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Discussion of the paper of E. C. HARDER, presented at the Pittsburgh meeting, October, 1914, and printed in Bulletin No. 94, October, 1914, pp. 2573 to 2586. I. C. WHITE, Morgantown, W. Va.-I have seen some of the great iron-ore deposits described in this paper. -One of these in the State of Minas Geraes appears to be an immense mountain of iron ore about 2,000 ft. in height. All over its surface from bottom to top may be seen large masses of rich iron ore, varying in weight from a few pounds to several tons, and from all that one can judge without exploitation, the quantity of available ore is certainly very large in this particular mountain. Whether it will prove a mere surface deposit or shell, like the famous Iron Mountain of Missouri, is for future exploration to determine. The question of transportation is the main factor in determining the availability for exportation of these Brazilian iron ores. There is no coal in Brazil that can be manufactured into coke without expensive previous treatment, since the best of the raw coal in the States of Rio Grande do Sul, Santa Catharina, and Parana, contains about 35 per cent. of ash, of which about 6 per cent. is sulphur, and coal of this composition cannot be utilized in iron smelting without purification. When I was chief of the Brazilian Coal Commission in 1904 to 1906, I had a cargo of this coal shipped to Balk, Germany, and treated in the great coal-testing plant of the Humboldt Engineering Works, located just across the Rhine from Cologne. It was found that by crushing and washing the Brazilian coal, it yielded 33 per cent. of briquetting coal, containing only 10 to 12 per cent. of ash (of which 1 per cent. was sulphur), and 42 per cent. of slack coal, with 25 per cent. of ash and low in sulphur, so that about 33 per cent. of the Brazilian coal could be converted into coke of fair quality, as shown by the following average of three analyses, using air-dried coal, of briquets made from the Barro Branco coal bed, State of Santa Catharina: Moisture 1.56 Volatile matter 31.66 Fixed carbon 56.73 Ash : 10.05 Total 100.00 Sulphur 1.34 Phosphorus 0.003 B.t.u 13,395

Jan 4, 1915

Application of Kutter's Formula to Gases Discussion of paper by F.-ERNEST BRACKETT, presented at the Pittsburgh Meeting and issued, as Pamphlet No. 1578-A-F, with MINING AND METALLURGY, June. 1926. C. S. WITHERELL, New York, N. Y..(written discussion).-There is no reason to doubt that the relationship between the rate of, flow and. the impelling force of all fluids can be expressed by a general typical equation that takes cognizance of all relevant factors such as density, viscosity (or its reciprocal, mobility) and nature of channel-walls. Most fluids that are commonly conveyed by flow in confined channels are so highly mobile that they may be considered non-viscous, hence for these fluids the factor of viscosity does not need to appear in the equation. Water is the outstanding example of this class of fluids and its dynamic behavior has been so thoroughly investigated that proven formulas pertaining thereto, be they rational or empirical, would naturally serve as prototypes for the other non-viscous fluids. As non-viscous fluids can be classed all gases and vapors, most unsaturated aqueous solutions, gasoline, alcohol, etc. Viscous fluids comprise those that have a sluggish flow such as most oils, tar, molasses, etc., the' high viscosity of which is due to shearing resistance between molecules, a force that must betaken into account in figuring the flow of fluids of this class.

Jan 10, 1926

By A. Q. Tool

THE necessity of accurate temperature measurements in the glass-making industries is today being much more widely appreciated than in the past. The introduction of the modern simplified and perfected pyrometric methods in connection with exact regulation of furnace temperatures has caused a marked improvement in the glass product with a quickened rate of production. An example of the processes in which much improvement has been and still can be made is that of annealing or heat-treating the glass. This is one of the most delicate processes in glass manufacture and one that requires a most careful furnace control. The heat treatment is undertaken to decrease the possibility of breakage and, in glass for fine optical instruments, to prevent serious warping of accurately ground and polished surfaces and to make the glass more uniform throughout to the passage of light waves. These objects are accomplished by removing all the harmful stresses that exist in a piece of glass when it has been cooled too quickly or unevenly. Such stresses exist, for example, after it has been pressed, cast, or otherwise worked. Thus the process of annealing consists of heating the glass evenly to the temperature at which it softens just enough to relieve these stresses in a reasonable time and then cooling slowly and uniformly until the glass hardens again. Accordingly, the things that must be investigated and determined in order to anneal glass without loss of time are, the annealing temperature, the time that the glass should be held at this temperature while the stresses relax, and the quickest cooling procedure that will give satisfactory results. After these characteristics of the glass are known the problem is one of pyrometry and temperature control entirely. In cases when it is known that a glass article will be required to withstand some definite type of heat or mechanical shock it is often possible, by a proper heat treatment, to produce such a distribution of the stresses in the glass that it will be enabled to resist these shocks more effectively.

