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Agitation Leaching Theory And Practice Biology Essay

This essay has been submitted by a student. This is not an example of the work written by our professional essay writers.

Agitation leaching is a chemical process where in the soil that is to be mixed or slurried is kept in contact for a certain period of time with fluid to be extracted.

The metal solubility rate is reduces quite noticeably, and the extraction gets completed on the approach of equilibrium between the metal present in the solution and the metal contained on the surface of the soil is approached

Excess metal will not be extracted from the surface of the soil unless the soil is accessed by fresh extraction solution and the contact time increases when the system is at equilibrium.

On reaching equilibrium, the soil is separated from the extraction fluid using sedimentation, thickening, or clarification.
Realistic propaganda on the other hand starts from the assumption that tiny groups of socialists cannot decisively influence large groups of workers at present in most circumstances. But ii also assumes that there are arguments over specifics around which socialists can attempt to build. So the realistic propagandist in a factory will not argue for abolition of the wages system. He or she will argue for a set of demands which hopefully can lead the struggle to victory, and certainly beyond the tokens of the trade union bureaucracy. So they will argue, far example, for a flat rate increase, the full claim, all out rather than selective strike, etc.

An agitation vat coupled with a solid-liquid separation vessel (typical processes like clarification or sedimentation) is considered to be a single stage The process of extraction is then generally continued in a separate extraction vat and the clear solution obtained from the extraction process is used to speed up the rate of extraction [1].
The pioneer Russian Marxist Plekhanov pointed out an important consequence of this distinction. "A propagandist presents many ideas to one or a few persons; an agitator presents only one or a few ideas, but presents them to a mass of people." Like all such generalizations this one should not be taken too literally. Propaganda can, in favorable circumstances, reach thousands and tens of thousands. And the 'mass of people' reached by agitation is a highly variable quantity. Nevertheless, the general point is sound.

Agitation leaching-Practice

Cyanide and the Gold Industry

Introduction

One of the most widely used industrial practices is the cyanidation process in the gold industry. Amount of gold present in ores typically occurs at very low concentrations in ores which generally range from less than 10 gm/tonne.

Abstract propaganda raises ideas which are formally correct, but which do not relate to struggle or to the level of consciousness which exists among those to whom the ideas are being put. For example to argue that under socialism the wages system will be abolished is absolutely correct to place such a demand to workers today is not agitation, but propaganda of the most abstract form. Similarly constant demands for a general strike regardless of whether the prospect is a real one in the present situation leads not to agitation but to abstaining from the real struggle in the here and now.

At the low level of the gold concentrations the most predominant method used extensively and one that is cost effective is the aqueous hydrometallurgical extraction processes to extract the gold from its ore.
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Typical hydrometallurgical gold recovery involves an agitation leaching step where the gold is dissolved in an aqueous medium, followed by the separation of the gold bearing solution from the residues, or adsorption of the gold onto activated carbon.
So what is the importance of the distinction today? For the most part socialists in Britain are not talking to thousands or tens of thousands. We are talking to small numbers of people, usually trying to win them through general socialist politics, rather than on the basis of mass agitation. So what we are arguing is basically propaganda. But it is here that the confusion arises. Because there is more than one sort of propaganda. There is a distinction between abstract propaganda, and that propaganda which can hopefully lead to activity, concrete or realistic propaganda.

After elution from the activated carbon the gold is further concentrated by electrodeposition or precipitation.

Gold is one of the noble metals and is not very much soluble in water. Complexes, like cyanide, is known for stabilizing the gold species in solution, along with an oxidant preferably oxygen thereby dissolving the required amount of gold.

Or take another example. Lenin speaks of "crying injustice." Yet as a profound student of Marx he knew very well that there is no 'justice' or 'injustice' independent of class interest. He is pointing to, and appealing to, here, the contradiction between the notions of 'justice' or 'fairness' which are promoted by the ideologists of capitalist society and the realities exposed in the course of the class struggle. And that is absolutely right from an agitational point of view.

