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By J. M. Menacho, J. M. Reyes

"Batch and continuous regrind tests were conducted in 3 kW and 15 kW tower mill units, respectively. Single particle size classes of a chilean copper sulphide concentrate were employed in the batch tests, while a fraction of the plant stream was deviated to the continuous unit operated under different conditions.Results are interpreted in terms of the simplified grinding kinetic model energy-based and conveniently adapted to this application. Based on the above figures plus some industrial data supplied by MPSI Inc., a scale-up relationship was developed for the apparent specific rate of breakage siE, as a function of the net power draw P, i.e.siE = siE text (P/P test) 0.089This equation fit very well the available data at the three scales and its application to regrind 4400 t/day of rougher copper concentrate from 70% below 325 Tyler mesh to 95% below same mesh, involves around 30% energy-saving compared to standard ball mill for same grinding task.INTRODUCTIONImpact and abrasion-attrition breakage are two extreme mechanisms present in any grinding system in a proportion defined by specific design and operating conditions. Impact breakage is generally efficient for coarse grinding, while abrasion-attrition is adequate to produce fine particles. Efficiency of conventional tumbling mills decreases as fineness of the product increases, even though distribution of applied stresses is always much stronger than internal force distribution in the particles. On the other hand.in a vertically stirred ball mill like the tower mill, distribution of applied stresses and particle strengths are in the same order of magnitude, making possible nearly ideal abrasion conditions (1).Tower mill configuration includes a cylindrical body vertically mounted and provided with a central screw with flights to produce circulation of balls moved up through the inner region to return down by the external space. Fresh material can be fed into the top , center or bottom in order to assure appropriate agitation of suspended particles. Size reduction and evacuation rates should compensate settling of coarse particles to avoid sanding of the screw. Detailed description of the tower mill and its operation have been given elsewhere (2),(3)."

Jan 1, 1989

By M. Pfeifer, M. N. Brodie, D. J. Barratt

"This paper reviews design trends related to the various SAG mill configuration and drive options available today. The impact of these options on capital and operating costs is assessed, and key technical issues reviewed. The discussion is based on the conventional North American ’pancake’ mill configuration. IntroductionDuring the past decade mill technology has evolved significantly in the following key areas:• improvements in variable speed motors continue with on-going advances in electronics;• ring motors, or gearless drives, are becoming more common in mill sizes 32 ft and larger, with ratings of 10 000 HP and greater;• geared drives have become available up to ratings of 9500 HP per pinion, compared to the earlier 6000 HP guideline;• improvements in speed reducer technology due to the use of carburized and ground precision gearing, make the high speed motor-speed reducer drive more competitive with the direct coupled low speed motor drive;• a unique speed reducer drive is being introduced to this industry which combines ring gear drive pinions with speed reduction. mprovement in gear alignment is claimed, and the overall drive arrangement is more compact than is possible with a conventional speed reducer drive;• the first 38 ft and 40 ft diameter mills have been designed and manufactured; and • application of large multi-shoe bearings have made shell supported mill configurations available for all, including the largest sizes. These designs have flat instead of conical mill shell ends, and have the potential for technical and cost advantages compared to conventional trunnion supported designs.This proliferation of mill design features provides several options to those involved in planning and design of milling plants, and requires more extensive evaluation to optimize mill design features to best suit specific project requirements."

Jan 1, 1999

By Terry Keough

Contents for discussion ?Current liner technology ?Innovation of magnetic products ?Development of magnetic wear liners ?Installation and change out method ?Uses and capabilities ?Internal wear liners ?Summary Vulcanized rubber ?Many of you are familiar with using vulcanized rubber to provide wear protection on mining equipment. For years, this was the standard for most mining equipment, and mines spent a lot of money fabricating and lining steel equipment.