Jan 9, 1919

By J. H. Wiggins

Granting that about 600,000,000 bbl. of light oil will be produced in the United States this year and taking the Bureau of Mines' statement that 71/2 per cent. of the total crude production will be lost before the finished gasoline is shipped from the refinery, the volumetric evaporation will be 45,000,000 bbl. of the cream of the gasoline. This is a ConseNative figure and is equivalent to 1,890,000,000 gal. The real value of this liquid is at least 150 per cent. of the value of an equal volume of motor fuel. At only 10 c. per gal., the value lost is $189,000,000; at 15 e. per gal. the loss is $283,000,000. If 750,000,000 bbl. of light and heavy oil are produced here this year and the average price per barrel is $1.333, the gross return to producers will be $1,000,000,000 and the net returns about $200,000,000, if the cost of production is only $1 per barrel. Thus, the evaporation bill is about 20 per cent. of the gross income and is equal to the net income of the crude-oil producers. Two other comparisons with popular phases of the petroleum industry will help give an adequate conception of the evaporation problem. These are: cost of preventing evaporation compared to cost of cracked gasoline and volume of gasoline evaporated compared to volume of gasoline manufactured from natural gas. When gasoline is manufactured from heavy oils by the cracking process, there are two important divisions of the total cost of the product: the manufacturing cost, such as plant cost, operation, maintenance, etc., and the cost of the barrel of heavy oil, from which the cracked gasoline is made. In preventing evaporation loss the cost first mentioned enters into the total cost, but the second cost is eliminated; that is, no charge is necessary for stock from which to manufacture the saving. A detailed analysis of these two costs on a large scale shows that the net income from a dollar spent in preventing evaporation loss from the lease through the refinery is twice the net income from a dollar spent in cracking. Of

Jan 1, 1924

By Howard S. Bryant

Kansas maintained its fourth position on the list of all oil-producing states, for the ninth consecutive year. Total crude-oil production during 1935, as reported by the Oil & Gas Journal, was 53,364,446 bbl. on 97 per rent tank table calculations. This represented an increase of 17 per cent over the production in 1934, which had been the all-time peak of production in Kansas up to that time. Many of the 51 new discoveries of the year, listed in Table 2, did not have a pipe line outlet until about January, 1936; therefore did not contribute to the 1935 production of the state. The potential of all wells in Kansas at the end of the year was 998,-000 bbl. per day, and the daily allowable was 143,000 bbl. per day, showing proration to the extent of 14 per cent of capacity, under the rules of the State Corporation Commission. Several important new pipe lines were built into western Kansas by extending older lines from east to northwest, providing additional outlets for new crude-oil production, and increasing the service facilities from the older oil fields. The crude-oil price level remained unchanged throughout 1935 as it did in 1934, the price of Kansas 36" gravity crude being quoted at $1 per barrel. However, on Jan. 9, 1936, the price of this gravity oil was raised to $1.10 per barrel. Following the trend of the past several years, drilling activity was largely in western Kansas, and showed a still farther westward push from last year. A relatively high percentage of successful wildcat wells at a relatively shallow drilling depth, combined with the expiration of leased acreage assembled before the depression, caused the rapid exploration and development campaign, begun in 1934, to continue. This has caused the opening of more new fields in 1935 than during any previous year in the history of oil production in Kansas. A summary of the results of drilling in western Kansas is given in Table 2. Eastern Kansas had considerable drilling, showed six new fields or extensions of oil fields, but in the limited space of this paper such developments cannot be described.

