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Correlation between Metallography and Mechanical Testing By H F MOORE (Henry Marion Howe Memorial Lecture Trans, vol 120 11,000 words ) The lack of effective correlation between metallography and mechanical testing from the days of Reaumur to the present is noted, and two general problems of such cor¬relation are stated (1) the correlation of qualitative test results with quantitative, and (2) the correlation of average results with maximum or minimum results Some correlation has been achieved, notably in the field of heat-treatment and in the study of elastic strength of metals Correlation is in the process of being developed in several other fields, including the quantitative study of the effect of grain size of metal on mechanical properties, of grain size and type of crystalline structure on the sensitivity of metals to weakening at holes, notches and other "stress raisers," and in the study of the starting phases of spreading, "fatigue" cracks Correlation of mechanical test results and metallographic study is needed in the study of such problems as the various theories of failure of metals, the meaning of and tests for service ductility of metals, and the relative damaging effect of defects inherent in metals, such as minute cracks and segregation, as compared with the damaging effect of "imposed" stress raisers, such as screw threads, sharp shoulders, etc The neces¬sity for more correlation of metallography and mechanical testing during student days is emphasized, and also the need of a better understanding on the part of engi¬neers of the significance and limitations of metallographic apparatus and results and of X-ray diffraction This should be matched by a better understanding on the part of metallurgists of the significance and limitations of mechanical tests of metals, of testing machines and strain-measuring apparatus

Jan 1, 1937

Industrial Preparedness To Cooperate with the U S War Department General Committee ARTHUR S DWIGHT, Chairman H FOSTER BAIN C K LEITH J EDWARD SPURR H. S MULLIKEN Alternate GEORGE OTIS SMITH POPE YEATMAN

Jan 1, 1923

By C. A. Rowland, M. D. Flavel

There are seven basic comminution circuits that can be used to prepare beneficiation feed from the product of a primary crusher. This paper gives a comparison of these circuits based on average process and economical data. The paper is principally devoted to a discussion of the test work required to obtain the process data needed to evaluate each circuit. The results of the test work in conjunction with geographic and economic factors can be used to narrow down the choice of possible circuits to one, two, or three before making a detailed engineering study.

Jan 1, 1985

By Carle Hayward

IN reheating quenched steel to remove part of the hardness, the softening effect has generally been considered to be a function of temperature and time. The temperature effect is well known, and long before pyrometers were heard of the blacksmith was able to do a good job of tempering, by rule-of-thumb methods and experience in judging temperatures. Modern conditions, which demand steel that will withstand the severest tests, require that the heat treatment he carried out with every possible precaution to secure the best results obtainable. Pyrometers and heat-treatment furnaces of many types are on the market and improvements are continually being made so that it is now possible to regulate the temperature in heat treatment very accurately. There is -still a question regarding the time that the steel should be subjected to treatment. It is customary with all operators to insure the desired tem-pressure throughout the specimen and it is generally supposed that a longer treatment of a hardened steel produces a further softening but there are few published figures showing the exact effect of time of treat-ment at constant temperature. A search of the literature disclosed several brief statements that the tempering effect was a function of both time and temperature, but in no case were any figures given. The opinion is very generally held that the well-known tempering colors are accurate indicators of the degree of tempering. This is disputed by Brearley (The Heat Treatment of Tool Steel, page 102) who states: It has been said that the result would be the same in respect to both hardness and other properties whether the colors were obtained by a shorter heating at a higher temperature or a longer heating at a lower one. This, to say the least, is a very doubtful conclusion, and is certainly not borne out by mechanical tests on oil-hardened and tempered motor car steels, which, after tempering for periods varying from 15 min to 2 hr., show no very great differences. The present investigation had for its object the obtaining of some definite data regarding the effect of time, which might serve as a guide to those engaged in the heat treatment of steel. The Rhode Island Tool Co. cooperated by furnishing the steel and machining the test specimens.

