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By I Mason, A Wellington, J Hargreaves

Many people are familiar with the use of marine echo sounders which are used by fishermen to monitor water depth and locate schools of fish. Similar technology has recently been used in some West Australian mines to provide detailed maps of ore contacts and other geological structures. Whilst drillhole intersections provide details of the location of a contact at a point, echo sounding can be used to obtain a continuous profile of the contact. A series of profiles together with drillhole intersection data can be used to build a more accurate geological model than can be inferred from drillhole intersections alone. The benefits of this are more complete ore extraction, less dilution and the ability to make more informed financial decisions. This paper presents a case history which demonstrates the successful application of the technology.

Jan 1, 2000

By M. M. Valenta

A number of challenges face platinum concentrator plant operators. These challenges include the increase in operating costs, the increase in smelter cost for the processing of concentrate, the shortage and cost of power, and the tightening of specifications on concentrate quality by the toll-smelting operations. Over the years the focus has moved from extracting the platinum group metals (PGM) from the Merensky Reef to the UG2 reef. This has a number of advantages, including the higher ?basket price? for UG2 concentrate, reduced mining cost per unit volume as a result of the higher density of UG2, and the reduction in overall concentrate tonnage to be smelted. In many cases the Merensky ore has been fully exploited and it makes sense for the focus to shift to the UG2 ore that can be accessed through the Merensky shaft infrastructure. The presence of relatively high levels of chromite in UG2 concentrate is, however, a major disadvantage due to the problems associated with smelting such a concentrate in conventional submerged arc furnaces. In addition to increasing the specification on the minimum PGM grade of concentrates, smelters have had to impose strict specifications on the levels of chromite in the concentrate. The threat of high penalties has forced concentrators to change their modus operandi, often resulting in a significant loss in recovery. The final concentrate grades and PGM recoveries are shown to vary significantly throughout the industry. The reasons for this include varying ore mineralogy and different operating philosophies. This would therefore imply that the opportunity exists to optimize the operations by considering fundamental aspects such as the PGM mineralogy and the application of appropriate technologies. By returning to the fundamentals of flotation and applying the findings of detailed process reviews, it has been possible to increase the concentrate PGM grade, reduce the concentrate chromite grade, and in some cases increase the recovery of PGM to concentrate. This paper presents case studies where this approach has been used to successfully optimize concentrator performance, resulting in lower operating cost and higher PGM production. Keywords Process optimization, platinum concentrator, milling, flotation, grade, recovery

Jan 1, 2011

By Peng Jiahong

With ultrasonics application during checking the large diameter cast-in-situ pile body, it is usualy applied the statistical method of probability and PSD. This paper presents a converse probabilistic-analytical method which can identify important anomalies, both strong and weak, during interfered situation. So the inhomogeneity in concrete pile may be ellectively distinguished. In order to ensure the capacity of bed rock support layer under large diameter pile, a test-in-situ is conducted to determine the compresive strength and shear force inserting rock of the support layer, so the compresive strength and modulus value of elasticity of bed rock tested will closely tally with the actual situation.

Jan 1, 1991

By Klaus Tietz, Hamish Adam, John Selby, Ian Glazier, Brian Sinfield

"Room-temperature tunable diode laser (TDL) analyzers are gaining in acceptance for highly critical safety monitoring applications in a variety of industries. This paper describes the testing, evaluation and deployment of a laser-based hydrogen cyanide monitoring system at the Campbell Complex of Goldcorp’s Red Lake Gold Mines in Balmertown, Ontario, Canada.A trial, single channel installation was followed by a staged multi-channel installation. Unexpected technical issues with the multi-channel installation were addressed and resolved.INTRODUCTIONLaser-based gas detection has several advantages over existing gas detection techniques (Ballangrud, 1993; Silver, 1992; Bomse, 1995; Table 1). For practical purposes, lasers generate light at a single wavelength. Room temperature tunable diode lasers (TDL) emit light in the near infrared (NIR) part of the electro-magnetic spectrum. Many gases of interest, including HCN, NH3 and others, absorb energy in the near infrared (NIR). Each gas has a unique absorption signature, or spectrum, made up of a large number of individual “absorption lines”. A TDL can be tuned to select a single absorption line of a target gas, which does not overlap with absorption lines from any other gases. Therefore, laser gas sensing is selective and does not suffer from interference from other gases. The single-wavelength nature of laser light also means that laser gas analysers have a linear response over a wide dynamic range.Tunable Diode Lasers (TDL) generate only a few mW of power. However, all this power is concentrated at one wavelength, the wavelength where gas absorption occurs, resulting in high signal-to-noise ratios and short response times, typically of about 1 or 2 seconds (Ballangrud, 1993). This also means that long path lengths can be used, enabling accurate measurements of very low concentrations, even with weakly absorbing gases. Tunable Diode Lasers provide all the advantages of other semiconductor devices: they are small, solid-state devices, operate at room temperature, and have long-term reliability (over 15 years). Currently, they can be obtained for any wavelength throughout the NIR (700nm to 2000nm). Because many gases absorb in the NIR, the technique is widely applicable."