Jan 1, 1936

By H. B. C. Nitze

A description of some of the magnetic ore-deposits in this region should be of interest to the mining and metallurgical public, inasmuch as very little has been said or written concerning them. I refer to the magnetite deposits of Franklin and Henry counties, Va., and of Stokes county, N. C. These deposits remained comparatively unexplored until recently, when the construction of the Roanoke & Southern R. R. through this territory has called attention to them, by furnishing the means of transportation for the ores. It is true that the ores have long been known, at least locally, and were smelted in catalan forges and old-fashioned, cold-blast charcoal-furnaces long before and during the late war. At the present time, however, the old workings are caved in, filled up and over-grown to such an extent that, as a rule, but little can be learned from them. No prospecting of any consequence has been done, and as my time was too limited and the territory to be examined too extensive to permit additional openings of a more satisfactory nature to be made, the incormpleteness of some of the data I have to offer (notably, those referring to the absolute width of the veins) will be pardoned. It will hardly be necessary to say that this ore-bearing formation belongs to the Archaean, or Eozoic age, the usually occurring rocks being schist, shale, gneiss, granite, sandstone and quartzite. The stratigraphy is, as a rule, quite regular (excepting in the Danbury section, Stokes county, N. C.), the general strike being northeast and southwest, and the dip nearly vertical. The country is gently roll-

Jan 1, 1892

By M. E. Wadsworth, P. H. Yu, C. K. Hansen

A study of the rate of dissc5lution of chalcopyrite (CuFeS2) in acidic solutions under oxygen overpressures was carried out by measuring the rate of formation of cupric ions in solution. Effects of temperature, oxygen partial pressure, surface area, and concentration of sulfuric acid were evaluated. A sized batch of chalcopyrite was leached in the temperature range of 125° to 175°C and in the pressure range of 75 to 400 psi of oxygen. In 0.5 N H2SO4 all products of reaction went into solution except for trace amounts of elemental sulfur. The dissolution of chalcopyrite followed linear kinetics and was essentially independent of hydrogen ion concentration for H2S04 concentrations between 0.2 and 0.5 N. The oxygen dependence indicated adsorption approaching limiting values with increasing oxygen pressure. The linear mechanism was explained in terms of steady-state adsorption of oxygen at the chalcopyrite surface followed by a surface reaction. The enthalpy of activation for adsorption of oxygen was found to be approximately 33 kcal per mole. An activation enthalpy of approximately 9 kcal per mole was observed for the surface reaction. Charge transfer reactions are not rate controlling in the process.

Jan 1, 1973

By George W. Riter

OUR mineral-land laws need revising so as to provide definite title at the outset to the mineral deposits within any definite piece of land. The laws as they now stand, especially those applicable to lodes, breed uncertainty as to rights of possession prior to patent; and to my mind this is the worst feature of all, worse even than the apex bugbear. It is now almost impossible for anybody to tell-with certainty what mineral rights exist within any area that is not covered by patent, or whether any valid rights exist at all. Our system is unique in permitting individuals to appropriate and exploit mineral lands of the public domain without notice of any kind to the Federal government, and to relinquish them without any ceremony at all. The result is a clouded record that cannot be cleared up until each claimant is put to some sort of final proof. In order to accomplish this, new Federal legislation will be required. The requirements for a mineral survey and the proceedings for patent have always been cumbersome and expensive; and perhaps out of regard for the poor claim owner, who can ill afford the outlay for that sort of thing, the law does not require him to go. through it unless he chooses to do so. Consequently, every active mining district has become encumbered with tangled groups of doubtful or conflicting locations, whose rights and boundaries, when any valuable ore is found, must usually be determined by lawsuits that are as expensive and as distressing as the stakes are high. So deeply has litigation entered into our mining system that a claim whose rights have never been disputed would probably be set down offhand, by $miner of the old school, as of no value. Think of the litigation over rights of possession on the Com-stock lode—12 leading companies involved 'in an aggregate of 245 suits within a period of less than eight years! Ambiguous local records; the chance of erroneously placed or obliterated monuments; doubt as to the sufficient performance of the statutory annual labor; uncertainty as to prior conflicting or overlapping locations; anxiety as to the changing attitude of the Department of the Interior and the Forest Service—such considerations as these make an unpatented mining claim an unclean thing in the eyes of possible investors. Is it any wonder that they keep themselvesand their money at a safe distance,

