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By W. A., Wasley

THE EL TIGRE MINE is a highgrade silver and gold producer located in the northern part of Sonora, Mexico. It has been worked continuously since 1903, producing 50,000.000 oz. of silver and returning handsome dividends. During 1930 and 1931 falling silver prices compelled the Tigre company to make representations before the Department of Labor in Mexico City showing the necessity for drastic reductions in wages and personnel. The delays in obtaining permission from the Federal Labor Board to make these readjustments caused the company to suffer considerable financial loss during those years. After the reduction in operations was finally effected, the Sonora state government headed by Señor Francisco Elias (former Governor, now Secretary of Agriculture) and Señor Rodolfo Elias Calles (present Governor and eldest son of Señor Plutarco Elias Calles, recently Secretary of War and former President of Mexico) have cooperated with the company to make continued operation possible by revising downward certain state taxes that would have been a factor in forcing the closing of this mine. Also, permission to change our workmen over to another system of mining was essential to continued operation.

Jan 1, 1933

By Lyon F. Terry

IN contemplating the prospects of natural gas being transported from the fields where it is produced to such distant points as Philadelphia, New Jersey, New York City, and New England, let us review the advance that natural gas has made and the projects currently scheduled for construction. This may give us a perspective of the point in the long-range development of the natural gas business in which we now find ourselves, and some basis for judging the further expansion of the industry. Authentic statistics of the total marketed production of natural gas in the United States have been compiled by the Bureau of Mines since the year 1906. The growth of the business is indicated by the following data on marketed production for each ten-year interval since 1906:

Jan 1, 1947

(Butte Meeting, August, 1913.) IN metallurgical circle it is. known widely, but somewhat vaguely, that the ease of reduction of metallic .oxides. depends largely on the way they have been prepared. It is likewise known that. different forms of carbon have different and greatly varying reducing powers. It is the purpose of, this paper to show somewhat more definitely and scientifically these facts. Sonic years ago the writer published an account of pyrometric determinations of the reduction temperature of zinc oxides variously prepared and of several kinds.1 In said paper it was shown that the temperature at which zinc oxide evolves zinc according to the equation, ZnO+C? Zn+CO depends upon the nature of -the two reacting bodies. The determinations bad a range of accuracy of from 2°to 6°C.,whereas differences were found to, amount to an extreme of 90° C. So the differences are real ones and must have a definite cause. The equation of boiling water, (H2 O)4 = 4 (H20) has a fixed temperature for? equilibrium of 100° C. at 760 mm. pressure. In general, all equations reacting in the liquid or the gaseous phase have well-defined constant physical conditions which govern the equilibrium point and reaction velocities.

Jan 7, 1913

By C. M. Young

THE safety lamp is the most common and convenient apparatus for detecting inflammable gases in mines, the presence of gas being shown by a blue flame, called the cap, if the wick has been lowered to suppress the luminous flame. The height of the cap increases with the proportion of gas and with the temperature of the lamp flame. Lamps of the Wolf type, the fuel of which is benzine, have a hotter flame than lamps in which vegetable oils are used, such as the Davy, and the Clanny, and are more sensitive than the latter and their many modifications. The Piehler alcohol lamp gives a still higher cap while the Clowes hydrogen lamp is most sensitive of all. While the effect of the temperature of the source of ignition is well known, the writer knows of no previous attempt to correlate the change of this temperature with change of the height of the cap produced. In order to determine the height of the cap at various temperatures, it was necessary to have a source of ignition the temperature of which could he accurately controlled over a considerable range. This condition was met by a coil of wire of high fusing point heated by an electric current controlled by a variable resistance. The use of a coil offered the further advantage of freedom from complications due to the flame of a burning fuel. Such a flame, being itself of variable height, would to some extent raise or lower the elevation of the base of the cap and therefore add to the difficulty of determining the height of the cap. Besides this, the presence of a small cap from the lamp fuel, commonly known as the "fuel cap, " would interfere with the observation of small gas caps. After some experiment, a coil was made of platinum wire, No. 26, diameter 0.016 in. The coil was 17/64 in. (6.746 mm.) in outside diameter and had eight full turns in a length of ½ in. (12.69 mm.). This was connected to an electric circuit through an adjustable resistance, as shown in