Jan 1, 2011

By A. R. Gaba

Phase I of the Canary Wharf development in London's docklands involves the construction of six fifteen storey buildings located predominantly over water of the West India Docks. The buildings are supported on some 1000 No., 25m long, open ended steel tubular piles driven through 10m of dock water to found in dense sand at a depth of about 15m below dock bed level. The piles are of composite section with reinforced concrete within the upper 17m of the steel tube. Three trial piles were installed in the dock to investigate the driveability and performance of the driven steel tubular piles. The piles were subjected to dynamic and static load testing. Loads were applied in both vertical and horizontal directions. Vibrating wire strain gauges were installed on the inside of the steel piles, on the reinforcement and in the concrete to determine the relative proportions of the applied load carried by the steel tube and concrete infill and to establish how these proportions varied along the length of the piles. Inclinometers were also installed to monitor the lateral deflection of the piles. This paper describes the driving, construction and testing of the three trial piles. The results of the vertical and horizontal loading tests are discussed and comparisons are made between dynamic and static tests carried out on the piles.

Jan 1, 1989

Geopolymerization is a process by which Al-Si minerals undergo dissolution and polymerization in an alkaline solution to form a monolithic material with a high mechanical strength (Davidovits, 1991; 1994). In this study, Na-feldspar (albite) and K-feldspar (microcline) have been selected to investigate their abilities to undergo geopolymerization. The interaction between alkali metals present in the alkali-feldspars and alkali metal cations contained in alkaline solution during geopolymerization has also been studied. It has been found that both albite and microcline can be applied in geopolymerization to produce geopolymers with a high compressive strength. Although the dissolution of M-feldspar (where M = Na and/or K) in concentrated MOH solution is inhibited when the alkali metal cations of the alkaline solution differ from the alkali metals structured in M-feldspar, the resulting geopolymers are found to demonstrate a higher compressive strength. Moreover, a proper molar ratio of Si/Al in the geopolymeric gel phase and a higher average hardness of the undissolved particles remaining in the geopolymers are found to greatly increase the ultimate compressive strength of the geopolymers.

Jan 1, 2002

By Earl Rau

Introduction Will cogeneration be a major power source in the future? The location of electric power generating plants has changed. In 1900, more than 50% of electricity was generated by industrial plants. Since then, industrial plant generation of electricity greatly decreased to 17% in 1950 and to only 3% in 1980. Changing economics in electric power generating costs, though, may allow cogeneration to reverse this trend. Cogeneration has been defined as the simultaneous production of electric (mechanical) and thermal energy from a single energy source. Some applications are considered to be byproduct generation of electricity from industrial, thermal operations. Cogeneration is not new to the mining and minerals industry. Smelters and steel mills have used waste heat to generate electricity. Public Utilities Regulatory Policies Act of 1978 The potential for increased industrial cogeneration of electricity is related to the March 9, 1978 enactment of the Public Utility Regulatory Policies Act (PURPA). The US Supreme Court ruled that PURPA is constitutional. The court upheld requirements that utilities interconnect to cogenerators. It also ruled that 100% of avoided costs be used as the guideline for electricity sales by a qualifying facility (QF) to a utility. The state of New York established a floor price $0.06/kWh for electricity sales from a QF to a utility. It is obvious, then, that a cogenerator must first establish price and then become a qualifying facility in order to sell electricity to a utility. Proposed cogeneration plants The estimated industrial cogeneration potential for the years 1986 to 2000 is 9500 to 25,000 MW. Industries represented in this cogeneration estimate are pulp and paper, petroleum, chemicals, food, textiles, rubber, plastics, steel, lumber and wood, cement, glass, metal fabrication, and industrial parks. A cogeneration plant has been proposed for the Union Carbide chemical plant in Institute, WV. A steam turbine/generator would be installed to replace the pressure-reducing valve in the 2.7 MPa (400 psig) header. Scott Paper Co., Mobile, AL, proposed a cogeneration plant using a coal- and wood-fired boiler and a turbine/generator to produce process steam and electric power. A cogeneration system has been proposed for a large oil refining plant. A pulverized coal boiler would produce high-pressure steam to operate a turbine, generator. The exhaust steam from the turbine will go to the process and an existing turbine. Kansas City, MO's Armour meat-processing plant has proposed a cogeneration plant. This proposal is to use a natural gas or oil-fired, gas-driven turbine and a generator. The waste heat from the gas turbine would go to a heat recovery boiler for use as process heat. Dade County, FL is implementing a central energy system to supply electricity, air conditioning, and domestic hot water for five buildings in downtown Miami. The cogeneration system is to provide flexibility, to optimize fuel use efficiency while serving the variable thermal demands. Generation of electricity from municipal waste is not considered to be a cogeneration process but is covered by PURPA. Special considerations are provided for waste/electric power generation to encourage the development of these systems. ?

