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By J. D. Doherty

A. R. POWELL*—Mr. Doherty has outlined in a most thorough manner valid arguments for the development of an industry in this country making syn. thetic liquid fuels from coal. No thoughtful person will dispute the statement that it is essential to carry on fundamental and applied research and acquire engineering "know-how" by the erection and operation of two or three large plants in the near future. Considerations of national security indicate that this should be done, irrespective of any temporary present surplus of natural petroleum. It is the belief of the discusser and of many others interested in coal technology that our energy picture of the future will include an increasing utilization of coal directly, without any conversion to liquid fuel, as a source of energy. A fact that is sometimes forgotten is that petroleum fuels have often been cheaper than coal in many locations and over long periods of time, and this price factor has been of great importance in expanding the use of petroleum fuels at the expense of coal. Synthetic liquid fuel made from coal must necessarily be several times as costly as the coal from which it is made, and this fact alone will have a profound effect on the future energy pattern of our country. This complete change in the economic relationship between solid and liquid fuels will lead to the substitution of coal itself for many uses now supplied by the relatively cheap petroleum fuels. From the standpoint of conservation of our natural resources, the substitution of coal itself for liquid fuels wherever possible when the age of synthetic liquid fuel arrives is also logical. At least 50 pct of the energy of coal is lost during conversion to liquid fuel. Nor is this com-pensated for by a higher utilization effi-ciency of the liquid fuel in most cases. For example, modern steam-boiler plants can operate at equal fuel efficiencies with either coal or fuel oil.

Jan 1, 1950

By E. C. Houston

The phosphate ores mined in middle Tennessee typically consist of granular rock phosphate particles disseminated in a clayey matrix. In the TVA plant near Columbia, Tenn., the phosphate ore is mined, made into a slurry with the addition of a small amount of sodium hydroxide as dispersant, and treated in a hydroseparator to remove minus 10 micron material. The hydro-separator underflow, comprising a rough concentrate, is transported by pipeline to the plant; the hydro-separator overflow, comprising a tailing, is flocculated by addition of calcium sulphate and is discharged to settling ponds at a rate of about 1400 gpm. Sedimentation in the ponds produces a clarified effluent, which may be recycled for use as process water or discharged to surface drainage. This method of tailing treatment is not entirely satisfactory since poor sedimentation characteristics of the tailing result in poor ultimate utilization of pond storage volume.

Jan 1, 1949

By George E. Roberts

THE gains of society from the state of primitive conditions in the past to the standard of living which prevails in the advanced countries today have been accomplished mainly by the increasing productive capacity of the population under the leadership and services of the engineer. Without improvements in the arts and industries the growth of population tends to place succeeding generations always at a disadvantage. In this country we have been exploiting with reckless prodigality a wealth of soil and minerals and timber that has been in preparation for thousands of years. We know that the prices of all national products have been advancing, and were on a rising scale even before the phenomenal increases resulting from the war. Over against this depletion of natural wealth we have the influence of improvements made in the methods of production and distribution-and the accumulation of wealth in the form of productive equipment. The net result of these opposing influences determines whether society moves forward or backward.