Jan 8, 1919

C. Edward Stafford, Chester, Pa.:—Doring all my business life, I have been engaged in the manufacture of Bessemer and open-hearth steels, but, during my long connection with the Shoenberger Steel Co. of Pittsburg, I had some experience in the manufacture of high-grade puddled iron for horseshoes, and in making, by Dr. Otto Wuth's process, extremely pure, low-phosphorus puddled blooms (analyzing from 0.005 to 0.01 per cent. of phosphorus and sulphur), which were melted with low-phosphorus pig-iron in acid open-hearth furnaces, to make extra locomotive fire-box steel. I have also seen the Danks puddlers in operation at different times and places, notably where they were most successful, at the Otis Steel Works, Cleveland, Ohio; then under the management of our friend, Mr. S. T. Wellman. These Danks blooms were made solely for open-hearth melting-stock, to which they were well adapted. (The unavoidable presence of bits of ore-fix imbedded in the mass of the metal always prevents the profitable manufacture of merchant iron from Danks' blooms.) With the experience just described, I was to some degree in position to value fairly the means, methods and results of Mr. Roe's mechanical puddling from the metallurgical or technical and economic points of view, when given an opportunity by Mr. Roe to see his puddling-furnace or machine in operation in Pottstown, Pa. Briefly, the furnace, with water-cooled bottom, is rectangular in plan, about 20 by 8 ft. in the clear, suspended by trunnions at the middle of the long sides, at a height of 17 or 18 ft. above the general level. The oscillation (65" each way from the vertical) is accomplished by geared segments (attached to the downward-projecting side or trunnion-plates) with which engage pinions driven by a reversing engine. The whole section

Jan 1, 1906

By A. C. Dorenfeld

In most mineral enterprises, what is the progress, and shift in responsibilities, as the young engineer advances in the corporation? You are all familiar with the normal pattern-in mine production from level boss, to shift boss, to superintendent to manager; in milling from test engineer, to shift boss, to foreman, to superintendent and then manager; in engineering from surveying on to Chief Engineer; and all then aspire to the corporation presidency. Note the shift-from purely technical jobs, say in the first five to ten years in the profession, to administrative positions for 30 to 40 years. What is the average preparation given to mineral engineering students, who can look forward to about 30 years of administrative work? From the catalogs of 21 institutions, offering 36 curricula of four years length, in mining and/or metallurgy, requiring the equivalent of about 150 to 160 semesterhours for graduation, the following results were obtained: Average number of semester hours of economics, 3 hr. Range of requirements, 0 to 8 hr. Thirteen curricula do not require any economics. Accounting and business law, average: 1 semester hr, 26 curricula do not require business law or accounting.

