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There were present twelve- Directors, the Secretary and the Assistant Secretary of the Institute, and fifteen guests. A committee of three was appointed to draft a suitable resolution of memorial of the services of Joseph Esrey Johnson, Jr. The committee consists of Joseph W. Richards, Chairman, J. V. N. Dorr and Allen H. Rogers. William R. Walker was elected a Director in place of J. E. Johnson, Jr., and Edwin Ludlow was elected a member of the Executive Committee in his stead. George C. Stone was appointed Chairman of the Committee on Membership in place of Mr. Johnson. The following resolutions were then adopted: RESOLVED, That a special business meeting of the Institute be and the same hereby is appointed to be, held at the office of the Institute, No. 29 West 39th Street, Borough of Manhattan, City of New York, on the 27th day of June, 1919, it 8.30 o'clock in the P. M. to consider and take action upon the proposal to change the name of the Institute to "American Institute of Mining and Metallurgical Engineers, Incor-porated," and the further proposal to extend the corporate purposes of the Institute so that it shall, in addition to its other powers, be empowered to promote the arts and sciences connected with the economic production of the useful minerals and metals, and the welfare of, those employed in these industries, by all lawful means.

Jan 6, 1919

By AIME AIME

THE Board of Directors of the Institute has authorized the appointment of a committee to draw up rules of procedure under which awards can be made from time to time to petroleum engineers for outstanding contributions to the art of finding and producing oil and gas. These awards will 11e sponsored by the Petroleum Division and are the first recognition by any professional society of outstanding achievement in "oil mining." They will be in the form of either a gold medal, scholar- ship, or other suitable prize. The awards will be financed from the income of the Anthony F. Lucas Memorial Fund, which was started about fifteen years ago, shortly after' his death, by admirers of Captain Lucas.

Jan 1, 1936

AALL, Christian H.,(M'49), Asst Res Dir Monsanto Chemical Co Anniston, Ala AALSETH, Earl P ,(J,51), Amerada Petr Corp Geological Dept Williston N Dak AAMOT, Olav Crone, (M'29), Met Pacific N W Alloys, Inc , Box 6215, Hillyard P 0 Spokane 14, Wash AARING, Floyd D ,(J'48), Petr Engr P 0 Box 130, Calgary, Alta Canada AARCNSON, Hubert Irving, (S'47), Carnegie Inst of Tech., Pittsburgh, Pa ABADIE, Henry G ,(M'43), Asst to the Sup- of Operations, Long Beach Oil Development Co ,255 So Santa Clara Ave Long Beach, Calif ABBISS, H. J., (A'50), Min. Engr., Buchans Mining Co., Ltd.. Buchans, Newfoundland ABBOTT, Clarence Eugene, (M'04), 901 Insurance Bldg , Raleigh, N C ABBOTT, George, (S'52), Mass Inst of Tech Cambridge, Mass

Jan 1, 1952

By Utley Wedge

(Cleveland :Meeting, October, 1012.) In general, the art of securing copper from sulphide ores or concentrates may be said to consist of : (1) separation, in the molten state, of copper sulphide with some iron sulphide, from the great bulk of gangue-material, followed by (2) elimination of sulphur and iron from the molten matte, by oxidation and fluxing, leaving metallic copper. The definition is made broad enough to cover the general practice, whether or not the ore or concentrate is given a preliminary roast for the removal of surplus sulphur. The above process, which I will designate as the smelting process, makes necessary the presence in the ore, or the addition thereto, of such silica, lime, and iron as may be necessary for the formation of a light and fusible slag, together with sufficient sulphur and iron for the formation of copper-matte, and also the addition to the matte of sufficient silica for the oxidation and fluxing-out of the iron. These items, together with the cost of fuel sufficient for melting the mass, constitute important items of cost in the copper-smelting process. Numerous cases where fluxing-materials are scarce or dear, or where fuel is expensive, have caused special attention to be given recently to the wet process of copper-extraction, which may be designated as consisting of forming soluble copper salts which are then washed or leached out of the ore or concentrates by dissolving in water or acid. Metallic copper may then be secured from the solution of copper salts by electrolysis; by cementation; or copper can be brought out of the solution as a * Presented also at the Joint Meeting of the Institute and Section IIIa, Metallurgy and Mining, of the Eighth International Congress or Applied Chemistry, New York, N. Y., September, 1912, and here published by mutual agreement.

