Search Documents

By Truman Aldrich

THE Clinton group of the Silurian holds the red or fossiliferous ore; its outcrops have been mapped by the State or U. S. Geological Survey. This group is from 100 to 500 ft. thick in Alabama. There are places where it is entirely missing (doubtless islands in the Silurian Sea). In Etowah County, in part of Greasy Cove and vicinity, the upper seam is a coral reef impregnated with the red ore; in this same county, step, faults bring up the ore in three or four separate ridges practically parallel. In Blount County and on Raccoon Mountain, the ore runs under the carboniferous rocks and outcrops in the valleys. In examining some bore holes made in drilling for oil, the writer found the Clinton group continuing under the Warrior coal field wherever the drill has gone deep enough. It demonstrates the possibility of a source for red ore not seriously thought of until lately. The following bore holes made principally for oil, given in Bulletin No. 22, Geological Survey of Alabama, show the presence of either ore or red rock, and suggest vast resources yet to be outlined and developed for ore in the future. The locations are given by number on the map. Hole No. 1 was drilled 6 miles southeast of Russellville, Franklin County, by the Woodward Oil & Gas Co. It passed through 160 ft. of Clinton, but only a small show of red ore was found at 1280-1400 feet. A test well, No. 2, drilled near Atwood, Franklin County, in section 26, township 8, range 14, penetrated the Clinton at 1608 ft. and found 38 ft. of limy red rock, also 8 ft. of some blood red ending at 1820 ft., making 46 ft. of red rock in all. It is reported that some good ore was cut through but this work was done by a churn drill. The hole was continued by diamond drill from here. At least 400 ft. of the formation was classified as Clinton.

Jan 10, 1924

By Edwin Shorey

IN THE southwestern Wisconsin zinc district, lying in Lafayette, Grant, and Iowa Counties, and the adjoining territory in northwestern Illinois, the orebodies are generally small, and are mined out in a few years. Many of the mines are developed with an expectation of five years or less of actual production. For this reason, as well as for considerations of economy, certain features in the development practice, which have been worked out with a view toward keeping the ratio of time required for, development to that occupied by actual production as small as possible, are of interest. ORGANIZATION The organization of a crew for, this work is as follows: Inasmuch as speed in sinking is desirable, the shaft crew comprises three shifts working 8 hr. each. In the smaller shafts, running up to 6 by 12 ft. (1.8 by 3.6 in.) in size, two men are employed on a shift; in larger shafts an additional man is usually employed. A mine foreman, or ground boss, has general control of the work of the three shifts. He is usually with the crew on the first and the early part of the second shifts, and plans the work to be done for the third shift when it comes on. His schedule, of course, is flexible and when pump changes, or other special conditions warrant, he, arranges his working time to suit the occasion. The surface crew for a sinking operation is made up of two hoistermen, each working 12-hr. shifts. Since the various operations in the shaft must be conducted in succession,. and not in combination, one with the other, separate attendance for hoisting and general plant is unnecessary. Drilling is done when no hoisting is necessary and vice versa. The hoisterman trams out and dumps the excavated material which the crew in the shaft is mucking, as a part of his regular hoisting work.

Jan 8, 1920

By A. L. Galpin

INTRODUCTION For many tailings ponds, particularly those having substantial watershed areas, the control of pond water levels will be a major factor influencing the operation of the pond and the design and construction of the dam retaining the pond. This paper summarizes the basic factors affecting the control of water in tailings ponds, methods of water control, and methods of estimating the variables involved. The influences that pond water levels can have on the design, construction, and stability of tailings dams are explained in order to emphasize the importance of water control in the overall planning of mine tailings disposal systems. Two examples of pond water control planning conclude the paper. BASIC FACTORS The principal factors influencing the control of water in tailings ponds are illustrated on Fig. 1. Fig. 1 (a) shows the general disposition of the tailings solids and water in the pond; the solids settle from the slurry to form "slimes", deposits sloping down into the pond from the points of discharge; these slimes hold volumes of water in the voids between solid particles; water in excess of this "retained" water forms a pool of "free" water laying over the slimes deposits. In some cases, tailings solids (and water) go to the tailings dam for its construction. Fig. 1 (b) indicates those ways additional to tailings disposal in which the pond gains or loses water. These include surface and sub-surface runoff from the pond watershed, water reclaimed from the pond for ore processing, evaporation, and seepage. Seepage losses sometimes include water draining from tailings sand placed in the dam, but a portion of the total seepage flow is often collected and returned to the pond in order to avoid downstream pollution and to recover water for re-use. PRINCIPAL REQUIREMENTS In relation to the control of water in a tailings pond, the first requirement is usually to maintain a pool sufficiently large to ensure adequate clarification of the free water prior to its reclaim for use in the mill, or its discharge from the pond.