Jan 2, 1917

Discussion of the paper of HOWARD N. EAVENSON, presented at the Pittsburgh meeting, October, 1914, and printed in Bulletin No. 94, October,' 1914, pp. 2637 to 2660. GEORGE S. RICE, Pittsburgh, Pa.-I think it is very wise to point out the greater liability to explosions in certain parts of the year, if there be such difference, with the caution, however, that vigilance be not relaxed at other times. In comparing the figures for the United States with those of Europe, I think we should separate them as far as possible according to cause of origin and means of propagation. That is to say, it would appear to me that the majority of our explosions are due more directly to the ignition of coal dust directly from the flame of explosives, whereas, judging from my inquiries and observations in some of the mines of Europe, the majority of their explosions have been caused by the ignition of fire damp. Now, in the case of fire damp, I do not think that anybody has yet attempted or has been able to find any connection between the seasons and the issuance of methane into mines. One thing must be borne in mind, that if you get a strong explosion of fire damp, dust of a character that might not ignite readily by itself might assist in the extension of an explosion of fire damp through a considerable area in the mine, if not throughout the mine. While it is true we have many lesser explosions in this country attributable to fire damp, it would appear that the majority of all the mine explosions of the country, in considering the means of propagation beyond the locality of the origin, are due to coal dust; and it is the liability to coal-dust explosions that appears to be affected by seasonal changes. Hence the desirability of separating statistically (if it could be done by the inspectors) fire-damp explosions from coal-dust explosions, in order to obtain the true value of the seasonal effect. Nevertheless, in spite of the inclusion of fire-damp explosions with coal-dust explosions, the preponderance of the evidence, as indicated in Mr. Eavenson's figures for American mines, has shown that' in this country there were more explosions in the winter and spring months, when the mines are drier; that is, when the mines are apt to be drier. Whereas, according to the European figures that he has gathered, it seems to be very clearly demonstrated that in France, England, and Belgium, the time when explosions occur has no connection with any particular season. That, I think, is partly due to the point just mentioned, that a majority of their explosions have originated from fire damp. The European mining men have been more careful, generally speaking, with the use of explosives than we have, so that the cause of ignition from that source has been less. Only comparatively few of the mines in foreign

Jan 4, 1915

By M. S. Abrahams

Germanium has been rolled in the temperature range of 700o to 800°C. The thickness has been decreased by as much as a factor of four, from a thickness of 0.032 in. to a thickness of 0.008 in. For deformations below 60 pet, the true strain per pass is found to be a constant; from the temperature dependence of this slope, an activation energy of about 2.5 ev is obtained. This energy agrees with that for dislocation climb in germanium . For reductions greater than 60 pet, complete rings are seen in the Lave photographs, new grains are observed in the microstructure, considerable softening occurs, and the hole mobility is very low. This evidence indicates that the recrystallization of gertnanium has occurred. GERMANIUM has been deformed in many ways1 including tension, compression, torsion, and bending since Gallagher2 first described its plastic nature at elevated temperatures. All of these studies indicate that the glide plane in germanium is (111) and that the glide direction is (110). Rolled germanium specimens were used by Kolm, Warekois, and Kulin3 in their X-ray study of deformed semiconductors, but no information is given on the rolling itself. The present experiments deal with the rolling of germanium at various temperatures and for different orientations. In all previous deformation studies, the phenomenon of recrystallization (i.e., the transformation of a single crystal into a polycrystal) in germanium has not been observed4 despite relatively large deformations at elevated temperatures. The proposed reason4 for this was that sufficient energy could not be stored in the deformed germanium lattice. In contrast to the earlier studies this work will present evidence indicating that recrystallization occurs in germanium during rolling at an elevated temperature. I) EXPERIMENTAL PROCEDURE A) Test Specimens. The samples used for rolling were in the form of rectangular parallelepipeds measuring 0.3 in. long, 0.06 in. wide, and 0.035 in. high. They were cut from an undoped single-crystal ingot of p-type germanium with a resistivity of 24.4 ohm-cm, a Hall mobility of 2300 sq cm v-' sec-l, and a hole concentration of 1.1 x 1014 cm"3 at room temperature. The surfaces of the specimens were metallographically polished prior to rolling. The initial dislocation density of the samples was about 10' cm-' as determined by etching in CP4. Two different specimen orientations were used. In the first case, the direction of rolling was parallel to (251), the surfaces in contact with the rolls were of the form (1021, and the normal to the third face was parallel to (211). The corresponding di-

