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By Peter Jackson

Over a quarter of a century ago a New Zealand physicist suggested the possibility of detecting coal seam discontinuities by a seismic method carried out underground in the mine workings (Evison 1955). Twenty years ago initial experiments were performed in Germany (Krey 1963). Since then research has continued, notably in Britain and Germany, in order to provide a reliable fault and washout detection system. The National Coal Board of Great Britain has now carried out more than 250 surveys in Britain, France and Australia. The first NCB survey in the U.S., a successful application of the technique to an Ohio coal seam, will be described and the strengths and limitations of the method explained.

Jan 1, 1984

By C. Fortin

ABSTRACT The subject of gold flotation has been reviewed extensively. Most of these reviews focus on the theories of gold flotation and the physical and chemical effects that may impact the efficacy of the gold flotation process. The current status of gold flotation chemistry as it is being applied in industry has not been widely addressed. This paper reviews current gold flotation practice and research advancements and discusses how these applications tie in with the current understanding of gold flotation chemistry. Survey results from worldwide gold flotation operations are analyzed. Potential future areas of gold flotation research are highlighted.

Jan 1, 2013

By Y Peng, B Guo

In gold processing plants, the water from the cyanidation stages is treated to detoxify cyanide species and this recycle water becomes the main part of the process water. Despite the low concentration of free and weak acid dissociable (WAD) cyanides in process water, the recoveries of gold and silver is still affected during flotation, especially when gold and silver are associated with iron sulfide minerals. This is a case at the Hidden Valley (HV) Mine. In this study, the effect of free and WAD cyanides on gold and silver recoveries by flotation from the HV Mine was considered.WAD cyanide (WAD CN) was prepared by mixing sodium cyanide and copper sulfate at a cyanide to copper ratio of 3:1 dosed at different cyanide concentrations. It was found that both free and WAD CN depressed gold and silver and particularly iron sulfides in flotation. The depressed gold and silver recoveries were closely associated with the depressed recovery of iron sulfide minerals, suggesting that free and WAD CN may not depress the flotation of liberated gold and silver minerals significantly. It was also found that 10 ppm free cyanide completely depressed the flotation of iron sulfide minerals and WAD CN depression is probably through the WAD dissociation to free cyanide species (mainly aqueous HCN) during the grinding process, resulting from a decrease in pH. Thermodynamic calculation showed that 5.5 ppm free cyanide was released in the end of grinding at an initial WAD CN concentration of 50 ppm. This research provides a guideline to counteract the negative effect of WAD CN in the flotation of gold and silver minerals.CITATION:Guo, B, Peng, Y and Espinosa-Gomez, R, 2013. The effect of weak acid dissociable cyanide on gold and silver flotation in Hidden Valley Mine, in Proceedings World Gold 2013 , pp 341-346 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 26, 2013

By J. McCreedy

The Ontario Division of The International Nickel Company of Canada, Limited, operates five underground mines and one open pit on the rim of the Sudbury Basin located in the Province of Ontario, 230 miles northwest of Toronto. Four of the mines, Frood-Stobie, Creighton, Murray and Garson, lie on the South range of the Basin within a 10-mile radius of the City of Sudbury; the fifth mine, Levack, is on the North range, about 30 miles northwest of the city. The ores are mined primarily for nickel and copper, the principal minerals being pentlandite and chalcopyrite. Other elements recovered from the ores in varying quantities are platinum, palladium, ruthenium, iridium, rhodium, cobalt, selenium, tellurium, iron, sulphur, gold and silver. In 1962, the total underground ore production was over 10,800,000 tons which was mined mainly by blasthole and caving methods with the remainder by cut-and-fill, square set, and undercut-and-fill techniques.

Jan 1, 1964

By C. J. Newman

Prior to 1995, the smelting process at the Kennecott Utah Copper Corporation (KUCC) smelter consisted of Noranda reactors and Pierce-Smith converters. In the consideration of expansion opportunities, the existing process did not lend itself to a program geared towards processing the total output of KUCC mining and milling operations. During 1989 and 1990, a number of smelting options were evaluated. The final selection was the Outokumpu flash smelting process, coupled with the new Kennecott-Outokumpu flash converting technology. Facilities were designed and installed to process 1.0 million tonnes per year of copper concentrate, with the ability to expand to 1.2 million tonnes per year. Following the shutdown of the smelter facility utilizing the Noranda technology in May 1995, the flash smelting furnace commenced operation in June with the flash converting furnace startup following a few weeks later. The smelter has achieved design production targets and environmental goals. Current operating rates are at or above design rates for concentrate and matte processing. Emissions are lower than the permit levels and equate to less than 3.5 kg of S02 per tonne of copper. This paper outlines the design, construction, startup and the first two years of operation of the modernized KUCC smelter.