Jan 1, 1972

By E. Ozberk, N. Gibson, W. G. Davenport

"In the 1950s, Canada produced more than ninety-five percent of the non-communist world's nickel and achieved dominance in terms of production, technology and pricing policies.Over the past thirty years there have been dramatic changes in the nickel industry to the extent that Canadian production is now less than thirty per cent of the total.In this document we have presented statistics relevant to this transformation and reviewed the technology, particularly with regards to energy and environmental considerations.Under the new market conditions nickel producers are likely to face more difficult competition than they have encountered in the past.The economic scene and measured nickel reserves dictate that for the purpose of increasing production, new nickel smelters will not be built in Canada in the foreseeable future. However, in order to reduce sulphur dioxide emissions, Canadian nickel smelters will possibly go through some modifications or rebuilding.IntroductionThis paper presents a review of the Canadian nickel industry in relation to the world nickel industry. Major changes are described which have occurred in the characteristics of the nickel market over the last thirty years. The pre sent status of the nickel market with respect to Forecasting future trends is reviewed and attempts are made to predict what further changes will take place in the next two decades. Comparisons are made of the economics of producing nickel from sulphide ores and oxide ores and the advantages and disadvantages the Canadian nickel producers face.A brief critique of the existing and emerging nickel production technologies in Canada and the world is carried out and attempts are mad e to predict the changes which may take place in the foreseeable future."

Jan 1, 1983

By T. Moyo

Ammoniacal solutions are attractive and effective lixiviants for the dissolution of chalcopyrite, allowing for the formation of stable ammine complexes with copper while rejecting iron. Chalcopyrite dissolution in ammoniacal solutions is reviewed from literature, and results from a recently completed study evaluating it through electrochemical and controlled leach studies are discussed. Ammoniacal leaching of copper ores dates back to 1916 in the leaching of low grade copper ores in the Kennecott leaching plant and in the Calumet and Hecla mines, followed by the commercialisation of the Sherrit Gordon process for the ammoniacal leaching of sulphide copper ores in 1948. Since then ammoniacal leaching has received intermittent focus from researchers with the development of the Anaconda’s Arbiter process and the unsuccessful Escondida process. In these leaching processes, the formation of surface deposits has historically been reported to result in the passivation of the chalcopyrite surfaces, whereas oxygen mass transfer in solutions has been the focus of process design improvements. Results of studies on high grade chalcopyrite material is presented in this paper which show that although a surface deposit was formed, it did not result in the passivation of chalcopyrite in ammoniacal solutions, and that while oxygen transfer is critical, it is not the direct oxidant in the reaction. INTRODUCTION Ammonia and its salts have been used in the hydrometallurgical treatment of non-ferrous metals such as copper, cobalt and nickel from oxide ores. Its chemistry allows for the selective dissolution of desired metals, leaving behind gangue including iron. Chalcopyrite is a copper sulphide ore known to be very stable and hence recalcitrant to many hydrometallurgical processing methods. Thus, the dissolution of chalcopyrite continues to be an attractive area of research. The dissolution of chalcopyrite in ammoniacal solutions is possible due to the stabilisation of copper(I) and copper (II) ions by ammonia in alkaline media. Ammonia has become more attractive as a lixiviant during the present socio-economic climate due to its low toxicity, relatively low cost and ease of regeneration by evaporation (Meng & Han, 1996). Ammonia processes are ideal when the gangue minerals are acid consuming e.g. with calcareous or dolomitic gangue (Paynter, 1973).