Jan 1, 1964

By J. S. Marsh

The student of steelmaking is all too well acquainted with the fact that in many instances he must deal with data that in graphical representation exhibit the property most desirable in bird shot. This is scarcely mystifying, since the effort to establish one variable as a function of another is usually hampered by the simultaneous operativeness of two or three other factors that may be important. A large part of arriving at relationships that have the pleasing self-consistency of, say, precise measurements of thermal expansion, consists of determining what factors must be held constant-—an even larger part usually consists of collecting data for which those factors have been so maintained. It is not intended to imply that functional relationships in the physical chemistry of steelmaking are hopelessly obscure; on the contrary, it is merely necessary to be undisturbed by marked deviation of some points from a curve that otherwise makes sense. A reaction mechanism suggested by such a curve may call attention to hitherto unsuspected factors operative in the origin of the deviating points, and thus permit another step to be taken in the direction of fuller understanding. It is proposed, therefore, to suggest several empirical relationships. Even though the approach is not always rigorous, deviations caused by simplifying assumptions appear to be too small to obscure a provisional It has been appreciated for some time that the carbon-oxygen reaction in liquid steel is highly important. For example, Körber et al.,' in introducing a summary of their extensive work on steelmaking reactions, said: "... the far-reaching and truly dominating action of carbon upon the metallurgical reactions will be especially stressed ..." In "Basic Open Hearth Steelmaking"2 (hereafter BOHS, for simplicity), it is accepted repeatedly that the various slag-metal interactions are nearly always controlled by the carbon-oxygen reaction. Before further discussion of this reaction, however, it will be worth while to consider briefly the carbon-oxygen equilibrium. In BOHS (p. 483) it is stated that: When liquid iron is brought into contact with gases containing carbon monoxide it absorhs carbon and oxygen. Conversely the carbon and oxygen in the metal unite to form carbon monoxide which is evolved from the bath during the open-hearth boil or while rimming ingots are solidifying. . . . When the equilibrium pressure is one atmosphere the equilibrium-constant equation simplifies, on the assumption that the activity of each element is equal to its percentage, to a constant which has been so much used that it has acquired a special symbol m. where m = %C X %O

Jan 1, 1945

By A. S. Adams

A GLANCE at the list of papers1 that have been published since 1920 on the general subject of flotation suggests the variety of ideas that exist regarding the underlying cause of the phenomenon. Among these ideas, we find several coherent theories, but none that adequately and completely explain the phenomenon. Ralston2 and Bains3 suggested an electrical theory which has to do with the attachment of mineral particles to a bubble by the attraction of unlike electrical charges. This theory has its root in the fact that a bubble of air in pure water is electrified in such a way that the surface is negatively charged while the body of the water is positively charged. This result, which was first discussed by Helmholtz, also obtains when the water contains anything except a high concentration of hydrogen ions, or ions which are trivalent or tetravalent. The theory also holds that the mineral particles have positive charges on their surfaces, and so there is attachment between bubble surface and mineral particles by the old law of electrostatics, which states that unlike charges attract.

Jan 1, 1928

By Albert Stazicker

AT Climax the warehouse department operates as an independent unit similar to the mine and mill departments. It has the responsibility of receiving, checking, unloading, and storing all material and supplies delivered to the plant. In addition, the transportation of all supplies comes under the direction of the warehouse so that prompt delivery of supplies to all departments is one of its major functions. The transportation division operates heavy and light trucks, trailers, two large tractors, and two snowplows. In addition to delivering supplies it is also responsible for snow removal from the roads, hauling of sand and gravel for concrete and domestic coal to employees. and all miscellaneous work involving the use of tractors or trucks.

