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By Gregory E. Smith

"Tensionable headed roof bolt systems are common in the U.S. mining industry. In the last 15 years or so, they have made a comeback as a hybrid system where a mechanical anchor is used in conjunction with resin. When such a system is used, it is common to use a spherical washer to comply with the requirements of 30 CFR Part 75.204(f)(8). This standard requires an angle-compensating device be used in installations where the bearing plate is offset from the roof bolt axis by an angle greater than five degrees. This paper evaluates system performance of four different traditional angle-compensating device/plate combinations including a new patented extruded plate/extruded washer system that improves overall load capacity and stretch.INTRODUCTIONA large western U.S. underground coal mine was using a fully grouted headed rebar system as their primary support. They had developed their component specifications over many years of working with suppliers to improve and optimize these components to integrate well as a system. As shown in Figure 1, the components included a patented 7 /8"" -diameter Grade 60 headed rebar bolt with a flange capable of full bar load (Walker, 2009) and a patented 8 in x 8 in Grade 3 extruded hole bearing plate manufactured by DieMatic Corporation.The mine decided to pursue a fully grouted tensionable system using a mechanical anchor as the tensioning device. Their primary goal was to eliminate the need for the roof bolt operator to secure (hold) the bolt during resin set time. An additional benefit was the increased initial tension on the bolt. To comply with the requirements of 30 CFR Part 75.204(f)(8), regarding tensioned roof bolts, they were required to include an angle-compensating device because a share of the bolt population would be installed at angles greater than five degrees from the perpendicular to the bearing plate. Also, to improve cycle time and torque/tension consistency, the mine desired to have the washers and anchors assembled at the factory. This required the use of a bearing plate with a center hole large enough to accommodate the 1-3/8-in-diameter mechanical anchor to pass though it during assembly by the roof bolt operator. The mine wanted to continue to use an extruded hole bearing plate in the tensionable system, and EMS was asked to propose a plate and angle-compensating device."

Jan 1, 2016

By B. Rezai, Z. Pourkarimi, M. Noaparast, S. Chehreh Chelgani

Nanobubbles (NBs) flotation separation can be an indicator for improving the efficiency of fine particles through the conventional process. Since flotation reagents such as frothers can reduce bubble size, they can potentially be used for the generation of NBs and develop a selective NB flotation separation. This study explored the flotation separation of fine phosphate particles from their associated minerals in the presence of NBs, which were generated by using a phosphate flotation reagent (Flo-YS: collector-frother). The results of flotation tests showed that in the presence of NBs, the flotation efficiency was significantly improved. However, in the presence of NBs, surface chemistry analyses (Fourier Transform Infrared Spectroscopy and High-Performance Liquid Chromatography) illustrated that the collector adsorption on the surface of phosphate particles decreased. A comparison between outcomes of various phosphate flotation conditions indicated that increasing the flotation efficiency in the presence of NBs may be due to the aggregation of fine particles by the generated NBs, and also selective adsorption of NBs (hydrophobisation) on the surface of particles. In other words, generating NBs by selective collectors may increase efficiency and decrease the collector consumption of a flotation process. Keywords: Phosphate, selective separation, fine particles, collector-frother, efficiency, mechanical flotation cell

