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Jan 1, 1910

By R. Maddin, N. Ujiiye

ALTHOUGH the cold-rolled texture for body-centered-cubic metals and alloys is well known (see, e.g., Barrett'), the pole figure representing the texture may be interpreted in two ways. It may be regarded as consisting of several ideal preferred orientations with an associated spread (a view which is shared among several investigators2), or it may be regarded as consisting of two sets of continuous preferred orientation also with an associated spread."." Recently, Chen and Maddin7 noted a stable (001) [loo] end orientation for molybdenum single crystals rolled at low rates of reduction provided the initial rolling. orientation" was close to the cube ori-

Jan 1, 1957

Richard Moldenke, New Pork, N. P. (communication to the Secretary*):—Iu following the discussion of the specifications for cast-iron and finished castings, I mas strongly impressed with two points which might be ventilated to advantage more fully from the view of the practical foundry-man. First, the reasons why only silicon and sulphur were specified and not phosphorus, manganese and carbon; and second, why but little was said concerning the presence of iron oxide in the material.

Jan 1, 1905

By F. V. Lene, E. J. Westerman

The recrystallization behaviors of two extruded and cold-drawn experimental sintered aluminum powder alloys, containing 1.75 and 3.0 pct Al2O3 by weight, were compared with that of extruded and cold-drawn commercially pure alumirzum. The kinetics of recrystallization of the alloys are described semiquantitatively. For the alloy containing 1.75 pct A l203 the rates of nucleation and of growth were also semiquantitatively determined. THE most striking property of aluminum alloys strengthened by a dispersion of Al2O3, the so-called SAP alloys, is their stability at elevated temperatures. One of the manifestations of this stability is their resistance to recrystallization after they have been cold worked. Most of the commercial grades of either the Swiss SAP or of Alcoa's Aluminum Powder Metallurgy Products have not been recrys-tallized after cold working, even when they are heated for a long time at a temperature near the aluminum melting point. Lenel, however, observed that the dispersion strengthened aluminum alloys with a larger spacing between the oxide particles than that of most commercial grades would recrys-tallize.1 It appeared to be of interest to further investigate the mode and kinetics of recrystallization of these alloys, and to compare their recrystallization behavior with that of commercially pure aluminum. Because homogeneous deformation of these SAP alloys in tension did not provide sufficient cold work to induce recrystallization, they were cold worked by wire drawing; the nonuniformity of this deformation unavoidably complicated the interpretation of the recrystallization studies. EXPERIMENTAL DETAILS Extrusions—Two types of sintered aluminum powder extrusions were used in this study. One type, designated AT-400, was produced from Reynolds atomized aluminum powder consisting of spherical particles averaging 3µ in diam and containing 1.75 wt pct of Al2O3. This powder was very similar to the R3M powder from which extrusions were previously prepared with an average spacing of 0.9µ between oxide particles.2 The second type, designated MD 2100, was produced from Metals Disintegrating Co. flake powder containing 3.0 wt pct of Al2O3, with an average flake thickness of 0.8µ. The average spacing between oxide platelets in MD 2100 extru- sions was 0.45µ.2 Powder compacts of 3/4-in. diam were extruded at 1000°F into 0.097-in. diam (AT-400) and 0.093-in. diam (MD 2100) wires by methods previously described.3 In order to compare the recrystallization behavior of sintered aluminum powder extrusions with that of wrought commercially pure aluminum 3/4 in. rod stock of 1100 F aluminum was extruded at 1000°F into 0.102-in. diam wire. Wire Drawing—Tungsten carbide dies were used for the AT-400 and 1100 F alloys. They had an included angle of about 15 deg and reduced the wire area approximately 7 pct per pass. Steel dies with an included angle of 11 to 13 deg and an average reduction per pass of 10 pct were used for drawing the MD 2100 alloy, because drawing this alloy through the carbide dies produced overdrawing defects. Heat Treatment—The cold-drawn wires were cut into small samples, and the deformed ends were etched off. The samples were each wrapped tightly in a single layer of aluminum foil, and individually isothermally annealed in a lead bath. Metallography—The modes and kinetics of recrystallization were determined by metallography. Mounted and polished specimens were anodized in a solution of 1.8 pct HBF4;4 examination under polarized light clearly revealed their grain structures. The recrystallized grains were generally much larger than those of the unrecrystallized matrix, and could clearly be distinguished because they alternated between maximum and minimum light reflection when the microscope stage was rotated, while the unrecrystallized matrix had a comparatively homogeneous "salt and pepper" structure. The fractional recrystallized volumes of the dispersion hardened alloy wires were determined by cutting and weighing of recrystallized and total transverse areas on photomicrographs. The recrystallized grains in the 1100 F alloy were too small to be cut out individually; therefore a combination of cutting and lineal analysis was used in this case. RESULTS AND DISCUSSION Modes of Recrystallization—The modes of recrystallization of the three alloys varied widely. In the 1100 F alloy nucleation and growth started in the region midway between the center and the surface;