Jan 1, 2019

By V. R. Garfias

. EVEN before the arrival of Cortes in 1519, the history of Mexico was closely linked to that of its mineral production; the mining activities of the Aztecs being thus described by Clavigero, one of the early historians: In the mountains of Anahuac there abound in veins all kinds of metals, and infinite variety of other fossiliferous products. The Aztecs obtained gold from the countries of the Cohuijques, of the Mixtecas, of the Zapotecas and from various other places. They gathered that precious metal usually in grain, from the sands of the rivers, keeping a certain portion for the crown. They obtained silver from the mines of Taxco, of Tzumpango and others; however, this metal was not as esteemed by them as by other neighboring nations. They had two kinds of copper; one hard, which they used instead of iron to make sickles; lances and all kinds of rural and military instru-ments and another, soft, with which they made kettles, goblets and other receptacles. This metal abounds mainly in the province of Zacatula and in that of Cohuijques, which at present is in the kingdom of Michoacan. They obtained tin from the mines of Taxco and lead from those of Izmiquilpan, located in the country of the Otomies. From the tin they made money, and the lead, we know they sold in the market places, but we ignore the uses to which they applied it. They also had mines of iron in Tlaxcala, in Taxco and in other places; but they either had not discovered them, or did not know how to make use of the metal they contained. In Chilapa there were mines of mercury, and in other places there were mines of sulphur, alum, vitriol, cinnabar, cohre and of a white earth which they esteemed highly. As regards mercury and vitriol, we do not know of what use (they were to them; the other metals they used in paintings and dyes. There were then great abundance of amber and asphalt-bitu-men of Judea-on the coast of the seas and many cities of that territory paid tribute of one and the other to the kingdom of Mexico. They mounted the amber in gold, and it was only used as ornament and display by them. With the asphalt they made certain perfumes.

Jan 1, 1937

By Thomas Fraser, H. F. Yancey

PRIOR to the war just ended, Germany was the greatest coal producer in continental Europe. In 1943 the production of coal, bituminous and higher in rank, together with brown coal calculated to the equivalent amount of bituminous coal, is estimated to have been about 240 million metric tons, according to the War Department. Before the war production in Germany exceeded consumption. No other country in continental Europe except Poland had a large surplus. However, England's surplus was the largest in Europe as a whole. Before World War II the Ruhr Basin normally supplied about 70 pct of the total production of high-rank coal, the Saar and Aachen about 6 pct each, Upper Silesia about 14 pct, and Silesia and Saxony the remainder. Nearly one third of the brown coal was produced in the Rhineland, a little less than one half in central Germany west of the Elbe River, and about one fourth east of the Elbe. Bituminous coal and brown coal together constituted by far the most important energy resources of the old German Reich. Bituminous coal furnished nearly 70 pct of the total energy requirement, brown coal supplied about 25 pct, and water power, wood, petroleum and alcohol together aggregated only 7 pct. Because it was the most important single mineral resource of Germany, an excess of coal enabled the Reich to import nearly all the other mineral products that she lacked, such as iron ore from Lorraine. The area adjacent to the coal fields was supplied with gas from an interconnected grid. Similar electric grids are based on brown coal with the power stations at the mines. Coal tar provided the foundation for the development of the extensive German chemical industries as exemplified by the I. G. Farbenindustrie. For almost a century, German scientists have been adequately supported both by the State and by industry in studying improved methods of utilizing coal. In Germany the mineral rights were reserved by the State and ordered extraction of coal was enforced. Each lease comprised a relatively extensive area, which accounts for the generally large size of the mines and mining companies. In 1938 there were 160 mines in the Ruhr, with a total output of 125 million tons but go pct of the production was controlled by 20 companies. By far the largest single coal-mining company in Germany was the Gelsenkirchener Bergwerke A. G., which produced nearly 27 million tons in the Ruhr in 1937. Second was Saargruben A. G., a State-owned company operating in the Saar, which produced more than 13 million tons. Third was Bergwerksgesellschaft Hibernia A. G., with 10 million tons, also in the Ruhr. Briquettes are made from both bituminous coal and brown coal, but in 1938

