Search Documents

By E. Gilpin

The following notes may serve to bring before your Institute an idea of the iron-ore resources of Pictou County. Enough work has been done to permit an estimate to be formed of their quality and probable extent. As yet the systematic mining and smelting of ironore in Nora Scotia is confined to the operations of the Steel Company of Canada, in Colchester County. Although the locality I am about to describe appears, in many respects, well adapted to iron smelting, etc., no attempts have yet been made to begin work. Nora Scotian capital is more readily turned to lumbering, fishing, and shipping ventures; and such an investment appears equally foreign to the rest of the Dominion. I need not, however, go further into this part of the subject, and can only hope that my notes may prove serviceable as indicating a probable field for future development. The accompanying map shows the position of the harbor of Pictou relative to the coal and iron-ore fields, and to the railways which intersect them. The branch of the Intercolonial Railway, running from Truro to Pictou, forms the western boundary of the iron-ore district, which extends beyond the point where the New Glasgow and Cape Breton Railway crosses the French River. The iron-ore district may be roughly described as a triangle formed by the ore-outcrops and the two railways, the former making the base, and the latter the sides of the triangle, the apex resting on the coal-field at New Glasgow. The drainage of the country is toward the Gulf of St. Lawrence, through the Middle, East, Sutherland's, and French rivers; and the surface is undulatory, seldom exceeding two hundred feet above the sea-level, except in the district lying between Glengarry and the upper waters of the French and Sutherland's rivers, where a maximum height of about five hundred feet is reached at several points. Geologically speaking, the district embraces two divisions, the Carboniferous and the Silurian, the latter resting on strata provisionally considered to be of pre-Cambrian age. As no geological

Jan 1, 1886

By Archer E., Wheeler

Producing copper companies were active during 1941 owing to the national defense program the United States and the requirements of the friendly belligerent nation. This activity extended to the American owned properties in South America, the major part of whose product was taken by the Metals Reserve Co., a U.S. Government agency. Anaconda Copper Mining Co. is building a new converter plant at Anaconda, with four units of the Peirce-Smith type. The addition is being built adjacent to the reverberatory plant so as to avoid the necessity of hauling matte and slag. It is expected to be completed this year.

Jan 1, 1942

By R. Lee-Aston

HALLOWAY mine of Tennessee Copper Co. at Copperhill, Tenn., has been under development for several years. It has two shafts, the A shaft, 1336 ft deep from the surface to the 16 level, and the B shaft, lying 500 ft to the southeast and extending 1385 ft deep from the 10 level down to the 24 level. A section through the two shafts, Fig. 1, shows the development work entailed by the proposal and the area involved. The Problem: For operational reasons it was necessary to extend the B shaft from the 10 level to surface, and the pilot hole and raising method was chosen. This method had been used to extend the Company's Boyd manshaft from the 10 to the 14 level in 1954, but no satisfactory hole surveying method had been employed. In that instance, when the hole was located it was found to be about 8 ft from its calculated position. The success of this shaft extension method lies in the ability to keep the pilot hole within the proposed shaft diameter for nearly the entire length. The approximate 670 ft of extension distance in one hole was thought to be excessive because of deflection encountered locally in other core drilling. Since a connection between the two shafts, intermediate between the surface and the 10 level, would be required at some future date, the pilot hole drilling was done in two sections. This intermediate level was fixed at the 6 level and distances became 470 ft from surface to the 6 level and 230 ft from the 6 to the 10 level. A rock pentice of 25 ft was left temporarily in place just above the 10 level.