Jan 1, 1998

By G. G. Richards

The zinc slag fuming process is used to recover zinc from molten iron-calcium silicate slags by treatment with pulverized coal and air. The rate of zinc fuming is controlled by the complex interaction of several kinetic factors including the rate of entrainment of coal in the slag, the extent of the coal-slag reaction and the rate of ferrous oxide oxidation to ferric oxide. This paper briefly outlines the mechanism of fuming and, on this basis, optimization of process parameters is discussed. Modelling analysis and recent industrial trials at Cominco show that coal entrainment in the slag, bath temperature, and bath depth are critical variables affecting process rate and efficiency. The first step in process optimization is to assess coal bypass of the bath. In general, changes which promote operation at a higher temperature, greater coal entrainment in the slag and extended residence time of the coal in the bath increase fuming performance. Coal entrainment is controlled by injection conditions whereas bath temperature is a function of coal combustion and ferrous oxide oxidation. Residence time of the coal is largely a function of bath depth. The implication of model predictions for continuous fuming is shown.

Jan 1, 1994

By J. Bilant, B. Carlson, N. Gow

"High-pressure grinding roll (HPGR) technology was evaluated to replace tertiary cone crushing at Coeur Rochester operations (Coeur Rochester Inc.) as an opportunity to improve silver recovery. In 2016 and 2017, onsite and third-party pilot programs were initiated to evaluate the impact on metallurgical recovery and heap leach performance of crushed product generated by an HPGR. In 2018, Forte Dynamics evaluated the HPGR laboratory metallurgical data from Coeur Rochester and all third parties to develop field-scale leach curves based on new crushing scenarios. The laboratory recovery test work data were consolidated and scaled to field conditions to determine projected heap leach performance. Based on the metallurgical testing conducted, the replacement of current tertiary cone crushers with HPGR technology has the potential to increase Coeur Rochester’s silver recovery rate by 8 percentage points, from 61 percent to 69 percent, and shorten the overall timing of silver recoveries from 20 years to just more than two years.The Rochester Mine, and associated valley fill heap leach facilities is an openpit silver and gold mine located in Pershing County, NV, approximately 42 km (26 miles) northeast of the city of Lovelock. In 2017, Rochester produced approximately 4.7 million oz silver (Ag) and 51,000 troy oz gold (Au). Ore mined at Rochester is either fed directly to the primary X-Pit crusher, crushed at an in-pit crusher system, or placed directly onto a heap leach pad as run-of-mine (ROM). Both crushing circuits are comprised of three stages of crushing to produce a nominal 3/8 in. ore. Primary crushing consists of jaw crushing while secondary and tertiary crushing are composed of varying cone crushers.Historical recovery rates of crushed Rochester ore averaged 61.4 percent Ag and 95.9 percent Au over a period of 20 years (Robinson et al., 2018). These rates were derived from third-party verification of in-house metallurgical test results, crusher production and heap leach production results from 1986 through 2004 in a private report for Rochester produced by KD Engineering Co., Inc. Recovery rates are regularly verified by compositing daily samples of ore delivered to each leach pad from the X-pit crusher, in-pit crusher and/ or ROM. A proportionate split of each sample is used to generate monthly composites for metallurgical analysis utilizing column leaching and bottle roll leaching. These tests are run in a manner analogous with production conditions and deliver test results that provide expected heap leach performance. As the Rochester oxide deposit has been mineralogically and metallurgically consistent, the gold and silver recovery trends have also been consistent over the life of the project."