Jan 2, 1955

By N. Schapiro, R. J. Gray, G. D. Coe

A petrographic and chemical investigation was conducted to determine the occurrence and distribution of the organic and inorganic forms of sulfur in various size and specific gravity fractions of a high volatile, A-rank, Pittsburgh seam coal. The investigation was conducted to aid in the resolution of the problem of how metallurgical coke of lower sulfur content can be produced from high sulfur coals. The Pittsburgh raw coal contains about 2.4% S in two dominant forms: pyritic and organic. Pyritic sulfur constitutes about 57% of the total sulfur in the raw coal and occurs in macroscopic and microscopic-size particles. A plant cleaning process mechanically separates between 50 and 60% of the pyritic sulfur, mainly the macroscopic particles. The organic sulfur constitutes 41% of the total sulfur in the raw coal and 55% of the sulfur in the washed coal. Thus, organic sulfur is not reduced by physical methods of separation. Organic sulfur occurs in all the coal entities, but in general, increases as the exinoid content of the coal increases. In this study, it was found that carbonizing certain selected low gravity coal fractions containing an average of 0.45% pyritic sulfur and 1.01% organic sulfur produced cokes containing an average of 0.22% pyritic sulfur and 0.91% organic sulfur. However, the organic sulfur in the coke is probably derived in part from the heating of pyrite in the presence of carbon. Thus, the total sulfur in the coal carbonized is the most important factor affecting the sulfur content of the coke produced. Concentration of microscopic pyritic and organic sulfur in the middling-type coal indicates the necessity for rejecting as much of this material as is economically feasible. Most of the sulfur introduced into the blast furnace originates from the coke. Although the sulfur content of the hot metal can be controlled by the addition of flux, the flux used restricts the productivity of the furnace by displacing ore and requires first to be smelted; therefore, low sulfur coke is highly desirable. Since the sulfur content of coke is dependent upon the sulfur content of the coals from which the coke is produced, low sulfur coals are required to produce low sulfur coke. In the western Pennsylvania area, large quantities of good coking coal are available from the Pittsburgh seam, but this coal unfortunately contains relatively large quantities of sulfur. To provide information that might be useful in reducing the sulfur content of this coal in the cleaning process, an investigation was conducted to determine the physical and chemical forms in which this sulfur occurs and with what petrographic components it might be associated. The Pittsburgh seam coal, like most other coals, contains two dominant forms of sulfur: one occurs as the minerals pyrite and/or marcasite and is referred to as pyritic sulfur; the other is combined with the coal substance and is called organic sulfur. Pyritic sulfur is amenable to physical methods of separation, whereas organic sulfur is not. Pyritic sulfur particles must be freed from the surrounding coal if they are to be removed in the washing process. Generally, this requires crushing; the required degree of crushing being a function of the size and distribution of the pyrite. The present investigation was conducted to 1) determine the size, distribution and association of sulfur-bearing minerals in the coal and 2) to determine whether the organic sulfur has a preferential association with specific coal entities. If a preferential association exists, this knowledge may be useful in devising a method for organic sulfur reduction. In addition, a study was made to determine the extent to which pyritic and organic forms of sulfur in the coal contribute to the sulfur in the coke produced from this coal. A representative 3%-ton sample of raw coal was crushed to —3 in. and screened into square-mesh sizes: 3 to 1 in., 1 to % in., % to % in., % in. to 10 mesh, 10 to 35 mesh, and 35 to 200 mesh. Separate samples of the -200-mesh fraction and the all-size composite were also collected. Each size fraction (except the -200 mesh) was fractionated on heavy liquids of the following specific gravities: 1.280, 1.300, 1.325, 1.350, 1.375, 1.400, 1.425, 1.450,

Jan 1, 1963

J. E. Stead, Middlesborough, England (communication to the author): Prof. Howe's valuable paper on cast-iron brings forward most prominently the correct explanation of the part played by combined carbon in pearlite and cementite, in determining the strength and hardness of cast-iron. On a previous occasioil I have shown that castings made by melting a white Cleveland iron and glazed iron, one containing 1.5 and the other from 4 to 5 per cent. of silicon, and each about 3 per cent. of carbon, were stronger than those made of ordinary foundry-iron; the difference in the final castings being a differ-

Jan 1, 1902

Gus C. Henning, New York City: In taking up the discussion of these specifications it is necessary that I give definitions of what I understand under the term " Specifications." There may be three kinds, viz.: (1) Specifications in general; (2) Standard Specifications; (3) Standard International Specifications. 1. A Specification is a document used in commerce which should clearly define the qualities of material to be supplied by the producer, the tests which shall be applied for their determination, and the methods which shall be applied for the purpose of determining that the entire product shall possess such qualities, properties and finish as are desired. The terms used in such document must be applied in accordance with their strict technical definitions as used by those most conversant with them, and the language should be of such accuracy that there can be but a single interpretation of each and every clause. A specification is a part of a contract, and should be legally perfect and accurate. Inaccuracy of definition and dic-

Jan 1, 1903

Discussion -of the paper of I. N. KNAPP, presented at the New York meeting, February, 1915, and printed in Bulletin No. 96, December, 1914, pp. 2783 to 2793. A. C. LANE, Tufts College, Mass.-Is there any noticeable effect in drilling against salt water? Mr. Knapp says that the mud settles very quickly when brine is added-. What is the effect when you strike a strong salt water ill boring? I. N. KNAPP.-You are supposed to have enough mud pressure in your well to keep the saltwater out. I have drilled against what I knew to be 80 ft. head of water, and hot water too at 99.5°; this water did not show until the well was bailed and the mud pressure reduced. HENRY Louis, Newcastle-upon-Tyne, England (communication to the Secretary*).-Mr. Knapp may be interested to learn that the use of mud in drilling through porous strata is much older than lie appears to be aware of. It has been used notably by Honigmann for boring shafts in Holland and in some of the adjoining portions of Germany. At the Oranien Nassau colliery, shafts about 12 ft. in diameter and 425 ft. deep were sunk in. this way-namely, by boring with a rotary borer, a thick mud puddle being pumped into the shaft, so as to maintain a pressure in the shaft greater than the hydrostatic pressure in the surrounding loose sands and thus keeping the sides of the shaft from collapsing. He will find references to this method in Das Abbohren von Schächten; Handbuch der Ingenieurwissenshaften, p. 134, also in the Transactions of the Institution of Mining Engineers, vol. xiii (1896-97), p. 155. The process appears to have been employed even before 1895, though I cannot give the exact date when it was first used.