Jan 3, 1958

By Lawrence Addicks

Some three years ago the smelter connected with the Chrome, N. J., refinery of the United States Metals Refining Co. found itself embarrassed by constantly increasing piles of unsmelted blast-furnace flue dust. The charge was fine and 10 to 15 per cent. of it was blown over into the flue. Sulphur was at that time too scarce to make the sintering of the finer part of the charge attractive, and raw-ore smelting in a reverberatory with a partly oxidized charge was not to be thought of. A great many schemes were considered, including leaching, blowing into the converters, and briquetting, the problem finally narrowing down to blast roasting and nodulizing. It was found by experiment that blast roasting would not yield a satisfactory sinter without the addition of coke dust or sulphide fines to augment the fuel value of the flue dust, and on this account, together with the low first cost of a kiln, the latter was decided upon. A couple of tons of flue dust were tried out in the experimental kiln in the laboratory at Yorktown, Va., of J. H. Payne, who acted as consulting engineer in this connection. This kiln was approximately 2 ft. in diameter and 20 ft. long and was fired with fuel oil. A run of several hours yielded excellent nodules. The ki1n showed no tendency to build in and form "nose rings" and gave a fuel consumption of 50 gal, of oil per ton of flue dust. There was no indication of any stack loss. The roasting was strongly oxidizing. A study of what full-size kilns were doing on cement clinker and on nodulizing pyrites cinder indicated that a 60 by 6 ft. kiln would certainly not consume over half of the oil per ton of flue dust shown on the test and as fuel oil at that time was selling around 2 1/2 c. per gallon it was decided to let it go at that. A 60 by 6 ft. kiln was decided on, as that size is standard in cement practice, although fast being replaced by much larger ones with their greater fuel economy, and as it fitted in the building space available. A 6-in. brick lining brought the net diameter down to 5 ft. The inclination

Jan 1, 1915

By S. Fisher Morris

THE New River coal-field embraces that portion of the Appalachian coal formation which lies on the waters of the New River, principally in Fayette and Raleigh counties, West Virginia, covering a strip of territory about forty miles in length along the line of the Chesapeake and Ohio Railroad from Quinnimont to Kanawha Falls, where the New River empties into the Kanawha, the railroad following the banks of the river the whole distance. (See map.) Between Kanawha Falls and the Valley of the Ohio lies the great Kanawha region, and these two coal-fields possess a greater variety of coal than can be found in any other portion of the country, enabling them to furnish the best fuels for any of the various demands of manufacture or domestic use, the Kanawha region possessing many varieties of gas, hard splint, and cannel coal, and the New River region bituminous and semi-bituminous, steam and coking coal. The New River, in its westward course towards the Kanawha, has cut its way entirely through the Seral conglomerate or No. XII of the Pennsylvania Reports, the Umbral red shales of No. XI appearing at the foot of the mountains at the eastern end of the region at Quinnimont, one of the upper ledges of the Conglomerate forming the summits; while at the western end, at Kanawha Falls, the top of the Conglomerate is nearly down to the level of the river, a portion of the " Lower Productive Measures" forming the greater portion of the mountains. These mountains rise abruptly from the banks of the river to a height of from 800 to 1200 feet, leaving only here and there narrow strips of bottom land, a few acres in extent; and as the measures consist principally of hard sandstones, shales, and conglomerates lying in a nearly horizontal position, the mountain-sides are very precipitous, with many long and high cliffs, which, with the great height of the mountains, give the country a very rugged appearance. Along the sides of these mountains fronting on the New River and its many tributaries there are exposed the outcroppings of several veins of bituminous and, semi-bituminous coal, varying in thickness from a few inches to over four feet, five of them being workable, or