May 1, 2010

By N. Ogbonna, D. G. Dixon

Although heap bioleaching has been recognized as an economic alternative for treating low grade mineral ores, the underlying physical, chemical and biological processes involved are complex. A detailed investigation into the dynamics of heap bioleaching processes has provided much insight into the underlying complexities, and has led to the development of a sophisticated modelling tool - HeapSim. This tool can be of great help in the design and operation of heap bioleaching processes. In this paper, the mathematical model implemented in HeapSim is examined. The model takes into account mineral kinetics, particle level effects, bacterial growth, oxidation and adsorption, gas absorption, pore diffusion, bulk advection, gas balance and heat conservation. Three case studies where the model has been applied are briefly discussed. Computational Analysis in Hydrometallurgy 35th Annual Hydrometallurgy Meeting held in conjunction with the 44th Annual Conference of Metallurgists of CIM Calgary, Alberta, Canada Edited by

Jan 1, 2005

By Jorge Loredo, Jesús Garía Iglesias

"Abstract - The Asturian fluorspar district consists of vein and stratiform deposits where mineralization is controlled by a combination of lithological and tectonic factors.It is postulated that these fluorspar deposits have been formed under disequilibrium conditions created during circulation of ascending hydrothermal solutions along faults and other high permeability conduits. Mixing of solutions is inferred from fluid inclusion studies. Cavity filing and replacement processes are very important in localizing the ore deposits and in determining their morphology.Permian volcanic rocks in the area yield a regional positive geochemical anomaly in fluorine implying that Permian vulcanism may be a possible primary source of fluorine.On a regional scale a relationship can be established between some of the ore deposits and important tectonic lineaments. The stratiform deposits preferentially occur within a calcareous-detrital facies located at the margins of basins. These basin margins are related to important synsedimentaryfaults.Fluorite is the only economic mineral in these deposits. Quartz, carbonates, barite and pyrite are comnmon minerals accompanying fluorite. Other minerals that may occasionally be present as minor components are: marcasite, chalcopyrite, fahlore, sphalerite, galena and related supergene minerals."

Jan 1, 1994

By T. R. Kostecki, K. V. Jessu

"Roof bolts are subjected to axial stresses, shear stresses, or both. Axial and shear stresses were compared between roof bolts machined with two and three slots. Shear stresses perpendicular to and at an angle to the shear planes were evaluated by analyzing a three-slot instrumented roof bolt, performing laboratory tests on two- and three-slot roof bolts, and conducting in-situ test analyses. Threeslot bolts appear to provide a complete bending strain profile, requiring no prior knowledge of the estimated shear-plane orientation. Minimum displacements occur in roof bolts installed perpendicular to rather than at an angle to the shear planes.RÉSUMÉ Les boulons d’ancrage dans le toit d’une mine sont sujets à des contraintes axiales, des contraintes de cisaillement ou les deux. On a comparé les contraintes axiales et de cisaillement de boulons d’ancrage usinés avec deux ou trois fentes. Les contraintes de cisaillement perpendiculaires et à angle aux plans de cisaillement ont été évaluées en analysant un boulon d’ancrage de toit à trois fentes, en effectuant des essais en laboratoire sur des boulons d’ancrage de toit à deux et à trois fentes et en effectuant des analyses de tests in situ. Les boulons à trois fentes semblent fournir un profil complet de résistance aux contraintes de flexion, sans avoir besoin de connaître l’orientation estimée du plan de cisaillement. Des déplacements minimums ont lieu dans les boulons d’ancrage de toit installés perpendiculairement, plutôt qu’à un angle, aux plans de cisaillement."

Jan 1, 2016

By S. A. R. Keneti

Predicting the geomechanical response of the shale gas material during hydraulic fracturing operation in the field needs better understanding of their geomechanical behaviour under laboratory testing. Anisotropy is considered as a critical factor during investigation and analysis of deviated boreholes, borehole stability, stress-strain and strength behaviour, generation and propagation of fracture and fluid flow. In this study, compressive elastic modulus (Ec) of the Montney shale has been investigated in two perpendicular directions: unconfined compressive strengths test was conducted on the Montney sample to measure its Ec in the vertical direction. This value then was compared to the Ec value in the horizontal plane (i.e. foliation plane) which was previously measured throughout a Brazilian test by Keneti and Wong (2011). From the results, the representative values of Ec in the vertical and in the horizontal directions were found as 25 GPa and 40 GPa, respectively. Computer tomography technique was also employed for the experimental data interpretation.