The amount of cyanide in solution required for complete dissolution may be typically of very low concentrations such as 350 mg/l which accounts for around 0.035% of 100% sodium cyanide

Alternative complexing agents for gold, such as chloride, bromide, thiourea, and thiosulfate form less stable complexes and thus require more aggressive conditions and oxidants to dissolve the gold.

The substance of his second proposition is that the ballot has not been shown a remedy for the evils complained of. That it will not open avenues of labor, will not make wages equal with those of men, and will not break up the liquor traffic. In 1774-5 the American colonists believed that representation and suffrage would remedy the evils imposed | | 176 on them; and failing to obtain them by persuasion they gained them by war, for which they have been commended ever since. In 1868-9, numbers of the best, wisest and shrewdest men of the nation declared the only way to relieve the negro and make him a man, was to give him the ballot. Still it won't help woman any.

These reagents present risks to health and the environment, and are more expensive. This justifies the dominance of cyanide as the primary reagent for the leaching of gold from ores since its introduction in the latter half of the 19th century.
The latter also aims at hurting but only as a means to some other end. The term ‘aggression’ is used more in wars, while the term ‘agitation’ fits in more with the youth’s collective behaviour, caus­ing anxiety to persons, their minds or feelings. Agitation is “to bring grievance and injustice to the notice of people in power”.

Manufacture, Transport and Storage of Cyanide

Approximately 1.1 million metric tons of hydrogen cyanide is produced annually worldwide, with approximately 6% used to produce cyanide reagents for the processing of gold. The remaining 94% is used in industrial applications including production of plastics, fire retardants, cosmetics, adhesives pharmaceuticals, food processing and as an anti-caking additive for table and road salts.

THE PROPAGANDIST, of course, must probe deeper, must examine the notion of justice, its development and transformation through different class societies, its inevitable class content. But that is not the main thrust of agitation. Those 'Marxists' who do not understand this are themselves victims of bourgeois ideology, of timeless generalizations which reflect an idealized class society. Most important, they do not grasp concretely the way in which working class attitudes actually change. They do not understand the role of experience, for example the experience of the role of the police in the miners' strike. They do not understand the difference between agitation and propaganda.

Cyanide is manufactured and distributed for use in gold mining industries in a variety of physical and chemical forms, including solid briquettes, flake cyanide and liquid cyanide. Sodium cyanide is supplied as either briquettes or liquid, while calcium cyanide is supplied in flake form and also in liquid form.

The propagandist, dealing with, say, the question of unemployment, must explain the capitalistic nature of crises, the cause of their inevitability in modern society, the necessity for the transformation of this society into a socialist society, etc. In a word, he must present "many ideas", so many indeed, that they will be understood as an integral whole by a (comparatively) few persons. The agitator however, speaking on the same subject, will take as an illustration the death of an unemployed worker's family from starvation, the growing impoverishment etc. and utilizing this fact, known to all, will direct his efforts to presenting a single idea to the "masses." Consequently the propagandist operates chiefly by means of the printed word; the agitator by means of the spoken word.

The strength of bulk cyanide reagents vary from 98% for sodium cyanide briquettes, 44-50% for flake calcium cyanide, 28-33% for liquid sodium cyanide and 15-18% for liquid calcium cyanide. The product strength is quoted on a molar basis as either sodium or calcium cyanide.
The Swadeshi movement could not unify the divided Bengal. Yet the importance of Swadeshi in the history of the freedom movement of India can in no way be denied.

The form of cyanide reagent chosen for use typically depends on availability, distance from the source and cost. Where liquid cyanide is used, it is transported to the mine by tanker truck or rail car and is off-loaded into a storage tank.

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The truck or rail car may have a single or double walled tank, and the location and design of the discharge equipment varies by vehicle.

Solid briquette or flake cyanide is transported to the mine in drums, plastic bags, boxes, returnable bins and ISO-containers.