Jan 1, 1880

By Nathaniel Arbiter, Arthur F. Taggart

THE chemical reaction occurring in collection of nonmetallic minerals with amine-type collectors was early postulated by students of flotation phenomena to be metathesis between the mineral and the collector, involving exchange between the amine-bearing (aminium) ion and the cation of the mineral, and formation at the mineral surface of an oriented film of the amine salt of the mineral anion. Qualitative evidence of exchange has been obtained on several occasions at Columbia. Thus 1000 c.c. of a solution containing 495 mg. of laurylamine hydrochloride was shaken 17 min. with 100 grams of barite and ground in a porcelain mill to pass a 200-mesh screen; the mixture was then set aside for 48 hr. Filtrate therefrom analyzed 476 mg. per liter of laurylamine hydrochloride. There was no substantial loss of chloride ion (78.4 mg. per liter in the original; 74 in the filtrate). No successful analyses were concluded for barium ion. Earlier, confessedly rough work with scheelite indicated a solution gain in Ca++ equivalent to about one-half the aminium ion lost. Real quantitative proof of the exchange, in the form of an established stoichiometric balance, is unknown to the authors. The data of the present paper, however, obtained from experiments designed on the basis of the exchange hypothesis, constitute strong evidence of its truth, and at the same time point the way to economic utilization of the expensive nitrogen-bearing collectors in concentration of the low-priced nonmetallic minerals. The basic postulate underlying the experiments performed was that, if the collecting reaction is of the type [R+ + Y- + MX =± RX + M+ + Y¬] where R = aminium ion, Y = the anion of the amine salt, and M and X are, respectively, the cation and anion of the mineral, the reaction should obey qualitatively the implications of the massaction and solubility-product laws. This is to say that coating and collection should be aided by the addition to the solution of either ion (R+ or X-) of the collector-coating compound, and hindered by the addition of either of the ions M+ or Y-. Experimental work comprised determination of (1) the relative solubilities of the laurylammonium salts of a variety of nonmetallic-mineral anions; and (2) the contact angles1 of various minerals in solutions containing different concentrations of the postulated controlling ions. Semiquantitative flotation tests were run with barite as checks on the diagnostic character of the contact angles. The amine

Jan 1, 1944

By N. A. Gokcen, John Chipman

D. C. Hilty (Union Carbide and Carbon Research Laboratories, Niagara Falls, N. Y.)—This paper is a very nicely detailed analysis of a difficult problem. I would like to point out that the results that Mr. Crafts and I published a few years ago had no reference to activity, or anything else of a similar nature; our results were strictly empirical. It is quite gratifying that we now have a case where results involving activity coefficients and results derived from direct observations on actual steel melts are practically identical. When two different laboratories, working from two entirely different approaches, come out with results in such good agreement in their major significance, that is an achievement. It is something that was not possible 15 or 20 years ago. There is one question I would like to ask Dr. Chip-man. It has to do with a very minor point of disagreement in these results. When we reported the kink in the Si-O solubility curve I think you may recall that it came at the different temperature levels at about the order of 0.015 to 0.03 pct 0 and 0.03 to 0.07 pct Si—we also pointed out that we had difficulty in obtaining data at that level, although we finally did get some. I note in going through the data for the present paper, that there are no samples in those particular silicon and oxygen ranges. I wonder if that was purely accidental or was there a reason for it. D. E. Babcock (Republic Steel Corp., Youngstown, Ohio)—Mr. Hilty, do you have any explanation for that discrepancy between Dr. Chipman's curve and your own Mr. Hilty—Our explanation for it at that time was that for some reason our system probably was not in true equilibrium with SiO, that is, in equilibrium with the silica crucible at that level. We did observe, however, that that was the level at which both the metal and the slag became saturated with SiO,. On the average, in studying inclusion formation in small ingots permitted to solidify normally from the molten state, we observed pure silica inclusions at silicon contents over about 0.05 pct and FeO type inclusions at silicon

Jan 1, 1953

By S. Frederick Ravitz

JUDGING from the inquiries that are constantly being received by the Utah Engineering Experiment Station as to the "Why," so to speak, of the flotation process of concentrating minerals, it occurred to me that perhaps a brief statement of the more important theories might interest those who have not followed the technical literature. Like many other industrial processes, flotation has hitherto been developed on an almost purely empirical basis, with relatively little practical contribution from the fundamental chemistry and physics on which the phenomena are based. In fact, its development by the trial - and - error method has been perfected to such a high state that it is becoming generally thought that further important advances can be brought about only by a thorough understanding of the actual mechanism of the process. Natur¬ally, such a complicated process has brought forth numerous theories, most of which have failed to withstand the test of time. It is significant that no theory has yet been advanced which is universally accepted.

