidizing and is converted into lime which rapidly rises to the slag. At the present time slugs can be shot at the rate of 12o to 15o per minute when the gun is hand operated, or 200 to 300 per minute if it is motor driven, and a 6o-ton ladle of steel deoxidized in a period of approximately 5 minutes when 2 lbs. of calcium per ton of steel is used. The price of calcium, which some 15 years ago was still in the neighborhood of $20 per pound, is now less than $1.5o. This price represents metal 98.5 to 99 per cent. pure. C. Plants That Build on Sand.--After seven months searching the deserts and foothills of Russian Turkistan and most of Turkey for plants to control soil erosion, H. L. WESTOVER AND C. R. ENLOW, plant explorers of the U. S. Department of Agriculture, have returned with nearly 18oo lots of seed. Most of the seed collections represent grasses or legumes which form a thick turf close to the ground, enabling them to bind the soil and hold it against the ravages of wind and water. One of the most promising collections is seed of a bunch grass, Aristida pennata, which grows in scattering clumps in the dry, windswept sands of the Kara Kum Desert. It will take root in moving sand, and when the winds become too strong this grass, through its ability to "land on its feet," may be blown for considerable distances and take root where it lands. If it will grow in this country it should be extremely valuable in regions where there are sand dunes. Another unusual plant is Carex physoides, a perennial sedge used extensively for grazing in the Kara Kum Desert of Turkistan. Roots were collected in June and arrived in this country about the first of October. They were planted in a greenhouse in Washington after four months of remaining entirely dry and are now showing signs of growth. C. How Little Radium Is Too Much?--(U. S. D. A. Clip Sheet No. 859. ) The Federal Food and Drug Administration has the task of
CURRENT
TOPICS.
[7. F. I.
the viscosity of the oil used, enough pressure can be applied to break it up into fine vapor through ten-thousandth-inch holes. C.
Mercury Pressure Lamps.--Characteristics of the high pressure mercury lamp are quite different from the lamps that have heretofore used mercury vapor, because the higher temperature of operation and high mercury pressure give the light a color more like that of the blue sky. In addition, these new lamps produce almost twice as much light for the same power consumption. They operate at an efficiency of 35 to 45 lumens per watt as compared to an efficiency of 15 to 2o lumens per watt for present mercury lamps. C. Calcium.--(C. L. M A N T E L L AND CHARLES HARDY,Chem. IndusCalcium, an uncommon metal, is produced by the electrolysis of fused calcium chloride. The commercial method uses a vertical contact cathode upon which the calcium is deposited as the electrode is continuously moved upward. The electrolyte is pure calcium chloride kept at 780 ° to 8oo ° C. Once in operation, the cathode is effectively one of calcium metal. Thin layers of calcium chloride protect the metal from the air. Laboratory applications of calcium metal are well known. It is used in freeing absolute alcohol from the last traces of water, by first digesting with calcium turnings then distilling. Calcium also is useful in the production of high vacua. If the metal be heated in a tube connected with a vessel at low pressure, it takes up the last traces of air, forming oxides and nitrides, thereby reducing the pressure in the system to very low values. Calcium does not react with that rare gas, argon, and therefore is employed to separate it from nitrogen. The number of industrial applications for calcium has increased rapidly in recent years. Three to four-hundredths per cent. added to lead greatly increases the latter's tensile strength and resistance to deformation. Lead so treated should be well suited for sheathing electric cables. Calcium's value as a deoxidizer for copper is now well established. It is preferred to silicon in that it alters the conductivity very little, while silicon affects it markedly. Highcalcium copper alloys are now commercially available, usually in powder form. Calcium added to cast iron to the extent of 0. 5 per cent. produces a casting that is denser and more uniform in grain structure. Good results have been obtained with steel. It has the advantages
tries, 35, 403.)
Jan., 1935.]
CURRENT TOPICS.
135
over other deoxidizers that practically none of the reagent is left in the metal. Methods had to be developed for introducing the calcium metal into the steel. Mechanisms are now used by means of which slugs or piecesof calcium are shot into the ladle of molten metal through an air-pressure gun. There is sufficient force to shoot the calcium projectile deep into the metal where it disintegrates, does its deoxidizing and is converted into lime which rapidly rises to the slag. At the present time slugs can be shot at the rate of 12o to 15o per minute when the gun is hand operated, or 200 to 300 per minute if it is motor driven, and a 6o-ton ladle of steel deoxidized in a period of approximately 5 minutes when 2 lbs. of calcium per ton of steel is used. The price of calcium, which some 15 years ago was still in the neighborhood of $20 per pound, is now less than $1.5o. This price represents metal 98.5 to 99 per cent. pure. C. Plants That Build on Sand.--After seven months searching the deserts and foothills of Russian Turkistan and most of Turkey for plants to control soil erosion, H. L. WESTOVER AND C. R. ENLOW, plant explorers of the U. S. Department of Agriculture, have returned with nearly 18oo lots of seed. Most of the seed collections represent grasses or legumes which form a thick turf close to the ground, enabling them to bind the soil and hold it against the ravages of wind and water. One of the most promising collections is seed of a bunch grass, Aristida pennata, which grows in scattering clumps in the dry, windswept sands of the Kara Kum Desert. It will take root in moving sand, and when the winds become too strong this grass, through its ability to "land on its feet," may be blown for considerable distances and take root where it lands. If it will grow in this country it should be extremely valuable in regions where there are sand dunes. Another unusual plant is Carex physoides, a perennial sedge used extensively for grazing in the Kara Kum Desert of Turkistan. Roots were collected in June and arrived in this country about the first of October. They were planted in a greenhouse in Washington after four months of remaining entirely dry and are now showing signs of growth. C. How Little Radium Is Too Much?--(U. S. D. A. Clip Sheet No. 859. ) The Federal Food and Drug Administration has the task of