Jan 1, 1946

By Emerson F. Heald

A systematic study was made of new and old data on chemical activities in Fe-Pt alloys at elevated ternperatuves. Experimental results may be expressed in terms of the excess free energy using Least-squares analysis of the data gave the following values for the constants: for the temperature range 1130° to 1350°C, and tentatively to 155O°C, B = -3.326564 and C = 0.221051; for the temperature range 650" to 850°C, B = -2.555690, C = 1.762735, and D =0.097196. In the study of iron-containing silicate systems, it is sometimes desirable to have a direct experimental measure of the activity of iron in the system. The well-known solubility of iron in platinum, often a headache in experimental work on iron compounds under reducing conditions, can be used to advantage in this respect. If the activity of iron in an Fe-Pt alloy in equilibrium with the silicate is known as a function of the composition of the alloy, chemical analysis of the alloy will give a knowledge of the activity of iron in all of the phases in the system. The present study was undertaken in order to elucidate the characteristics of Fe-Pt alloys as iron activity indicators. This work is intended to tie together some previous work, which may be summarized as follows. Larson and Chipman1 determined the activity of iron in Fe-Pt alloys at 1550°C by equilibrating platinum metal with calcium oxide-iron oxide-silica melts of known iron activity. Compositions of the resulting alloys were determined by chemical analysis. A similar study was carried out by Taylor and ~uan,' who worked at 1300°C. They brought the Fe-Pt alloys into equilibrium with iron oxide under conditions of known partial pressure of oxygen, and thus, from the work of Darken and ~urr~,~ conditions of known iron activity. Compositions were determined indirectly, by following the change in weight of the sample. Sundaresen et el* used the electromotive force of cells in which the alloy formed one electrode in order to measure the activity of iron in the alloy at 650" and 850°C. These temperatures were chosen to be above and below the first-order phase transition which takes place upon the ordering of Fe3Pt and the second-order transition which occurs upon the ordering of FePt3. EXPERIMENTAL 1) High Temperatures. The starting materials used were thin platinum foil, about 0.002 mm thick, and Fisher Certified reagent ferric oxide, Fez03, which had been heated for 24 hr at 1000°C. An intimate mixture of 80-mesh Fez03 and platinum platelets was placed in a thin platinum foil envelope. The latter was suspended from thin platinum wires in the hot zone of a vertical-tube, platinum-wound furnace of the type described by Muan and ~sborn.~ A capillary gas mixer similar to that used by Darken and Gurry3 was used to prepare a precisely known mixture of carbon dioxide and hydrogen, which was allowed to flow upward through the furnace tube. The partial pressure of oxygen in contact with the sample was thereby fixed at a value which was calculated from the charts prepared by porter? Temperatures were measured with a Pt-10 pct Rh-in-platinum thermocouple, which was calibrated using the melting points of gold (1062 .@C) and diopside, CaMgSizOB (1391.5"C). Temperature control was maintained to within i3"C with a Geophysical Laboratory proportional controller, using the furnace resistance as the sensing element. Samples were quenched by passing a small current through the platinum suspension wires, allowing the sample to drop into a bath of dibutyl phthalate at the bottom of the furnace tube. Prior to chemical analysis the samples were washed with acetone and dried. 2) Chemical Analysis. It proved possible, in almost all cases, to separate the Pt-Fe platelets physically from particles of iron oxide. The platelets were dissolved in a small volume of aqua regia, evaporated to dryness, and redissolved to 0.1 M HC1. In order to determine iron in the platinum alloy potentiometrically, it is necessary first to remove the platinum. A 10-cm column of Amberlite IR-120 cation exchange resin in the hydrogen form provided separation quickly and quantitatively: The mixture of iron and platinum in 0.1 M HC1 was added to the top of the column, and washed with about 100 ml of 0.1 M HC1. Under these conditions, the iron, principally in the form of cations such as FeC1" and FeCl;, is held quantitatively in the uppermost centimeter of the column. The platinum, in the form of anions such as PtC&- , is washed through without being adsorbed. After a qualitative test with stannous chloride indicated all of the platinum was removed, the iron was