Jan 1, 1926

By THOMAS G. FEAR

THE COAL DIVISION started its share of the annual meeting Monday morning with a study of coal classi fication. A. C. Fieldner was in the chair. The report of the tellers of the ballot for division chairman, stating that Thomas G. Fear had been elected to that office, was read by M. D. Cooper. Mr. Fear acknowledged the honor in a few words. In reviewing the history of the Coal Classification Committee the chairman pointed out that this was its third symposium, the last previous one having been held at the 1930 Annual Meeting. Throughout its work the com¬mittee has had the active cooperation of the Canadian workers who are interested in the subject which should result in a uniform scheme of classification in Canada and the United States. F. E. Lathe, of the National Research Council, Ottawa, abstracted the first two papers of the session entitled "Determination of the Alkali-Soluble Ulmins in Coal," by Edgar Stansfield and K. C. Gilbart, and "Moisture Determination for Coal Classification," by the same authors. The third paper "Condition of Water in Coals of Various Ranks"' was presented by its author, A. W. Gauger. Written discussions of these papers were presented by H. C. Porter and Gilbert H. Cady. In the oral discussion which followed, W. T. Thom, Jr., brought out the advisability of considering age as a factor in classification. Mr. Fieldner favored retaining bed moisture as a partial classification basis, stating that a review of many coal analyses revealed a remarkable consistency in this item in samples from a given mine particularly where the moisture content was not high. Mr. Porter pointed out that the structure and porosity of coal often have much to do with its moisture content and that these vary in different parts of a seam, particularly in anthracite. Mr. Gauger expressed doubt as to whether the Stansfield method gives the true moisture content of coal, which is needed for classification purposes.

Jan 1, 1932

By Cleveland Dodge

THE present organization of Copper Queen employ-ees, known as the Employees' Conference Com-mittee, is really an outgrowth of the former Grievance Committee, which, in turn, had developed from the original Hospital Committee. The relatively small membership of these older organizations, the practical limitation of their activities to the presenting of grievances, and their lack of initiating powers, were the principal defects which the plan now in operation seeks to overcome. A somewhat parallel scheme was instituted in our Sacramento Hill division about four years ago; this gradually developed into the Ways and Means Committee, which, in addition to providing a forum for the discussion of operating problems, was instrumental in establishing an excellent and mutually satisfactory bonus system. Before recommending adoption of the plan now in force, we made extensive inquiries among those who have had any experience in such matters, and ended by proposing a modification of a scheme developed by John Leitch,1 which was characterized by its similarity to the constitution of the Federal Government. As finally remodeled, the. plan was submitted to vote of the entire working forces at the Copper Queen mines, and was adopted by them in May, 1920. Mining opera-tions since that date have been so interrupted that it is scarcely possible to state exactly what the results have been. The following quotations are from a printed pamphlet containing the constitution of the organization, as finally adopted. The first extract is from a letter addressed by the management to the employees: The plan submitted for your approval and adoption is modeled after the constitution of our own country, under which every individual is given an opportunity for advancement, according to his ability and determination, and every citizen is given a voice in the laws that shall govern him. So it is to encourage the individual employee in advancement, and to give him a voice in making the rules that shall govern his conduct, that we favor the adoption of the proposed constitution.

Jan 1, 1923

By H. Foster Bain

Jan 1, 1910

By C. J. Huffman

MAGNESIUM alloy tubing and hollow shapes are finding increasingly wider usage in practical applications today. Square and rectangular tubing and hollow shapes find [ ] greater diversification in use than standard round tubing. Typical applications are roller conveyors, ladder rungs, spools, furniture, tank car loading tubes, athletic equipment, and business machine parts. In general, the amount of tubing and hollow shapes produced represent a minor portion of the magnesium extrusion business. The magnesium alloys in which tubing and hollow shapes are being produced together with typical properties are presented in Table I. MI A alloy is a low cost alloy possessing good welding and stress corrosion characteristics together with moderate formability and corrosion resistance. It is widely used for low strength applications. AZ31 B, alloy is used for moderately stressed applications and possesses good corrosion resistance and formability with fair welding characteristics. AZ61 A alloy has slightly higher physical properties than AZ31 B alloy together with good formabil- [ ] ity and corrosion resistance but slightly poorer welding characteristics. AZ80 A, ZK60 A-F, and ZK60 A-T5 alloys are used where the maximum in physical properties is required. AZ80 A alloy possesses fair corrosion resistance but with formability and welding characteristics inferior to' the other alloys. ZK60 A-F and ZK60 A-T5 alloys, while only recently offered for com¬mercial use, are finding favor due, to the higher permissible extrusion rates. These alloys possess greater toughness than AZ80 A alloy and, while of moderate formability at room temperature, are very formable at 300° to 500°F. The major portion of tubing and hollow shape production at the present time is in AZ3I B alloy. Magnesium alloy tubing is commercially available in the as-extruded condition or, in the case of ZK60 A-T5, in the as-extruded and aged