Jun 1, 2012

By G. Herget

"A brief visit to European longwall mining operations in potash showed that retreating longwall mining provides a very attractive alternative to room-and pillar mining, especially in areas with bad roof, narrow seams and areas with high ground pressures. Mines de Potasse d'Alsace, France converted all potash operations to longwall mining in 1980. Recovery rates per panel vary between 75o/~ to 85% which compares very favourably with Saskatchewan values. Ground pressure in Saskatchewan are comparable to those of some of the deposits in Europe, but the presence of water in the hanging wall of Saskatchewan orebodies has to be given serious consideration. However, given the mining experience in Saskatchewan and the improved technology f or laboratory and field investigations, a review of present mining practice in Saskatchewan is desirable. IntroductionLongwall mining is practiced widely in coal mining and allows complete mechanization. It is applicable at great mining depth, in thin seams, weak roof and has been applied recently even to coal bed s dipping more than 65 degrees. Ideally this system allows complete extraction of an orebody. However, with high mechanization and emphasis on obtaining high outputs per man shift, extraction ratios rarely reach more than 80010 per panel.France, Spain and the U.S.S.R. have had longwall operations in potash for some time and a brief description is given below. Two of the operations were visited and the Russian operation is described based on German literature"

Jan 1, 1986

By M. Ruel

In today's highly competitive worldwide market, it is becoming extremely important for managers to make sure that all resources are used where needed the most. That way, all resources are generating added value, process control equipments are maintained in an optimal state for best performance, and final product is produced at least cost. Performance monitoring is the only way to ensure that everyone is working on top priorities toward the same goal. How can we add value to these warehouses of data? The data is there and the information is hidden; it is just waiting to be extracted. A process performance monitoring system is able to determine if a loop, a system, a unit, or a plant meets the expected performances. The system prioritizes the areas that need attention. It also provides historical reports of the plant status by areas, by loops, and by identified problems. This information is provided to different categories of users in an appropriate format for each one. The system also includes diagnostics and tools to detect and analyze problems.

Jan 1, 2007

Project Details ? Located 420 km northeast of Yellowknife, Northwest Territories ? Jericho kimberlite discovered in 1995 ? Feasibility study showed +3,000,000 carats recovered from 2.6 million tonne reserve ? Nine year mine life ? Approx. 100 person workforce in full production ? First mine for Tahera, First new mine for Nunavut Completed Ambitious Construction Schedule During 2005 o Feb ? Mar/05 Winter road mobilization o Mar ? Dec/05 Pre-stripping, earthworks o Mar ? Apr/05 Camp facility, occupied May 3 o May ? Dec/05 Process plant o Jun ? Dec/05 Maint. shop, fuel storage, power plant o Jan ? Mar/06 Commissioning, start-up o April 2006* COMMERCIAL PRODUCTION

May 1, 2006

By L. M. Pidgeon

MAGNESIUM metal, with a specific gravity of 1.73, is two-thirds the weight of aluminium and one-quarter that of steel. It is the lightest metal which is stable in the atmosphere. Before the war it had begun, though somewhat slowly, to take a place among the established metals. In 1939, magnesium production on this continent amounted to some 3,000 tons per annum and was confined to one company. At that time, Germany produced perhaps 20,000 tons. The advent of war, however, increased the demand to fantastic heights and introduced production problems of unprecedented magnitude. By the end of 1943, North American production is expected to reach 300,000 tons per annum (1), an increase of one hundredfold. Such a rate of expansion has not been witnessed previously in the history of metallurgy. It has given the metallurgist an opportunity to try new production methods and to learn in a short time what might otherwise have taken many years. The metallurgy of magnesium is still in its formative years and at this time widely different production methods are in operation side by side. This paper will discuss these methods in so far as information is available for publication at this time. A general description of the new Canadian industry will be included.

Jan 1, 1944

By Chuck Edwards

"The development of two large, high-grade uranium projects has been proposed for northern Saskatchewan. The projects are now under review by a joint federal/provincial panel. The McArthur River project is owned by the McArthur River joint venture (Cameco Corporation 53.991 %, Uranerz Exploration and Mining Limited 29.775%, Cogema Resources Inc. 16.234%) and operated by Cameco. Cameco proposes to mill the McArthur River ore at the existing Key Lake mill. The Cigar Lake project is owned by the Cigar Lake joint venture (Cameco Corporation 48.75%, Cogema Resources Inc. 36.375%, Idemitsu Uranium Exploration Canada Ltd. 12.875%, Korea Electric Power Corporation 2.000%). The Cigar Lake joint venture proposes that Cameco operate the Cigar Lake mine for the owners, and that Cogema mill the ore at their McClean Lake mill, now under construction. Proposed systems provide safe mining and ore handling, and allow the milling of McArthur River ore at Key Lake and Cigar Lake ore at McClean Lake. This avoids the disturbance of new sites for milling and tailings disposal.The McArthur River and Cigar Lake deposits are the largest known high-grade uranium deposits in the world. The ore grades at McArthur River and Cigar Lake are at least 100 times those that are mined elsewhere. It is proposed to mine these deposits using remote underground mining methods, to crush and grind the ore underground, to pump a thickened ore slurry to surface, and to transport it in special containers by truck to the mills.During all mining and processing stages the ore is fully contained. Radon emission is controlled by positive ventilation of all process vessels, with the process ventilation backed up by the primary mine ventilation system. Radiation is controlled by heavy steel pipe and vessel walls, concrete walls and sometimes lead sheeting."