Jan 1, 2020

By A. D. Rich

The term "bleaching clay" or "bleaching earth," as used in the oil industries, refers to clays that in their natural state, or after chemical or physical activation, have the capacity for adsorbing coloring matter from oil. There are three common types of bleaching clays: fuller's earth, activated clays, and activated bauxite. Fuller's earth, or naturally active clay, is prepared from bentonites (see Chap. 5) that possess natural activity. It is not activated commercially; in fact, earths of this type ordinarily do not respond satisfactorily to acid activation. Fuller's earth is prepared in pulverized as well as granular form for use in the contacting and percolation processes, respectively. Acid-activated clays also are of bentonitic origin. The basic raw clay, however, is of a type that has a very low natural activity but is highly activable by treatment with mineral acid. Commercial acid-activated clays generally possess several times the decolorizing power (bleaching efficiency) of the best quality of fuller's earth. The former are prepared commercially only in the pulverized grade because of the difficulties in obtaining a satisfactory granular product, and hence are used only in the contact process. Activated bauxite is made by heat-treating bauxite ore, which in its natural state has very little natural activity. The commercial product is prepared in granular form for use in the percolation process on petroleum oils. For the most part, bleaching clay is used commercially in the decolorization of animal, vegetable and petroleum oils, fats and waxes. It is applied in two ways: (1) by the percolation method and (2) by the contacting method. Percolation refers to the passage of oil through a bed of granular clay whereas contacting refers to direct agitation of oil and pulverized clay followed by removal of the clay from the oil by filtration. In either case, the decolorizing effect is obtained by intimate contact between the liquid oil and the solid adsorbent. Petroleum oils are treated commercially by either the percolation or the contact process. Animal and vegetable oils are treated by the contact process only. Composition The raw clays from which both fuller's earth and acid-activated clays are prepared are composed of hydrous aluminum silicates containing varying quantities of magnesium, iron, calcium and other elements. These raw materials are usually nonswelling bentonites derived from volcanic ash or lava by weathering and hydrothermal chemical reactions. The bentonites have as their chief mineral constituent montmorillonite, which has the formula [(OH)4Si6A14O20•nH2O], according to Grim. (See Chap. 5, ref. 6, p. 91.) The underlying reasons are not fully known for the natural activity of the fuller's earth type of clay and its usual failure to further activate with mineral acid in contrast to the natural inactivity of the activatable type of clay. However, it may be said that the bentonites that are responsive to the acid-activation treatment generally have not undergone any drastic metamorphism. The chemical composition is not a reliable means of discrimination between a nonactive, a naturally active, and a nonactive but activable clay, therefore it is not possible to forecast the ultimate quality of a clay on the basis of the raw-clay analysis alone. Table 1 gives typical analyses of representative clays of the foregoing classifications.

Jan 1, 1960

By Paul M. Godlewski, Joseph P. Gildner, David S. McAllister

With construction underway on the 22.5 km (14 mile) Initial Segment of the Link Light Rail transit system in Seattle (including the one-mile EPB-driven running tunnels and mined station at Beacon Hill), the Sound Transit Board on May 20, 2004 voted on selection of a preferred route for an approximately eight-mile extension northwards from the central business district to Northgate, and authorized immediate start of advanced conceptual/preliminary engineering and geotechnical exploration programs scheduled to be completed in Spring 2005. The extension includes approximately914 m (30,000) route-feet of bored running tunnels, a mined station with platform level approximately 60 m (200 ft) below grade, three (possibly four) cut-and-cover stations and a cut-and-cover cross-over structure, as well as an aerial terminal station at Northgate and other line-section below-grade and aerial structures. All tunneling will be in glacial soils.

Jan 1, 2005

By Robert L. Dean

THE pioneer mining company in Idaho to use airplanes extensively is the Yellow Pine project at Stibnite now owned by the Bradley interests. From 1901 to 1903 the gold boom at Thunder Mountain, in central Idaho overflowed to adjacent areas, prospectors discovering cinnabar and stibnite near the present site of Stibnite in Valley County. The workings were practically abandoned by 1911 through lack of capital and high costs of transportation on pack train roads over several mountain passes open only five months each year. During the World War there was some prospecting and production, and in 1921 twelve of the original companies were merged. Small-scale mining up to 1927 proved that an expenditure of several million dollars would be necessary to operate profitably. These properties were purchased by the Bradley interests during the period of 1927 to 1930. In 1927, there was no mining equipment except hand tools, no telephones, and only one building. Two mountain

Jan 1, 1935

By Toru Yamasaki

A concept of plate-tectonic controls for the formation of seafloor massive sulfide (SMS) deposits in back-arc settings was established by Franklin et al. (2005). According to Franklin et al. (2005), a consequence of extension and rifting is subsidence, thinning of the crust, and the rise of hot, athenospheric mantle into the base of the crust. Underplating of the crust by mafic magmas results in low-pressure partial melting of the hydrated crust at a <15-km depth, and the generation of felsic anhydrous melts. The rapid ascent of hot felsic melts, along with mantle-derived mafic melts, results in bimodal volcanism that characterizes rift and volcanogenic massive sulfide deposits (VMS) environments. The rapid and focused advection of the magmatic heat within the rift to the near-surface environment which are required to sustain vigorous long-lived VMS hydrothermal systems. Faults within rift environments may also allow seawater to penetrate into subvolcanic intrusions and mix with magmatically generated metalliferous fluid or allow a direct magmatic contribution from shallow crustal level (3–12 km) magma chambers (Franklin et al., 2005, and references therein). In addition, the caldera-forming processes are favorable for the formation of VMS deposits and the focused high heat flow and cross- stratal structural permeability that is restricted in time and space to caldera development provides an explanation for the clustering of VMS deposits and their restriction to specific time-stratigraphic intervals and structures in the evolution of submarine central volcanic complexes (Franklin et al., 2005, and references therein). The concept is persuasive, although it is based on a series of logically constructed reviews mainly focused on ancient on-land deposits.

