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By E. T. Turkdogan, P. Grieveson

STAFF: Editor, Gerhard Derge Acting Editor, Paul G. Shewmon Carnegie lnstitute of Technology Sc hen ley Park Pittsburgh 13, Pa. Editorial Assistant, M. A. Redmerski Production Editor, Otto T. Johnson THE METALLURGICAL SOCIETY: Karl L. Fetters, President; J.S. Smart, Jr., Past-President; R. C. Cole, Vice President; R. L. Hennebach, Treasurer; R. W. Shearman, Secretary. PUBLICATIONS COMMITTEE OF THE METALLURGICAL SOCIETY: W. 0. Phil-brook, Chairman; H. L. Bishop, R. C. Cole, J. N. Hobstetter, W. A. Krivsky, E. R. Morgan, F. C. Langenberg, R. E. Lund, Paul Queneau, L. L. Seigle, R. L. Smith, and T. '4. Wainwright. Review and selection of manuscripts is under the supervision of the following Publications Committes: Extractive Metallurgy Division: R. E. Lund, Chatrmon; M. E. Wodsworth, Vice Chairman; D. H. Baker, Jr., G. M. Bell, R. E. Groce, W. A. Krivsky, R. A. Lewls, Charles O'Neill, A. W. Schlechten, R. E. Shinkoskey, and W. W. Stephens. Iron and Steel Division: T. V. Wainright, Choirman; H. L. Bishop, R. E. Boni, T. E. Dancy, C. W. Murphy, Johonnes M. Uys, J. B. Wagstaff, and R. G. Ward. lnstitute of Metols Division: J. N. Hobstetter, Chairman; P. A. Beck, J. J. Becker, G. F. Bolling, J. O. Brittain, J. 8. Clark, R. S. Davis, A. E. Dwight, R. W. Fountain, L. R. Girifalco, J. C. Gurland, H. S. Kclish, E. L. Harmon, J. J. Heger, A. A. Hendrickson, L. Himmel, J. P. Hirth, H. H. Johnson, Jr., R. R. Nosh, T. N. Rhodin, R. H. Richman, H. C. Rogers, W. Rostoker, C. Sherby, C. W. Spencer, L. Slifkin, J. K. Stanley, R. Steinitz, H. C. Stumpf, and R. Swolin. Published bimonthly by the American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc., 345 East 47th Street, New York 17. N. Y. Telephone PLaza 2-6800. Subscription $30 per year for non-AIME members in United States and North, South, and Central America; $32, foreign; $7.50 for AlME members. Single copies, $6.00, single copies foreign, $6.50. The AlME is not responsible for any statement made or opinion expressed in its publications ... Copyright 1962 by the American lnstitute of Mining, Metollurgical. and Petroleum Engineers. Inc. . . . Registered cable address, AlME New York . . . Indexed in Engineering Index, lndustriol Arts Index, and Chemical Abstracts . . . Second class postage paid at New York, N. Y., and Ann Arbor, Mich. Volume 224, Number 6.

Jan 1, 1962

By Oliver Bowles

A NORTH CAROLINA miner dreamed that he found high-grade mica by excavating a certain corner of his mine. The next day he sank a hole on the exact spot and found mica of excellent quality. The dream came true. May not this be as good a method as any yet known for forecasting the valuable mineral content of pegmatites? The Federal Geological Survey has found in its recent detailed studies in New England that good sheet mica occurs most abundantly in zoned pegmatites, particularly in zones lying along the wall or contact of the pegmatite mass. Although this conclusion may be a valuable guide, pegmatite mining operations must still be classed as most uncertain and hazardous enterprises. Finding of the second largest diamond ever discovered in the United States-a stone of good gem quality weighing more than 34 carats-during the course of a horseshoe pitching contest at Peterstown, W. Va., is another example of unorthodox mining methods. These should not be considered, however, as characteristic mining methods developed in 1944.

Jan 1, 1945

By CHARLES F. RAND

PRESIDENT CHARLES F. RAND,1 NEW YORK, N. Y. PAST PRESIDENTS CHARLES KIRCHHOFF,1 NEW YORK, N. Y. JAMES F. KEMP,2 NEW YORK, N.. Y. FIRST VICE-PRESIDENT BENJAMIN B. THAYER,1 NEW YORK, N. Y. TREASURER GEORGE C. STONE,1 NEW YORK, N. Y. SECRETARY EMERITUS ROSSITER. W. RAYMOND, NEW. YORK; N. Y. SECRETARY BRADLEY- STOUGHTON NEW YORK, N. Y.