Jan 1, 1968

By George D. Dub

INTRODUCTION OWENS LAKE is at present a source of important nonmetallic minerals, sodium carbonate (soda ash, Na2CO3); sodium sesquicarbonate (trona, Na2CO3.NaHCO3.2H20) and borax, (Na2B407.10H2O). Owens Lake is a closed basin in the southern part of Inyo County, California, at the southern end of Owens Valley, east of the Sierra Nevada Mountains and west of the Coso and Inyo Mountains. Broadly considered, it is in the Great Basin area, but at no time was it a part of Lake Lahontan. CLOSED BASINS Closed basins are phenomena of arid or semiarid regions where outflow is considerably less than inflow and where accordingly soluble salts concentrate in residual liquid. When inflowing waters originate in areas where the rocks are predominantly marine sediments, the residual basin liquid is primarily a chloride brine; if the rocks are largely igneous, the residual brine tends to be alkaline containing carbonates, and sometimes borates as well. Since normally, both types of rocks occur in regions contiguous to closed basins, residual liquids do not often fit into the two broad divisions mentioned. No two residual brines are exactly alike, just as no two ore deposits are exactly alike. Even out of the same closed basin, it is possible to get widely different analyses of liquids since underground and surface flows, as well as local evaporation rates and other conditions might have a marked influence on residual-liquid compositions. At Searles Lake, The American Potash and Chemical Corporation is building a plant to process a lower-level brine which is considerably higher in sodium carbonate and borax, and lower in potassium chloride, than that company has processed for many years. F. W. Clarke1 has classified waters of closed basins as follows: I Chloride type; largely sodium chloride (NaCI) and of oceanic type, such as Great Salt Lake. Related is the Dead Sea, a bittern residue of magnesium, potassium and sodium chlorides. 2. Sulphate type; largely sodium sulphate (Na2S04) with considerable sodium chloride such as Sevier Lake, Utah; Laramie Lakes, Wyoming; Dale Lake, California. 3. Carbonate type; high in carbonates and fairly high in sulphates, such as Moses Lake, Eastern Washington; and the Nebraska Potash Lakes. 4. Carbonate-chloride type; lower in carbonates than type 3 and about equally rich in sulphates, such as Pyramid Lake, Nevada. 5. Sulphate-Carbonate type; quite high in sulphates and carbonates, such as Pelican Lake, Oregon. 6. Triple type; considerable quantities of carbonates, sulphates and chlorides

Jan 1, 1947

By R. W. Raymond

to same extent, the assumptions tinderlying Dr. Ilu?ley's con alusions. These amrrmptions are: that 'the loss of metal per million tons of trafffc, depends, first upon the circrtnistances under which the rail is worn; secondly, upon the proportions of its various constituents, ancl that the anlorlnt of loss is afEect~d by eacb constitnent in a cer tain ratio, so that if the circunlstances were the same for all tlie mils, the wear per nliilion tons might he upproxi91ately expre~sed by an equation of the form I + Cc + Pp + SR + Mm = R, io wtlioh I is an unknown valne, dependi~.rg on the quantity of iron (and other ingre dients not determined) in the rail, and assumed to be constant for all the rails ; c, p, s, and m are the experimentally determined quan tities of carhon, phosphorus, sulphur, and manganese, as tabulater1 in YIates VT and VII of Dr. Dudley's paper; and R is the experirnen tdlly dcterlnincd wear per million tons; while C, P, S, and M are onknown wfficients. In other words, it is assunled that the differ ence in wear is proportional to a difference in c, p, s, or m, and that the effects of a change in the amonnt of either are independent of the amount of the rest-—within the experinlental limit5 of the problem. It is also assr~med that sulphar, copper, and other ingredients, not determined, are qually present in all the rails, or at least {lo not affect the wear, since I is taken as constant. Dr. Dudley tacitly assumes the coefficient6 C, P, S, and M to be positive; and assigns certain valries to them, by means of which he redom t.he equation to the form I + Pa: = R, x being equal to cc + Es +Mm i Pp, or tjje uanjbe,. of so-called phosphorus units in the rail. But we do not have R directly given under constant circumstances. The varying weights (per engine, car, or train) and the varying epds, we must neglect for lack of data, and assume that in these rwpects the rails examined have been treated srlbstantially alike. But there remain the varying conditions as to track, which mnst he elirninsted. Dr. Dudley gives six clrlsses, four of which contain 8 rails each, and two 16 rails each. Beginning with the 6~st (tangent grade), take the mean of the figures expressing wear for that clam; and continaing tliis process through the other five, we obtain six expressions in quantity of loss 'by wear, which we assome tc, represent, in their differences, the varying conditions of the trarli, with respect to grade and direction. We now take the mean of these moans (giving double weight to the gmiip containing 16 ohwrvafieras). This general rnean is the 10 of metal per million tons of trafio for a rail of avorage constitution under mean ciroumstances.