Jan 7, 1987

By D. Mohan

Soft to medium dense silty and clayey soils are found in many parts of India and conventional friction piles have normally been used for foundations of high rise buildings and other structures on such soils. The author investigated the use of Bored Compaction Piles and these have been used on these soils achieving substantial economies in cost over conventional friction piles. Similarly highly expansive clays, commonly known as Indian Black Cotton Soils occupy about 20 percent of the Indian land area. Short bored underreamed piles have been developed for such soils and a very large construction of various types of buildings and other structures have come up on such piles over the last thirty years in various parts of the country. The paper describes investigations leading to the design and development of both these type of foundations.

Jan 1, 1989

Mr. Chairman, distinguished guests, ladies and gentlemen. Thank you for asking me to your conference, with its most fundamental and appropriate topic of 'Investment in Mining'. I must confess at the outset that I am one of those Australians who has rarely visited your fair land of New Zealand. This is in fact only my third visit, with all three related to Institute Conferences, and all much too brief. In so many ways your country provides a counterpoise to ours, despite the obvious disparities in size and population. And I am not only referring to the Bledisloe Cup! We would certainly each be much more lonely without the other, in this strange long-lost corner of the globe û if globes can have corners. Such an important factor in common in our shared heritages has been the mineral industry we have won from our alluvials and our rocks û especially for gold. So much of the major mineral developments which have supplied the world's appetite for metals and fuels in the past two hundred years has come from the countries settled in that period by people from Europe, especially those from the British Isles. So much of the technology for mineral and metal extraction has come from the skills of those people in New Zealand and Australia. And so much of the further development of metal processing and manufacturing of productive equipment has come from those people and from their cousins throughout the world. It is, I believe, a fair question to ask why we have failed to build on those early and considerable successes, and why we have in so many ways apparently been so content to allow others to add value to our raw materials, and to take our technological developments on to levels far beyond those that our domestic markets could sustain.

Jan 1, 1988

By H. Kose

In this research, a model quarry with an annual production capacity of 1 000 000 tonnes has been studied for both pit and hillside quarry cases with constant overall slope angle and variable bench slope angle, considering road grades of 8 per cent and 10 per cent. First, technical requirements have been determined and then the effect of production parameters, such as hole diameter, type of quarrying (pit or hillside) and road grade, on the cost has been investigated to determine bench height. Based on the results, it has been concluded that hole diameter has to be kept large in both pit and hillside quarrying to reduce drilling unit costs. In addition, in order to take advantage of gravity and reduce transportation cost, it has been suggested that bench height and road grade have to be kept high and low respectively in the case of hillside quarrying (downhill transportation) while, in the case of pit quarrying (uphill transportation), bench height and road grade have to be kept low and high respectively, in order to transport the blasted material to a lower height and distance, to save energy, thus decreasing the transport cost. Keywords: Quarry, pit, hillside, road grade, bench height