Jan 2, 1914

By M. J. Spendlove, H. W. St. Clair

An automatic surface-follower mechanism was used to measure the surface temperature and the rate of evaporation of molten zinc while undergoing distillation at low pressure. At pressures of 50 to 100 microns Hg, the rate of evaporation may be 60 to 80 pct of the theoretical maximum corresponding to the measured temperature. The rate decreases rapidly at pressures above 100 microns Hg, to only 7 pct of the theoretical maximum at 2000 microns Hg. Measured temperature gradients at the surface are in agreement with theoretical gradients calculated from the heat of vaporization, rate of evaporation, and thermal conductivity of molten zinc. THIS paper covers a series of careful measurements of the rate of evaporation of molten zinc at low pressures, undertaken as a part of a general investigation on the separation of metals by distillation.' Preliminary results on the rate of evaporation of zinc were described in a previous publication.' The results of the preliminary study are as follows: 1—The observed rates of evaporation of zinc were as high as 0.60 g per sq cm per min, corresponding to 75 pct of the maximum rate as determined by the temperature of the metal. 2—The evaporation rate was decreased from 0.30 g per sq cm per min at a pressure of 25 microns to only 0.09 g per sq cm per min when the pressure was increased to 5 mm. 3—The temperature of the surface during rapid evaporation may be 35" to 100°C less than the main mass of metal. Observed temperature gradients at the surface are consistent with those calculated from the heat of vaporization and the thermal conductivity of liquid zinc. In the preliminary experiments, the rate of evaporation was determined from the loss in weight of the metal in the crucible during the test. This was compared with the weight of the condensate. Obviously, this method was subject to error because of some uncertainty as to the period of evaporation that should correspond to the loss in weight. Furthermore, this method did not permit taking into account probable variations in the rate of evaporation during the test. A more serious shortcoming was that the temperature at the evaporating surface was not known, so the maximum theoretical rate of evaporation could not be calculated accurately. To improve the precision of rate measurements and to allow accurate measurements of the surface temperature, a refined experimental technique was developed whereby the temperature and position of the surface could be measured accurately. This was done by an automatic surface-follower mechanism that gave a continuous record of the surface temperature and the amount of zinc evaporated. These data permitted an instantaneous determination of the actual rate of evaporation and the surface temperature throughout the test. Pure zinc (99.99 pct Zn) was used in all experiments. Description of Distillation Furnace The details of construction of the distillation furnace are shown in Fig. l. The furnace is enclosed in a large quartz tube open at one end. The open end of the quartz tube is sealed by means of a water-cooled head. The entire enclosure is vacuum tight. The connection between the water-cooled head and the quartz tube is sealed by means of a rubber gasket which fits tightly against the smooth end of the tube. The metal is heated by induced current set up in the molten zinc and the walls of the graphite crucible by means of a water-cooled induction coil outside the quartz tube. High frequency current is passed through the induction coil from a 6 kw mer-

Jan 1, 1952

PRESIDENT BENJAMIN B. THAYER,1 NEW YORK, N. Y, PAST PRESIDENTS JAMES F. KEMP,1 NEW YORK, N. Y. CHARLES F. BAND,': NEW YORK, N. Y. FIRST VICE-PRESIDENT SIDNEY J. JENNINGS,1 NEW YORK, N. Y. TREASURER GEORGE C. STONE,1 NEW YORK, N. Y. SECRETARY EMERITUS ROSSITER W. RAYMOND, NEW YORK, N. Y. SECRETARY BRADLEY STOUGHTON NEW YORK, N. Y.

Jan 2, 1915

PRESIDENT. CHARLES F. RAND,1 NEW YORK, N. Y. PAST PRESIDENTS. CHARLES KIRCHHOFF,1 NEW YORK, N. Y. JAMES F. KEMP,2 NEW YORK, N. Y. FIRST VICE-PRESIDENT. BENJAMIN B. THAYER,1 NEW YORK, N. Y. TREASURER. GEORGE C. STONE,' NEW YORK, N. Y. SECRETARY EMERITUS. ROSSITER W. RAYMOND NEW YORK, N. Y. SECRETARY. BRADLEY STOUGHTON NEW YORK, N. Y.