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The mine generally designs and constructs the necessary equipment to safely dissolve the solid cyanide in a high-pH solution considering the packaging of the reagent. The pH value of cyanide solutions during dissolution must be maintained above pH 12 to avoid the volatilization of the hazardous hydrogen cyanide (HCN) gas.
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The resulting cyanide solution is then pumped to a storage tank prior to introduction into the process.

The cyanide solution is fed from the storage tank into the metallurgical process stream in proportion to the dry mass of solids in the process stream.

With a wide range of services to our clients and contractors Futura Deutschland are able to take on labour leasing employees, temporary employment of freelancers and permanent solutions to the automotive industry and beyond.

The feed rate of cyanide is controlled to maintain an optimum cyanide level as demanded by the metallurgy of the ore being treated.

Ore Preparation

Preparation of the ore is necessary so that it can be presented to the aqueous cyanide solution in a form that will ensure the optimal economic recovery of the gold. The first step in ore preparation is crushing and grinding, which reduces the particle size of the ore and liberates the gold for recovery.

This essay by Duncan Hallas is from a collection of "What do we mean by..." articles first published in Socialist Worker Review in September 1984, and later republished in Education for Socialists No. 6. This text is republished from the Marxists Internet Archive.

Ore that contains free gold may not yield a sufficiently high recovery by sole use of cyanide leaching, due to a very long dissolution time for large gold particles. Such ore may first be subject to a gravity recovery process to recover the free gold before being subjected to cyanide leaching.

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Gold bearing ores that contain gold associated with sulphide or carbonaceous minerals require additional treatment, other than size reduction, prior to gold recovery. Gold recovery from sulphide ore is poor because the cyanide preferentially leaches the sulphide minerals rather than the gold, and cyanide is consumed by the formation of thiocyanate.

On this last point Lenin was wrong, because he was too one-sided. As he himself had argued, before and after he wrote the statement above, the revolutionary paper can and must be a most effective agitator. But this is a secondary matter. The important thing is that agitation, spoken or written, does not try to explain everything. So we say, and must say, that those individual miners who resort to the capitalist courts against the National Union of Mine Workers are scabs, villains, in terms of the struggles today; quite apart from the general argument about the nature of the capitalist state. Of course we make the argument but we seek to 'excite', 'stir up', 'rouse discontent and indignation' against the courts among as many working people as possible. This includes those (a big majority) who do not yet accept that the state, any state and its courts, is necessarily an instrument of class rule.

These ores are subject to a concentration processes such as flotation, followed by a secondary process to oxidize the sulphides, thereby limiting their interaction with the cyanide during the gold leach.
He says further: "Many of both sexes who would give the question of Woman's Rights careful and candid consideration are repelled and disgusted by the atrocious sentiments of those who advocate it. How can it be otherwise, when these women proclaim from the platform and through the press that there are 'too many children,' and that when Cornelia finds her children too many for her they are 'Tarpean jewels?' These women 'wonder children do not open their mouths and curse the | | 174 fathers begat them and the mothers that bore them.'" There are too many children unless their parents can be induced to care for them more and protect them better. Look at the numerous inmates of foundling and orphan asylums. Look at the multitudes of forlorn children whose mothers were killed by lust and by child-birth pain; at the hosts of worse than orphans subject to the abuse of drunken, licentious fathers and inheritors of their brutality. The stamina which should have been given to one is diffused among five or six, thereby swelling the lists of mortality among infants, and the number of effeminate, prematurely old men and women.

Carbonaceous minerals adsorb gold once solubilised; oxidizing the ore prior to leaching prevents this. To counter this affect, the leaching process may also be modified by the addition of activated carbon to preferentially adsorb the gold.
The fact Is, the great majority of married women, who advocate and favor "woman's rights," are "sensible wives and mothers." The foundation principle of the movement is the elevation and full development of women, and the immediate consequences of a practical adoption of that principle are true, pure wives, and educated, affectionate mothers; notwithstanding the assertions of editors and divines to the contrary. Witness the active interest of Mrs. Horace Mann in the Kindergartens, the spicy common sense of Mrs. E. Cady Stanton, the excellent papers on the proper rearing and culture of children by Mrs. E. Oakes Smith in the Herald of Health, etc., etc. Multitudes of wives and mothers, pure and womanly as Dr. Holland's "Kathrina," are claiming human rights for their sex.