Jan 5, 1915

By William Glenn

The taking of proper samples of crude ores seems to he less thoroughly understood, or less carefully practiced, than its impor tance requires. We all know how often we encounter the reports of very accurate assays and analyses, the weight of which as evidence wholly depends on the method of obtaining the sample, and is very probably nil, because there has been no proper sampling. Pissages might be cited from technical books, and from current technical literature (all the work of writers whom we delight to honor) to show that even among high scientific authorities there is too little acquaintance with the practical art of the sampler. There is no metallurgical or chemical establishment which does not frequently receive samples truly representing nothing. They consist usually of bits of ore, or what not, selected because they are worse or better than the average of what they are meant to represent. And they are worthless, no matter who made the selection. Where conscious choice is permitted to enter into the operation, a fair sample will not result, unless by a miracle. The work of sampling is often looked upon as within the realm of boys and of pensioners only. At least, though the manual labor be left to subordinates, the principles on which it is conducted and the safeguards with which it is surrounded are not unworthy of the study of experts; and experts should he ready to teach these principles and enforce them in practice. For exact sampling is the indispensable first step towards learning the value of any boxful, carload or shipload of ore. I propose to give a simple account of the method of sampling by hand, such as I have always pursued. There is nothing new about it. So far as I know, it is the immemorial old method, as old at least as Cornish copper-mining. Perhaps my fellow-members in the Institute may suggest improvements in it. If not, it will constitute a record in our Transactions to which laymen and beginners may be referred.

Jan 1, 1892

By S. H. Williston

IT not often that bore hole surveys can be checked by actual. civil engineering methods. A recent Arizona survey was checked by normal surveying methods and the comparison of the results should be of value to both oil and mining men. During the summer of 1948 the Phelps-Dodge Corporation, at its Copper Queen property near Bis-bee, Ariz., drilled a 1245 ft, 8 in. diarn, churn drillhole in a mineralized area and cased part of it, intending to use it to transfer mill tailings for stope fill. The hole, as frequently occurs, was not straight, and, in endeavoring to locate the bottom in the underground workings, they found no evidence of the hole at the underground coordinates directly below the surface location. The noise of the drilling tools was reasonably clear, but the direction of sound was uncertain. Preliminary tests with available equipment were not successful in locating the bottom of the hole. Because of the mineralized character of the area and the fact there was some casing in the hole, any magnetic method of well surveying would give results of doubtful value. Sperry-Sun gyroscopic well-surveying instruments were finally used to locate the bottom of the hole. These instruments consist of a gyroscope to determine azimuth and either a pendulum or bubble inclino-meter. A multiple shot camera photographs both instruments on a single film and superimposes the photograph of a watch. Coordination of depth with time at the surface makes it possible to select the corresponding picture for any depth. After making several runs of the empty instrument housing from the top of the hole to the bottom to make sure there were no obstructions in the hole, three surveys on wire line were completed during the afternoon. The three surveys, in which readings were taken at different points in the hole on each survey, were computed and gave the following locations of the bottom of the hole in relation to the surface collar: survey No. 1—24.92 N, 30.30 W; survey No. 2—24.24 N, 31.11 W; survey No. 3—26.54 N, 27.72 W. Then the data from the three surveys were combined into a single set of calculations which gave a location for the bottom of the hole: combined surveys—24.27 N, 30.16 W. (Fig. 1.) Immediately upon the determination of the coordinates at the bottom of the hole, a drift on the 1300 ft level was started toward the indicated loca- tion some 38 ft northwest of the coordinates of the surface location, The bottom of the hole was located within the drift round in which it was expected, and the transit survey run to the actual location of the hole indicated N 27.18, W 29.71. This shows a discrepancy between the well survey and the transit survey of 0.45 ft in the westerly direction and 2.91 ft in the northerly direction. All surveys, both gyroscopic and transit, fell well within the width of an ordinary drift. While this is satisfactory for almost any and all mining requirements, a theoretical examination was made as to reasons for the discrepancy. A study of the course of the hole indicates that considerable right turn or spiral existed, and in all probability the surveying instrument was pulled out of alignment while traversing the turn by approximately 0.05 ft at the top and another 0.05 ft in the opposite direction at the bottom of the instrument. If such an allowance were to be made, the survey calculations would almost exactly correspond with those determined by transit. This sort of discrepancy would be minimized by the use of stabilizing guides. It is unfortunate that physical laws probably effectively prevent the use of gyroscopic instruments in EX and AX diamond drill holes. The directive power of a gyroscope falls off inversely at some rate between the third power and the sixth power of the diameter. Present instruments can be run in casing 53/4 in. ID or over and might be adapted to somewhat smaller diameters, but the difficulty of reducing these diameters to 11/4 in. or 2 in. is almost insurmountable at the present time. Acknowledgment The author wishes to express his appreciation to the Phelps-Dodge Corporation for permission to publish this article, and to the Operating and Engineering Departments for their cooperation on the survey; also to Donald Hering, of the Sperry-Sun Well Surveying Co., who actually made the survey and calculated the results.