Jan 1, 1915

By Herbert Clark Hoover, Lou Henry Hoover

SINCE I have written of the varied work of pre- paring the ores, I will now write of the various methods of smelting them. Although those who bum, roast and calcinea the ore, take from it something which is mixed or combined with the metals ; and those who crush it with stamps take away much ; and those who wash, screen and sort it, take away still more; yet they cannot remove all which conceals the metal from the eye and renders it crude and unformed. Wherefore smelting is necessary, for by this means earths, solidified juices, and stones are separated from the metals so that they obtain their proper colour and become pure, and may be of great use to mankind in many ways. When the ore is smelted, those things which were mixed with the metal before it was melted are driven forth, because the metal is perfected by fire in this manner. Since metalliferous ores differ greatly amongst themselves, first as to the metals which they contain, then as to the quantity of the metal which is in them, and then by the fact that some are rapidly melted by fire and others slowly, there are, therefore, many methods of smelting. Constant practice has taught the

Jan 1, 1950

By G. Sachs, S. I. Liu

Introduction In a previous investigation on the effects of repeated strains of large magnitude on the aluminum alloy 24 ST, it was found that the reduction in ductility by straining in tension was partially restored by a subsequent compression.&apos; As illustrated by the dashed line in Fig I,$ the ductility (e~) retained after prestraining in tension by a certain amount (el) and measured in a subsequent tension test is represented by a straight line sloping down under 4s°. If a compression of the same magnitude as the first tension is inserted (€2 = — €1) between prestraining and final testing in tension, such a "balanced" tension-compression cycle yields a ductility considerably higher than that present after prestraining in tension only. The results of these tests can be correlated with those of an investigation on the effects of prestraining in compression.~ As also shown in Fig I, the ductility in subsequent tensile tests decreased with com- pression, at a rate considerably slower than that after prestraining in tension. The above discussed testing conditions can be considered as special cases of a general straining cycle, consisting of first, straining in tension by an amount el, subsequently straining in compression by an amount e2, and finally determining the retained &apos;ductility, e,, in a tensile test. Prestraining in tension is then represented by el > o and e2 = o. Prestraining in compression is given by e~ = o and e~ < o. Balanced cyclic straining is defined by the condition el > o and cz = — 61. In order to obtain further information on the effects of straining cycles consisting of tension and subsequent compression, further tests were made, varying both the tension strain, el, and the compression strain, e2, within extreme limits; el varied between 0.06 and 0.28 and e2 between — 0.008 and —0.h approximately. Apparently, such tests have not been previously performed. They revealed phenomena which have not been recognized to date, The results of the investigation are herewith reported, without attempting to correlate them with internal processes within the metal structure. However, in order to assist in an analysis of this type, the results have been represented in various manners. In addition, further test data on the effects of prestraining by compression were provided by using specimens of various contours (notched specimens) in the sub-

Jan 1, 1949

By N. M. Raju, B. Singh

The paper seeks to present the results of experimentation in room and pillar stopes with different ground conditions to determine the safe working span. In the experimental stopes, ground movement was monitored with gradual widening of the room span. The field measurements included closure between the stope walls and the extent of ground movement in the hangwall using borehole extensometers. hock bolting was used as an exclusive support system which enabled introduction of scrapers for improving productivity. In one nine, phosphate bed, 3 to 3.5 m thick dipping at 45O and overlaid by weak laminated shale, was worked at shallow depth of cover. h the experimental panel, five s topes were worked with spans varying from 5.5 to 7 m. In the second mine, the chalcopyrite orebody up to 6 m in thickness dipping at 25 - 30" was worked at a depth of 1100 m. The hangwall consisted of fairly competent schistose rocks and therefore 10 to 15 m wide spans could be experimented. The field measurements confirmed that in the phosphate mine with weak shale roof, 7 m span could be safely worked with subsequent caving of the bolted roof. In the copper mine, 15 m span could be worked and the stopes required subsequent backfilling for better ground control.