Dec 1, 1912

By GUY C. RIDDELL

ZINC, manganese, and aluminum received attention at the two nonferrous metallurgy sessions at the Annual Meeting. L.P. Davidson, general superintendent of the rebuilt Monsanto zinc plant, described its operation, which reflects Polish practice and is really a combination of electrolytic, Waelz, and retort procedure. Briefly, it embraces leaching of roasted concentrate with sulphuric acid, electrolysis of sulphate solution using Tainton lead-silver anodes with ?goulac? added to the electrolyte, treatment of tailing in Waelz kilns, and retorting of the recovered zinc oxide, casting furnace dross and residues. Recovery is good, equipment and maintenance costs low. Ferrate zinc that might be lost in the electrolytic process appears to be recovered as oxide in the Waelz treatment.

Jan 1, 1942

By Wayne A. Greenwalt

A method that determines venture participation when the decision maker's level of risk aversion varies according to venture profitability and risk investment is presented. The decision maker's fundamental aversion to risk is established by the selection of a desired working interest for a venture that anticipates only a discounted payout.

Jan 1, 1982

By ALBERT F. J. BOARDEAUX

(Canal Zone Meeting, November. 191(j.) I. GENERAL INTRODUCTION. 1. Historical. ALLUVIAL gold was first discovered in Guiana in 1852, in the sands of the Arataye river; by Paulino, a Brazilian convict. During the following years, gold was found also in the rivers Orapu, Cirubé, etc. In 1873 the famous placers of the Sinnamary system were opened: Saint-Elie, Dieu-Merci, Adieu-Tat, and Couriége. This group of mines has produced nearly $10,000,000, according to official records, not including the gold that escaped the taxes. The discoverer was a mulatto named Vitalo. Except in a few rich spots, the gold was rather evenly distributed along the creeks. In one instance, gold was found in the red dirt from the slope of a hill, which, after transport to the creek, gave an amount of 150 kilograms. The placers of the Mana system, Enfin, Elysée, Pas-Trop-Tot, date from 1878, and their production has been about $5,000,000. In 1888, the Awa placers, along the boundary between the French and Dutch Guianas, on the Maroni and its tributaries, were discovered. They have yielded $12,000,000. The only industrial company,, the Dutch Guiana French Mining Co., produced in 15 years about 2,500 kg. of gold, worth $1,500,000. From 1893 dates the famous Carsewene discovery, in territory then in dispute between France and Brazil. A settlement was made recently in favor of Brazil, by arbitration of the Switzerland State Council. Carsewene is said to have pro-duced about $18,000,000 in six years (1894-1900), but not even one-fourth of the production went through French Guiana and

Nov 1, 1910

By Milton T. Pana

Computer techniques now have been applied to the solution of a wide variety of scientific and engineering problems in the mining industry, but generally not in great depth in any one area. In mining, the area covered in greatest depth and with the greatest success has probably been mine planning and to a lesser degree production scheduling. A rather comprehensive review of the literature related to mine planning and production scheduling indicates that contributions in these areas have been geographically, as well as organizationally, widespread. Of twenty-six papers reviewed, eleven were from industry, eight from educational institutions, four from computer vendors, two from the Bureau of Mines, and one from a private consultant. The conclusions that can be derived from the literature are: First, the-state-of-the art has advanced to the point that computing ore reserves and developing mining plans with the aid of the computer is now a routine practice; second, the application of the computer to mine planning problems has markedly improved our ability to estimate ore reserves, more accurately define pit limits, and determine an optimum mining sequence. MINE PLANNING The papers in this section deal essentially with the problem of determining the final pit limits of an orebody and the ore reserves associated with a given pit limit. The problem is probably best described by Soderberg25 and more recently by Reibell. 23. There are two techniques currently being applied to this problem by several mining companies: 1) the multiple-cone technique and 2) the Lerch-Grossman algorithm. The multiple-cone technique is the older of the two techniques and has the advantage of being more flexible, allowing an engineer to easily vary pit slopes in different sectors of the design. The technique can also be used to define intermediate pit contours. The Lerch-Grossman algorithm is appealing in that the final solution is given in the form of a true mathematical optimum. The technique is limited, however, in that the size of the blocks in the orebody model are a function of the desired