Jan 1, 1951

By Walter Bradley

MINING by hydraulic process of the important gold-bearing gravels of the Sacramento Valley in the basins of the Yuba, Bear and American rivers began in 1853, and continued at an ever-increasing rate for 30 years. In its most active days it reached an annual production of $15,000,000, and averaged $10,000,000 per year over the 30 years. During that period no provisions were made to prevent the debris from being dis-charged into the water courses, and ultimately large quantities of silt, sand and gravel were washed down to the lower valleys; filling channels, causing overflow of agricultural lands and difficulty in maintaining navigable depths in the Sacramento River. Agitation and suits filed because of these damages finally resulted in the injunction decision of Judge L. B. Sawyer,1 in the U.S. Circuit Court, Jan. 23, 1884, which closed down practically all hydraulic mining operations not having means to restrain their debris. In 1893 (approved March 1, 1893), Congress passed the act introduced by Representative Anthony Caminetti, of California, creating the California Debris Com-mission, composed of three officers assigned from the Engineer Corps of the U.S. Army, and since that time it has been legal and possible within the drainage systems of Sacramento and San Joaquin rivers to conduct hydraulic mining of gold-bearing gravels behind dams built under this commission's permit and supervision. In the watersheds of the Trinity and Klamath rivers, which flow directly to the Pacific Ocean and do not affect navigation or agriculture, operating permits from the California Debris Commission are not required. There is a measure of restriction there, however,. through what is known as the Trinity and Klamath River Fish and Game Dis-trict. Chap. 215, Stat. 1931, in order to secure relatively clear water for the fishing season, provides that between July 15 and October 15 each year there must not be discharged into these rivers debris that will cause a turbidity greater than a content of 50 parts per million in the

Jan 1, 1936

By L. C. Uren

Field studies and laboratory research have established the fact that the expulsive force which drives petroleum into wells, from the reservoir sands in which it is stored by nature, is primarly an expression of the energy latent within compressed natural gas dissolved or occluded in, or otherwise associated with the oil. Each barrel of oil produced is forced into the recovery well by the expansive energy of a certain volume of compressed gas, originally stored with the oil in the pores of the reservoir rock; and each cubic foot of gas so produced with the oil and expanded to atmospheric pressure reduces by so much the total natural energy available for oil expulsion. This relationship between the volumes of gas and oil produced has seemed so important that petroleum production technolo-gists have come to regard the "gas-oil ratio," or the "gas factor" as it has been more conveniently termed, as a measure of oil-production efficiency. Different methods of oil recovery and production devices are now Com pared on this basis and estimates of ultimate recovery obtainable through their use are considered by many to be inversely proportional to the values of their respective gas factors. The writer has been among those who have given support to a widcspread movement toward a proper recognition of the significance of the gas factor as a guide in the control of producing oil wells, and does not wish to oppose its more extended application. It seems necessary, how-cvcr, in view of the almost elemental faith with which the principle of the gas factor has been received in many quarters, to point out that it is a most complex factor, and one which cannot be regarded as an absolute index of production efficiency without due regard to other contributing factors by which it is influenced to an important degree. Variables Influencing Gas Factor The mere recording of a low gas factor, obtained through the use of some method or device, does not necessarily imply efficient oil production; and conversely, a high gas factor does not always signify inefficient recov-

Jan 1, 1928

[FUQUA, H. B. and Thompson, B. E.: Oil and Gas Development and Production in North Texas for 1933, 107, 320; for 1934, 114, 417 Oil and Gas Development in West Texas 114, 438 FURMAN, W. F.: Heat and Corrosion-resisting Alloys. Printed in Oil & Gas Jnl., June 13, 1935 Furnace-bottom sand, uniformity, 73, 390 Furnace control, Isley apparatus, M27, 502 Furnaces (See also Holt-Dern; Blast Furnaces; Roasters; Wirebar, etc.): annealing: electric, 89, 424 gas-fired, 89, 425 gas vs. wood for nonferrous metals, 89, 422]