Jan 1, 1983

By Carl Henrich

I have read with particular interest that portion of the discussion by Anton Eilers referring to the high-lime (and also high-alumina) slags made by August Raht in 1881, while smelting the Horn Silver ores at Franklin, Utah. The two analyses of such slags, furnished by Mr. Raht to Mr. Eilers are: (a) Not determined in this analysis. (b) Not given in Mr. Eilers&apos; paper. Oxygen ratio, A1 as base. I. 0 in acid: O in base:: 18.1:18.9:: 0.96:1 11. 0 in acid :O in base:: 18.7:17.5::1.06:1 Average: 18.4:18.15=1.01:l Oxygen ratio, AI as acid. I. O in acid: O in base: :23.2:13.8:: 1.68:1 11. O in acid: O in base::23.1:13.5:: 1.76:1 Average: 23.15:13.4 = 1.73:l By assigning to alumina the the of a base, Mr. Eilers deduces the formula 3Feo.-2SiOa + 4Cao.2SiO². The nearest approach to a simple formula expressing the average composition of these slags, which I can figure, is 9RO.Al2O3.6SiO2. Allowing a ratio of 4Feo : 5Cao, we have for this formula:

Jan 1, 1917

By Yoshinao Nakada

In many experiments involving electropolishing such as electropolishing during deformation and electrothinning of deformed metals for electron microscopy, it is usually assumed that the specimen temperature is the same as the temperature of the polishing bath. In order to test this assumption, the interior temperature of aluminum single and polycrystals was measured while they were being electropolished. Specimens were 1/4 by 1/4 by 6 in. and were of 99.99 pct purity. A small hole 1 in. deep was drilled axially at one end of the specimen so that a copper-constantan thermocouple could be inserted. The electropolishing solution was 4 parts methanol (reagent grade) and 1 part perchloric acid (70 pct). The electropolishing was performed using an apparatus shown in Fig. 1. The electropolishing solution was stirred by a motor-driven stirrer and was cooled to —5°C with a mixture of methanol and dry ice. Electrolyte temperature was measured and remained at -5°C during the electropolishing. Current density of 0.3 amp per sq. cm was used. When the current was turned on, after about a 5-sec delay, the temperature began to rise rapidly until it reached 65°C. In order to determine whether the temperature measured was localized, the thermal expansion of the specimen was meas-

Jan 1, 1965

By V. F. Hollister, M. Bernstein

The Copaquire porphyry copper deposit lies in an island of pre-Upper Tertiary rocks surrounded by Quaternary and Upper Tertiary formations. The pre-Upper Tertiary appears to be a horst block in a typical basin-range setting. Major right lateral faults have been mapped within the range from Chuquicamata north to Copaquire. All of the major porphyry copper deposits known in the block (e.g., Quebrada Blanca, El Abra, Chuquicamata, and Copaquire) are on or are very close to one of these major right lateral shears. In the Copaquire district, an epizonal igneous complex with diorite, quartz diorite, quartz monzonite, and intrusive dacite (in that intrusive order) invade folded Jurassic shale. Mineralization appears spatially and temporally associated with the quartz monzonite porphyry and dacite. Alteration zoning shows two separate core phyllic (quartz-sericite-pyrite) zones within one large argillic (clay-pyrite) zone. A propylitic (chlorite) zone is peripheral to the argillic zone. No potassic zone has been recognized yet at the surface. The intrusive petrology together with the phyllic, argilic, and propylitic alteration zoning as well as the chalcopyrite-molybdenite ore mineralogy characterize this deposit as being typical of the Lowell and Guilbert model. Copper and molybdenum minerals appear to be most strongly developed in the phyllic zone, in either a breccia or a zone of veinlets and stockwork which trend dominantly northeast, conjugate to the district&apos;s largest fault, the Sulfato fault. The setting is basically similar to that found in some other porphyry copper deposits in this block, in that the ore body is a zone of veinlets which appear to be genetically related to movement on a major north-south trending right lateral fault. The presence of the major fault in each deposit, and the speculative hypothesis that paleo-subduction zone operated at the time of mineralization, suggest the possibility that mineralization took place when a major fault permitted escape to the surface of cal-calkalic magma generated in a subduction zone as proposed by Ericksen. A hypothesis such as that proposed by Ericksen explains the near linearity of porphyry copper deposits in Chile, since the source of calc-alkalic magma would exist at about the same distance from a paleo-trench throughout the length of the paleo-subduction zone.