Jan 1, 1997

By J. Dilbeck, J. K. Ratliff, T. Petrov, Z. Brown

"In efforts to improve dust control during deep cut continuous mining a supplemental atomizing spray system, mounted on 14CM15 continuous miner, has been designed and successfully implemented in a U.S. coal mine. The mine is 2.1 m (7-ft) high and uses a blowing curtain face ventilation system with 1.1 m (3.5-ft) curtain offset from the rib. The face ventilation design parameters were set to 9.4 m3/s (20,000-cfm); 4.2 m3/s (9,000-cfm) line curtain flow rate, and 3.8 m3/s (8,000-cfm) scrubber capacity. The performed in-mine measurements, before and after the implementation of the atomizing spray system, showed a significant decrease in the respirable dust levels at the operator place as well as at the return. The paper describes the supplemental water spray system design and performance supported by three-dimensional computational fluid dynamics (CFD) simulations and in-mine test data.INTRODUCTIONThe work on this project have started in 2015 with a study of the conventionally applied face ventilation layouts. The specific behaviour of the face ventilation system have been analyzed trough in-mine measurements and computer modeling of typical cut scenarios. An computer modeling methodology have been developed for estimation the respirable dust concentration (RDC) using tracer gas to RDC contour mapping, calibrated by a single point value, provided by in-mine measurement. Utilizing the results of this study the engineering staff of the mine designed and implemented a supplemental atomizing spray system to improve the dust control during the deep cut continuous mining. Today the atomized spray system is successfully applied demonstrating steady performance and a significant decrease in respirable dust concentration on the working places of the continuous miner (CM) and coal transporters (CT) operators as well as at the return air stream. Information about the applied type of spray nozzles provided by other researchers (Cheng, 1973; Dick et al., 1996; Organiscak & Page, 1998; Pollock & Organiscak, 2007) and spray system manufacturers (Spraying System Co, 2011–2018; Steinen Mfg., 2016) have been used in this project. CFD code and simulation approach validated in a study conducted in 2000-2014 have been applied (Turner et al., 2002; Wala et al., 2004, 2007; Petrov, 2014)."

Jan 1, 2019

By Éric Létoumeau, Julie Fournier, Sylvain Caron, Yves Breau, Martin Plante, Dominique Girard, Luc Tardif, François Robichaud

"Since 1999, COREM (formerly the Centre de Recherche Minérale) has conducted and coordinated research and development activities for a consortium of mining companies that uses the benefits and advantages of collaborative pre-competitive research. In particular, COREM’s “In Situ Optimization Group” is involved in the development and implementation of modem information technologies related to process optimization and control.The POP Project was launched in order to increase and consolidate the use of such technologies applied to mineralurgical and metallurgical processes. To ensure a successful transfer to the industry, there are a number of essential activities that have to be undertaken. These activities have been identified by COREM’s members and are grouped into three main modules:- R&D Module: research and development in universities and research centres;-Technology Transfer Module: integration of new tools into the POP Software, industrial applications and technical support;- Training Module: education of new engineers in universities and continuing education of plant personnel through on-site workshops.This paper outlines the opportunities that led to the definition of the POP Project, presents its main objectives and describes its main modules. The main features of the POP Software are outlined, the first applications at COREM’s member plants are presented and, finally, future developments are discussed."

Jan 1, 2002

By K. D. Mills, R. G. Robins, C. G. Anderson, L. G. Twidwell

Arsenic is a metalloid which has attracted great environmental scrutiny in recent decades. Moreover, its control and deportment is becoming increasingly important in the metallurgical processing of modern complex ores and concentrates. As such the authors of this publication have a combined professional experience of well over 100 years in the study and hydrometallurgical treatment of arsenic. Hence, this paper will cover arsenic fundamentals along with a review of technology for removal, fixation and stabilization. Finally, an application of industrial Alkaline Sulfide Leaching (ASL) of a copper enargite concentrate will be elucidated.