Jan 9, 1913

PRESIDENT BENJAMIN B. THAYER,1 NEW YORK, N. Y. PAST PRESIDENTS JAMES F. KEMP,1 NEW YORK, N. Y. CHARLES F. RAND,2 NEW YORK, N. Y. FIRST VICE-PRESIDENT SIDNEY J. JENNINGS,1 NEW YORK, N. Y. TREASURER GEORGE C. STONE1 NEW YORK, N. Y. SECRETARY EMERITUS ROSSITER W. RAYMOND, NEW YORK, N. Y. SECRETARY BRADLEY STOUGHTON NEW YORK, N. Y

Jan 3, 1914

PRESIDENT. CHARLES F. RAND,1 NEW YORK, N. Y. PAST PRESIDENTS. CHARLES KIRCHHOFF,1 NEW YORK, N. Y. JAMES F. KEMP,2 NEW YORK, N. Y. FIRST VICE-PRESIDENT. BENJAMIN B. THAYER,1 NEW YORK, N. Y. TREASURER. GEORGE C. STONE,1 NEW YORK, N. Y. SECRETARY EMERITUS. ROSSITER W. RAYMOND, ..... NEW YORK, N. Y. SECRETARY. BRADLEY STOUGHTON, NEW YORK, N. Y.

Jan 7, 1913

PRESIDENT. CHARLES F. RAND,1 NEW YORK, N. Y. PAST PRESIDENTS. CHARLES KIRCHHOFF,1 NEW YORK, N. Y. JAMES F. KEMP,2 NEW YORK, N. Y. FIRST VICE-PRESIDENT. BENJAMIN B. THAYER,1 NEW YORK, N. Y. TREASURER. GEORGE C. STONE,1 NEW YORK, N. Y. SECRETARY EMERITUS. ROSSITER W. RAYMOND NEW YORK, N. Y. SECRETARY. BRADLEY STOUGHTON NEW YORK, N. Y.

Jan 10, 1913

PRESIDENT BENJAMIN B. THAYER,2 NEW YORK, N.. Y. PAST PRESIDENTS JAMES F. KEMP,1 NEW YORK, N. Y. CHARLES F. RAND,2 .NEW YORK, N. Y. FIRST VICE-PRESIDENT SIDNEY J. JENNINGS,1 NEW YORK, N. Y. TREASURER GEORGE C. STONE,1 NEW YORK,. N. Y. SECRETARY EMERITUS ROSSITER W. RAYMOND, NEW YORK, N.Y. SECRETARY BRADLEY STOUGHTON NEW YORK, N. Y.

Jan 9, 1914

PRESIDENT BENJAMIN B. THAYER,1 NEW YORK, N. Y. PAST PRESIDENTS JAMES F. KEMP,1 NEW YORK, N. Y. CHARLES F. RAND,2 NEW YORK, N. Y. FIRST VICE-PRESIDENT SIDNEY J. JENNINGS,1 NEW YORK, N. Y. TREASURER GEORGE C: STONE,1 NEW YORK, N. Y. SECRETARY EMERITUS ROSSITER W. RAYMOND NEW YORK, N. Y. SECRETARY BRADLEY STOUGHTON NEW YORK, N. Y.

Jan 1, 1915

PRESIDENT BENJAMIN B. THAYER,1 NEW YORK, N. Y. PAST PRESIDENTS JAMES F. KEMP,1 NEW YORK, N. Y. CHARLES F. RAND,2 NEW YORK, N. Y. FIRST VICE-PRESIDENT SIDNEY J. JENNINGS,1 NEW YORK, N. Y. TREASURER GEORGE C. STONE,1 NEW YORK, N. Y. SECRETARY EMERITUS ROSSITER W. RAYMOND, NEW YORK, N. Y.

Jan 4, 1914

By AIME AIME

THE Industrial Conference appointed by President Wilson has presented the following tentative plan for preventing or retarding strikes and industrial conflicts by proposing new Federal machinery for the adjustment of differences between employers and employees. Theplan is signed by William B. Wilson, Secretary of the Department of Labor, 'as chairman of the conference; Herbert Hoover, former Federal Food Administrator, as vice-chairman; Martin H. Glynn; Thomas W. Gregory, former Attorney Gen¬eral; Richard Hooker; Stanley King; Samuel W. McCall former Governor of Massachusetts; Henry M. Robin¬son; Julius Rosenwald; Oscar S. Straus; Henry C. Stuart, former Governor of Virginia; F. W. Taussig; William O. Thompson; Henry J. Waters; George. W. Wickersham, former Attorney General; and Owen D. Young.