Sep 1, 2019

By Derek V. Ellis, Jack L. Littlepage

"Marine ecosystem effects ar1smg from the discharge of man-generated wastes to the sea can be schematized as: acute poisoning, chronic poisoning, enrichment, suffocation, temperature effects, salinity effects, toxin bio-concentration, changed production rates and changed species equilibria. A professionally designed site-specific monitoring program to check for such effects can not only safeguard the marine ecosystem from degradation, but it can also protect the industry involved from unanticipated remedial action after expensive construction has been undertaken. Monitoring programs should consist of three steps. Step 1 is an ecosystem survey which should be undertaken prior to final design of the discharge system and submission of applications for permission to discharge, because there can be considerable cost savings in obtaining information at an early stage in development. Step 2 involves location of the effluent field at the time of starting discharge, and analysing its dispersal behaviour. Step 3 consists of ecosystem monitoring with sampling stations and specific tests based on the accumulated prior information."

Jan 1, 1972

By A. H. Lang

"IntroductionMUCH PROSPECTING, exploration, and development work was done for uranium in Canada in 1952, chiefly in northern Saskatchewan and in the Great Bear Lake region of the northwest Territories. The outstanding feature of the year was the great amount of work done in preparing for production at the Ace mine of Eldorado Mining and Refining, Limited, in the Goldfields region . of Saskatchewan. Many private companies and prospectors were also active in this region. Most of the other parts of Canada where uranium has been found received less attention than during the last few years, partly because so much interest was taken in the Goldfields region.In presenting this short summary of the year's activities now, the writer is handicapped because the season is not yet over; some discoveries have probably not yet been announced, and there has not yet been time to digest the numerous reports that have been sent in by companies and prospectors. In any case it would be impossible to give details for most of the discoveries and properties, because that would require a long report, and because that information is classed as confidential until released by the discoverers and companies concerned. It is only possible, therefore, to give a few generalizations, a brief out-line of the activities in northern Saskatchewan, even briefer ,accounts of the work in other parts of the country, and a few details that property owners have informed the writer he may publish or that have already been published by the owners."

Jan 1, 1953

By S. Kelebek, E. Yalcin

This paper reports bulk flotation characteristics of a pyritic gold ore sample from the Barry District, Quebec using isopropyl and amyl xanthates. The ore sample was highly floatable with particles showing tendencies for self-aggregation that was most apparent in the first stage of flotation. A possible reason for this is discussed. The gold concentrate grade-recovery performance with respect to the particle size is presented for the rougher-scavengers as well as for the cleaners. The effects of copper sulphate as an activator, fuel oil and NaSH as a sulphidising agent are discussed along with the recovery by size behaviour.

Jan 1, 2011

By A L. Randriamanjatosoa, G Small, C Greet

In flotation simulation models, the effects of pulp chemistry other than pH are often ignored and reduced to particles hydrophobicity or contact angle, neither of which can be measured readily in real time in an operating plant. The flotation response of a given sulphide mineral is known to be influenced and can be improved by changing the chemical characteristics of the pulp during grinding and flotation. The on-line measurement of pulp pH, potential, dissolved oxygen, temperature and oxygen demand of a process stream was completed with the PCM® (Pulp Chemistry Monitor) developed by Magotteaux in this study. The data generated together with relevant plant operating parameters were used to construct an empirical model and simulate the metallurgical performance of the ore. The same approach was also applied to laboratory flotation tests data using various grinding media types. The flotation models better fit the actual data when the chemistry of the pulp is taken into account.CITATION:Randriamanjatosoa, A L, Greet, C and Small, G, 2018. Effects of pulp chemistry on plant and laboratory flotation modelling, in Proceedings 14th AusIMM Mill Operators' Conference 2018, pp 423–432 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 29, 2018

By K. C. Dean

During the investigation of the occurrence of manganese deposits in western United States, the Bureau of Mines collected 2-ton samples from three oxide manganese ores in the Columbia and Elberta Mining Districts, Tooelo and Juab Counties, Utah. To determine the amenability of these ores to standard ore-dressing methods: of concentration, extensive laboratory tests were made. The Wildcat property, one of those sampled, is 7 miles east of Fairfield, Tooele County, Utah. The ore is described as a replacement deposit and occurs along fracture and bedding planes of shale and limestone. Experimental work was done on a sample taken from a stockpile at the mouth of the shaft. The Wildcat manganese ore is intermediate in grade (25.7 percent manganese) and contains clay as the principal gangue constituent. A high-grade product was obtained with high recovery of Manganese by simple washing.