Jan 1, 2018

By Q. X. Yun

This paper provides a new approach to optimize the production planning in underground mines by means of evolutionary algorithms. Firstly, genetic algorithm is used to reach the global optimization in planning. Then, evolutionary programming is employed to obtain the partial optimization for each year. The application proves that the new approach is reasonable and useful. Keywords: Evolutionary algorithm, Genetic algorithm, Evolutionary programming, Optimization, Mining engineering.

Jan 1, 2003

By J. A. Snyder, W. L. Finlay

G. Edmunds—Solid solubility is considered to be of either the interstitial or the substitutional type. Is it possible, in a binary alloy as the simplest case, that some of the solute atoms are present in the normal lattice sites (substitutionally or filling lattice vacancies) while simultaneously others are in interstitial positionss One might even ask whether a distribution of the two types may be the normal situation. H. M. Meyer—Metastable states of interstitial atoms occupying vacant lattice sites possibly occur as well as of substitutional atoms squeezed in between regular matrix positions. However (as we know since Hume-Rothery), the solute atoms choose between the two kinds of solutions; consequently, every solute will be unequivocally either substitutional or interstitial in the equilibrium state of the solid solution. M. Balicki—In view of the fact that the authors apparently correlate the analysis of the alloys at the ingot stage with the properties exhibited at the testing stage, I would like to ask whether this is a fully justifiable procedure. In other words, how good are their determinations of solute concentration for correlating them with the mechanical properties. The answer to this question may explain some of the divergencies. Assuming good enough homogenization of the samples and exact determination of mechanical properties the position of the plotted experimental points will depend solely upon the accuracy of composition determination. If this is not accurate, say due to loss or pickup of elements during processing from the ingot to the testing stage, or due to a systematic error in the method employed for obtaining solute concentration data, the points will deviate from their true position and may align themselves along a different curve than the one expected. H. V. Kinsey—We have been studying the creep-rupture properties of titanium-base alloys at 1000°F. In the course of this work, anomalies in behavior of the alloys that would suggest that the material under test was becoming stronger as the test progressed have been observed. If this was so, the most likely explanation that we could think of was that the test bars were absorbing oxygen and nitrogen from the air during the test and were thereby becoming strengthened. In an attempt to determine the strengthening effect of absorbed oxygen and nitrogen the following experiment was conducted. A length of cold-rolled titanium was supplied by the E. I. du Pont Co. Two test bars, having a 1/4 in. diam gauge length, were prepared from this material. One bar was tested in the as-received condition. The second bar was heated in air at 1550°F for 100 hr and subsequently air cooled prior to testing. A testing temperature of 1000°F was employed. The results of these tests are tabulated in table 11. In the author&apos;s opinion, is it reasonable to assume that the bar that was exposed to air at 1550°F for 100 hr was stronger because it absorbed oxygen and nitrogen from the air during this heat treatment? W. L. Finlay (authors&apos; reply)—Direct experimental evidence for or against Mr. Edmunds&apos; interesting suggestion will probably never be available. It seems possible, however, that mixed interstitial-substitutional solid solution might well occur with interstitial elements. The less likely possibility of interstitial solution of a normally substitutional element like copper in aluminum was recently discussed at length by the

Jan 1, 1951

By Jan K. Wolski

The PC computer program PCVENT, version 3.3, for the ventilation network analysis now incorporates a real-time fire simulator. Position of the fire or a source of contamination and the character of the event are input from the keyboard. There are several options of type of fire: heat only, contaminant only, or both with a constant burning rate or with oxygen as the only limiting factor. Airway resistances or fan characteristics can be modified during a fire simulation. This allows testing of various fire suppression strategies. Program application in the analysis of a real mine fire is presented.