Jan 1, 1976

NEW MEMBERS The following list comprises the names of those persons who became members during the period June 10, 1919, to July 10, 1919. ANDERSON, JOHN EDWARD, Min. Engr., Lehigh Valley Coal Co., 121 N. Laurel St., Hazleton, Pa. BENBOW, B. L., Mgr., Cleveland Wire Division, National Lamp Works, General Electric Co., 1770 E. 45th St., Cleveland, Ohio. BLAIR, CHARLES S., Geol., Tennessee Coal, Iron & R. R. Co., Birmingham, Ala. BOLAND, FRED L., Chief Draftsman, Mine Dept., Chile Exploration Co., Chuquicamata, Chile, South America. COLLIER, OTTO L., Civil & Min. Engr., Secretary, Ernest M. Merrill Engrg. Co., Mullens, Wyoming Co., W. Va. DELAMATER, GEORGE RICHMOND, Asst. Supt:, By-product. Coke Oven Dept., Steelton Plant, Bethlehem Steel Co., Steelton, Pa. DOELL, WILLIAM R Chief Engr., Mahuomen Iron .Co., Crosby, Minn. ENDO, SHINZO 365 Komagome Shimmeicho, Hongo, Tokio, Japan. EVANS, CHARLES E., Chief Draftsman, American Smelt. & Refin. Co., Murray, Utah. FISCHER, OSCAR A 62S First National Bank Bldg., Denver, Colo. FISHER, GEORGE KINGSBURY, Met. Engr 47 Baker St., Saranac Lake, N. Y. FRAZEE, VERNE, Min. Engr Moweaqua, Ill. FURNICHI, ROKUZO, Supt. of Min. Dept., Besshi Copper Mine, Baron Sumitomo Co. Ehime Japan

Jan 8, 1919

By Edgar Trask

EACH branch of engineering seems to depend on the cooperation and contribution of some other branches to enable it to produce more efficient methods and appliances for man to use. The purpose of this paper is to show approximately the gain in efficiency of self-propelled merchant ships when steel of greater elasticity is substituted for mild steel in some of the strength members and alu-minum alloy is substituted in some of the parts where strength is not essential. The new steel will have some greater strength and a much greater elastic limit in the as-rolled condition, and must be readily weld-able under ordinary conditions of shipbuilding. Naturally, its cost may be more than mild steel, but if the demand is great that excess cost may be reduced to an amount that will make its use more economical than that of the present mild steel. There appears to be a well defined axiom in engineering today that to use the least power to carry a given load the weight of the carrier must be reduced to a minimum. This minimum must be, of course, consistent with the necessary strength, rigidity and durability and it must not be attained at an excessive cost where the fixed charges of the carrier will exceed the savings in, operating the motive power. Recent railroad equipment is a notable example of this, and in these trains alloy steels and aluminum together with less weight per horsepower of the power plant are reducing the weight of the carrier and hence the total power required for moving the paying load. Before considering the application of these metals to shipbuilding, it is well to explain some of the fundamentals of ship design.

Jan 1, 1936

By J. L. W. Birkinbine

This paper is a discussion of a part of the mineral wealth of the States of Oaxaca and Paebla, Mexico. It does not refer to the precious metals, sonie mines of which, in these States, are said to have been worked before the advent of the Spanish conquistadores in the sixteenth century, as my purpose is to invite attention to the exploration of deposits of coal and iron-ores in the Mixteca region. The prominence given to coal is warranted by the great effect of the scarcity of fuel upon the industrial development of Mexico. Under the progressive administration of President Porfirio Diaz, the Republic has made wonderful advances in the past three decades; and this progress would have been greater but for the limitations imposed by expensive fuel. In the spring of 1906 I was detailed by the Birkinbine Engineering Offices, of Philadelphia, to accompany A. B. Adams, of New York, in a reconnoissance of reported deposits of iron-ores in the State of Oaxaca. The result of this expedition was the formation, in 1907, of the Oaxaca Iron & Coal Co., of which Mr. Adams became, and has remained, President and General Manager, and I have spent the past three years as Chief Engineer of this company in Mexico, principally in western Oaxaca, where field-headquarters were established. GEOGRAPHY AND POPULATION. Although the geographical and topographical features of the Republic of Mexico are well known, few realize that the majority of its population is domiciled in the States which immediately surround the capital city of Mexico, including the Federal District, Mexico, Tlaxcala, Morelos, Puebla,