Jan 1, 1881

ALTHOUGH I have already described to you the procedure for making assays of the ores (a thing that is not very different from what I wish to describe in the present chapter), I shall repeat it in substance, with the addition of the method of assaying gold, in order to tell you certain rules for weights which are very necessary to know, and above all in order to demonstrate to you the method of refining a small quantity of silver by the use of a cupel, and in order to tell you how there are (I find) only two ways that are customary for bringing silver to fineness. One is that of the cupel [copella] and the other is that of the cupeling hearth [cenneraccio], one for a small and the other for a large quantity. But although they are called by two names and appear to be two methods, the aim and the procedure of both is actually the same. Nor do I know of other difference between them than the carrying out of the method and the large or small quantity. Cupeling is a very useful thing for anyone who handles gold or silver to know. Indeed it is necessary, because it not only throws light on the work that is to be done but it also shows the truth [55] and the correct weights in large quantities. It is a quicker and easier way of bringing the work to the desired perfection than is afforded by the method for large quantities. Therefore, as you have heard, it is used in making assays in order to know exactly what quantity of the substance of silver or gold is in copper and lead or in ores, as well as in that melted material which remains among the charcoal and ashes. In short, it is the measure by which you have the certainty and safety of knowing that you have not been deceived by art or by your workmen, who had no other interest than their simple wages. Many workmen are found who are so untrustworthy that they no sooner get control of a thing than they think up some fraud, and even though some know that they must give an accounting they do not restrain themselves, although sometimes they would perhaps act with greater security and more deception than they do if they did not fear detection. For, truly, since silver is a valuable thing and every bit is worth much, a man should not enter into refining it with closed eyes. If for no other reason this pro-

Jan 1, 1942

ON Coal's Horizon one development rises above all others. That is the swift expansion of output to make Soviet Russia the largest coal producer on earth next to the United States. Few Americans are aware of the speed and extent of that expansion nor of the accompanying creation of a strong, resourceful mining machinery industry, nor of the extent and character of the mechanization of Soviet coal mining. Two initial clarifications are necessary for better understanding. First, we must keep in mind the sharp distinction between the Russian people and the communist Soviet dictators who rule them. The great mass of the Russian people are not members of the Communist Party as people here are Republicans or Democrats. They are not permitted to be members. There are, by various estimates, only 2 to 4 million members of that party in all Soviet Russia. The other 196 to 198 million are the victims of their tyranny and their terror. It is the activity of the Soviet rulers that concerns us here.

