Theory of Comminution

H. J. Kamack (E. I. du Pont de Nemours & Co., Inc., Wilmington, Del.)—Rittinger’s law usually is stated to the following effect: “The work (or energy) consumed in particle size reduction is proportional to the new surface area produced.” The law has been stated substantially in this way by Taggart, Berry, Dalla Valle, Coghill and … Read more

Surface Tension of Solid Gold

In the original Udin, Shaler, and Wulff technique for measuring the surface tension of copper, variously weighted wires were allowed to extend or contract in a copper cell held at elevated temperatures in vacuum. By plotting stress vs. strain for a wire array in one test, the stress at zero strain is obtained. This is … Read more

Re-solution of Precipitated Silver in Copper-Silver Alloys

During preliminary tests on the aging of a Cu-plus 5 pct Ag alloy, a specimen which had been overaged 24 hr at 550°C was annealed in a nitrogen-hydrogen atmosphere first for 2 hr and then for an additional 28 hr at 600° C. Conceivably, for Cu-Ag alloys, the matrix-transition-precipitate precipitation sequence is reversible for the … Read more

Photoelectric Sorting of Optical Fluorspar

The crystal laboratory, Dept. of Physics, Massachusetts Institute of Technology, was confronted with the problem of obtaining a supply of optical grade calcium fluoride (CaF2) for use in growing synthetic CaF2 crystals. A search of the known fluorspar deposits did not indicate that any quantity of optical spar could be obtained. Even the best material … Read more

Effect of Rare-Earth Metals on the Properties of Extruded Magnesium

The effects of rare-earth metals on the properties of sand-cast magnesium were discussed in some detail in earlier paper by the author. The present paper deals with the effect of the same alloying elements on the properties of extruded magnesium. This investigation also had as its aim the development of a wrought alloy having a … Read more

Laboratory Crushing Tests

Crushing has always been a major operation in the chemical and metallurgical industries, yet little is known about the theory of crushing, and today, the design of crushers is still based almost entirely on empirical knowledge and accumulated practical experience. In view of the increasing national need for the economic working of poorer grades of … Read more

Magnetic and Chemical Analyses of Magnetite and llmenite

Investigation of the methods of analyses for magnetite and ilmenite in the Otanmaki iron-titanium ore and respective mill products has resulted in certain improvements in the methods conventionally employed. The outcome of the investigations is summarized as follows: Development of a diamond-drill core analyser for the determination of magnetic susceptibility of drill cores containing magnetic … Read more

Pegmatites Geology

  Granitic pegmatite deposits are the chief source of commercial feldspar, sheet mica, beryllium, tantalum-columbium, and lithium minerals, and certain types of kaolin. They also have yielded significant quantities of cassiterite, gems, scrap mica, molybdenite, tungsten minerals, uranium-thorium and rare-earth minerals, and zircon, either directly or as the sources of placer deposits. The output from … Read more

Adsorption of Sodium Ion on Quartz

When a mineral particle is fractured, bonds between the atoms are broken. The unsatisfied forces that appear at the newly formed surface are considered to be responsible for the adsorption of ions at the mineral surface. A knowledge of the mechanism and extent of ion sorption from solution onto a mineral surface is of interest … Read more

Flotation Rates and Flotation Efficiency

The separation of minerals by flotation can be regarded as a rate process, with the extraction of any one mineral determined by its flotation rate, and the grade of concentrate by the relative rates for all the minerals. So regarded, the significant variables for the process are those that control the rates. These variables are … Read more