Jan 1, 1951

By S. H. Williston

IT not often that bore hole surveys can be checked by actual. civil engineering methods. A recent Arizona survey was checked by normal surveying methods and the comparison of the results should be of value to both oil and mining men. During the summer of 1948 the Phelps-Dodge Corporation, at its Copper Queen property near Bis-bee, Ariz., drilled a 1245 ft, 8 in. diarn, churn drillhole in a mineralized area and cased part of it, intending to use it to transfer mill tailings for stope fill. The hole, as frequently occurs, was not straight, and, in endeavoring to locate the bottom in the underground workings, they found no evidence of the hole at the underground coordinates directly below the surface location. The noise of the drilling tools was reasonably clear, but the direction of sound was uncertain. Preliminary tests with available equipment were not successful in locating the bottom of the hole. Because of the mineralized character of the area and the fact there was some casing in the hole, any magnetic method of well surveying would give results of doubtful value. Sperry-Sun gyroscopic well-surveying instruments were finally used to locate the bottom of the hole. These instruments consist of a gyroscope to determine azimuth and either a pendulum or bubble inclino-meter. A multiple shot camera photographs both instruments on a single film and superimposes the photograph of a watch. Coordination of depth with time at the surface makes it possible to select the corresponding picture for any depth. After making several runs of the empty instrument housing from the top of the hole to the bottom to make sure there were no obstructions in the hole, three surveys on wire line were completed during the afternoon. The three surveys, in which readings were taken at different points in the hole on each survey, were computed and gave the following locations of the bottom of the hole in relation to the surface collar: survey No. 1—24.92 N, 30.30 W; survey No. 2—24.24 N, 31.11 W; survey No. 3—26.54 N, 27.72 W. Then the data from the three surveys were combined into a single set of calculations which gave a location for the bottom of the hole: combined surveys—24.27 N, 30.16 W. (Fig. 1.) Immediately upon the determination of the coordinates at the bottom of the hole, a drift on the 1300 ft level was started toward the indicated loca- tion some 38 ft northwest of the coordinates of the surface location, The bottom of the hole was located within the drift round in which it was expected, and the transit survey run to the actual location of the hole indicated N 27.18, W 29.71. This shows a discrepancy between the well survey and the transit survey of 0.45 ft in the westerly direction and 2.91 ft in the northerly direction. All surveys, both gyroscopic and transit, fell well within the width of an ordinary drift. While this is satisfactory for almost any and all mining requirements, a theoretical examination was made as to reasons for the discrepancy. A study of the course of the hole indicates that considerable right turn or spiral existed, and in all probability the surveying instrument was pulled out of alignment while traversing the turn by approximately 0.05 ft at the top and another 0.05 ft in the opposite direction at the bottom of the instrument. If such an allowance were to be made, the survey calculations would almost exactly correspond with those determined by transit. This sort of discrepancy would be minimized by the use of stabilizing guides. It is unfortunate that physical laws probably effectively prevent the use of gyroscopic instruments in EX and AX diamond drill holes. The directive power of a gyroscope falls off inversely at some rate between the third power and the sixth power of the diameter. Present instruments can be run in casing 53/4 in. ID or over and might be adapted to somewhat smaller diameters, but the difficulty of reducing these diameters to 11/4 in. or 2 in. is almost insurmountable at the present time. Acknowledgment The author wishes to express his appreciation to the Phelps-Dodge Corporation for permission to publish this article, and to the Operating and Engineering Departments for their cooperation on the survey; also to Donald Hering, of the Sperry-Sun Well Surveying Co., who actually made the survey and calculated the results.