Jan 1, 1969

By AIME AIME

The following acts of the Directors are reported for the information of members:¬ At a meeting held November 3, 1905, Messrs. Henri Le Chatelier, of Paris, France, and Andrew Carnegie, of New York, N. Y., having been nominated by a large number of members, and recommended by unanimous vote of the Council, were unanimously elected Honorary Members, in recognition of their distinguished services to the arts and professions represented by the Institute. At a meeting held February 7, 1,906, Dr. James Douglas, of New York, N. Y., having been" nominated by a large number of leading members, and recommended by unammous vote of the Council, was unanimously elected an Honorary Member, in recognition of his distinguished services to the practice and the literature of mining and metallurgy, his zealous and loyal devotion to this Institute, his fraternal generosity towards professional colleagues, and his effective advocacy, by public utterance and private example, of the free communication of technical knowledge and experience. At the same meeting, By-Law IV., which now authorizes the Secretary to appoint an '1 Assistant Editor," was amended by substituting the words, " Assistant with the title of Editor." At the same meeting, the resignation of Mr. Theodore Dwight, as Assistant Secretary and Assistant Treasurer of the Institute, was presented and accepted, and the Secretary was instructed to express to Mr. Dwight the thanks of the Board for his loyal and efficient services, and its regret that he could not continue in that position. . [SECRETARY'S NOTE.-Mr. Dwight's resignation, dictated solely by the demands of private business, covers only his immediate management of this office. He is still a Director and Councilor, and a representative of the Institute in matters connected with the new Carnegie Building, etc.-R. W. R.] At the same meeting, the Secretary and the Treasurer reported respectively their appointment of Mr. Henry WT. B. Howard as Assistant Secretary and Assistant Treasurer, to fill

Mar 1, 1906

THE first session of the Institute was held at the Smithsonian Institution, on Tuesday evening, February 22d. The members were welcomed to Washington and to the Smithsonian by Prof. Joseph Henry. President Holley responded to the cordial welcome of Professor Henry, and then read an introductory address on the subject of Technical Education. Following the discussion on President Holley's address the following persons, duly proposed and indorsed by the Council, were elected members and associates of the Institute : MEMBERS. Emile R. Abadie, - St. Louis, Ma. R. J. Anderson, - Pittsburgh, Pa. Commander L. A. Beardslee, - Washington, D. C. Charles Bender, - New York City. Channing M. Bolton, - Richmond, Va. Thomas E. Bowman, - Silverton, Colorado. Calvin E. Brodhead, - Bethlehem, Pa. M. L. Brosius, - Lewistown, Pa. Harvey H. Brown, - Cleveland, Ohio. James A. Burden, - Troy, N. Y. J. P. Clemes, - Sonora, Mexico. N. H. Cone, - Nederland, Colorado. W. F. Durfee, - New York City. Robert Frazer, Jr., - Ashland, Pa. Joseph E. Galigher, - Bingham, Utah. William Golding, - Steel Works P. O., Pa. Samuel E. Griscom, - Pottsville, Pa. Gen. E. Burd Grubb, - Beverly, N. J. Arthur R. Guerard, - Charleston, S. C. Edward Hart, - Easton, Pa. Prof. Lewis M. Haupt, - Philadelphia. . R. S. Hawley, - Buffalo, N.Y. John W. Hoffman, - Philadelphia. Nelson P. Hulst, - Milwaukee, Wis. H. C. Humphrey, - Philadelphia. Ed. P. Jennings, - Ithaca, N. Y. B. F. Jones, - Pittsburgh, Pa.