Jan 1, 1920

PRESIDENT. CHARLES F. RAND,1 NEW YORK, N. Y. PAST PRESIDENTS. CHARLES KIRCHHOFF,1 NEW YORK, N. Y. JAMES F. KEMP, 2 NEW YORK, N. Y. FIRST VICE-PRESIDENT. BENJAMIN B. THAYER,1 NEW YORK, N. Y. TREASURER. GEORGE C. STONE,1 NEW YORK, N. Y. SECRETARY EMERITUS. ROSSITER. W. RAYMOND NEW YORK, N. Y. SECRETARY BRADLEY STOUGHTON, NEW YORK, N. Y.

Jan 12, 1913

PRESIDENT BENJAMIN B. THAYER,2 NEW YORK, N. Y. PAST PRESIDENTS JAMES F. KEMP,1 NEW YORK, N. Y. CHARLES F. RAND,2 NEW YORK, N. Y. FIRST VICE-PRESIDENT SIDNEY J. JENNINGS; NEW.-YORK, N. Y. TREASURER ' GEORGE C. STONE,1 .NEW YORK, N. Y. SECRETARY EMERITUS ROSSITER W. RAYMOND, NEW YORK, N. Y. SECRETARY BRADLEY STOUGHTON NEW YORK, N. Y.

Jan 8, 1914

PRESIDENT CHARLES F. RAND,1 NEW YORK, N. Y. PAST PRESIDENTS CHARLES KIRCHHOFF,1 NEW YORK, N. Y. JAMES F. KEMP,2 NEW YORK, N. Y. FIRST VICE-PRESIDENT BENJAMIN B. THAYER,1 NEW YORK, N. Y. TREASURER GEORGE C. STONE,1 NEW YORK, N. Y. SECRETARY EMERITUS ROSSITER W. RAYMOND NEW YORK, N.Y. SECRETARY BRADLEY STOUGHTON NEW YORK, N. Y.

Jan 1, 1914

PRESIDENT BENJAMIN B. THAYER,1 NEW YORK, N. Y. PAST PRESIDENTS JAMES F. KEMP,1 NEW YORK, N. Y. CHARLES F. RAND,2 NEW YORK, N. Y. FIRST VICE-PRESIDENT SIDNEY J. JENNINGS,1 NEW YORK, N. Y. TREASURER GEORGE C. STONE,1 NEW YORK, N. Y.. SECRETARY EMERITUS ROSSITER W. RAYMOND, NEW YORK, N. Y. SECRETARY BRADLEY STOUGHTON, NEW YORK, N. Y.

Jan 10, 1914

PRESIDENT BENJAMIN B. THAYER,1 NEW YORK, N. Y. PAST PRESIDENTS JAMES F. KEMP,1 NEW YORK, N. Y. CHARLES F. RAND,2 NEW YORK, N: Y. FIRST VICE-PRESIDENT SIDNEY J. JENNINGS,1 NEW YORK, N. Y. TREASURER GEORGE C. STONE,1 NEW YORK, N. Y. SECRETARY EMERITUS ROSSITER W. RAYMOND, NEW YORK, N. Y. SECRETARY BRADLEY STOUGHTON NEW YORE, N. Y.

Jan 12, 1914

PRESIDENT. CHARLES F. RAND,1 NEW YORK, N. Y. PAST PRESIDENTS. CHARLES KIRCHHOFF,1 NEW YORK, N. Y. JAMES F. KEMP,2 NEW YORK, N. Y. FIRST VICE-PRESIDENT. BENJAMIN B. THAYER,1 NEW YORK, N. Y. TREASURER. GEORGE C. STONE,' NEW YORK, N. Y. SECRETARY EMERITUS. ROSSITER W. RAYMOND NEW YORK, N. Y. SECRETARY. BRADLEY STOUGHTON NEW YORK, N. Y.

Jan 11, 1913

PRESIDENT. CHARLES F. RAND,1 NEW YORK, N. Y. PAST PRESIDENTS. CHARLES KIRCHHOFF,1 NEW. YORK, N. Y. JAMES F. KEMP,2 NEW YORK, N. Y. FIRST VICE-PRESIDENT. BENJAMIN B. THAYER,1 NEW YORK, N. Y. TREASURER. GEORGE C. STONE,' NEW YORK, N. Y. SECRETARY EMERITUS. ROSSITER W. RAYMOND NEW YORK, N. Y. SECRETARY. BRADLEY STOUGHTON NEW YORK, N. Y.

Jan 7, 1913