Jan 1, 1954

By J. B. Cheatham

The influence of friction on the force required for an idealized bit tooth to penetrate a "plastic" rock is analyzed. The rock is assumed to obey the Coulomb-Mobr yield criterion and the tooth is represented by a two-dimensional sharp wedge. At the tooth-rock interface the stress field not only satisfies the yield condition but also is such that the ratio of the shearing stress to the normal stress is equal to the coefficient of friction. The solution relates the force on the tooth to the depth of penetration, the tooth angle, the coefficient of friction between the rock and bit tooth and the angle of internal friction and compressive strength of the rock. INTRODUCTION Most rocks are brittle at atmospheric pressure but exhibit ductility and increased strength as the confining pressure is increased. In a previous analysisl the force required for a bit tooth to penetrate a rigid-plastic rock was computed for two limiting conditions: (1) a perfectly lubricated tooth-rock interface which should correspond to a lower limit for the penetrating force, and (2) a perfectly rough interface which should provide an upper limit. Experimental results2 for rock indentation under confining pressure have confirmed that the analysis generally predicts upper and lower limits for the penetrating force as a function of rock properties and tooth angle. The present analysis extends the previous work to account for the friction between the rock and the tooth. ANALYSIS The force required for incipient plastic flow of an idealized model of a rock under a bit tooth is computed subjected to the following assumptions. BIT TOOTH 1. sharp two-dimensional wedge (end effects neglected) 2. rigid tooth (elastic deformation of tooth neglected) 3. displacement of tooth is normal to rock surface 4. friction exists between tooth and rock ROCK 1. semi-infinite, isotropic and homogeneous 2. rigid-plastic (elastic deformation of rock neglected) 3. non-work hardening (horizontal stress-strain curve) 4. Coulomb yield condition* (linear Mohr envelope) 5. smooth, flat surface According to the Mohr theory of failure it is assumed that failure occurs when the state of stress is such that the Mohr stress circle becomes tangent to an experimentally determined envelope. The Mohr failure curve is frequent1y approximated by a straight line and referred to as the Coulomb-Mohr failure criterion. If the rock is under sufficient pressure to be ductile we can use the linear envelope as a yield condition. The Coulomb-Mohr yield criterion is illustrated by Fig. 1 and is expressed by the following equation:l

Jan 1, 1916

By J. M. Steininger

The mechanism of flotation of sphalerite with sulthydryl compounds of different acidities has been interpreted in terms of chemisorption of unionized collector molecules on hydroxylated zinc surface sites. At a constant collector concentration of 1.5 x 10 -4 M, the upper pH limit of flotation has been found to be directly and closely related to the negative logarithm of the collector acidity constant, pKa The experimental results indicate that flotation is prevented when about 95% of the collector is ionized. At low pH, collector adsorption decreases because of the reduction in number of hydroxylated zinc surface sites. These two effects explain why sphalerite does not float with the more acidic sulfhydryl compounds. Typical anionic collectors for sulfide minerals are short chain xanthates or dithiophosphates which are nearly completely ionized in the generally alka- line flotation circuits.1,2 Flotation mechanisms have therefore been usually interpreted in terms of ionic collector adsorption and competition with ionic depressants of the same sign as the collector. A few attempts have been made, however, to consider adsorption of neutral collector molecules. Contact angle measurements obtained by Wark and cox3 have been interpreted by Cook and Nixon4 as representing adsorption of the free acid molecules on sulfide minerals such as pyrite, galena, chalcopyrite, and sphalerite. Cook and Nixon tried to show that the free acid concentration of the collector was substantially constant along the curves relating collector addition and minimum pH for bubble adherence. However, in a review of the subject,5 Sutherland presented new data on the flotation of pyrite with mercaptobenzothiazole which did not support the hypothesis of constant concentration of either collector ions or collector free molecules. He further showed that, with the assumption of constant occupation of surface sites, both theories lead to relations between pH and collector addition having similar mathematical expressions. In fact, with the more likely assumption of variable occupation of surface sites which results in more complex relationships, it appears impossible to