Jan 1, 1876

The first session of the Institute was held at the Smithsonian Institution, on Tuesday evening, February 22d. The members were welcomed to Washington and to the Smithsonian by Prof. Joseph Henry. President Holley responded to the cordial welcome of Professor Henry, and then read an introductory address on the subject of Technical Education. Following the discussion on President Holley's address the following persons, duly proposed and indorsed by the Council, were elected members and associates of the Institute : MEMBERS. Emile R. Abadie,. .. .. St. Louis, Mo. R. J. Anderson,.....Pittsburgh, Pa. Commander L. A. Beardslee,. .. Washington, D. O, Charles Bender,. .. .. New York City. Charming M. Bolton,. .. . Richmond, Va. Thomas E. Bowman,. .. . Silverton, Colorado. Calvin E. Brodhead,. .. . Bethlehem, Pa. M. L. Brosius,. .. .. . Lewistown, Pa. Harvey H. Brown,. .. .. Cleveland, Ohio. James A. Burden,.. .. . Troy, N. Y. J. P. Clemes,. .. .. . Sonora, Mexico. N. H. Cone,. .. .. . Nederland, Colorado. W. F. Durfee,.. .. . New York City. Robert Frazer, Jr.,. .. . Ashland, Pa, Joseph E. Galigher,.. .. . Bingham, Utah. William Golding,.. .. . Steel Works P. O, Pa. Samuel E. Griscom,.. .. . Pottsville, Pa. Gen. E. Burd Grubb,.. .. Beverly, N. J, Arthur R. Guerard,. .. .. Charleston, S. C. Edward Hart,.. .. .. Easton, Pa. Prof. Lewis M. Haupt,. .. . Philadelphia. E. S. Hawley,.....Buffalo, N. Y. John W. Hoffman,.. .. .. Philadelphia. Nelson P. Hulst,.. .. . Milwaukee, Wis. H. C. Humphrey,.. .. . Philadelphia. Ed. P. Jennings,.. .. .Ithaca, N. Y. B. F. Jones,......Pittsburgh, Pa.

By Paul W. Zimmer, Carl E. Dutton

Iron ore in the Menominee district is mined from two iron-formations of middle Precambrian age. The older formation is present in the northeastern part; is composed mainly of hematite, magnetite, quartz, and minor silicates; and contains about 34 per cent iron. The rock has been so coarsened by meta- morphism that concentration of magnetite and hematite is feasib!e, and pellets containing more than 60 per cent iron are being produced. The older formation is also present in the southeastern part where it has 1:een only slightly metamorphosed. Ore containing more than 50 per cent iron was formerly mined from local residual concentrations of iron oxides from which silica had been sufficiently leached, or replaced by iron oxide, or affected by combinations of these processes. The younger iron-formation occurs in the western part of the district and, if unaltered, is interlayered siderite and chert. The ore in this area also contains more than 50 per cent iron and formed as local residual concentrations but in two stages. The siderite was converted to iron oxides (hematite and "limonite"), and silica was contemporaneously or subsequently removed by leaching, or replacement, or combinations of these processes.