Jan 1, 2014

By F. Vagnon, A. M. Ferrero, M. Pirulli, A. Segalini

"The topic of this study is the design of flexible fences to mitigate the risk due to debris flow phenomena by means of theoretical and experimental studies analysed in framework of the Rock Engineering System (RES).The study of the interaction between debris flows and flexible barriers is a major challenge since many different aspects concerning both the slope characteristics and the structure features are involved. Debris flows are often triggered by the mobilization of debris deposits that are generated by rock fall of adjacent rock walls. The rock debris deposits are difficult to be characterized by the physical and mechanical point of view due to their large variability in volume distribution and, moreover, when dealing with high mountains environment, they are also strongly affected by the presence of water at different phases (solid or liquid) depending on the temperature. The debris deposit turns unstable in relation with the geotechnical and environmental features of the areas and the instability evolution in high mountain steep valley is often a debris flow. Debris flow destructive potential is very high and protections are often needed to reduce the debris flow risk.This complexity determines the needs of comprehensive study able to include the global basin dynamic and the environmental conditions. An a-priori analysis of the influence of the different aspects can be useful to focus on the real driving aspects of the problem. Due to the complexity of the system the application of the RES methodology is recommended in order to clearly define the different assumptions needed, their influence on the simulations and a comparison among them.RES allows investigating triggering criteria, flow and depositional processes and interaction of flows with protection fences in a rational way. For this purpose, an interaction matrix is created: it summarizes the key geotechnical parameters that influence debris flows, their interactions and debris/engineering protection opera behaviour. The goal is to quantify the diagonal-off terms to assess the residual risk after barrier construction, using back analysis from real debris flow event and data collection from literature.This methodology is applied to analyze a debris flow event in the Italian Western Alps where numerical analyses are carried on to assess flow characteristics to be used for fence design through the application of an analytical and numerical model developed by the authors (Brighenti et al, 2013). In particular, the velocity and deposition heights have been estimated using the numerical code RASH3D (Pirulli, 2010), which is a single-phase model based on depth-averaged Saint Venant equations. Pathways of different lengths are studied to assess the input data necessary to design the protection barrier and to determine the associated risk. Simulation of the barrier at different places along the valley will also allow to determine optimal barrier location in terms of minimum residual risks by comparing the velocity, the volume and the energy of the debris after the barrier impact.The work will produce a possible design scheme to be adopted in this environment."

Jan 1, 2015

By A. Ouchi

This paper presents ground control best practices in weak rock environments including the "Unsupported" Weak Rock Updated Span Design Curve and awareness pertaining to the potentially detrimental effects of using resin grouted rebar in weak rock masses and the false sense of security that the use of resin grouted rebar may instill. Ground support is almost always used in weak rock environments, though the type of support used can vary widely. The development of the Weak Rock Updated Span Design Curve by the addition of 463 case histories of RMR76 values ranging from 25 to 60, has also been calibrated to four different support categories; Category A: Pattern Friction Sets, Category B: Pattern Friction Sets with Spot Bolting of Rebar, Category C: Pattern Friction Sets with Pattern Rebar Bolts and Category D: Cablebolting, Shotcrete, Spiling, Timber Sets or Underhand Cut and Fill. Design of underground man-entry type excavations in North America relies heavily upon empirical analysis. This design requires a higher Factor of Safety than other non-man entry type excavations. A comparison of the calculated ½ span failure Factor of Safety between all the categories is also presented.

May 1, 2009

By M. Uszko

The paper presents the conditions for determining the selection of methods for methane drainage in Polish hard coal mines. Various factors for the evaluation of methane drainage performance are used, including the methane drainage effectiveness ratio. However, as will be discussed there are limitations to the methane drainage ratio approach resulting from the characteristics of the deposits extracted in Kompania Weglowa S.A. coal mines.