Jan 1, 1961

By J. W. Spretnak, G. W. Powell, J. H. Bucher

Tlze room-temperature tensile fracture oj smooth, round specitnens of three ultrnhigh- strength steels tempered to a wide range of strength levels was studied by means by light and electron-microscopic examination of the fracture surfaces. The fracture of AISI 4340 and 300 M at all the strength levels studied, and H-11, except after tempering at 1200° and 1300°F, occurs in three stages. The initiation of fracture is internal (except in some lightly tcmpeved specimers in which fracture is initiated at surface flaws), and is nucleated largely by separation at metal-second phase intevjaces. TIze voids grow and, coalesce to form a crack. When the crack has reached a sufficienl size, rapid propngutio~z ensues. Failure in this stage of fracture usually occurs by dimpled rupture of inicroshear stefis. In the case of H-11 tempered in the 1125° to 1300°F range, fracture in the shear steps is predominantly by concentrated deformation without void formation. The termination of fracture is usually occomplished by the formation of a shear lib in which fracture occurs by shear dimpled rupture. In the case of H-11 tempered at 1200° and 1300°F, no shear lip was obserued, and the radial elelments extend to the surface—a true termination slage does not exist. ThE tensile fracture of several metals and alloys has been investigated.2-4 In the case of polycrystal-line materials, cup-cone fracture usually results. The mechanism of cup-cone fracture may be summarized as follows.5 Cavities are formed in the necked region of the specimen. They usually are initiated by inclusions or second-phase particles. The cavities extend outwards by means of internal necking, and a crack lying about perpendicular to the length of the specimen is formed in the necked region. Subsequent crack growth occurs by the spread of bands of concentrated plastic deformation inclined at an angle of 30 to 40 deg to the tensile axis. Cavities are formed in the bands of concentrated deformation. The deformation bands zigzag across the bar with the net result that mac-roscopically the crack extends about perpendicular to the specimen axis. The final separation, or cone formation, appears to occur by continued crack propagation along one of the deformation bands out to the surface of the specimen. The micromechanics of the tensile fracture of ultrahigh-strength steels have not been thoroughly investigated. Larson and carr6,7 studied the tensile-fracture surfaces of AISI 4340 with a low-power microscope and reported that three stages of fracture could be observed in general. A centrally located region characterized by circumferential ridges, an annular region characterized by radial surface striations, and a peripheral shear lip were found. It was first pointed out by 1rwin8 that the central region is very probably one of fracture initiation and slow growth, and that the annular, radially striated region is one of rapid crack growth. Presumably the crack grows slowly, assuming roughly a lenticular shape, until it is large enough for the initiation of rapid propagation. In this investigation, it was attempted to determine the fine-scale aspects of the room-temperature tensile fracture of some ultrahigh-strength steels, and to relate the variation in fracture mode with microstructure. The steels studied were AISI 4340, 300M, and H-11 tempered to a wide range of strength levels. I) EXPERIMENTAL PROCEDURE The compositions of the steels studied are given in Table I. The steel was received in the form of hot-rolled bar stock 5/8 to 1 in. in diameter from which oversized specimens were machined and heat-treated. The heat treatments employed are given in Table 11. Subsequent to heat treatment, the specimens were ground to the final dimensions and stress-relieved by heating for 1 hr at 350°F (with the exception of the as-quenched steel). Standard smooth round specimens of 0.252-in. diameter and 1-in. gage length were tested in a Tinius Olsen Universal Testing Machine using a cross-head speed of 0.025 in. per min. The relatively coarse aspects of the fracture topography were determined by light-microscopic examination of sections through the fracture surface of nickel-plated specimens. A direct carbon-replication technique9 was used in the electron-microscopic study of the fracture surfaces. The replicas were examined in the electron microscope, and stereo pairs of electron micrographs were taken. The stereo pairs were then examined using a Wild ST4 Mirror Stereoscope. Carbide and inclusion particles extracted in the replicas were analyzed by selected-area electron diffraction. II) EXPERIMENTAL RESULTS The mechanical testing data are summarized in Table 111. The values reported are the average of