Jan 1, 1946

By James K. Stanley

PREFERRED orientation, particularly in irons and low-carbon steel, is a phenomenon that is both of considerable importance and theoretical interest. At times it is a liability and at other times an asset. In deep-drawing operations, preferred orientation is extremely undesirable because it necessitates trimming operations and increases scrap loss. Furthermore, oriented metals are likely to crack more easily than randomly oriented material because the forming of symmetrical and unsymmetrical shapes out of preferentially oriented metals and alloys increases the probability of rupture in regions of high stress, owing to differential ductility.1 In the electrical industry, on the other hand, preferentially oriented silicon irons are in demand for transformer application because of the improved magnetic permeabilities in the rolling direction.2 This phenomenon of preferred orientation in soft magnetic materials has been responsible for the tremendous improvement in transformer design and construction in recent years. Directional properties in metals have received a great deal of attention in the metallurgical literature,3-9 in which much of the information reported about orientation has been obtained by conventional methods, mechanical properties and X-rays. A wealth of data has been obtained and often at a great expenditure of time. The recent introduction of the magnetic torque measurements on ferromagnetic materials provides a very simple and rapid method of evaluating orientation. The judicious use of the method can supply important in- formation, but it should be borne in mind that such studies must be supplemented by X-rays, optical methods,10 and etch and pressure figures" to get a rational under- standing of the orientation phenomena. No claims are made that the magnetic torque of evaluating orientation will reveal the behavior of the metal in deep drawing. For this purpose the accepted tests for deep-drawing quality must be used. For a good drawing 'stock, which must have low impurities, desirable grain size, ductility, strength, hardness, good surface, random orientation, and good recrystallization behavior, it cannot be expected that any simple test will be satisfactory for appraising all the factors. The only factor on which the magnetic method can be used is orientation, which is, of course, of considerable importance. When directionality can cause a 10 to 15 per cent change in tensile strength and a IOO to 300 per cent change in tear length,12 it goes without saying that a reliable as well as rapid method for detecting these changes would be desirable. There are certain inherent advantages in testing orientation by the torque method: The method is rapid with the proper type of equipment; no elaborate preparation of specimens is required-it is only necessary punch or machine a disk of the sheet material and insert it into the testing device.

Jan 1, 1943

The mechanism of thiosulfate decomposition and the products formed were investigated in the presence of pyrite or pyrrhotite in copper-ammonia solutions used for leaching gold. The presence of the sulfides significantly increased the decomposition of thiosulfate. The sulfide-surface-catalyzed oxidation of thiosulfate to tetrathionate by dissolved oxygen or the cupric tetra-ammine complex was proposed to be the dominant thiosulfate decomposition mechanism. The catalysis of the sulfides in this reaction could originate from their strong affinity for aqueous sulfur species and their semiconducting properties. Oxygen was found to be the initial driving force for thiosulfate decomposition in the absence of cupric ions and the driving force for the continuous decomposition of thiosulfate in the presence of cupric ions. Under an oxygen free atmosphere, the decomposition of thiosulfate was limited to reduce the cupric ions and the catalytic effect of the sulfides was also marginal. The dominant oxidative product of thiosulfate was trithionate in alkaline solutions especially in an oxygen rich or cupric ion rich environment. Tetrathionate was found in relatively smaller amounts in an oxygen and cupric ion deficient environment. Tetrathionate was not stable and would further decompose after extended periods. Trithionate concentrations increased almost linearly with time.