Jan 1, 1936

By R. W. Bond

The gas-lift is a comparatively recent development in the Oklahoma and Kansas fields. It was used to some extent in the old Dilworth field several years ago, but the first extensive installations were made in the Tonkawa and Garber fields in Oklahoma early in the year 1926. Compressor Equipment During the early development of the system, the equipment used generally consisted of small tandem compressors of about 250 cu. ft. per min. displacement, driven by automotive-type gas engines, using a short belt drive. These compressors were first installed at the individual wells largely as an experiment. After the experimental installations had proved the method a success, it was considered economically advisable to centralize the compressor equipment in strategically located stations. However, as the information in regard to "gas-lift flowing life" was anything but definite, and the most optimistic estimates in regard to it did not exceed six months, portability of equipment was still the first consideration in the minds of many operators, who continued to install srnall semi-portable com-pressors in their centralized stations. As electric power became available in the fields, the electric motor came rapidly into use as the prime mover for the small compressors. The operating cost of this motor is greater than that of the automotive-type gas engine for the same power output, but the greater continuity of service tends to balance the extra cost. Aside from the semi-portable units, a number of strictly portable compressors were used. These consisted of automotive-type gas engines direct connected to vertical compressors. The unit was assembled on one base and could be mounted on wheels or skids as desired. The chief objection to these, in the writer's opinion, was their small capacity— approximately 150 cu, ft. per min.—which made it necessary to use two, three, and sometimes more units per well, thus making the installation rather costly. However, they have been found valuable for test purposes and emergencies, where installation time is an important factor.

Jan 1, 1928

By C. L. Mantell

When considered from the viewpoint of world annual output, tin is one of the rarest metals. Its annual production is exceeded by that of iron, copper, lead, zinc. aluminum, magnesium; probably by that of the ferroalloys of manganese, chromium, and silicon, and possibly by the world production of sodium; while it exceeds only the output of such common metals as nickel, antimony, mercury, tungsten, molybdenum, silver, gold and the precious metals. Cassiterite, or tinstone, until the second World War was the only mineral that was an important source of tin. This mineral is frequently called "tin ore." The use of the term should be restricted to the ore containing the mineral, and not, in addition, to the concentrates of the mineral obtained from the ore or from stanniferous alluvial deposits. There is a general misuse of the term "tin ore" in the Malay Peninsula and adjacent localities, particularly where most of the mineral is obtained from secondary stanniferous deposits. The term "cassit-erite" is exclusively used in mineralogical, geological, and other scientific writings; it is unfortunate that it is not mole frequently used when referring to the occurrence of the mineral on an economic scale. Ores "Tinstone" js a very convenient old English term deserving a more frequent use. Tinstone is a dioxide of tin, or stannic oxide. When chemically Pure, as in the very rare transparent variety, it has a metallic content of 78.6 per cent tin. Frequently, however, the crystals and grains contain appreciable amounts of impurities, chiefly iron and tantalum. The impurities here referred to are those actually in the mineral itself. Tinstone usually has a deep brown or black color with an adamantine luster. Several other colored varieties are known, among them red ruby tin, yellow rosin tin, and yellow wax tin. the names jn each case being descriptive of the mineral's appearance. Ainalite is a variety of cassiterite con-taining almost g per cent of tantalum pentoxide. Sparable tin, tooth tin, and needle tin, as a result of their acute dite-tragonal pyramidal crystalline form, re-ceive their names from their crystallo-graphic appearance. Wood tin is a compact variety of cassiterite composed of radiating fibers resembling dry wood. Toad's-eye tin is a similar variety on a smaller scale in which the fibers appear to resemble the eye of a toad. Stream tin is water-worn tin-stone. Float tin is sometimes employed to describe the cassiterite occurring in soil derived from the weathered surface of a mineralized area. Stannite is an ore of tin of lesser impor-tance than cassiterite. It is a sulphide of tin, copper, and iron, sometimes known as tin pyrites or bell-metal ore. Its chemical com-position is sometimes expressed by the for-mula Cu,S.FeS.SnSz with zinc usually present in varying quantities. The tin con-tent varies from 22 to 27 per cent and there is about 29 per cent of copper, 13 per cent of iron, and 30 Per cent of sulphur.