Jan 1, 1949

By Kari Niiranen, Patrick Krolop, Viktoria Töyrä

Luossavaara-Kiirunavaara AB (LKAB) operates an iron ore mine, three beneficiation plants and three pelletizing plants in Kiruna, Sweden. The current methods of separation in the beneficiation plants are wet low intensity magnetic separation (WLIMS) and reverse apatite flotation, where the WLIMS stage is regarded as the crucial part of silica separation from the ore. Currently, the high-grade iron ore deposit of Kiirunavaara has a low grade of silica in situ, of approximately 3.0% SiO2, but the silica grade is expected to increase in the deeper parts of the deposit with a complex silicate mineralogy. An increasing silica grade will affect especially the production of direct reduction pellets (LKAB DR Oxide Pellets), one of the main products of LKAB in Kiruna with an average silica grade of under 0.75% SiO2. The silica grade in the magnetite concentrate is normally limited to a maximum level of 0.55% SiO2 in order to achieve the required chemical composition in the pelletizing process. In order to study the possibility to reduce silicate content in the magnetite concentrate (pellet feed) in the beneficiation plants in Kiruna obtained by wet low intensity magnetic separation (WLIMS), enlarged mineral processing test work was carried out in the LKAB’s mineral processing laboratories in 2016. The test work consisted of comminution, low intensity magnetic separation and reverse cationic silicate flotation at laboratory scale, complemented by screen analysis, chemical assays and mineralogical investigation. The results of these mineral processing test work showed that the magnetic separation is not sufficient to reduce the silica content in the magnetite concentrate, particularly in the case of the high-SiO2 ore type B2-a. The reverse cationic flotation can be regarded as a possible solution to reduce the silicate content in the magnetite concentrate obtained by WLIMS and to achieve the required silica grade of less than 0.55 % SiO2 in the pellet feed. The results of this study provide a good basis to understand the behaviour of different silicates in the existing beneficiation process. Furthermore, it serves valuable information for development of new beneficiation processes and for investment in new equipment at the beneficiation plants in Kiruna in the future.

Jan 1, 2018

While this paper is directed towards the ?Bellambie? type of rope attachment, the principles can be applied to any brand of rope fitting however, it is a only a broad outline and the specific installation and maintenance procedures can be obtained from the attachment supplier. The types of attachment to be discussed are:- ?Thimble Type rope cappel ?Wedge Type cappel ?WRC Rope Clamp ? (Rope Glands) ??Hoist and Balance Rope Sockets In each case, the assembly and stripping (disassembly) plus the basic maintenance procedures is briefly described. A guide for Risk Assessment is also included but because of his familiarity with the installation, the end-user is in the best position to draft the final version.

May 1, 2003

By Y. Okita

The Goro Nickel Process, developed over a ten-year period, uses a number of novel processing steps and treats two ore types, limonite and saprolite, together. Nickel and cobalt are solubilized using a 270°C pressure acid leach in sulphuric acid, which rejects the bulk of the Fe into the leach residue as hematite particles. The leach liquor, after CCD, is aerated to oxidize any ferrous iron to the ferric form and is neutralized with limestone to precipitate iron as hydroxides together with gypsum from the neutralization of the free acid. Further neutralization with lime, together with steps to remove suspended solids, reduces the iron to trace concentrations. Nickel and cobalt are directly recovered from the low-iron leach solution by primary solvent extraction using Cyanex 301® (SXl) in a high-strength hydrochloric acid solution. Nickel is subsequently separated from cobalt in a secondary solvent extraction circuit using tri-isooctylamine. A granular nickel oxide is made by pyrohydrolysis, and this allows the recycling of hydrochloric acid to SXl. The process is currently being commercialized to produce approximately 60,000 t/y of nickel as nickel oxide granules and approximately 5,400 t/y of cobalt as cobalt carbonate. This paper describes the process development to control the Fe concentration in the SX1 feed solution.