Jan 1, 1933

Ira B. Joralemon, one of the world's most noted mining geologists, died last year at the age of 91. "His long professional career," says Donald H. McLaughlin, chairman of the executive committee at Homestake Mining Co., "covered an epoch in the history of mining that was unique in its opportunities and achievements," adding that many mining companies (Bunker Hill, Bralorne Mining, Copper Range, Anaconda, Newmont, Phelps Dodge, Homestake, etc.) greatly benefited from Joralemon's experience and wisdom.

Jan 12, 1976

By Eugene McAuliffe

It is not possible to include in this paper, limited as it is in scope, the many diverse steps toward the reduction of mine accidents that are taken in the mines that produce the nation's coal. Every coal-producing state has enacted laws covering proper mining practices, and the major portion of these are directly related to the safety of the mine employees. The United States Bureau of Mines, the American Institute of Mining and Metallurgical Engineers, The American Mining Congress, a number of national, regional and state organizations, as well as the coal technical press, have covered time and time again all of the '(do" and "don't" phases of mine operation that bear on the important question of mine and employee safety. Within the past 15 years The Union Pacific Coal Co, has attempted to put into practice in its mines in southern Wyoming these many good recommendations, finding some value in all, and yet, to secure substantial results, the management found it necessary to resort in the end to what might be referred to as i'extra-territorial" methods. It is the writer's purpose to show in this paper that marked and even extraordinary betterment, can be brought about when employer and employee work together with due sincerity. In presenting our own experience, one that has been duplicated in so far as results are concerned on numerous other properties, no theory of perfection of management exists; on the other hand, our organization feels that as long as our record of accidents remains as shown by even our latest and best performance we still have far to go. Safety work in some form has been carried on in and about the mining properties of The Union Pacific Coal Co. since the first mine was opened at the now long-abandoned town of Carbon, Wyo., in 1868. On June 30, 1903, an explosion and subsequent mine fire occurred in mine No. 1 at Hanna, taking 169 lives, and a second explosion occurred in the same mine on March 28, 1908, in which 59 additional lives were lost. Looking back with impartiality on the causes leading up to these two unfortunate disasters, we can only conclude that shooting from the solid, the absence of adequate ventilation, rock dusting, the use of water at the face to allay

Jan 1, 1938

By James C. Bayles

The ideal pressure-tube is obviously the one which combines the greatest strength with the least weight of material consistent with the uses for which it is designed or employed. The inside of the pipe is the first concern of the engineer. It should be cylindrical, smooth, and of the requisite capacity for the purpose in view. It should be in lengths as great as can be oonveniently handled, so that the couplings may be as few as possible. With the walls of the tube the engineer has no further occasion to concern himself than to make sure they are adequate to carry the internal and external pressures to which they will be subjected. It is as true of a pipe as of a truss, that when it is strong enough to give the requisite factor of safety, nothing is gained by having it stronger. Anything more than this means dead weight, which has to be paid for many times, first as material, and again and again in the costs of transportation and handling, until it reaches its place in the trench or on supports. In use it must be and remain tight against all leakage, and must sustain whatever is placed over or upon it, or suspended from it, without deformation or injury. Finally, in addition to meeting all the immediate requirements of service, it must possess qualities of durability which warrant a reasonable expectation of a long life of usefulness. The wise engineer no longer regards it as reasonable to depend upon mere bulk of its own material for the protection of a metal as readily impaired or destroyed by oxidation as iron or steel. The metal must have a coating which will be and remain impervious and indestructible. When all these conditions are met, we have as near an approach to the ideal tube as can be attained with the materials now available for their manufacture. Steel wed constructively, to the best advantage, meets these requirements most perfectly. Gold alone would do it better. If we search through the whole list of metals and alloys we find nothing available which so perfectly meets the requirements as a pipe material as steel. Mr. Hamilton Smith, Jr., in a paper on the expedients adopted on