Jan 1, 1944

By Cyril Stanley Smith

Jan 1, 1949

By Cyril Stanley Smith

Jan 1, 1949

By J. Hunter

LouisiaNa ranks fifth among the oil-producing states. In 1941 the state-wide production was slightly in excess of 118,000,000 bbl. of crude oil and conden-sate—an increase of 15,000,000 bbl. over the total production for the year 1940. During 1941, south Louisiana produced approximately 90,900,000 bbl. of oil, while north Louisiana produced approximately 27,000,000. South Louisiana, therefore, produced about 3¼ times more oil than north Louisiana. During the past year, 574,800,000 M cu. ft. of natural and casinghead gas were produced in Louisiana; thus 1941 gas production exceeded the 1940 production by 104,900,000 M cu. feet. Completion records for the year 1941 show that 1512 wells were completed in or adjoining producing fields. These wells, which were drilled to extend known producing areas or were located within producing areas, are not considered as wildcat wells. Of the total number of field wells drilled, 1152 wells found production; the remaining 360 were junked or dry and abandoned. This means that 76 per cent of the wells drilled were successful. Considering the precarious nature of oil-field development, this percentage of new producing wells is exceedingly satisfactory. Of the total number of field welis com-pleted as producers, approximately 86 wells found new and distinct producing sands. During the past year, 30 new fields were found. Four parishes—namely, Caldwell, Catahoula, Orleans, and Natchitoches— entered the ranks of oil-and-gas-producing parishes in the state during that period. This brings the total number of oil-and-gas-producing parishes in the state up to 48. Thus, 75 per cent of the parishes in Louisiana now contain one or more oil and/or gas fields. Although sufficient data are not available to list the addition reserves found in Louisiana during 1941, it is felt that such reserves undoubtedly exceed twice the total production for that year, or at least 200 million barrels. In reserves, therefore, Louisiana ranks third among the various oil-producing states. South Louisiana Although 16 new fields were found in south Louisiana, the outstanding developments in that part of the state were not limited to new discoveries. In fact, most of the increase in reserve in that area has been most consistently accumulated through extensions of known producing sands and through the finding of new sands in already productive fields, especially at depths below the presently producing sands. Since data concerning most of the new extensions and sands are too extensive for discussion here, the more important developments arc briefly outlined below: Abbeville, Vermilion Parish.—Production extended ½ mile to the west. Anse La Butte, St. Martin Parish.—New oil sand discovered at 9400 ft., thus extending production to east flank. West flank defined by dry holes. Barataria, Jefferson Parish.—New oil sand discovered on east side of field at 7620 ft. New