Jan 1, 1951

By Roland Kammel

For electrolytic recovery of silver from dilute aqueous solutions improved mass transfer is necessary to achieve favourable current efficiencies and high space-time yields. The many cell designs proposed for this application can be divided into two different groups: cells from which the silver must be redissolved and cells from which the deposit can be reclaimed as a metal. Introduction Electrolytic silver recovery methods have proven advantageous under technical and economic aspects for the treatment of rinse water, still rinses and spent silver solutions in the electroplating and surface finishing industry, of exhausted fixing baths from photographic processing, bleed electrolytes from silver refining processes and leach liquors. Examples of the compositions of typical dilute silver solutions are listed in Table I.

Jan 1, 1984

By Clarence P. Linville

(Pittsburg Meeting, March, 1910.) IT is recognized that, in all metallurgical operations, the greatest possible uniformity in all conditions is essential to the best results. It is the constant aim of metallurgists to secure this uniformity, and their success in this respect has been in many cases the cause of great advances in the metallurgical processes themselves. Of all such processes, the production of pig-iron in the modern blast-furnace is perhaps the most complex and the most difficult of control. Notwithstanding the great progress of recent years, there is still great difficulty in obtaining anything like uniform conditions and results in the manufacture of pig-iron. The reason is not far to seek. The ores vary in composition and physical properties, often carrying a varying amount of gangue material, unevenly distributed The coke may vary in composition, cell-structure, moisture, hardness, and other properties. The blast, the weight of which far exceeds that of any other constituent, varies in its moisture-content and consequently in its chemical composition ; and its temperature, by reason of the method of heating, is not uniform, but, besides varying from time to time with atmospheric and other outside conditions, has a maximum and minimum for every changing of stoves. Now, with regard to these variations, the modern demand for uniformity has been greatly aided. Chemical analysis has made it possible to select ores so that the composition of the charge can be kept fairly constant; coal may be obtained from a given field, and coked in the same kind of ovens under conditions which . make the fuel practically uniform ; the Gayley

Mar 1, 1910

By B. F. Tillson, C. M. Haight

I. General Remarks..........................723 1. Location............................723 2. Characteristics of the Orebody..................725 (a) Mineralogical (b) Shape, Strike, Dip, Size, Etc. (1) Ore (2) Country Rock 3. Historical Sketch........................725 11. Mining Method..........................726 1. Outline of Methods Now in Operation............... 726 (a) Stopes (b) Fill . (c) Pillars (d) Slices (e) Transportation (f) Miscellaneous 111. Mining Operations........................727 1. Shaft..............................727 (a) Sinking (b) Dimensions and Equipment, Sketches (1) Size, Inclination. Direction, Etc. (2) Timbering (3) Stations (4) Track (5) Hoisting Equipment (a) Skips (b) Engines and Ropes (c) Idlers (d) Man Cars (6) Loading Pockets (a) Operating Figures (7) Headframe

Jan 1, 1918

By R. W. Smith

It is well known that certain silicates such as the feldspars and beryl can be readily floated from quartz at a low pH value using a long chain cationic collector in the presence of a fluoride.1-3 However, the mechanism whereby the fluoride activates feldspars and beryl is not known. Indeed, only a few authors have even speculated about possible mechanisms.1,3,4 As a first approach to the problem, it is perhaps best to look closely at the interesting character of hydrofluoric acid and how it dissolves silica and silicic acid. Hydrofluoric acid, unlike hydrochloric acid, is a weak acid with a dissociation constant of about 3.53 x 10-4 at 25°C.5 The reason for the weak acidic character of HF lies in the very small size of the fluoride ion.6 The pKa value is 3.45 which means that at pH 3.45 half the HF is present in molecular form and half in ionic form. The anion present is probably HF2.-6 At pH values below the pKa value, molecular concentration increases rapidly at the expense of the HF2- anion. It is known that HF readily attacks glass, silicates, quartz and silicic acid. The equation usually cited pertaining to the first step in HF attack of silica is6-'