Jan 1, 2005

By Qingxia Liu, Mingbo Zhang, Hongbo Zeng

The shortage of freshwater has been a major challenge for mineral flotation in arid areas. When using high salinity water, certain electrolytes are detrimental to flotation while others can improve the flotability of minerals. In this paper, the flotation behaviors and contact angles of pyrite in both Milli-Q water and high salinity water were investigated using different collectors at various pH levels. Results show that the thionocarbamate has a less affinity to pyrite in different solutions under mildly alkaline conditions as compared with potassium amyl xanthate (PAX) and N-isopropoxypropyl-N’-ethoxycarbonyl thiourea (iPOPECTU). At high pH levels, the slime coating on pyrite surfaces, which is caused by colloidal precipitates of magnesium and calcium ions in seawater, was confirmed by SEM, EDX and in-situ zeta potential measurement. The slime coating of colloidal precipitates on mineral surfaces led to low recovery of pyrite at high pH levels. The study of flotation behavior of pyrite in high salinity water improves our fundamental understanding of mineral flotation in seawater.

Jan 1, 2015

By T. B. Linde

The Morenci In-pit Crusher and Conveyor System has been designed with safe production and cost savings in mind. Large open pit mines around the world have been installing semi-mobile crushers and linking them with a pit conveyor system to lower unit cost. At Morenci two 60/89 in. gyratory crushers are incorporated into the semi-mobile crushing plants. The ore is reduced to -8 in. and transported out of the mine on a 60 in. steel cable belt. This paper includes an overview of the Morenci In-pit Crusher and Conveyor System from the drawing board to open pit installation and finally a discussion on operating and repair considerations.

Jan 1, 1990

By R. A. Brown

RIGHT NOW the Canadian oil business is suffering from growing pains brought on by developments outside our borders. I would like, therefore, to place our industry in perspective for you in two ways. I would like first to describe it briefly and let you see it in relation to the world oil industry. Then I would like to bring it back and place it into perspective against a strictly Canadian background. Naturally, in such a discussion, it is necessary to use a certain amount of statistical material. I'll endeavour, however, to keep it to a minimum. Eleven years ago, before the discovery of Leduc, Alberta could boast of having 21,000,000 barrels of crude oil reserves. Five years ago we had 1,810,000,000 barrels. At year end, 1957, our remaining recoverable reserves totalled more than 3,000,000,000 barrels. In 1957, our potential production in Alberta reached an all-time high of 756,000 barrels a day. Unfortunately, our actual average daily production dropped from 393,000 barrels per day in 1956 to 376,000 barrels per day in 1957. And in 1958, to date, it has dropped sharply to around 300,000 barrels per day.

Jan 1, 1958

By F. B. Plummer

PERHAPS the greatest progress made in the technical methods of oil production during the last year has been in handling gas from the new fields that yield light distillate fractions. At least sixteen recycling plants have been perfected and installed in South Texas fields alone during 1939 having a daily capacity of more than one billion -2 cubic feet of gas and capable of producing more than a million gallons of distillate daily. The process consists of running the gas under pres- sure through especially designed plants, separating out the condensate, then compressing the gas to 3000 lb. or more, depending on the subsurface pressure in the formation, and injecting gas back into the reservoir to be produced again later, along with more of the liquid hydrocarbons, and again recycled. Hence production in these distillate fields in sense has changed from that of producing a constantly diminishing and much-wasted product to a more or less continuous manufacturing process, in which practically all the gas is conserved-a real triumph in engineering practice.

Jan 1, 1940

By Harry H. Peek

Artesian pressures of unusual magnitude occur in the deeper aquifer units beneath a considerable part of southeastern North Carolina and extend into South Carolina. The high pressures were first observed in 1968 in wells near Wilmington that were drilled to "basement" rock and which were screened between depths of about 260 to 300 m (meters). The pressure was recognized by Peek and Heath1 as an anomalous geo-pressure and unrelated to recharge conditions in the region. Since 1973, much new information has been obtained on hydro-geologic conditions in the area and a preliminary report on the deep artesian pressures was published in 1975.2 Most of the basic information has been obtained from groundwater research stations constructed by the Groundwater Section of the North Carolina Department of Natural and Economic Resources as a part of Ground-water studies in the Coastal Plain Region. These stations consist of an exploratory well drilled to basement rock with wells completed in each principal aquifer unit to provide data on aquifer characterestics, water levels and water quality.