Jan 1, 1968

THE CHAIRMAN.- This meeting is under the auspices of the American Institute of Mining and Metallurgical Engineers, and I think the germ of the idea originated in the steel business. Last year there was a meeting of prominent people in the steel industry with the idea of getting together and discussing practical phases of their business, so that everybody could contribute and from that there might be benefit derived for the industry. Several months ago when Mr. Bain was in Salt Lake City, he and Mr. Oldright asked me what I, as an individual, thought of it. From that originated this idea of having the copper people come together to discuss reverberatory smelting and all its phases. In starting out, it seemed the best plan to ask members what particular subjects they wished to discuss first; that is, the ones that would be considered more important. We asked Mr. Oldright, or suggested sometime ago that the meeting be postponed until May because May is a lovely month in Salt Lake. There are a number of attractive features around the city. We have a number of smelters here and I think that probably the most of the benefit will be derived from talking in an informal way and visiting the various plants around. the valley. At any rate, speaking as a resident of Salt Lake, I am glad to see all of you gentlemen here, and hope you have an interesting and instructive time. The tentative list of subjects for discussion at this conference is as follows: Construction Walls, etc. Walls, proper design and thickness of brick for various types of charging. Bottoms, construction of. Binding steel, correct weight and arrangement, where thrust of arch should be taken. Refractory materials, feasibility of using different material in various parts of the furnace. Water jackets, where applicable. Should bricks be used inside of same. Gas space, proper design for, height of roof above bath, etc. Roof Shape of Roof, in hot zone and elsewhere, longitudinally. Construction of roof, in various zones, around openings.

Jan 1, 1930

[Aase, Qlenn D., (Junior Member '40) Jr. Met.. American Smelt. & Refin. Co., Selby. Calif. Abadie, Henry G., (Junior Member '43) Petr. Engr.. Avenal, Calif. Abbott, Clarence E., (Member '04) Civil En=.. V.P.. Tennessee Coal. Iron & R.R. Co., 1542 Brown biarx Bldg.. Birminpham, Aln. Abbott. Fred E., Jr., (Member '44) Petr. Engr., C/O Arabian Anierican Oil Co.. A.P.O. 816. c/o Postmaster, New York, N. Y. Abel, Raymond L., (Member '28) Chem. Engr.. C. O., Pittsburgh Chem. Warfare Procurenlent Dist.. American Bank Bldg., Pittsburph. Pa. Abel, Walter D., (Member '32) Min. Engr.. Supvr. Engr.. RFC, Los Angeles, Calif.]

Jan 1, 1946

Jan 1, 1962

By Henry P. Ehrlinger, James C. Bradbury

Tripoli is a naturally occurring, very finely divided form of silica found chiefly in some midwestern and southeastern states and used commercially as fillers and abrasives. Definitions Tripoli is a microcrystalline, finely particulate, more or less friable form of silica that appears to be the product of leaching of siliceous limestone or calcareous chert. The term was originally applied to a deposit near Seneca, Mo., that resembled material of that name found near Tripoli in North Africa (Hovey, 1894). The two deposits were subsequently found to have different physical characteristics -the North African tripoli, now called tripolite, is a diatomite, composed of the siliceous skeletons of microscopic marine plants called diatoms, and the Missouri tripoli contains no diatom remains; the term tripoli, however, continued to be used for the Missouri material and is now applied in a general way to most silica deposits similar to it in characteristics and geologic origin. In commercial trade tripoli is commonly understood to designate material from the Missouri-Oklahoma field; silica from southern Illinois, the other major producing area, is referred to commercially as amorphous silica. Each term, however, may be used commercially for material, regardless of place of origin, that has the characteristics or uses commonly ascribed to the material from one or the other major producing area. For example, in the commodity price listings, Engineering and Mining Journal routinely lists under Tripoli, prices "f.0.b. Elco, III." and "f.0.b. Seneca, Mo., and Rogers, Ark.," and under Silica, amorphous, prices "f .o.b. Ill.," and "f .o.b. Dierks, Ark." Amorphous silica, the commercial designation given to southern Illinois tripoli, is, like the term tripoli, a misnomer. Mineralogically, the southern Illinois deposits are composed of microcrystalline quartz, and no amorphous material has been detected during X-ray and scanning electron microscope investigations (Leamnson, Thomas, and Ehrlinger, 1969; Thomas et al., 1970). Soft silica is another term that has been applied to Illinois and Tennessee tripoli, presumably to distinguish it from the more compact Missouri material. It has also been used in the ceramic trade to distinguish tripoli from "hard" silica, or silica flour, produced by pulverizing silica sand (Heinz, 1937). Rottenstone, produced commercially in Pennsylvania, is similar to tripoli in that a major constituent is finely particulate silica, and its uses are much the same as those of tripoli- as abrasives and fillers. The origin of rottenstone also is similar to that of tripoli-decomposition of a siliceous sedimentary rock. The parent rock is defined as a siliceous limestone (Gary, McAfee, and Wolf, 1972; Thrush, 1968) or as shale (personal communication). Heinz (1937) quotes a brief statement describ-