Jan 1, 2006

By C Bartle

In many operations the use of less electrochemically reactive grinding media in the first grinding stage (for example, rod milling and high aspect ratio SAG milling) is rarely considered. Therefore, in reality a plant may inadvertently be using a 'mixed' media charge. That is, whilst employing inert grinding media during secondary grinding, electrochemically active forged steel grinding media may be used in the primary grinding stage. This paper discusses the impact of such a circuit on the pulp chemistry and flotation response of a refractory gold ore. The Wiluna concentrator has two grinding circuits operating in parallel. Line 1 operates a single ball mill in closed circuit with cyclones, and utilises high chrome grinding media, while the second circuit (Line 2) consists of a rod mill (with forged steel rods) in series with a ball mill, which also utilises high chrome grinding media. The cyclone overflows from both circuits are combined to feed a sulfide flotation circuit. Pulp chemistry surveys were completed around both grinding circuits, and laboratory flotation tests were conducted on the cyclone overflows. The results demonstrate clearly that the rod mill/ball mill circuit operated at significantly lower Eh and dissolved oxygen values, while the percentage EDTA extractable iron was considerably higher, when compared to the single stage ball milling circuit. These variations in pulp chemistry had a marked negative impact on the laboratory rougher flotation response, and suggests that plant performance may be affected.

Jan 1, 2008

By Alexander V. Epiforov, Stanislav V. Balikov

This paper describes of processing tests of 8 flotation concentrates containing precious and base metals by pressure oxidation (POX) method. Concentrates 1 and 2 were gold-copper concentrates. Zinc and silver were by-products in these concentrates. These concentrates were processed by POX with following cyanidation of POX solid residues, copper solvent extraction and zinc carbonate precipitation. The recoveries of gold, copper, silver and zinc from these concentrate were 98, 99, 30 and 99%, respectively. Concentrates 3 and 4 were lead-zinc concentrates. Silver was by-product in concentrate 3. Gold, silver and copper were by-products in concentrate 4. Concentrate 3 was processed by POX with following reduction smelting of POX cakes for primary lead recovery and zinc carbonate precipitation from POX solution. The recoveries of lead and silver into ingot were 96 and 98%, respectively. The recovery of zinc was 99%. Concentrate 4 was processed by POX with following zinc carbonate precipitation and reduction smelting of POX cakes. Copper was precipitated from the POX solution using sodium sulphide prior zinc precipitation. The recovery of zinc into carbonate concentrate was 99%. The recoveries of lead, gold and silver into lead bullion were 95, 99 and 98% respectively. The recovery of copper into sulphide concentrate was 99%. Concentrate 5 was gold-pyrite concentrate, and concentrates 6-8 were double refractory gold-arsenopyrite concentrates. Silver was by-product in these concentrates. These concentrates processed by POX and CIL. The recovery of gold from concentrate 5 was 98%, and from concentrates 6-8 was 85-90. Low gold recovery from concentrates 6-8 was associated with preg-robbing factor. The recovery of silver from gold-sulphide concentrates did not exceed 10-20%. The low silver recovery was associated with argentojarosite formation that is resistant to cyanidation. The flowsheets for complex processing of precious and base metals sulphide flotation concentrates based on this test work results were proposed.

Jan 1, 2018

By Y. Tang

"Rare earth elements (REEs) have many key applications in traditional and advanced technologies. A shortage of several critical REEs is expected due to the discrepancy between the availability of REEs from REE deposits and the REE demand from the market. REE recovery and separation from secondary resources such as uranium wastes and recycled materials might help balance the shortfall in a cost-effective way. This paper presents data concerning the recovery of heavy REEs (HREEs) from uranium raffinate. It also discusses the design, commissioning, and operation of a solvent extraction pilot plant for the separation of REEs.RÉSUMÉ Les éléments des terres rares (ÉTR) trouvent de nombreuses applications importantes dans les technologies classiques et de pointe. On prévoit une pénurie de plusieurs ÉTR critiques en raison des divergences constatées entre la disponibilité des ÉTR provenant de gisement d’éléments des terres rares, et la demande d’ÉTR sur le marché. La récupération et la séparation des ÉTR à partir de ressources secondaires telles que les déchets générés par le traitement du minerai d’uranium et les matériaux recyclés pourraient contribuer à équilibrer cette pénurie de manière rentable. Cet article présente des données relatives à la récupération des ÉTR lourds (HREE, de l’anglais heavy REEs) à partir de raffinat d’uranium. Il aborde également la question de la conception, de la mise en service et de l’exploitation d’une usine pilote d’extraction par solvants pour la séparation des ÉTR INTRODUCTIONSignificant amounts of strategic specialty heavy rare earth elements (HREEs) are present in waste streams in Saskatchewan uranium operations. Selective precipitation including neutralization, oxalate, and double-salt precipitation, as well as sulfide precipitation, ion exchange (IX), and solvent extraction (SX) are commonly used technologies for the recovery and purification of rare earth element (REE) solutions. REE oxalate precipitation can effectively remove Fe, Al, Ca, Si, and other impurities by taking advantage of the solubility difference between REE oxalates and impurities in the acidic solution (Xu, 2005)."