Jan 1, 1942

By J. Hunter

LouisiaNa ranks fifth among the oil-producing states. In 1941 the state-wide production was slightly in excess of 118,000,000 bbl. of crude oil and conden-sate—an increase of 15,000,000 bbl. over the total production for the year 1940. During 1941, south Louisiana produced approximately 90,900,000 bbl. of oil, while north Louisiana produced approximately 27,000,000. South Louisiana, therefore, produced about 3¼ times more oil than north Louisiana. During the past year, 574,800,000 M cu. ft. of natural and casinghead gas were produced in Louisiana; thus 1941 gas production exceeded the 1940 production by 104,900,000 M cu. feet. Completion records for the year 1941 show that 1512 wells were completed in or adjoining producing fields. These wells, which were drilled to extend known producing areas or were located within producing areas, are not considered as wildcat wells. Of the total number of field wells drilled, 1152 wells found production; the remaining 360 were junked or dry and abandoned. This means that 76 per cent of the wells drilled were successful. Considering the precarious nature of oil-field development, this percentage of new producing wells is exceedingly satisfactory. Of the total number of field welis com-pleted as producers, approximately 86 wells found new and distinct producing sands. During the past year, 30 new fields were found. Four parishes—namely, Caldwell, Catahoula, Orleans, and Natchitoches— entered the ranks of oil-and-gas-producing parishes in the state during that period. This brings the total number of oil-and-gas-producing parishes in the state up to 48. Thus, 75 per cent of the parishes in Louisiana now contain one or more oil and/or gas fields. Although sufficient data are not available to list the addition reserves found in Louisiana during 1941, it is felt that such reserves undoubtedly exceed twice the total production for that year, or at least 200 million barrels. In reserves, therefore, Louisiana ranks third among the various oil-producing states. South Louisiana Although 16 new fields were found in south Louisiana, the outstanding developments in that part of the state were not limited to new discoveries. In fact, most of the increase in reserve in that area has been most consistently accumulated through extensions of known producing sands and through the finding of new sands in already productive fields, especially at depths below the presently producing sands. Since data concerning most of the new extensions and sands are too extensive for discussion here, the more important developments arc briefly outlined below: Abbeville, Vermilion Parish.—Production extended ½ mile to the west. Anse La Butte, St. Martin Parish.—New oil sand discovered at 9400 ft., thus extending production to east flank. West flank defined by dry holes. Barataria, Jefferson Parish.—New oil sand discovered on east side of field at 7620 ft. New

Jan 1, 1942

By J. R. Long, T. R. Graham, R. S. Dean

FOLLOWING the development of elec¬trolytic manganese production by the Bureau of Mines, an extensive program was planned to study the character of this high-purity product and its possible utilization in various alloy combinations. Previous work reported in the literature concerning alloys containing substantial amounts of manganese dealt largely with material prepared from relatively impure grades of the metal, and in many instances the impurities thus introduced did not permit true evaluation of manganese as an alloying element. One phase of the Bureau's program included a general review of the system and the establishment of the physical properties of copper-manganese-zinc alloys, using electrolytic manganese, and with particular emphasis directed to com¬positions within the alpha solid solution area. A number of reports of the work on alloys in this system, giving specific data concerning the equilibrium system and some of its alloys, have already been published. One study1 established the alpha solid solution area at various temperature levels and composition ranges up to 50 pct manganese. Other investigation reports presented the properties of selected alloys; namely, a 65 pct copper, 10 pct manganese, 25 pct zinc alloys' a sensibly white manganese brass composed of 70 pct copper, 20 pct manganese, 10 pct zinc,3 and a series of alloys with a constant copper content of 60 pct and 5 to 25 pct manganese, balance zinc.4 In these reports tensile properties as influenced by cold-working and subsequent annealing were given in detail. Additional data are now available on other alloys of the alpha region up to 50 pct manganese, and these, together with previously published information, are sufficiently complete to establish the relationship between properties and composition for this portion of the ternary system. The present report is a summary of the tensile properties of wrought alloys in the form of sheet and rod stock. The summary is necessarily limited to data for only one condition of cold-work and a single annealing temperature, since a complete exposition of all the data available would be too extensive for this presentation. Nevertheless, it is possible to make a reasonable approximation of the tensile properties in other conditions of cold-working and annealing by a correlation of the data previously presented on specific alloys and the data given here.