Jan 1, 1977

By Shu Bin, Lin Chen, Tian-zu Yang, Wei-feng Liu, Wan-da Bin

"Antimony resources are rich in china, its reserves and productions are ranking the first in the world. The Chinese antimony mineral resources are mainly existed in the form of three types, such as stibnite, antimony-gold ores andjamesonite. The antimonial dust that produced from lead smelting process is an important secondary antimony resource. The different process that was adopted to extract antimony depends on the different raw materials. The process of blast furnace volatilization smelting is mainly used to treat stibnite and antimony-gold ores. But jamesonite is treated by the process of roasting-sintering-blast furnace smelting. And antimonial dust is treated in the reverberatory furnace. Many new technologies that are applied in these traditional antimony smelting processes play important roles, such as deleading agent, antimony white production, air-oxidation method, direct-blowing method, bath smelting technology, and so on. At the same time, the development of antimony smelting technology in china is prospected according to the requirement of the state environmental protection.IntroductionThere are five countries that produce antimony in the world, such as china, Tajikistan, Bolivia, Russia, and South africa, but China is the largest country of antimony production in the world. In the world, the antimony productions of 2008, 2009, and 2010 are 182,000 tons, 154,000 tons, and 167.000 tons respectively, but Chinese antimony productions are 166.000 tons, 140,000 tons, and 150,000 tons respectively. So Chinese antimony production was accounted for more than 89% of the world in 2010. It indicates that China have irreplaceable advantages in antimony resource and production all over the world."

Jan 1, 2013

Zircon producers are often required to lower impurity levels to meet customer specifications as most of these impurities adversely effect the end use. For example, zircon sand in foundry applications needs to be free of any surface impurities (eg clay, gibbsite and goethite) which otherwise could cause sintering or fusion between cast metal and the zircon mould. Light coloured ceramic grade zircon, typically low in iron oxides and titania, is preferred in ceramics applications. The presence of impurities in zircon sands is a problem in the magnetic and electrostatic separation stages of their concentration. Previous work (Aral et al, 1997) showed that impurities in zircon sand concentrates occurred in the form of stains on grain surfaces, discrete gangue minerals and in the mineral grains. The gangue minerals such as rutile, garnet, xenotime, monazite, spinels, ilmenite, and aluminium silicates in the concentrate in some cases (Aral et al, 1997) contribute significantly to the impurity content of the concentrate. A careful hand picking of the impurity grains from a Western Australian zircon sand showed that the impurity content of the concentrate could be lowered significantly as a result of the removal of the surface stained grains and gangue minerals. The hand-picked ædirtyÆ fraction, comprised about eight per cent by weight of the concentrate, and consisted mostly of iron-oxide/hydroxide-stained zircon, silica grains and rutile, and occasionally ilmenite, monazite, gahnite and other (unidentified) coloured grains. The chemical analysis of the remaining æcleanÆ fraction showed that the major impurities (Fe and Ti) were reduced significantly (Table 1). The reduction in the uranium content was about 30 per cent. The other measured impurities, P, Mg, Al, Th, and Ca remained mostly unchanged as shown in Table 1. The contribution of ilmenite to the overall iron content of æcleanÆ zircon was insignificant as it comprised about 0.1 per cent weight of the æcleanÆ zircon. Rutile was the major source of titanium contamination (about one per cent by weight). Recent work (Aral and Calle, 1999) on zircon sand concentrates from the Murray Basin showed that, under the electron microprobe, the bulk of the impurities occurred in the dark back scattered electron (BSE) regions of the zoned zircon grains. The impurity contents of the light BSE regions and unblemished (unzoned) grains were low. The impurity content in zoned zircons has been investigated on single, relatively large, crystals (McLaren, Gerald and Williams, 1994; Smith et al, 1991; Romans, Brown and White, 1975). These studies generally aimed to investigate the incorporation of U in zircon as zircon is used extensively for U-Pb geochronology owing to its relatively high content of uranium. Smith et al (1991) identified a striking difference in composition between the areas of lower (dark BSE) and higher (light BSE) average atomic number in the zoned zircon. Their work showed in particular that the zones of lower atomic numbers contained very significant amounts of trace metals such as Y, REE, Nb, U, Al, Fe, Ca, Ba and, by difference H2O. In this paper the impurity distribution in zoned zircon grains was investigated on statistically significant number of grains before and after a leach treatment. The distribution of impurities was also measured in unblemished areas to compare the results.