Leaching with Aqueous Cyanide Solutions

When gold is leached in an aqueous cyanide solution it forms a gold-cyanide complex by oxidizing with an oxidant such as dissolved oxygen and cyanide complexation. This complex is very stable and the cyanide required is only slightly in excess of the stoichiometric requirement.

These definitions are not a bad starting point. Agitation focuses on an immediate issue, seeking to 'stir up' action around that issue. Propaganda is concerned with the more systematic exposition of ideas.

However, in practice the amount of cyanide used in leach solutions is dictated by the presence of other cyanide consumers, and the need to increase the rate of leaching to acceptable levels.

Typical cyanide concentrations used in practice range from 300 to 500 mg/l (003 to 0.05% as NaCN) depending on the mineralogy of the ore.

The importance of the distinction is twofold. Those socialists who believe that they make propaganda in their small discussion groups, and agitate in their workplace, are very likely to overestimate their influence among the mass of workers and therefore miss the opportunity to build a base among a tiny number of supporters. Those who believe they just raise abstract propaganda in their discussions with other socialists and in their workplace are likely to adopt an abstentionist attitude when real struggles do break out.

The gold is recovered by means of either heap leaching or agitated pulp leaching.

In heap or dump leaching the ore or agglomerated fine ore is stacked in heaps on a pad lined with an impermeable membrane.

Along with the bonfire of the foreign cloth the weavers in villages as well as the Indian mill-owners were encouraged to produce cloth.

Cyanide solution is introduced to the heap by sprinklers or a drip irrigation system. The solution percolates through the heap leaching the gold from the ore, and the resultant gold bearing solution is collected on the impermeable membrane and channelled to storage facilities for further processing.
He personally came to Calcutta to offer his support and express solidarity with the people of Bengal.

Heap leaching is attractive due to the low capital cost involved, but is a slow process and the gold extraction efficiency is a relatively low 50-75%.

In a conventional milling and agitated leaching circuit, the ore is milled in semi-autogenously ball or rod mills until it is the consistency of powder.

NONE OF this is agitation in the sense that Lenin talked about it; it is one or two socialists raising a set of ideas about how to win. But neither is it abstract propaganda because it relates to a real struggle and so can relate to a sizeable minority of the workforce. This means that realistic propaganda can strike a chord with a much larger group of people than those who are fully open to socialist ideas. That at present very small group of people will be open to all the ideas of socialism. The larger group will not be but may still accept much of the propaganda of socialists about not trusting the officials, organizing among the rank and file and so on.

The slurry is conveyed to a series of leach tanks. The slurry is agitated in the leach tanks, either mechanically or by means of air injection, to increase the contact of cyanide and oxygen with the gold and enhance the efficiency of the leach process.
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The cyanide then dissolves gold from the ore and forms a stable gold-cyanide complex.

The use of oxygen or peroxy compounds instead of air as an oxidant increases the leach rate and decreases cyanide consumption, due to the inactivation of some of the cyanide consuming species present in the slurry.

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The pH of the slurry is raised to pH 10-11 using lime, at the head of the leach circuit to ensure that when cyanide is added, toxic hydrogen cyanide gas is not generated and the cyanide is kept in solution to dissolve the gold.

Both are necessary, indispensable, but both are not always possible. Agitation requires bigger forces. Of course an individual can sometimes agitate effectively against a particular grievance, say, lack of soap, or decent toilet paper in a particular workplace, but a widespread agitation with a general focus is not possible without a significant number of people who are suitably placed to carry it, without a party.