Jan 1, 1975

By W. L. Zeigler

During the middle 1880's, shortly after the discovery of silver-lead ores in the Coeur d'Alene district of northern Idaho, it became apparent that concentration of the ores would be necessary to obtain a profitable product. Too much siliceous material was present for direct smelting, and the majority of the ores found at depth were too low in metallic content for economic smelting processes at the time. As the ores occurred in quartzite shear zones with siderite and quartz gangue, a large quantity of waste material was present in all the mines. As the galena was not finely disseminated, this made possible relatively good extraction of the argentiferous galena by coarse concentration. The first concentrators consisted mainly of coarse crushing, screening and jigging, principally by Harz jigs, the slimes being treated on buddles. Later Wilfley tables took the place of sand jigs and vanners superseded the buddles. Because of the marketing conditions, no attempt was made until 1900 to effect a recovery on the zinc minerals present, which were found associated in varying amounts with the galena. All through this period, the greater part of the production was obtained from mines containing ore assaying high in lead and low in zinc. Parts of some ore bodies would be reversed in this respect, so that ores high in zinc were left intact. During the decade after 1910, several important mines, The Success and The Interstate Callahan, containing ores high in zinc, were put into operation and were a material aid in the needed zinc production during World War I. Gravity concentration by jigs and tables was used during this period, with bulk flotation increasing in popularity for the treatment of the fine material that had already been treated by ordinary slime concentrating machinery. No extra fine grinding for flotation concentration was thought profitable at the time. Tailings Discharged into Streams From the start of mining and milling operations in this district until 1904, no attempt was made by the various mills in the upper district to impound or stack their tailings. They discharged them directly into the adjacent creeks or streams, to be carried away by high water. The Bunker Hill and Sullivan and the Last Chance mines, both in the relatively flat valley of the district, stacked huge piles of the coarse jig tailings on the near-by river bottom. Rain and snowfall are heavy in the Coeur d'Alene district, as it is on the heavily timbered Pacific slope of the Bitter Root Mountains. A heavy runoff occurs every spring and there is an occasional flood of disastrous proportions when warm "Chinook" winds accompanied by rain

Jan 1, 1949

Eight members of the Board, the Secretary of the Institute, and eleven guests were present. Vice-president Henry S. Drinker presided. The President was authorized to appoint delegates to a meeting, on May 16, of the League to Enforce Peace. The Joint Conference Committee reported that the American Institute of Metals had accepted the invitation to form the Institute of Metals Division of this Institute. The Committee on Publications of the Institute of Metals was added to the Committee on Publications of the A. I. M. E. Exchange of one volume of Transactions of the A. I. M. E. at reduced price to members of the British Institute of Metals was authorized, in return for the reduced price given to our Institute of Metals Division on the annual proceedings of the British Institute.