Jan 1, 1991

By J. J. Becker

Changes in magnetic properties with particle size are used to study the precipitation process in a Cu-Co alloy. In particular, the effect of a field during aging in producing anisotropy is shown to occur entirely during the growth of the particles, after precipitation is complete. HEAT-treatment in a magnetic field is done commercially to improve the magnetic properties of a number of materials. These can be divided into solid-solution alloys and precipitation alloys. The Permalloys are representative of the first type, and magnetic annealing greatly increases their maximum permeability. On the other hand, in precipitation alloys such Alnico 5 the important result is an increase in maximum energy product. The effect of the field in all cases is to bring about an additional magnetic anisotropy, uniaxial in nature, which makes the hysteresis loop more upright when measured in the direction in which the field was applied. The structural origin of the anisotropy brought about by magnetic annealing is not well understood. In the solid solution alloys, one possible explanation is based on ordering.&apos; Another possibility is the orientation of like-atom pairs.&apos; The precipitation systems known to respond to magnetic heat treatment are Alnico 2, in which the effect was first discovered," Alnico 5, cobalt ferrite (oxide),&apos; and Cu-Co alloys.3 n these materials, the field affects the precipitation process itself in some way. Although there has been much work on Alnico 5. its nature is still incompletely understood. According to Geisler,&apos; the precipitation reaction is of the

Jan 1, 1959

By P. Schmieder

"The close vicinity of mining companies to other sites that are used for commercial and residential purposes or to areas under conservation as well as the fact that the people become more and more sensitive to emissions have led to a negative attitude towards mining operations in the neighborhood. It is above all the use of drilling and blasting techniques that give rise to objections, in the course of which demands for more environmentally-friendly production methods have been voiced. It is in this context that production methods without the use of explosives are considered as an option. After all, the use of such production methods is the only alternative for some quarry operators. The question is what are the true benefits of these techniques and what is the relation between a possible improvement of the environmental effects on the one hand and the technological potential as well as the costs on the other. It is intended to assess the mining techniques for solid rock in their entirety. This paper will therefore look at the aspects for assessing mining techniques in the context of their environmental impact and the costs."

Jan 1, 2005

By A M. Purba and A Sjadat, A D. Wilson

Ongoing mining of the East Ertsberg Skarn System orebody below the Gunung Bijih Timur and Intermediate Ore Zone caves has been relatively successful and a ramp up to 80 000 t/d was achieved in the Deep Ore Zone Mine. However, the distribution of production, the overall drawpoint availability as well as the rate of change of the cave back profile has not followed the anticipated path. Several key factors influencing cave growth and progress, grade variation, fragmentation, wet muck and surface subsidence have been recognised over the life-of-mine that now have to be taken into account for planning the later stages of mining.The paper will discuss the influence of geological controls of lithology and structure – how this as well as other contributing aspects have impacted ore flow, contributing to some of the widespread panel damage, and been a key factor in compacted draw columns and caused an accelerated appearance of water ingress. This in turn has rapidly changed the distribution of wet drawpoints requiring remote mucking and special controls that also affect the call from the remaining dry drawpoints. Comment is also made on the potential final cave profile if it continues along the current trend and some discussion is offered about possible mitigation measures if this were to come about.CITATION:Wilson, A D, Purba, A M and Sjadat, A, 2016. Progressing cave performance into the later stages of the Deep Ore Zone mine, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 285–292 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

By P. Lloyd

Perceptions of disaster caused by burning fossil fuels have reached such a pitch that they seriously threaten the very future of the industry. Coal is a dirty word. A leader in Business Day(January 192009) claimed ?There is no disputing that renewable and non-polluting energy sources are preferable to the country?the true cost of so-called cheap coal-fired power stations is neither reflected nor accounted for by Eskom?the true and immediate but unacknowledged cost of continued coal mining is apparent in the catastrophic level of acidification from mining runoff of all significant natural water resources in the country?and their waters have been rendered unfit for human consumption. Air quality is in a similar state with?increases in pulmonary disease causing workforce absenteeism and compromised childhood development, among many other health problems recorded in areas polluted by coal mining.? The upshot is that our latest coal-fired power station, Kusile, is being required to use flue gas desulphurization. The costs are considerable, and the benefits minimal. Meanwhile, exports are being threatened by EU directives and an assumption that South African coal gives off excessive quantities of SOx and NOx when burned. The industry needs to arm itself with clear responses to these and similar misconceptions, and to communicate those responses loudly and clearly, if it is to survive.