Jan 1, 1891

By Eugene McAuliffe

It is not possible to include in this paper, limited as it is in scope, the many diverse steps toward the reduction of mine accidents that are taken in the mines that produce the nation's coal. Every coal-producing state has enacted laws covering proper mining practices, and the major portion of these are directly related to the safety of the mine employees. The United States Bureau of Mines, the American Institute of Mining and Metallurgical Engineers, The American Mining Congress, a number of national, regional and state organizations, as well as the coal technical press, have covered time and time again all of the '(do" and "don't" phases of mine operation that bear on the important question of mine and employee safety. Within the past 15 years The Union Pacific Coal Co, has attempted to put into practice in its mines in southern Wyoming these many good recommendations, finding some value in all, and yet, to secure substantial results, the management found it necessary to resort in the end to what might be referred to as i'extra-territorial" methods. It is the writer's purpose to show in this paper that marked and even extraordinary betterment, can be brought about when employer and employee work together with due sincerity. In presenting our own experience, one that has been duplicated in so far as results are concerned on numerous other properties, no theory of perfection of management exists; on the other hand, our organization feels that as long as our record of accidents remains as shown by even our latest and best performance we still have far to go. Safety work in some form has been carried on in and about the mining properties of The Union Pacific Coal Co. since the first mine was opened at the now long-abandoned town of Carbon, Wyo., in 1868. On June 30, 1903, an explosion and subsequent mine fire occurred in mine No. 1 at Hanna, taking 169 lives, and a second explosion occurred in the same mine on March 28, 1908, in which 59 additional lives were lost. Looking back with impartiality on the causes leading up to these two unfortunate disasters, we can only conclude that shooting from the solid, the absence of adequate ventilation, rock dusting, the use of water at the face to allay

Jan 1, 1938

By Morris Muskat

ALTHOUGH the problem of well spacing is one of the most important involved in the production of oil, it must be considered at the present time as still subject to further development. The published literature on this question is so voluminous that we cannot enter here into a review of it, except to refer to the recent papers by L. L. Foley1 and E. A. Stephen-son,2 where other references are cited. However, a decisive and conclu-sive answer to the problem of well spacing in any general form does not seem to have been developed. And while we shall be unable to present the desired solution in the present paper, it is nevertheless felt that the material to be given here not only provides the physical ground work for the ultimate solution, but shows qualitatively the essential factors that enter the well-spacing problem. Field studies of the well-spacing problem, in which the ultimate recoveries from different fields with different well spacings have been compared, have generally suffered from the lack of knowledge as to the similarity of the inherent characteristics of the producing reservoirs being compared, such as the sand volumes, the sand porosities, the sand permeabilities, the original reservoir pressures, the presence or absence of gas caps, the presence or absence of effective water drives, and the economic limits of production rates at which the various fields were considered to have yielded their ultimate recoveries. Certainly no one who is evaluating originally the economic significance of any oil reservoir would deliberately ignore these phases of the problem. And it is equally certain that no one would reasonably expect the ultimate recoveries from two reservoirs, even with the same well spacing, to be identical regardless of these other factors. More reliable results might be expected from comparisons of the recoveries obtained from different leases with different well spacings, but producing from the same reservoir sand. Unfortunately, however, even conclusions for such studies may be subject to serious errors. The reason simply is that however much one may insist that an operator is entitled only to the oil immediately underneath his surface acreage he will nevertheless drain the surrounding properties as long as his reservoir