Jan 6, 1918

By F. Julius Fohs

CENTRALLY located with relation to the largest iron- and steel-producing districts of the United States, the fluorspar-deposits of Kentucky possess increasing interest and importance. As typical of the numerous fluorspar-mines of Kentucky and Illinois, I have selected for description the Memphis., because it and others of its immediate group exhibit the conditions characteristic of all. I. THE MEMPHIS MINE. This mine lies 5 miles NW. of Marion, in Crittenden county, Kentucky, a station on the Chicago and Nashville division of the Illinois Central R. R. For the first mile and a half out of Marion we see only Birdsville or Middle Chester sandstones of Mississippian age. Then we cross a fault of some 350 ft. displacement, and the Ste. Genevieve oolite sets in. Beyond the fault, oolite is the predominant rock, except that the bills to the north have a capping of Cypress or lowest Chester sandstone, 80 ft. below which is an outcrop of from 6 to 10 ft. of Ste. Genevieve (Rosiclare) sandstone. Occasional sink-holes are noticed, and as the mines are approached evidence of faulting is again seen.. A line of crude head-frames and open-cut dumps, extending for more than a quarter of a mile, marks the Klondike vein. The open-cuts are from 15 to 20 ft. deep, and in most of them, from the surface down, was found the reddish gravel which is really fluorspar-some of it white or purple and crystal-clear (if the red clay is washed off), and some carrying iron and silica, and stained by waters from the decaying limestone walls. In one of these cuts, at a depth of 20 ft., white and purplish honey-combed fluorspar was found, in which the larger cavities are due to limestone and calcite leaching, and the minute ones to the leaching of zinc-blende.

Apr 1, 1909

By F. H. Ellinger

TI HE crystal structure of neodymium has been re-A ported by Quill1 and by Klemm and Bommer"s to be hexagonal-close-packed, Strukturbericht-type A3, with a, = 3.650.4, c, = 5.890.4, c/a = 1.614. Klemm and Bommer,% owever, pointed out that the observed intensities of the lines of the neodymium powder pattern agreed only in part with the intensities calculated for the type A3 structure, and that the neodymium powder pattern showed extra lines which could not be traced to impurities. They found that these extra lines could be accounted for by doubling the c-axis, but apparently they did not consider their evidence to be sufficiently conclusive to justify reporting the doubled c-axis. In the present work, the structure of neodymium was found to be double hexagonal-close-packed. The neodymium metal used in the present investigation was obtained through the courtesy of F. H. Spedding of the Ames Laboratory. Its major impurity was stated to be 0.03 pct Ca. The author's spectrographic analysis indicated high purity and carbon was determined to be less than 30 ppm. X-ray powder specimens were prepared from filings stress relieved in vacuum at 200°C for 50 hr. Powder photographs were taken in an 114.6 mm diam camera (Straumanis film mounting) at room temperature and in a 19 cm diam Unicam high temperature camera at elevated temperatures. Copper x-radia-tion was used for all the photographs. The powder pattern of neodymium was found to index to a hexagonal unit cell with dimensions, as determined from the high angle Ka doublets, of: a.= 3.655+0.001.4; c, = 11.796+0.004.4; and c/a = 3.227 at room temperature. The measured density of neodymium shows that this cell contains 4 atoms, the calculated density is accordingly D, = 7.02 g per cu cm. The diffraction data for the first 15 lines of the powder pattern are listed in Table I. In a double hexagonal-close-packed unit cell, the 4 atoms would be in the positions (0,0,0), (0,0,%), (1/3, 2/3, 1/4), and (2/3,1/3,%) of space group P 6,/mmc. On the basis of these positions, the relative intensities of the reflections were calculated using the expression: 1+cos2 20 I oc \Frp 1 ' sin2 0 cos 0 where F is the structure factor and p is the multi- plicity factor. Since absorption was not taken into consideration, comparison of observed and calculated intensities should be made only for neighboring reflections. Each atom has 12 neighbors, 6 in the basal plane at a distance of 3.655.4 and 3 above and 3 below at the closer distance of 3.626.4. These distances correspond to an average radius of the neodymium atom of 1.820.4. The description of this structure in terms of A, B, and C close-packed layers of atoms is ABAC ABAC. ...... The structure repeats every fourth layer and the stacking sequence of the second, third, and fourth layers corresponds to cubic-close-packing of atoms. A series of powder photographs taken at successively increasing temperatures up to 680a10"C revealed that the double hexagonal-close-packed structure is stable up to this temperature. Acknowledgments The authw wishes to thank W. H. Zachariasen and A. S. Coffinberry for their helpful comments on this work and also Marion Gibbs for measuring the diffraction films. This work was sponsored by the United States Atomic Energy Commission.

Jan 1, 1956