Jan 1, 1965

By J. H. Wernick

IN temperature-gradient zone-melting1 a molten zone is moved through a solid or across a solid surface by the establishment of a temperature gradient. This technique has both practical and fundamental aspects. One practical application is to make p-n junctions for semiconductive devices, particularly for devices in which the junctions are desired within the semiconductor. From a fundamental point of view, the technique is being investigated as a method for determining diffusivities in liquid alloys, and preliminary diffusivity results have been reported by the writer." In this paper, the effects of crystal orientation, temperature, and molten zone thickness in temperature-gradient zone-melting, and the bearing of these effects on diffusivity measurements and n-p-n junction formation are discussed. Experimental Procedure An effect of crystal orientation was noted in early experiments. To facilitate its study, movements of wire zones across a surface, rather than through the body of a single crystal, were observed for various surface planes and travel directions. The experirr-entai setup is illustrated in Fig. 1. The graphite end-section for the high temperature heater has an apron about 1/16 in. above the upper surface of the crystal. This apron insures that the surface temperature of the block is equal to or greater than the temperature within the block at every point, Thus, the zone does not penetrate the block and convection in the liquid is minimized. The experi-through a block is shown in Fig. 2,

Jan 1, 1958

By V. H. Wilhelm

WITH rapidly diminishing oil reserves: a great percentage of which are uneconomical at present prices, some of the existing methods of development and production will have to undergo radical re- visions to meet the changes continually taking place in the petroleum industry. Imagination in an engineer is a great asset. The fancy of today is found to be the realization of tomorrow, and with this thought in mind, there is here presented a more or less imaginative picture which, to my mind, has a meritorious basis. Directed drilling has reached a stage of accuracy sufficient to allow the prediction that this art will be used in the future development of oil structures, especially those \\,it11 thin sand bodies 'and steep dips. Directional drilling in a number of fields in California has gratifying results. Wells which practically laid pipe lines through the oil sands have enjoyed a greater drainage radius with a consequent greater initial and cumulative production. In one field where the vertical thickness of sands was approximately 550 ft., wells drifting at an angle as great as 55 deg. fro111 vertical had over 1100 ft. of perforated pipe in contact with these sands. These wells were, and are, remarkable for their great initial pro-

Jan 1, 1936

By J. W. Harshbarger, E. L. Montgomery

The region of metallic ore deposits in northern Chile, southern Peru, western Bolivia, and northwestern Argentina occurs in arid zones at altitudes as high as 6 km (19,700 ft). Because surface water supplies are meager, new mines require unexploited sources of water. Prolific ground water aquifers occur in salar basins in this region of the Andean Highlands. Exploration water wells have been constructed and aquifer characteristics have been tested in eight salar basins. Results indicate ground water quality is good. Aquifer transmissivity and storage computed from results of pumping tests indicate maximum capacities of more than 170 L/sec (2700 gpm) for individual production water wells. Results of investigations conducted by the authors demonstrate that ground water reservoirs in the Andean Highlands comprise a source of large quantities of water for the mineral industry.