Jan 1, 1939

By William Metcalf

IT is the object of this paper to oppose unnecessary changes, and the introduction of new and confusing terms. From the earliest times of which we have any record on the subject, iron has been divided into general classes. Whether iron was first known in the form of wrought iron or of steel, is a matter of no importance; but at the time when cast iron first became a prominent article of commerce, wrought iron and steel were old products¬steel, at that time, being generally made from wrought iron by the process of cementation. As steel was then properly defined as iron containing more carbon than wrought iron, so cast iron was appropriately defined as iron containing more carbon than steel. Until the year 1776, when Huntsman first began the manufacture of a new kind of iron by melting wrought iron and steel in crucibles, the above definitions were all that could be desired. At first, probably, owing to imperfect appliances, only a highly carburized iron was melted in crucibles, and this led to its being called cast steel. If our ancestors had found a name for this material not involving the use of the word steel, we would have been saved the trouble of the present discussion. As the arts developed, new uses were found for steel, and the products of the crucible were varied, until at the present day it is quite common to find steel containing no more carbon than average wrought iron, and other steel containing nearly or quite as much carbon as some cast iron. All of these various products of the crucible have retained, or received, the name cast steel, usually abbreviated to the simple word steel, without causing any confusion among producers or consumers in regard to terms or their meaning. In 1855, twenty-one years ago, the Bessemer process was introduced ; this was followed in a few years by the Siemens-Martin process, and the products of both were at once, and have ever since been, called steel, from the fact that they were identical in chemical and physical properties with crucible cast steel. At the present time, then, we have three subdivisions of cast steel, viz.: Crucible cast steel, Bessemer cast steel, and Siemens-Martin,

Jan 1, 1877

By L. W. Casteel, E. A. Jones

MINING the lead deposits of Southeast east Missouri has reached a high stage of technical development dictated by the scattered occurrences of low-grade ore through favorable horizons in the Bonne Terre formation. The rock-breaking, handling, and related practices described here have evolved as the best way of mining these particular deposits. These methods are applied in the production of about 19,000 tons of lead ore per operating day from four mines in Southeast Missouri. Development drilling Drifts 10 ft wide and either 8 or 9 ft high are driven in this district on contract. Miners are guaranteed standard wages plus a bonus on the footage advanced, if earned. Labor, fuse, caps, wire, and dynamite used are charged against the contract. Normally the cycle of operations in drifting is performed by a two-man crew, a motor operator and a shovel operator who first load out the rock broken by the preceding shift. The drift crew then sets up two vertical column and mounts the drills. Cleveland HC-10's are used which have a steel lug integral with the cylinder for connection with the air feed. All drilling in drifts is wet. Air pressure is 85 to 100 lb at the face. From 28 to 32 holes are drilled per swing in a pyramid cut. Cut holes

Jan 1, 1947

By Christie A. Callender, Harry M. Dahl

The Hobson uranium deposit is located in Karnes County, Texas, along the prominent south Texas uranium trend. The uranium mineralization occurs in the Deweesville Sandstone of the Whitsett Formation of the Eocene Jackson Group. The host rock is a friable, fine-grained, well-sorted, highly porous and permeable sandstone interpreted to be an ancient beach deposit. The sandstone contains significant volcanic constituents and ranges in composition from arkosic to tuffaceous. Locally, the host sandstone contains hard, dense opal cement. Bentonitic shales underlie and overlie the mineralized sandstone unit. Geometrically, the Hobson uranium-bearing zone resembles an elongated roll front type deposit. Chemical uranium values compared with gamma ray equivalent uranium values indicate that the uranium has been dissolved from the updip side and precipitated on the down- dip side of the roll front. Details of the uranium mineralization were studied using thin section microscopy, autoradiography, x-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) techniques. The uranium mineralization occurs in the pores of the sandstone, as grain coatings and as replacement of sand-size and smaller grains. It is commonly associated with pyrite and other opaque minerals. Other favored hosts for uranium (other than pore openings) appear to be clay aggregates, altered rock and glass fragments, and carbonaceous plant debris. Aggregates of coffinite were identified by XRD and SEM/EDS analyses. Some uranium mineralization also appears to be dispersed and is postulated to be adsorbed on the clay and carbonaceous matter.

Jan 1, 1985

By WILLIAM E. NEWNAM

THE molding and loading of pig lead has, in the past, been accomplished mainly by the strong arm method and, as the pigs are usually loaded directly into the cars, it has been a hot and laborious task. Of late years it has been difficult to obtain men willing to perform such labor and the need has been felt for loading and molding machinery which would eliminate all manual handling of the hot pigs and which would be sufficiently compact to permit of installation in existing plants with little or no