Jan 1, 1947

By E. A. von Hahn, T. R. lngraham

Cementation rates ulere studied by rotating an elec-tropolished or etched copper strip in aqueous solutions, of either perchloric acid or alkaline cyanide, containing silver ions. The rates of cementation were more rapid in acidic media than in cyanide media. In both, the rates varied with the rate of rotation of the copper strip. The deposits formed in the acidic solutions were finely divided, loosely adhering powders. Those formed in the cyanide solutions were dense and adherent. The presence of the deposits influenced the cementation rates. In the acidic solutions the rate was enhanced, possibly because of the increased cathodic area. In the alkaline solutions the rates were decreased in the presence of the deposits. This has been attributed to restricting the diffusion of the copper ion from the rnetal outward into the bulk of the solution. In an earlier paper1 the authors described a kinetic study of the cementation of palladium on copper in perchloric acid solutions. That work indicated that there were two stages in the palladium cementation process. The first, more rapid stage was consistent with rate control by the diffusion of Pd11 ions to the copper surface and/or by chemical reaction at the surface. The second stage was consistent with rate control by the diffusion of copper ions from the copper surface, through the deposit, out into the main body of solution. The effect of the type of deposit on the rate of cementation is of particular interest because it may be one of the primary features involved when large quantities of metal are to be cemented from solution. No substantial investigations of the effect seem to have been made. Accordingly, an extension of the previous work was arranged to study the cementation of silver on copper. This system was selected because of the convenience of the analytical methods, the previously established technology with copper, and the fact that the system could be studied in both acidic and alkaline media. By selecting perchloric acid and alkaline cyanide solutions as the media, it was hoped that some assessment might be made of the effects, on cementation, of having the silver ion present in a virtually uncomplexed state and in a highly complexed state. EXPERIMENTAL The cementation rates were studied, as previously described,' by rotating a copper strip (1.0 by 23.2 cm) clamped to the peripheral surface of a lucite cylinder. The solutions were kept at constant temperatures (±0.05°C) under an atmosphere of purified nitrogen, and samples were taken periodically for analysis. The initial solution volume was 1000 ml and the sample volume 5 ml. The initial silver(1) ion concentrations were made low (0.5 to 1.0 x 10-4 moles per liter) to minimize the influence of the cemented deposit on rates. The solutions were prepared by dilution of suitable aliquots of silver perchlorate and silver cyanide stock solutions. Both stock solutions were prepared from purified silver powder (Johnson, Matthey, and Mallory Ltd.) with redistilled deoxygenated water, and they were kept under an atmosphere of purified nitrogen. To prepare the stock solutions, weighed amounts of silver powder were dissolved with nitric acid. For the AgC104 stock solution the silver nitrate solution was evaporated twice to near dryness with perchloric acid and then made up to volume: For the NaAg(cN)2 stock solution, the silver ions were precipitated with sodium hydroxide solution. The precipitate was filtered, washed thoroughly with redistilled water, dissolved with 1.1 times the required stoichiometric amount of sodium cyanide solution, and made up to volume. The small amounts of free perchloric acid and sodium cyanide present in the stock solutions were disregarded in the preparation of the solutions. The copper strips were cut accurately from 0.025-in. sheet (American Metal Climax OFHC brand) and annealed for 1.5 hr at 470°C in a stream of nitrogen. Analyses of the solution samples for silver and copper were done with a Techtron Model AA-3 atomic absorption spectrophotometer. Calibration standards of the same composition as the experimental solutions were prepared and analyzed simultaneously with the samples. No difficulty was experienced in the analyses, and the reproducibility was within 1 to 2 pct in both alkaline cyanide and perchloric acid solutions.