Jan 1, 1986

Papers in Classes A-Metal Mining, B-Milling and Concentration, H-Industrial Minerals, and I-Mining Geology are distributed in MINING TECHNOLOGY, which is issued every other month. Papers in Classes C-Iron and Steel Division, D-Nonferrous Metallurgy and E-Institute of Metals Division are distributed in METALS TECHNOLOGY, which is issued twice quarterly. Papers in Class G-Petroleum Division are distributed in PETROLEUM TECHNOLOGY, which is issued every other month. TECHNICAL PUBLICATIONS in Classes F-Coal Division, J--Mineral Industry Education Division, K¬-Mining Administration, and 1-Geophysics, are issued as separate pamphlets. Contributions are papers that when printed or mimeographed are available but only on request.

Jan 1, 1944

By AIME AIME

AT a recent meeting of the Utah Section. A.I.M.E., P. D. Nielson, general plant superintendent of the new Geneva steel plant at Provo, Utah, spoke on "General Operations of the Geneva Plant." Mr. Nielson explained that the plant was located at Provo, Utah, on account of railroad facilities, the proximity of coal, iron, and limestone, and the nearness of water for operating the plant. Water probably was the most important item in making the decision.

Jan 1, 1944

By Lawrence H. Van Vlack

The energy of the y-iron grain boundary was determined to be 850 ergs per cm2 at 1105°C. The a/a and the a/y boundaries possess somewhat less energy. The microstructures of several iron alloys are discussed in terms of the interfacial energy relationships. THE dependence of the shape of liquid interfaces upon their energies has been studied for some time.1"3 Recently, Smith' concluded that many of the microstructures observed in metals may be attributed to the energies of the interfaces between the grains and phases. While the energies of liquid surfaces have been measured by numerous different methods: only two attempts have been made to determine experimentally the energy of surfaces involving crystalline solids. Udin, Shaler, and Wulff8 used a procedure introduced by Berggren7 to measure the surface tension of solid copper. It consisted of determining the load required on a thin copper wire so that the surface tension was counteracted, and no net strain resulted. Bailey and Watkins8 sed a different technique and were able to determine both the surface tension of copper and the tension of the copper grain boundary. They measured the contact angle which liquid lead makes against a copper surface. They then calculated the above energies from the surface energy of liquid lead by using the Pb vs. Cu/CuY dihedral angle and the surface groove angle formed during thermal etching. They obtained a value of 1800 dynes per cm for the surface tension of clean copper and approximately 640 dynes per cm for the tension of copper grain boundaries. The former value was somewhat higher than Udin's value of 1500 dynes per cm. This paper includes a determination of the energy of the y-iron grain boundary. In addition, the micro-structural relationships of several other metallic and nonmetallic phases with iron were examined and an attempt was made to interpret the observed structures in terms of interfacial energy relationships. Theoretical Considerations In a three-phase material containing a solid and two liquids, there may be two solid/liquid interfaces, one liquid/liquid interface and one inter- granular interface. Liquid/liquid interfacial energies can be measured directly. Therefore, by determining the energy of such an interface and by measuring the required interfacial angles: the energies of the interfaces involving solids may be obtained.10 They may be shown schematically as in Fig. 1. The above procedure requires the following assumptions: 1—The interfacial energies are, in general, unaffected by boundary orientation, and 2— the shapes of the interfaces are unaltered between annealing and sectioning for microscopic examination. The first assumption is good to a first approximation as shown by Dunn and Lionetti11 except for a few critically orientated boundaries. Two conditions may alter the shape of a boundary upon cooling: 1—Precipitation of dissolved material upon one side of the interface, and 2—a change in volume during the transition from one phase modification to another. The former must be detected by microscopic observation. The latter may become appreciable in systems containing an interface between two liquids which solidify after annealing. However, possible movement of the two-liquid interface may be checked in the system diagrammed in Fig. 1 by measuring 8, for example, and comparing it with its value as calculated from the other interfacial angles by: tan8, C11 05 COS- o- + cos 8, cos- The choice of a suitable pair of liquids is limited by several factors. The relative values of the several