Jan 1, 1924

By Graham Bright

THE rapid increase in reliability, the low cost f operation, the ready application of safety devices, and the growing availability of central-station power have made the question of installing a hoist of the electric type no longer debatable. Where adequate electric power is available, there are few cases where it would be advisable to install a steam or air hoist. The type of electrical equipment depends largely on the nature of the power supply, its capacity, and the form of the power contract under which power is purchased. In a large majority of cases, the available electric power is alternating current, three phase, 60 cycles. There is, however, considerable 25-cycle power in use; and in a few instances constant voltage direct current is the only power available for a small or an occasional medium-size hoist. Where a new hoist is to be installed, the designer of the mechanical parts can readily take care of the maximum stresses likely to be imposed by the' motor. Where the hoist is already installed and operated by steam or air and it is desired to substitute an electric motor for the engine, a careful check should be made to determine the advisability of using the old mechanical parts. In most cases it is better to install a complete new hoist than to attempt to use old mechanical parts. A steam engine has a definite maximum torque, which the hoist has been designed to withstand, while a motor may be able to deliver momentary torques beyond the strength of the mechanical parts of the hoist. The selection of the proper type of electrical equipment can only be made after complete information is obtained and certain calculations made to determine the capacities required. There are several methods used in making hoist calculations, but no matter what method is utilized a fair degree of familiarity with hoists and hoisting conditions is necessary before an intelligent analysis and proper selection can be made.

Jan 9, 1921

By C. W. Dunham

DESIGN of the structures for the Morenci Reduction Works involved many interesting problems. Naturally, the chief purpose of these structures is to house and support the equipment and other things necessary for or incidental to the conduct of production. hence most of the features of the design were developed to suit these particular conditions; however, several are so generally applicable as to warrant description.

Jan 1, 1942

By S. J. Hruska

Rate expressions for the formation of two-and three-dimensional nuclei on foreign substrates are developed, taking into account previously neglected contributions to the standard Gibbs free energy of formation of critical nuclei. The temperature dependence of critical super saturation data predicted using these expressions is in accord with data for cadmium on copper and sodium on CsCl. EXPERIMENTAL data on the heterogeneous nuclea-tion of metal crystals from the vapor phase1&apos;2 exhibit the temperature dependence predicted by a nucleation rate equation derived by Pound et al.3 In their treatment, the critical nuclei are visualized according to the Volmer4 model as cap-shaped (three-dimensional). Accordingly, it seems desirable to compare these data with a nucleation rate equation which is derived on the assumption of disk-shaped (two dimensional) nuclei. Further, Lothe and Pound5 have recently shown that the standard Gibbs free energy of formation of these critical nuclei contains a contribution which has heretofore been neglected. Thus it is necessary to re-examine these nucleation data using a rate equation which contains this contribution. The van&apos;t Hoff isotherm relates n(i), the concentration of nuclei of critical size i (i = number of atoms), to nil), the concentration of adsorbed single atoms: where standard Gibbs free energy of formation of critical nuclei given by is temperature insensitive and is the bulk free energy change/volume of transformed material], T = substrate temperature and k = Boltzmann&apos;s constant. Previously,3 was determined by considering only the contributions of bulk and surface free energies in transforming i atoms from the population nil) to a cluster of i atoms. It has been shown5 that this procedure does not take into account the free energy contribution arising from the multiplicity of sites, q, where the clusters can be situated. If this contribution, -kT In q/n(l),is added to iG3 [Note that this increases n(i) by a factor q/n(l).] Since the above does not affect the remaining terms in the rate expression of Pound et al., the details are referred to their paper. The resulting nucleation rate is If the experimental AGV and T values at some common value of are employed, a plot of vs T(ln C3/l + In p&apos;) should yield a straight line of slope k/B<p and intercept . The corresponding plots for / = 1 nucleus per sq cm sec and C3 = 1018 are shown in Figs. 1 and 2 for cadmium on copper1 and sodium on CsCl2 and the values of obtained therefrom are entered in Table I. It is apparent that the data yield reasonable straight lines with about the same scatter as found using the equation of Pound et al. When the configuration of minimum free energy for a nucleus is a circular monatomic layer, the standard free energy of formation is

Jan 1, 1963