Jan 1, 1911

By D. R. Walker, M. C. Shaw

THE laws of comminution of Kick and Rittinger have been debated for many years. Certain data obtained from ball mill and drop tests are found to be in approximate agreement with Rittinger&apos;s law while other data would seem to support Kick&apos;s law. In all these tests the energy required to produce a wide variety of particle sizes has been studied. Surface area has also been measured with considerable difficulty, at first because it was thought that the energy associated with crushing was that required to create new surface, later because of precedent and because a more fundamental variable was unknown. Tests made with the machine shop type of grinding process show that normally brittle materials that are usually crushed can behave like the more ductile metals. Brittleness is then a relative property largely dependent on specimen size and stress state. The machine grinding operation offers a convenient means for studying the comminution of materials in which the important size variable retains its identity. The energy required to grind a certain volume of material is shown to be strongly de- pendent on size. Kick&apos;s law is found to hold very well for particles below 1 micron in size, while Rittinger&apos;s law holds approximately in the comminution of larger particles. While a physical origin of Kick&apos;s law is established in terms of the theoretical strength of materials having a perfect lattice structure, there is found to be no physical basis for Rittinger&apos;s law.

Jan 3, 1954

By Morris Cohen

It has been known for several years that in certain age-hardenable alloys precipitation of finely divided particles occurs simultaneously with the changes in physical properties; while, in other alloys, these changes take place prior to, or without any, precipitation. The silver-copper alloys are generally considered to be the classical example of the first group, and the aluminum-copper alloys (duralumin) are typical of the second group. The two types of aging are explained by the precipilation theory and the knot theory respectively.‡ It is well recognized now that these theories do not conflict with each other; the one used for a given aging system depends upon which way the alloy in question happens to age-harden. However, previous work on the aluminum-copper al1oys1,2 has shown that if the aging temperature is raised sufficiently the hardening will be accompanied by actual precipitation. In fact, it is quite probable that all of the so-called knot-hardening alloys will harden by precipitation at elevated temperatures. Therefore, a combination of the knot and precipitation theories is necessary to give a complete picture of the agehardening of these alloys, and indicates that knot formation and precipitation are not independent processes. To test the generality of this concept, it is necessary to show that the alloys that commonly harden by precipitation will harden prior to precipitation if the aging temperature is sufficiently lowered. For this reason, it would be well to carefully re-examine the aging characteristics of the silver-copper alloys at aging temperatures somewhat below those used by previous investigators. If hardening can be detected prior to precipitation in these alloys, it will lend great weight to the idea that knot forma-

Jan 1, 1937

By H. C. Miller

The energy stored in the compressed natural gas absorbed in or otherwise associated with the oil in reservoir sands is usually the most important factor in oil recovery. It is recognized that hydrostatic pressure and gravity may aid materially in the drainage of oil, but in the early life of the majority of fields the principal source of propulsive energy is the expansive force of the gas associated with the oil. Since gas is admittedly the most important factor in the production of oil, its control so as to produce the maximum amount of oil with the minimum amount of gas will be reflected in increased oil recovery from reservoir sands. Controlling the gas means regulating its expansion so that the velocity of flow of oil through the channels in the reservoir sands is neither so great that frictional resistance becomes excessive nor so slow that the gas, because it can travel more rapidly than oil through the irregular passageways in the sands, will by-pass and reach the well without. doing useful work in bringing oil from the sands. Oil and gas flow from the reservoir sands to the well because of differences in pressure. The rate of flow is dependent upon the differential pressures existing in the sands and in the well. By altering the amount of back-pressure maintained on the well this differential pressure can be regulated and changed from a maximum (well flowing "wide open") to a minimum when there will be no flow. Oil and gas flow through the irregular channels in reservoir sands at different rates mainly because of the fact that one is a liquid and the other a gas. Therefore, because oil and gas have different characteristics of flow, application of back-pressure, changes the rates of flow with relation to one another so that wide variations in gas-oil ratios are possible. Obviously, the formation gas energy will be utilized most efficiently when a unit of gas delivers the maximum amount of oil to the well. Determination of Necessary Back-pressure The amount of back-pressure that should be maintained against the producing sand in order that the minimum amount of gas will be produced with each barrel of oil can be determined only by actual field tests made

Jan 1, 1929