Jan 1, 1952

By Ch. J. Raub

A review will be given on the electrodeposition of Au, Ag and Pd and their technically important alloys focusing on recent work at the Forschungsinstitut. Special emphasis will be given to the influence of impurities on the behaviour of the electrolyte and the properties of the deposits, e.g. on resistance and on thermal and mechanical behaviour. The importance of C in gold and silver deposits and of H2 in Pd and its alloys at normal and high speed deposition rates will be discussed. Among Pd alloys attention will be focused on the Pd-Ni and Pd-Ni-Co systems. Comments will be made on deposition of Rh and Pt.

Jan 1, 1984

By A. O. Drysdale

In Canada, the market for cement is not a national one but rather a collection of local or regional markets. Excess capacity on a national basis does not necessarily preclude a shortage on a regional basis. with portland cement selling for less than a cent a pound, the low price-to-weight factor makes transportation to the market a major cost item and thus a small plant can be justified to serve a limited regional market. The Brookfield plant of the Canada Cement Co. is designed to supply the Province of Nova Scotia, a regional market that shows promise of growing to a point where it will support a one-kiln plant. The market is presently being served by boat shipments from the Canada Cement Co. plant at Montreal East, Quebec, and from the North Star Cement Ltd. plant at Corner Brook, Newfoundland, and by rail and road shipments from the Canada Cement Co. plant at Havelock, N. B.

Jan 4, 1965

By G. Hileman

At present there are three fields in commercial exploitation in the Argentine. In order of production they are: (1) Comodoro Rivadavia, (2) Salta, (3) Plaza Huincul. Comodoro Rivadavia.—This field is on the coast of the Territory of Chubut in the southern part of the republic. It is being developed and exploited by Yacimientos Petroliferos Fiscales, the government oil entity, and five private companies. The immediate coastal portion of the field, which embraces the original discovery area, is almost completely developed. This is especially true of the original government reserve and one private property. The Y.P.F. has extended its explorations and developments westward to Escalante, 27 km. distant on the state railway. This extension has been the most active and prolific section of the field for the past three years. The government has also continued its exploration drilling in the region lying south of Colonia Sarmiento and east of the Rio Senguer. Private companies have not been able to extend their operations beyond the claims they had in process of acquisition in 1924, when the government reserve areas were established. The Y.P.F. is the major producer of the field and employs modern methods and appliances. Practically all its drilling and pumping operations are electrically operated, from a central power plant. In view of t'he scarcity of water supplies, this facilitates operations and is an economic factor of considerable importance.