The slurry may also be subject to other preconditioning such as pre-oxidation at the head of the circuit before cyanide is added.

Highly activated carbon is used in the dissolved gold recovery process, either by introducing it directly into the CIL (carbon-in-leach) tanks or into separate CIP (carbon-in-pulp) tanks after leaching.

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The activated carbon adsorbs the dissolved gold from the leach slurry thereby concentrating it onto a smaller mass of solids. The carbon is then separated from the slurry by screening and subjected to further treatment to recover the adsorbed gold.
Hundreds of thoughtful mothers daily make that avowal to themselves, as they think of the dangers with which custom, society, conventionalism and ignorance have surrounded their daughters. One, who has reflected upon the degenerating, hot-house culture of women, upon her oppression from the laws, upon her degradation by man, upon the wounds her too delicate nature must receive, upon the physical suffering she must endure from others' sin and ignorance, cannot look upon a prattling girl-baby, or upon blithe innocent girlhood, without sending up a wailing prayer, God protect her, and God help her!

When carbon is not used to adsorb the dissolved gold in the above-mentioned leach slurry, the gold bearing solution must be separated from the solids components utilizing filtration or thickening units.

His third proposition is: "There is little doubt that female suffrage would greatly augment, if not double, the political power of the Roman Catholic Church in the United States." Because ignorant, Irish Catholic women would abuse the privilege, it must be denied to intelligent American women. "It is a poor rule that won't work both ways." Not only are there Irish Catholic men, but ignorant Germans, and ignorant, corrupt Americans both North and South, who cast their vote "solidly on the side of political corruption and against an honest and efficient government;" hence no man in the United States should have the right of suffrage. Why didn't our political Solons think of these things--of misplaced power,--when they gave the right of ballot into the majority of the hands which but a short time ago were fighting against the government? "O Consistency, thou art a jewel!" When woman suffrage is to be dealt with, policy must be considered; when man suffrage is to be dealt with, policy is ignored and "inalienable rights" are prominent.

The resultant solution, referred to as pregnant solution, is subjected to further treatment (other than by carbon absorption) to recover the dissolved gold.

The waste from which the gold was removed by any means is referred to as residue or tailings material.

Agitation is a privilege. The waves and currents of the ocean keep its waters pure. But in the general stirring up, so much filth and scum are found floating on the ocean of current literature, that one is astounded at the display of human depravity, until memory recalls the electioneering papers and stump-speakers. The misconstruction, the defamation, the ridicule, and the false statements concerning the "Woman Movement" and its champions, now going the rounds of the would-be witty press, is but a continuation of the Billingsgate for which our corrupt men-politicians are notorious throughout the land. Every candidate for office, however moral, conscientious and upright in character, has been the object of its foulness, but it mostly subsides the day after the election. Of late years, one party has refrained, somewhat, from its extensive use, and it is to be hoped that all speakers and journals, claiming to be respectable, may yet be shamed into decency.

The residue is either dewatered to recover the solution, treated to neutralize or recover cyanide, or is sent directly to the tailing storage facility.

Recovery of Dissolved Gold

Gold is recovered from the solution first using either cementation on zinc powder or concentrating the gold using adsorption on activated carbon, followed by elution and concluding with either cementation with zinc or electro winning. For efficient cementation, a clear solution prepared by filtration or counter current decantation is required.

Lord Curzon's sole motive behind the Partition of Bengal was to weaken Bengal by sowing the seeds of dissension between the Hindus and the Muslims.

The most cost-effective process is to create adsorption of the dissolved gold onto activated carbon, resulting in an easier solid-solid separation based on size. To achieve this; the ore particles must typically be smaller than 100 µm while the carbon particles must be larger than 500 µm.

But when the Partition was finally affected to utter disregard to the popular sentiment, the people of Bengal launched a powerful movement against it.