Jan 1, 2005

By K. H. J. Clarke

SINCE the beginning of this century the non-ferrous mineral industry has contributed $17,809,-000,000 to the economic growth of Canada. To contemplate the vast amount of investment capital required and the resultant beneficial distribution of these billions of dollars for labour, transportation, supplies, taxes and dividends, challenges the imagination. It is the purpose of this paper, (a) to trace the development of the industry since its formative period to the present; (b) to discuss the current situation and problems; and ( c) to attempt to peer into the hazy future. Although there are 21 metals currently being produced in Canada which are classified as non-ferrous, or as alloying metals, copper, lead, zinc, nickel-the metals which will be discussed in this paper-constitute almost 60 per cent of their total value. ;The story

Jan 1, 1961

By Derek J. Cyr

Climate has an immense impact on the properties of Athabasca oil sands and the ease or difficulty with which it is excavated and extracted. During the winter months, exposed oil sands surfaces freeze. When hydraulic and electric shovels used in the various operations in the Fort McMurray area excavate the benches, large frozen lumps are created. These lumps are either destined for a lump dump where increased costs are incurred due to rehandle, or they are sent to the primary crushers where they can cause significant downtimes by jamming the crusher. The crusher down time can sometimes be in the order of hours of lost production. Studies on data from two consecutive winters at Syncrude Canada?s North Mine show a high correlation between climate and the generation of frozen oil sands lumps. Temperature, ground cover, traffic, bench exposure time, oil sands grade and moisture content all contribute to this problem. A 1D frost penetration model was used to predict the depth of frost expected in oil sands and the corresponding likelihood of frozen oil sands lumps. To combat the challenge of frozen lump generation, a number of proactive and reactive measures can be taken: artificial snow, shallow ponds, scheduling, blasting or ripping.

May 1, 2004

By D. F. Smith

The thermodynamic data presented in the literature for zirconium compounds are incomplete. Among the compounds for which adequate data are Zacking are zirconium fluoride and sulfate. This paper reports experimental heat-content values determined by the Bureau of Mines for these two zirconium salts throughout the temperature range of 273° to 1,200° K. No crystalline transformations were found in the two compounds investigated, and neither of the compounds melted over the temperature range studied. MATERIALS TESTED The Oak Ridge National Laboratories, Oak Ridge, Tenn., supplied the two zirconium salts used in this investigation. The zirconium fluoride was high- purity reactor grade material. The zirconium sulfate contained between 0.01 and 0.10 percent hafnium and calcium, and other elements in concentrations below 0.01 percent, A spectrographic analysis of the two compounds is given in table 1. Before use the compounds were dried at 400° C. for several hours to removed adsorbed moisture.

Jan 1, 1962

By Cary Hirner

The Metropolitan Water Reclamation District of Greater Chicago (District) is in the final phase of completing the Calumet System component of the Tunnel and Reservoir Plan (TARP) by bringing the Thornton Composite Reservoir online by 2014. The Thornton Composite Reservoir will provide nearly 30 billion liters (7.9 billion gallons) of additional storage for minimization of combined sewer overflows(CSO) and flooding in the Chicago metropolitan area. The project requires that the existing 6.7 m (22 ft) diameter Thorn Creek tunnel conveying overbank flood flows is re-routed and connected to the Thornton Composite Reservoir. This paper presents the components of the Thornton Composite Reservoir and specifically the detailed evaluation of a drill-blast tunnel. Other project features include an access shaft, control gate, energy dissipating structure, bulkheads, and live tunnel connection. The construction contract will be procured in late 2009.