Jan 1, 1968

By I. R. Kramer

The apparent activation energy, U, JOY plastic deformation of aluminium, copper, and gold single crystals and polycrystalline aluminum was found to he dependent upon surface condition. At low strains, the value for U for aluminum single crystals was 4200 cal per mole ; however, this value decreased to 920 cal per mole when the specimens were polished during the test at a rate of 50 X 10-5 win-1 The activated volume also was found to increase with the rate of metal removal. That the surface plays an important role in plastic-deformation processes has been adequately demonstrated.1-4 Of particular interest at this time are the observations4 that the creep rate of single crystals of fee metals is increased markedly when specimens are polished during the deformation process. These observations were interpreted in terms of a dislocation debris layer at the surface regions of the crystal. This layer, which appears to be a region containing a high concentration of dislocations or segments of dislocations, not only will impede the egress of dislocations on the primary slip system, but will also provide a barrier against which dislocations may pile up. By this means, a stress which opposes the motion of dislocations will be generated. It is considered that this stress must be taken into account in any theory which describes the plastic-deformation process. Although a detailed dislocation model cannot be given at this time, it may be stated that the stresses opposing the motion of dislocations arise from the dislocations in the debris layer, Ts, and ti due to the resistance to motion imposed by internal obstacles such as Lomer-Cottrell barriers, subgrain and grain boundaries, forest dislocations, and so forth, as well as the resistance due to the presence of jogs on dislocations and the interaction of the stress fields of dislocations, and so forth. In essence, we have added an additional term, ts, to the usual form of the equation T = Ta- Tb, where Tb is the back stress due to the various types of obstacles which impede the motion of dislocation. Accordingly, the net stress, t, acting on a dislocation may be written as where Ta is the applied shear stress. For deformation which occurs by a thermally activated process5,8 ?=Ae-u/kT = A e(u,-VT)/kT [2] and U = Uo- Vt PI where U = activation energy for plastic flow, y = shear strain rate, Uo = activated energy for plastic deformation in the absence of stress and depends upon the particular deformation process, V = activated volume, k = Boltzmann constant, T = temperature, OK, and A = frequency factor. From Eqs. [I] and [3], U = Uo- V(Ta - Ti - TS) [4] and it is seen that if Ts decreases, the activation energy, U, must decrease if V remains constant. However, as will be shown, V is a function of the surface conditions. In their work on aluminum, Lytton and coworkers7 reported that at low strains the activation energy was 3400 cal per mole and at high strains it was 28,000 cal per mole. The lower value was interpreted in terms of the energy necessary to overcome the Peierls force, while the higher value was associated with the energy necessary for dislocations to move by a cross-slip process. It will be shown that the lower activation energy is associated with the surface debris layer rather than with the Peierls force. EXPERIMENTAL PROCEDURE Single crystals having a nominal cross section of 1/8 in. and a 3-in. gage length were prepared by a modified Bridgman technique using a multiple-cavity graphite mold. The initial purity of the metals was 99.997, 99.999, and 99.999 pet for aluminum, copper, and gold, respectively. The orientation of the specimens is given in Fig. 1. The measurement of the activation energy as a

Jan 1, 1964

By Charles White Merrill

Mankind's progress is measured in minerals. Man's emergence from prehistory is marked by passage through a Stone Age and a Bronze Age and into the present era, sometimes called the Iron Age or the Age of Metals. With the evolution of civilization and the development of a modem industrial economy, minerals become more and more important. Structures, roads, and machines are built largely of minerals; the energy to heat the structures and to drive the machines is mostly mineral; agricultural fertility is maintained by mineral fertilizers and water; and military strength is provided by fortresses, armaments, and munitions, largely of mineral origin. Thus in the material world, in the productivity of the economy, access to minerals has paramount importance. Every evidence indicates increasing dependence on minerals in the modem economy, particularly on the mineral fuels as energy sources to provide the power base for advancing industrialization. Both the total and the per capita consumption of almost every mineral is increasing in the industrialized nations. Moreover, nations with predominantly agrarian economies call themselves underdeveloped and universally strive to industrialize. Most mineral consumption trends in the more advanced economies have been greatly exceeding population growth-which itself has been advancing at an accelerating rate-and sometimes have surpassed the growth in real income. Some minerals have only recently been adopted or grown to importance in use. Titanium metal did not appear as a commercial product until 1948, and even coal seriously displaced wood as a source of heat less than two centuries ago. On the other hand, minerals have always played an important role in construction. The prehistoric megaliths that form the dolmens of Salisbury Plain are stone; the pyramids are andesite faced with limestone; and many other ancient structures are built of mineral materials. In modem times the whole course of architecture has been redirected by new building materials, mostly mineral. Most conspicuous is the sky-

Jan 1, 1964