Jan 1, 2000

Tile National Research Council announces further appointments to National Research Fellowships in physics and chemistry. The object of the National Research Council in maintaining a system of research fellowships is to promote fundamental research in physics and chemistry primarily in educational institutions in the United States. Fellowships are awarded to persons who have demonstrated a high order of ability in research for the purpose of enabling them to conduct investigations at educational institutions which make adequate provisions for research: in physics and chemistry. The new appointments are as follows: In Chemistry.-Warren C. Vosburgh, of New York City, B. S. Union College, 1914, A. M. Union College, 1916, Ph. D. Columbia University, 1919. Research assistant to the Professor of Chemistry at Columbia University for the past six months. George Scatchard, of New York City, A. B. Amherst College, 1913, Ph. D. Colt tibia University, 1917. Formerly research assistant to the Professor of Chemistry at Columbia University and instructor in organic chemistry: First Lieutenant. Sanitary Corns. U. S. A.

Jan 7, 1919

By Veal FL

Technological changes in Portland cement manufacturing during past years have reflected changes in the economics and availability of various types of fuel such as coal, fuel oil and natural gas. The industry consumes a sig- nificant quantity of both thermal and electric- al energy. The nature of the process and its chemical constraints does however permit the use of comparatively low grade fuels such as high ash coal and high sulphur oil. In striving for increased daily kiln outputs and conservation of energy, there is a worldwide trend towards the use of dry process plants. Wet process kilns of about 2 500 tonnes per day assume massive component sizes which present difficulties in manufacture, and transport to plant sites. Large capacity dry process units in excess of 8 000 tonnes per day are now in operation using precalcination techniques in which part of the fuel is introduced in the static preheater section ahead of the kiln while the balance is added to the kiln in a conventional manner. This technique has virtually doubled the potential output of any given single kiln.

Jan 1, 1976

R. L. Bullock (St. Joseph Lead Co., Bonne Terre, Mo.)— The progressive approach of The International Salt Co. as described by Mr. Ryon is certainly commendable as is his paper. St. Joseph Lead Co. has been shooting AN/FO in 13/8 to 1 1/4-in. holes for several months now (as of October 1960) on a trial basis. The results thus far obtained are excellent, but conclusive evidence at this date is premature. One point that he gave should interest even the most ardent skeptic. That is, they are getting a detonation of the 1 1/4-in. ANDO charges in 2 1/4-in. holes. In light of its low sensitivity and critical diameter, this would appear to be one of the worse conditions that one could expect in which to get proper detonation of AN/FO. It has been shown* that partial confinement sometimes decreases sensitivity of a column of explosive because the air space above the explosive becomes highly compressed and in turn compresses the explosive prior to passage of the detonation front. Apparently, this does not happen in their shooting and the poor explosive coupling caused by the 2 1/4-in. holes yields a minimum of overbreak and is an ideal condition for their back.

Jan 1, 1961

By C. W. Hill

IN a previous article preliminary experiments were described, indicating the possibilities of a quantitative spectroscopic method for the determination of small amounts of lead in copper, which would be accurate and rapid, and could be carried out in the refining plant by one not skilled in chemical analysis. The present paper deals with the development of the method in the factory, giving the details of apparatus and its standardization, and presenting a comparison of the accuracy of the method with that of the standard electrolytic determination. (For variations and other applications of the method, the reader is referred to the first article.) FIG. 1.-STEPS IN THE ELIMINATION OF LEAD. (The lead line, at point 105.8 in the violet portion of the spectrum, is seen between the two copper Lines,-102.29 and -106.29, lying close to the latter. The crowded faint lines are due to the carbon are.) 1. OUTLINE OF METHOD A carefully weighed sample (0.4 gm.) of the copper to be tested is placed in a cavity in a graphite positive electrode. An arc capable of

Jan 10, 1918