Jan 1, 2018

By Mostafa Benzaazoua, Emilie Ré, Raphaël Mermillod-Blondin, Hassan Bouzahzah, Jean-François Wilhelmy, University of Québec in Abitibi-Témiscamingue

"We analyzed two copper and lead flotation concentrates from the LaRonde mill using MLA technology (Mineral Liberation Analyzer) to identify the contaminants and to quantify their size and liberation. The MLA mineral quantification was compared with traditional mineralogical techniques (Scanning Electron Microscopy, Optical Microscopy, X-Ray Diffraction and Chemistry). The accuracy of MLA data was then quantify in application to metallurgical decision (mineral identification, mineral quantification, particle sizing and liberation quantification). We prepared five well-known materials from pure minerals and analysed them by MLA. MLA concentrates analyses showed the lead concentrate is mainly contaminated by pyrite and sphalerite. These minerals are liberated above 70 % and present a floatable size around 15 to 35 µm. Surface activation by dissolved lead from galena is therefore assumed for these contaminants. The analyses of the known samples show that mineral quantification and size distribution given by the MLA are consistent with the chemical analyses and the laser particle sizer. The liberation measurement is affected by the stereological effect. Modelling quantifies the overestimation of the particle liberation. Based on the modelling, the stereological shift on liberation should not impact metallurgical conclusions on the concentrate contaminations.INTRODUCTIONTo face the diversity of mineral processing challenges, the process mineralogy includes phase quantification, measurement of mineral size, liberation by exposure and by grade, association, surface contact proportion and texture. In the last decades, two SEM commercial tools emerged: MLA and QEMSCAN R. Both are based on specific combinations of backscattered electrons and X-ray images as well as image analysis routines developed at CANMET (Petruk & Pinard, 1976, Petruk, 1989), CSIRO (Frost, O'Hara, Suddaby, Grant, Reid, Wilson & Zuiderwyk, 1977, Reid, Gottlieb, MacDonald, & Miller, 1984) and JKMRC (Hall, 1977, Gu & Sugden, 1995). Recently, TIMA (TESCAN) and Mineralogic MiningR (ZEISS) supplied automated mineralogy for mining industry (Bouzahzah, Benzaazoua, Graham & Cropp, 2015, Gottlieb & Dosbaba, 2015a). In parallel, home-made routine were developped to resolve mineralogy challenges in mineral process but also in geometallurgy and mining environment (Kahn, Mano, & Tassinari, 2002, Knight, Klassen & Hunt, 2002, Mermillod-Blondin, Benzaazoua, Kongolo, de Donato, Bussiere & Marion, 2011, Hunt & Bradshaw, 2015). SEM mineralogy become essential to operation by setting units on mine sites (MacDonald, Latti, Adair, Bradshaw, & Dunn, 2011, Goergen et al., 2013, Dobbe et al., 2014, Gottlieb & Dosbaba, 2015b)."

Jan 1, 2016

By D J. Murray

This paper outlines the principles of friction hoisting and the components involved, and gives a description of a specific mine hoist. Friction hoisting is compared with conventional drum hoisting, and the depth of shaft at which friction hoists become more economical than drum hoists, with respect to power consumption, is determined. Introduction T HE purpose of this paper is to outline the principles of friction hoisting, to describe the components and to show the advantages of multi-rope friction hoisting. Some calculations are made to show that the power requirements and the initial costs of friction hoists are less than those of conventional drum hoists, once a certain depth of shaft has been reached. The use of multi-rope friction hoists is gradually superseding the employment of the conventional drum hoist in many parts of the world. It results in heavier payloads from deeper levels, an increase in shaft safe-ty and a more compact installation for protection against adverse weather conditions. It was observed that where drums and friction sheaves exceeded 30 feet in diameter, a number of mechanical disadvantages were being experienced;

Jan 1, 1965