Jan 1, 2011

By Gente P, Eissen JP, Lafoy Y, Charlou JL

The North Fiji Basin (NFB) is delineated by the Vitiaz trench to the North (paleo sub duction zone, Brocher, 1985), the Vanuatu is- land arc (called before New Hebrides arc) to the West and South, the Hunter Fiacture Zone to the South-East and the Fiji islands to the East (Brocher, 1985 ; Larue et al., 1982 ; Carney and MacFarlane, 1982 ; Falvey, 1978). The NFB is characterized by shallow water depths (about 3 km) (Chase et al., 1982 ; Scla- ter et al., 1972 ; Karig, 1971), high heat flow (average of 2.29 HFC) (MacDonald et al., 1973 ; Halunen, 1979), strong positive free air anoma- lies (Worzel, 1965 ; Kogan, 1976 ; Luyendick et al., 1974 ; Solomon and Biehler, 1969) and a geoid anomaly (Malahoff and Larue, 1979) inter- preted as a geoid swelling. Few refraction data reveal a relatively thin crust and sediment co- ver, and the existence of low speeds in the up- per mantle beneath the NFB (between 7,1 and 7,7 km/s) (Larue et al., 1982 ; Raitt, 1956), which could indicate the existence of active spreading zone(s) in this area (Barazangi et al., 1974). Global seismicity of the SW Pacific clearly de- fines the.limits of the NFB, as well as the Lau basin (Sykes et al., 1969). But one can note the low level of shallow seismicity of the NFB (Ham- burger and Isacks, in press) which concentrates in three distinct trends :

Jan 1, 1987

By Sikko Doornbos

For the extension of the Paper Mill of Parenco in Renkum, the Netherlands, the application of a pile foundation was required. The demands for this pile foundation were very explicit a vibration free and soil displacing pile systems with low allowable settlement. Another important aspect was the total amount of piles (originally over 1600 auger piles) which had to be executed within 3 months, in very difficult and unhomogeneous soil. Based upon these conditions the Tubex Grout Injection Pile was chosen to be used for this project. This system involves the drilling of a steel tube with a conical pile shoe while grout is injected at the point simultaneously, creating a mixed-in-place layer around the tube. INTRODUCTION After extensive marketing, the board of directors of Parenco, decided to a large extension of the production capacity of its paper mill by building a new production building called Paper Mill 1 or PM-1. The new PM-1 extension had to be constructed beside the existing PM-2 because of limited terrain. The site is located right between the Rhine river and Renkum, approximately 15 kilometers (10 miles) west from Arnhem (see figure 1). The construction involved the building of the PM-1 extension of approximately 250 meters (820 ft.) long by 40-60 metres wide (130-200 ft.). The main structure was to be constructed of precast concrete beams and columns.

Jan 1, 1987

By C. J. Hartley

"Scandium oxide can be recovered as a by-product from process streams in a number of chemical and metallurgical plants including TiO2 sulphate pigment, Ni/Co laterite, zirconium oxychloride and uranium operations. The feed materials available for processing can be either mid or end of process streams containing many species in solution. This paper describes the strategies available to limit coextraction of elements into scandium containing streams from TiO2 pigment production and the removal of these elements to deliver high purity scandium oxide.A critical part of process development is to work within the constraints of the main process in terms of introducing new unit processes and producing minimal additional process intermediates and residues. This requires flexibility in designing flowsheets and plants to find novel process routes that avoid production of intermediates and/or the introduction of reagents that can compromise the main process operations.Bloom Energy has developed novel solvent extraction processes for the extraction and refining of scandium oxide that minimise impacts on core process streams within TiO2 pigment plants. The additional unit processes are designed to have minimal contact with pigment plant process streams to produce a concentrate that is refined to nominal 3N purity scandium oxide in a simple, small scale commercial plant."