Jan 1, 1968

By ALFRED KAUFFMAN

NO matter what position we hold, workman, foreman, superintendent, manager, president, or what not, let us fail to give or to make good products, then see how quickly we'll be called to account for- our work by the buying public. The waves of progress taught us that millions were wasted in unnecessary strikes-we also learned that many losses were due to neglect on the part of manufacturers to give the same consideration and attention to the human element of their factory as they gave to their machinery. The employees learned also that the employer was their agent who found purchasers for the product of their labor. So between the two we learned that many years of labor were needed in order for a worker to recover his wasted savings, or for the manu¬facturer to replenish his loss. Treat 'em rough, and tell 'em nothing, was not very far from the true relationship between management and employees in manufacturing plants in the early days. Today just exactly the opposite views are held by executives whose function is the handling of employees. Men today want to know what it is all about. They are intelligent enough to comprehend the facts, and to use them constructively, and it is good business to give them the information.

Jan 1, 1929

By John W. Langley

The papers of Mr. W. J. Keep, read before this Institute, have called attention to the influence of aluminum in cast-iron and on iron and steel castings. The information in these papers is interesting and valuable, as showing the modifications which iron undergoes when dosed with sufficient aluminum to form a distinct alloy, the quantity of the alloying metal used being such that the amount remaining in the casting is sufficient to be readily discovered by analysis. The same is also true of the so-called aluminum-steel patented by R. A. Hadfield, where the proportions specified are such as to leave in the finished steel from one-twentieth to one-tenth of one per cent. of aluminum. Whether these alloys are of practical utility or not has thus far . not been proved by any extended tests on a large scale, and until such evidence is forthcoming it may be safely held, provisionally, that such a use of aluminum is of doubtful utility. But there is another function which this metal can perform that has been known for some time, and which has passed beyond the experimental stage, viz.: its beneficial effect in securing sound ingots. It appears to be a general property of all metals when in the fluid state and at a temperature considerably above their points of fusion, to contain gas, either dissolved from the air or frorn the furnace, or else self-evolved by internal reactions. Silver, perhaps, shows this power in the highest degree, and mercury and lead in the least; midway stands steel—the quantity of gas which it can hold in solution, or " occlusion " as it has been called, varies with its temperature, its composition, and its mode of manufacture. When the steel sets in the mould, a portion of this gas escapes, causing blow-holes, surface defects, boiling-over, wildness, and quite a long train of troubles, familiar to all practical steel-makers. Ferro-silicon has long been used as a quieting agent. The first extended use of it for this purpose was made at Terre-Noire, in

Jan 1, 1892

By R. G. Knickerbocker

THE copper smelter and refinery of The Messina (Transvaal) Development Co. Ltd., at Messina, South Africa, was erected in 1920 and 1921, but initial operations were deferred until late in 1922 on account of the collapse of the copper market in the interim. Because the anticipated production was to be only 20 tons of copper per day from a high-grade matte containing 60 per cent copper, and because the ore did not contain gold or silver in quantities sufficient to pay for separation from the copper bullion, it was decided to design the plant along lines quite different from the modern smelteries treating large quantities of sulfide ores carrying appreciable amounts of gold and silver. The plant was built, therefore, for the production of copper by the Nicholls-James process. By this method two-thirds of the copper matte produced was roasted in a Merton calciner and charged into a bath of the remaining one-third portion of unroasted matte in a reaction furnace. The original design was not only novel in providing for the Nicholls-James process, but also in comparison with new plants built elsewhere, because of factors inherent in the locality. Sources of supply for machinery were very remote; it takes three months after the placing of an order to accomplish delivery of machinery into Messina from the United States. Native labor was available at 30 to 40¢ per 8-hr. shift. These factors permitted plant design which provided no overhead cranes, no matte ladles, no slag pots or other usual mechanical means of transportation between departments. The design resulted in a compact simple plant with furnaces arranged close together and. terraced so as to provide for gravity transfer of molten material from one furnace to another and for manual disposal of products. Fig. 1 shows the relative location of furnaces. The three furnaces are parallel on successively decreasing elevations. A superimposed feed floor was provided above the furnaces. All three furnaces were provided with coal-dust burners served from a Bonnot system of coal-dust transportation, and the waste gases were discharged into waste-heat boilers.

Jan 1, 1932