Jan 1, 1934

The following is an incomplete list of members and guests who. called at Institute headquarters during the period Dec. 10, 1917 to Jan. 10, , 1918: A. A. Arluck, Camp Merritt, N. J. W. Spencer Hutchinson, Boston, Mass. C. L. Bruns, Santiago de Cuba. William F. Jahn, New York, N. Y. Henry C. Carr, New York, N. Y. C. H. James, Tucson, Ariz. L. J. Charles, Santa Fe, N. M. Charles Janin, San Francisco, Cal. W. A. Deane, Waxhaw, N. C. Joseph T. Kupferstein, Shreveport, Pa. P. St. John Dixon, Rio de Janeiro, Brazil. Richard Lamb, New York, N. Y. M. C. Drake, Marquette, Mich. Walter R. Malm, San Francisco, Cal. F. W. Draper, Petrograd, Russia. W. H. Nash, Buffalo, N. Y. Paul W. Gaebelein, Boise, Idaho. Edmund Newton, Minneapolis, Minn. H. F. E. Gamm, Rutherford, N. J. Guy C. Riddell, Port Pirie, South Australia. C. A. Grabill, El Paso, Tex. Williams A. Simkins, San Francisco, Cal. William H. Hampton, New York, N. Y. Henry B. Smith, Northampton, Mass. R. M. Henderson, Brackenridge, Colo. H. E. Smith, Chicago, Ill. Geo. B. Holderer, Northpines, Ont., H: C. Spaulding, Washington, D. C. Canada. Y. Wakabayashi, Tokyo, Japan. H. H. Howry, Camp Upton. N. Y. A. P. Watt, Mine La Motte, Mo. L. Douglas Anderson", superintendent of the Midvale, Utah, smeltery of the United States Smelting Co., has been appointed manager of smelteries for the company at Salt Lake City, Utah.

Jan 2, 1918

Jan 1, 1969

By W. Philippoff, Donald E. Cadwell, S. R. B. Cooke

THE importance of contact angles in flotation has long been recognized, but little has been done to get quantitative relationships between the surface coverage of the mineral by the reagent, the length of the hydrocarbon chain, and the contact angle. It is well known that for a complete monolayer on the surface of a mineral the contact angle 8 is determined only by the reagent1 and principally by the chain length of the hydrocarbon radical. Although for flotation the monolayer usually is regarded as being complete, early experiments of Wark and Cox&apos; showed that at very small concentrations of potassium ethyl xanthate the contact angle on galena changed in a continuous way from 0&apos; to the equilibrium value of 60". Further, Gaudin and Vincenta showed a similar continuity using heptylic acid and sphalerite. This shows that with probably incomplete monolayers, 0 varies with the degree of surface coverage. At the time these experiments were made it was impossible to measure the actual amount of surface coverage, especially since the decrease of the collector concentration in the liquor could be influenced by chemical side reactions. Through the use of the radioactive tracer method for the measurement of the amount of collector adsorbed on the surface of the mineral, Gaudin and Bloecher&apos; were able to determine accurately the actual surface coverage of dodecylamine acetate on quartz, but they did not measure any contact angles. It is believed that the relationship between the surface coverage and the contact angle is extremely important in flotation, especially as Gaudin and Bloecher showed that a 95 pct recovery is possible with a coverage of only 5 pct. Theoretical Considerations The work of adhesion W is the energy bound (in ergs per sq cm) when an interface is formed. It is determined by the difference of the free surface energies (surface tensions) of the respective phases 7j and yZ before contact and the interfacial free surface energy y, after contact. The definition of the contact angle permits the elimination of the unknown surface energy of the solid and hence the calculation of W from the surface tension of the liquid y and the contact angle 8: W = y (1 + COS0) [1] Consider a surface consisting of two components, identified as 2 and 3, 1 being the liquid. The amount of 2 in the composite surface is x, where 0 < x < 1. The respective contact angles with 1 and air are 8, and 8.. The total work of adhesion of such a surface is the sum of the values of the components multiplied by their respective areas. A formal relation can be written: Wm = x-W2+ (l-x)-W, [2] in which W, is the work of adhesion of the composite surface. Eq 1 can be introduced into Wt and Wa, but in the case of W, some discussion is needed. If the two components are segregated, each component forming an integral part of the composite surface there is no physical meaning for a contact angle 8m calculated from W,, by using eq 1. If, on the other hand, the area of each patch of the components is small in comparison with, say, the diameter of the bubble used in measuring, it could be expected that 0m would have a physical significance, because of the action of the surface tension of the liquid-gas interface tending to smooth out sharp corners. How small these patches would have to be is difficult to predict, but by using composite surfaces with microscopically