By K. K. Landes

The north central and northeastern states supply over 50 pct of the chemical and metallurgical limestone produced annually in the United States, and Ontario is the leading source of this material in Canada. About three fourths of the chemical and metallurgical stone produced in this area comes from Michigan, Pennsylvania, Ohio, and Ontario. The specifications, physical and especially chemical, for chemical and metallurgical stone depend upon the end use, but in general the tolerance for impurities is so low as to rule out most limestones and dolomites. Both high calcium limestone and dolomite are used in the metallurgical and chemical industries. The principal metallurgical use is as a flux in iron ore blast furnaces and open hearth steel furnaces. The major chemical uses are in lime burning and soda-ash manufacture. Other important uses include glass manufacture, in making calcium carbide, and in sugar factories. All deposits of high quality carbonate rock are definitely finite. Invariably and inevitably they diminish in either thickness or quality laterally so as to become unworkable as chemical and metallurgical stone. The size of these high quality lenses ranges from a few thousands of tons to hundreds of millions of tons. The best hunting for new supplies is in the geologic formations known to contain premium quality deposits. However, because of high transportation costs, carbonate rocks, to be workable, must be close to market, dollarwise. Definitions: Chemical stone is limestone or dolomite used as a raw material by the chemical industry. The major chemical uses are in lime burning and soda-ash manufacture. Other important uses include glass manufacture, making calcium carbide, and in sugar factories. The specifications for chemical stone depend entirely upon the end product. Some uses require dolomite, some require high calcium limestone; in a few instances, notably in lime burning, either type of carbonate rock can be used as raw material. As a general rule, a fairly pure stone is necessary and for certain particular uses the tolerance for some elements such as sulfur, iron, and phosphorus may be extremely small. Metallurgical stone is used as a flux in furnace operations, especially in the blast furnace where iron ore is converted into pig iron and in the open hearth furnace where pig iron is made into steel. Either limestone or dolomite can be used in the blast furnace, but only high calcium stone is charged in the open hearth (except for rice-size dolomite used as a refractory). There are no rigid chemical specifications for blast furnace stone, but low silica, alumina, sulfur, and phosphorus are desirable. For open hearth use, in addition to low magnesia, a very low sulfur content is also specified by many furnace operators. For furnace use, fluxstone also must be sufficiently shatter resistant that it will remain in lump form during transport and charging into the furnace. Commercial stone is the term applied in the trade for crushed stone used for roadstone and in concrete aggregate. Many of our best chemical and metallurgical limestones are too soft to qualify in the Los Angeles abrasion test for use as commercial stone. However, some limestones, and a higher proportion of dolomites, do qualify for commercial stone and so can be sold to either market. Place Value: Even the highest grade limestone is still a bulk commodity with a relatively low value per ton. As a matter of fact there is very little difference in the average price per ton between high grade chemical and metallurgical stone and crushed limestone used commercially. Most high quality stone is produced in large operations with consequent low cost per ton whereas most commercial stone is produced in relatively small local quarries. As in the case of other bulk commodities most limestone buyers pay more for transporting the raw material than the cost of the stone at its source. For this reason steel furnaces and chemical plants

Jan 1, 1961

By James A. Madonna

Several universities and colleges in Australia, Canada and the United States, recognized the need to establish or reorganize geoscience programs at the vocational and two-year technical levels. To accomplish this, a cooperative study with industry in one state or province from each country was initiated. These include Tasmania in Australia, British Columbia in Canada and Alaska in the United States. The objective of this work was to develop a diversified geoscience educational model at the two-year technical, vocational and continuing education level that provides the source from which any nation can draw the proper educational tools to create a new geoscience program, modernize an existing program or strengthen a weak program. More than 100 mineral industry organizations provided information regarding their specific training needs for support personnel. The data gathered have been used to identify training areas for semi-skilled, skilled and technical personnel in geochemical mineral exploration. These included geological, geochemical, environmental and computer skills. With the areas of major educational need defined for geochemical exploration, an educational field skills model was developed for the three levels of training. The international need for a study of this type was recognized as early as 1980, following numerous contacts from domestic and foreign geoscience educators regarding the structure and success of training within the University of Alaska Fairbanks Mining Extension program, located in Fairbanks. Contacts, correspondence and visits included educators from Australia, Brazil, Canada, Mozambique and the conterminous United States. The need was magnified between 1985 and 1989 at the University of Alaska Fairbanks, when an attempt failed at initiating and developing a two-year geoscience vocational-technology program leading to an Associate of Science degree.