Jan 1, 1965

By Ralph H. Sweetser

BENEFICIATION of iron ores from the blast-furnace point of view means more than the usual enrichment of the iron contents by the removal of a large part of the clay, carbonic acid gas, silica, or moisture of the natural ore; it includes all these, but it also embraces several other mechanical .processes made , necessary by the exacting requirements of present-day blast-furnace practice. The increasing use of iron- bearing by-products, to as much as a third or more of the total ore burden, has introduced still another series of processes for improving the blast-furnace ore burden. As we look back over the past three decades of blast- furnace practice 'in. this country, we see that many of the blast-furnace troubles were directly due to lack of proper preparation of the iron ore burden,, and we realize that beneficiation in one form or another would have remedied the trouble. This was particularly true in the smelting of magnetic iron ores, where run-of- mine ore included such big lumps of 'magnetite along with rich fines that the furnace operations were greatly retarded and control of the furnace such as is usual today, was completely unknown.

Jan 1, 1930

By H. C. Babbitt

The Effect of Arsenic.—A question involving the temperature of precipitation of ammonium phospho-molybdate, which was brought to my attention some time ago, led to the following experiment :*

Jan 1, 1893

By James T. Waber, Allen C. Larson, Karl Gschneidner, Margaret Y. Prince

The original graphical method proposed by Darken and Gurry for predicting which elements are soluble in a given element was slightly modified and was used to predict terminal solubilities in 1455 known binary combinations. it was found that the modified Darken and Gurry method had a reliability of 61.7 pct in predicting extensive solid solubility (greater than 5 at. pct) and of 84.8pct in predicting limited solid solubility (less than 5 at. pct), an over-all reliability percentage of 76.6. Using the same experimental data, it was found that using only the simple Hume-Rothery size-effect criterion was 50.1 pct reliable in predicting extensive solid solubility, only slightly better than a purely random choice. and 90.3 pct reliable for predicting limited solid solubility, an over-all reliability percentage of 67.6. THE first rational rules for determining a priori whether two metals are not freely soluble in the solid state were announced by Hume-Rothery and coworkers.1,2 These well-known rules have been accorded a special place in metallurgical literature. Since the "electronegative" and "relative valence effect" rules of Hume-Rothery were only qualitative in nature it was difficult to use them in a quantitative analysis. The next major step was made by Darken and gurry3 and apparently went unexplored for a number of years. They prepared graphs illustrating the influence of both electronegativity and size difference on the solubility of elements in silver, magnesium, and aluminum, and they drew elliptical figures, whose maximum width was ±15 pct of the solvent radius and the maximum height was ±0.4 electronegativity units. The purpose of the present paper is to assess and compare the effectiveness of using the simple size-factor and the Darken-Gurry criteria to predict which elements will be soluble and insoluble in a given solute. In 1957, waber4 prepared Darken-Gurry plots for determining the solutes that were likely to be soluble in 6 and plutonium and introduced an inner ellipse as an aid to determining which elements should be soluble to a considerable extent. As illustrated in Fig. 1, the major axis of the outer ellipse corresponded to ±0.4 electronegativity units (OD) while the minor axis corresponded to ±15 pct of the radius of the solvent phase (OB). This simultaneous "action" of the two Hume-Rothery criteria was used to indicate which elements would have little or no solubility in the host lattice, namely those elements whose points lay outside this ellipse. An inner ellipse, "centered" over the same point of the solvent was drawn with ±0.2 electronegativity units (OC) and ±8 pct (OA) as the major and minor axes. Solutes with points lying within the inner ellipse were expected to be capable of forming extensive solid solutions with the host element. Use of this method of applying the earlier Hume-Rothery criteria was moderately successful for plutonium. For 6-phase plutonium, only one element out of the eight predicted to be extensively soluble was known to be almost insoluble, and of the sixteen elements predicted to have more restricted solubility, five were known to be essentially insoluble. The success of discerning solubility in the E phase by this method was comparable. One prediction made on the basis of this analysis was that the heavier rare earth metals, such as holmium, erbium, and thulium, should be soluble in the 6 phase, whereas the lighter rare earth elements, such as lanthanum or

Jan 1, 1963