Aug 1, 2013

By K. Negishi, H. Izui, Y. Komiya

"Aluminum has the disadvantage of low strength. In order to obtain the high strength composites, crystals were refined in the composites. Grain refinement was approached at two process points, generating new grains and grain growth. It is important for refinement how to control the grain growth. Spark plasma sintering (SPS) technique and TiB2powder addition prevent grain growth. To investigate effects of strain and additives to the alloy, aluminum powder was sintered at 70 MPa and 80 MPa, changing the content of TiB2additive powder by SPS method. As the results, the crystal grain size was finer in the composite sintered at higher sintering pressure and with larger amount of additive, though over 1.0mass% TiB2addition dissuades grain refining. These grain refinements improve hardness and tensile strength of sintered aluminum alloys.INTRODUCTIONAluminum matrix composites have low density, high specific strength, and low cost. Their applications are growing continuously in the field of automotive and aerospace industries. Recent studies to improve their good mechanical and tribological properties use different ceramic materials such as Al2O3(Das, Munroe, & Bandyopadhyay, 1996; Ashwatha & Anthony Xaviorb, 2014),SiC(Hassani, Bagherpour, & Qods, 2014), B4C(Ehsan, Masoud, Touradj, Amir Hossein, & Ali, 2015),TiC(Ehsan, Ali, Masoud, Kamyar, & Touradj, 2017), and TiB2(Fei & Zhong-Hua, 2013).On the other hand, grain refinement is also an important techniques for improving the properties of aluminum alloys. Finer grains improve the mechanical properties of the alloy. For cast and wrought alloys, addition of grain refiners in molten alloys accelerates generation of nucleus and suppresses grain growth. Al-Ti-B alloy is generally added as grain refiners in the molten aluminum alloys(Easton & Stjohn, 2001). Especially, TiB2has very high melting point, low density, and excellent hardness. Therefore, TiB2was selected as additions into aluminum alloys. Liquids reaction leads to high cost, oxidation, discoloration of molten alloy, and clustering of additive powder as compared with solid reaction such as sintering. However, sintering of aluminum alloy powder with ceramic powders is difficult for oxide layer surface. Recently, we take attention to spark plasma sintering (SPS) as advanced sintering process. SPS process can easily sinter a high quality specimen at a lower sintering temperature and in a shorter time than conventional sintering processes. By SPS process, we have sintered titanium powders that are as difficult to be sintered by any other processes as aluminum powders, and improved mechanical properties by adding hard ceramic powders TiC and TiB(Kamegawa, Izui, Komiya, Kobayashi, & Arimoto, 2015; Sampei, Izui, Komiya, Shigimura, & Suzuki, 2015). Furthermore, it is important to consider not only pure aluminum but alloys for solid-solution or precipitation strengthening. Actually, pure Al does not have enough strength compared with the alloys. Al-Cu alloy and Al-Mg alloy demonstrate adequate strength for industrial and commercial sectors. Al-Mg alloy retains good formability, and has high resistance to corrosion. It is therefore used for many applications. We must consider alloying processes. The most cost effective process is blended elemental technology where alloying elements are added to base powder as elemental or master alloy powder (Smugeresky & Dawson, 1981; Yasue, Radjai, Miwa, & Sakaguchi, 2003; Bolzoni, Esteban, Ruiz-Navas, & Gordo, 2012)."

Jan 1, 2018

By J. J. Denny

IN a preliminary paper (1) it was shown that the addition of small quantities of metallic aluminium powder almost completely inhibited the solubility of siliceous material in the beaker. Six rabbits exposed to quartz dust for six months all showed well developed silicosis. Seven rabbits exposed to quartz dust plus 1 per cent metallic aluminium powder for the same period did not develop silicosis. At that time, we were not in a position to state either the manner in which metallic aluminium reduced the solubility of siliceous material, or, from the animal experiments, whether the aluminium was acting locally or systemically, or for what period after the cessation of dusting it would continue to act. This paper reports the further progress of this investigation. CHEMICAL EXPERIMENTATION The technical details pertaining to the various substances used in the experiments are given in an appendix which is on deposit with the American Documentation Institute, Washington, D.C. For lack of space, it is not printed here. The term 'solubility' is used to indicate the concentration of silica in the solution under the conditions as noted, determined colorimetrically (2), and expressed as parts per million (p.p.m.). The term 'reduction in solubility' indicates the difference between the solubility of the .silica in the presence of the aluminium powder and its solubility in the absence of aluminium powder. It will be noted that the solubility figures for different samples of quartz with no added aluminium vary considerably. The figures do not refer to an equilibrium solubility of silica but to the actual amount of silica dissolved from a given sample in a given time at a given temperature. In view of the fact that quartz dissolves extremely slowly, it is evident that the actual figures in any case will depend upon the surface exposed, i.e., fineness of grinding of the different samples.

Jan 1, 1939