Jan 1, 1994

By M. Fan, M. Mankosa, G. Luttrell

"Column and other non-conventional flotation approaches continue to provide benefits where conventional flotation processes have exhibited limited success. This is particularly evident with respect to flotation of ultrafine and coarse particles. Advancements in air sparging technology have provided the ability to produce finer bubbles than previously possible. The generation of finer bubbles coupled with the froth washing capabilities of a flotation column has demonstrated improvements in ultrafine particle recovery while simultaneously producing a high-grade float product. On the other side of the spectrum, the use of these sparging technologies while applying flotation fundamentals to a fluidized-bed reactor has increased the maximum floatable particle size up to and in excess of 3 mm. Benefits of higher recoveries and reduced reagent consumption have resulted from the use of these technologies. An additional benefit includes a reduction in plant grinding requirements. As such, this paper describes the application of Cavitation-Tube sparger technology and fluidized-bed flotation (HydroFloat). A review of data from industrial and pilot-scale applications is also provided.INTRODUCTIONConventional (mechanical) froth flotation is considered the workhorse of the minerals processing industry. This low-cost process makes it possible to selectively recover minerals by exploiting the difference in surface characteristics (e.g., wettability) of the valuable component and the waste material. Unfortunately, the upper particle size limit for flotation rarely exceeds 0.600 mm, and is typically maintained at less than 0.300 mm for most industrial applications. For many commercial base metal plants, the particle size range for optimum recovery is typically between 0.01 and 0.1 mm (Lynch et al., 1981). This finding is not novel. In fact, the effect of particle size on flotation recovery was studied as early as 1931 by Gaudin et al. who showed that coarse (+0.250 mm) and extremely fine particles (-0.010 mm) are more difficult to recover than particles of an intermediate size. The loss of recovery is due to inherent limitations associated with the flotation process, including bubble-particle adhesion and collision, detachment, buoyancy, and transport."

Jan 1, 2010

By James M. Spear

The U.S. Bureau of Mines and the U.S. Geological Survey conducted a mineral survey of the Elk Creek RARE II area during the summer of 1981. The study area encompasses 18,900 acres [29.5 sq mi (7,680 ha)] along Elk Creek, 18 mi (30 km) southeast of Covello, California. No mineral resources were identified by the U.S. Bureau of Mines during this survey. Assay results of samples taken in this area indicate only trace amounts of manganese and chromium. No radioactive or fluorescent minerals were detected. No oil and gas, coal, or geothermal leases have been recorded for the study area.

Jan 1, 1982

By C. A. Young

Cyanide is a toxic species that is found predominantly in industrial effluents generated by metallurgical operations. Cyanide's strong affinity for metals makes it favorable as an agent for metal finishing and treatment and as a lixivant for metal leaching, particularly gold. These technologies are environmentally sound but require safeguards to prevent accidental spills. Various methods of cyanide remediation by separation and oxidation, including photolytic advanced-oxidation processes, are therefore reviewed. Reaction mechanisms are presented throughout the paper. The methods are compared in regards to their effectiveness in treating various cyanide species: free cyanide, thiocyanate, weak-acid dissociables, and strong-acid dissociables.

Jan 1, 1996

By K. K. Kelley

The collection and correlation of thermodynamic data concerning substances of metallurgical interest have constituted one of the major activities of the Pacific Experiment Station of the Bureau of Mines, at Berkeley, Calif., for the past several years. Earlier bulletins (32, 33, 34, 36, 36, 37, 38) s in this series are entitled: (1) Contributions to the Data on Theoretical Metallurgy. I. The Entropies of Inorganic Substances; (2) Contributions to the Data on Theoretical Metallurgy. II. High-Temperature Specific-Heat Equations for Inorganic Substances; (3) Contributions to the Data on Theoretical Metallurgy. III. The Free Energies of Vaporization and Vapor Pressures of In¬ organic Substances; (4) Contributions to the Data on Theoretical Metallurgy. IV. Metal Carbonates--Correlations and Applications of Thermodynamic Properties; (5) Contributions to the Data on Theoretical Metallurgy. V. Heats of Fusion of Inorganic Substances; (6) Contributions to the Data on Theoretical Metallurgy. VI. A Revision of the Entropies of Inorganic Substances-1935; and (7) Contributions to the Data on Theoretical Metallurgy. VII. The Thermodynamic Properties of Sulphur and its Inorganic Compounds. The present paper collects and discusses thermodynamic data relating to metal carbides and nitrides, with the view of obtaining usable heat and free energy of formation relationships. Pertinent data on both classes of substances are difficult to obtain experimentally and consequently are extremely rare; it is therefore necessary in many cases, if equations are to be derived, to introduce certain approximations and assumptions. Lack of adequate means of checking results by utilizing data of different types, such as was done frequently in the bulletins dealing with carbonates and sulphates, are readily apparent to anyone who has made even a cursory examination of the available information. Consequently, some of the relationships derived undoubtedly will be found to be inaccurate when more or better data become available. Nevertheless, in view of the importance of some of these substances, it appears worth while to consider the information available at present and to attempt the formulation of as complete a

Jan 1, 1937