Jan 1, 1953

By S. R. B. Cooke, W. Philippoff, Donald E. Cadwell

THE importance of contact angles in flotation has long been recognized, but little has been done to get quantitative relationships between the surface coverage of the mineral by the reagent, the length of the hydrocarbon chain, and the contact angle. It is well known that for a complete monolayer on the surface of a mineral the contact angle 8 is determined only by the reagent1 and principally by the chain length of the hydrocarbon radical. Although for flotation the monolayer usually is regarded as being complete, early experiments of Wark and Cox&apos; showed that at very small concentrations of potassium ethyl xanthate the contact angle on galena changed in a continuous way from 0&apos; to the equilibrium value of 60". Further, Gaudin and Vincenta showed a similar continuity using heptylic acid and sphalerite. This shows that with probably incomplete monolayers, 0 varies with the degree of surface coverage. At the time these experiments were made it was impossible to measure the actual amount of surface coverage, especially since the decrease of the collector concentration in the liquor could be influenced by chemical side reactions. Through the use of the radioactive tracer method for the measurement of the amount of collector adsorbed on the surface of the mineral, Gaudin and Bloecher&apos; were able to determine accurately the actual surface coverage of dodecylamine acetate on quartz, but they did not measure any contact angles. It is believed that the relationship between the surface coverage and the contact angle is extremely important in flotation, especially as Gaudin and Bloecher showed that a 95 pct recovery is possible with a coverage of only 5 pct. Theoretical Considerations The work of adhesion W is the energy bound (in ergs per sq cm) when an interface is formed. It is determined by the difference of the free surface energies (surface tensions) of the respective phases 7j and yZ before contact and the interfacial free surface energy y, after contact. The definition of the contact angle permits the elimination of the unknown surface energy of the solid and hence the calculation of W from the surface tension of the liquid y and the contact angle 8: W = y (1 + COS0) [1] Consider a surface consisting of two components, identified as 2 and 3, 1 being the liquid. The amount of 2 in the composite surface is x, where 0 < x < 1. The respective contact angles with 1 and air are 8, and 8.. The total work of adhesion of such a surface is the sum of the values of the components multiplied by their respective areas. A formal relation can be written: Wm = x-W2+ (l-x)-W, [2] in which W, is the work of adhesion of the composite surface. Eq 1 can be introduced into Wt and Wa, but in the case of W, some discussion is needed. If the two components are segregated, each component forming an integral part of the composite surface there is no physical meaning for a contact angle 8m calculated from W,, by using eq 1. If, on the other hand, the area of each patch of the components is small in comparison with, say, the diameter of the bubble used in measuring, it could be expected that 0m would have a physical significance, because of the action of the surface tension of the liquid-gas interface tending to smooth out sharp corners. How small these patches would have to be is difficult to predict, but by using composite surfaces with microscopically

Jan 1, 1953

By Brahm Prakash, R. Schuhmann

Maurice Rey—It may be interesting to note that depressing effects can also be obtained from cyclic compounds other than dyes. One such compound which is a dispersing agent for carbon, pigments and other compounds is known in France by the trade name "dispergine" and in the United States by the name of Lomar P W (Jacques Wolf & Co.) Dr. Rey admits that the compound is not very selective and is similar in its action to starch and dextrin.

Jan 1, 1951

By Brahm Prakash, R. Schuhmann

Maurice Rey—It may be interesting to note that depressing effects can also be obtained from cyclic compounds other than dyes. One such compound which is a dispersing agent for carbon, pigments and other compounds is known in France by the trade name "dispergine" and in the United States by the name of Lomar P W (Jacques Wolf & Co.) Dr. Rey admits that the compound is not very selective and is similar in its action to starch and dextrin.

Jan 1, 1951