Jan 1, 2016

By Leonid Pevzner, Valerie Dmitriev, Yuri Babitchev

Performance of belt conveyors, service life of belts and mechanical elements can be radically improved if the automatic adjustment of the belt speed movement is made in such a way, that the unit load over the conveyor length be constant and close to the rated one under random input freight traffic. Such an adjustment is possible when the system of a controllable thyristor electric drive on the basis of induction squirrel cage motor is used. Computer-aided adjustment of the belt conveyor movement is effected via bicontour digital control of the main drive in order to redistribute loads when the loading of conveyor and contour of the control of tension drive are changed. The system envisages control and condition monitoring of the conveyor electromechanical system, as well as metering of electrical power and the amount of conveyor freight. The results of the simulation of speed control of the conveyor belt are given in the report. Mathematical model of the conveyor electromechanical system describes the movement of the belt with cargo and the tension drive. The input cargo traffic is assumed as stationary ergidic random process with the assigned characteristics. The solution of the problem of the synthesis of a closed-loop control system, the structure and parameters of adjustment, the conditions of asymptotic stability of the control back-up system and the condition of minimization of mean square error of shadowing are also given in the report. Microprocessor controller is used to realize the function of the adjustment unit. Under this control system standard mode of conveyor operation, different modes of start-up, operating mode with decreased speed when transporting people, service and emergency braking of a conveyor and some other modes are realized. The digital model of a conveyor as an instrument for decision making in case of emergency is used in those modes. MASTER TEXT Long-standing practice of belt conveyor operation in mines of Russia has proved their inefficient use with 40-70% capacity and 20-25% availability factor. It is associated with unreasonable power intensity and reduction of service life of mechanical components, and as a result, with the growth of total transportation costs. Low efficiency of conveyor application can be explained by the extremely irregular distribution of conveyor freight traffic. Usually, the width of a conveyor belt is identified in accordance with the possible maximum traffic value, engine power capacity for long-term operation under rated loads. However, actually a conveyor often runs without any load and its average load in most cases is lower than the rated one. The problem can be eliminated by way of the adjustment of the operational mode of a conveyor according to an actual input freight traffic via belt speed control providing for the conveyor regular linear load which is nearly equivalent to the rated one. Experimental research into freight traffic under working conditions of the operating underground and open-cast mines proves the fact that the actual freight traffic can be adequately presented through the model of stationary random function of time, for ex- ample, as a J (t) continuous random Gaussian process that is modulated with a G(t) elementary pulse flow:

Jan 1, 1996

By Garland E. Likins

High-strain dynamic testing of drilled shafts and cast-in-place piles has become routine procedure in many parts of the world today. Field testing is performed by measuring strain and acceleration records under impact of a falling mass. Wave equation analysis is utilized to design the weight, drop height and cushion of the hammer apparatus to assure a successful test. The Pile Driving Analyzer* (PDA) and CAPWAP* methods are used for data acquisition and analysis. Testing results yield information regarding pile static bearing capacity, structural integrity, and pile-soil load transfer and pile load-movement relationships. This paper discusses application of high-strain dynamic testing to cast-in-place shafts with emphasis on aspects unique to this type of pile. Suggestions regarding minimum requirements for good quality tests are offered. Five case histories reported in the literature are summarized and a sample specification is also included.

Jan 1, 1995

By Nur Hossain

Analysis of Linear Elastic Fracture Mechanics (LEFM) parameters via the Virtual Crack Closure Technique (VCCT) has been obtained for SENT specimens of AM6OB magnesium alloy. It is found that the ratio of initial crack length to initial monotonic plastic zone size is one of the critical factors in establishing the limit of using LEFM concepts. If this ratio is below a certain limit (i.e. when crack lengths are small in comparison to the plastic zone size), loss of similitude stress intensity factor range would occur. This ratio, therefore describes the limit below which the use of LEFM would no longer be admissible. In this study, the above limit was established for AM6OB magnesium alloy. In addition, fatigue crack propagation tests were conducted to ascertain the fatigue response of the alloy and determination of the coefficients of Paris model.

Jan 1, 2010

By E. C. Lane

This report presents the results of the Bureau of Mines&apos; twenty-first semiannual survey of motor gasoline marketed in the United States. The 12 cities in which samples were collected have teen chosen as representative of the more important marketing territories, as it is obviously impractical to obtain a sample of every gasoline sold in the entire country. The survey reveals that the motor gasoline which is being marketed in the United States this winter is decidedly more volatile than that sold a year ago. Samples from all cities show a decided improvement in volatility except those from Laramie, Wyo., which show a small decrease in volatility.

Jan 1, 1930