Adsorption is achieved by contacting the activated carbon with the agitated pulp. This can be done while the gold is still being leached with the CIL-process, or following leaching with the CIP-process.
Only one who has been a slave can fully realize the blessing of liberty ; but a slave, while a slave, cannot comprehend liberty.

The CIL-process offers the advantage of countering the adsorption of gold on carbonaceous or shale ore particles, but is more expensive due to less efficient adsorption, increased gold inventory and increased fouling and abrasion of the carbon.
Though the Partition of Bengal directly affected the people of Bengal yet the tidal wave of the Boycott and Swadeshi swept away the country as a whole.

Activated carbon in contact with a pulp containing gold can typically recover more than 99.5% of the gold in the solution in 8 to 24 hours, depending on the reactivity of the carbon, the amount of carbon used and the mixer's efficiency. The loaded carbon is then separated from the pulp by screens that are air or hydro dynamically swept, thus preventing blinding by the near sized carbon particles.

In the programme of movement greatest emphasis was laid on boycott. People of Bengal unitedly took the vow that so long as the Partition was not undone they would reject all foreign articles.

The pulp residue is then either thickened to separate the cyanide containing solution for recovery/destruction of the cyanide, or sent directly to the tailings storage facility from which the cyanide containing solution is recycled to the leach plant.
Social protest may lead to aggression, agitation, and movement. Aggres­sion is a hostile act intended to harm or object, often the result of frustration. It is an unprovoked attack. It is directed at the source of indi­vidual’s frustration. Myres (1988:395) defines aggression as “physical or verbal behaviour that hurts harms or destroys”. This excludes acci­dental hurts or unintentional hitting; but it certainly includes gossipy ‘digs’ about a person which hurt him. Feshbach (1970) has given two types of aggression—hostile aggression and instrumental aggression. The former springs from anger and its goal is to injure. It is resorted to as an end in itself.

The gold adsorbed on the activated carbon is recovered from the carbon by elution, typically with a hot caustic aqueous cyanide solution. The carbon is then regenerated and returned to the adsorption circuit while the gold is recovered from the eluate using either zinc cementation or electro winning.

The former include problems at college/university level and at national level while the latter refer to taking interest in state/country’s politics and policies and programmes. Student-oriented agitations are generally discontinuous and problem-oriented rather than value-oriented.

If it contains significant amounts of base metals, the gold concentrate is then either calcined or directly smelted and refined to gold bullion that typically contains about 70 - 90% gold. The bullion is then further refined to 99.99% fineness using smelting, chlorination, and electro-refining. High purity gold is taken directly from activated carbon eluates, using recently developed processes that utilize solvent extraction techniques to produce intensive leaching of gravity concentrates [2].
It is to shake up, to move, to stir up, to cause anxiety, and to disturb the power-holders. Social movement is the activity of diffused collectivity oriented towards changing the social order. According to Turner and Killian (1972:246), social movement is a collective behav­iour based on some continuity to promote or resist change in society or group of which it is a part.

Agitation leaching-Applications

Commonly applied to a wide range of ore types, agitation leaching has been in use for well over 200 years. Leaching is typically performed in steel tanks, and the solids are kept in suspension by air or mechanical agitation.

He further asserts, "for years to come there would be no corresponding vote in favor of law and good government to counterbalance the one given by these bigoted and ignorant Catholic women." The Catholics will work energetically for the wrong, but American women will not move an inch in behalf of the right. A compliment indeed! Awaken American women to a sense of duty, and they are ready and willing to perform it. Our women, I do not mean vagrants or butterflies respond when called upon. The women of '76 were applauded to | | 177 the derogation of their descendants, but the war proved the women of '61 equal to their great-grandmothers.

Air agitation in carried out in conical-bottomed leach tanks (Browns or Pachuca tanks) was widely practiced in the early years of cyanidation but has been overtaken in recent times by more efficient mechanical agitation with reduced energy requirements and improved mixing efficiency.
Agitations could be violent or non-violent. In 1988, of the total inci­dents of students’ agitations in India (5,338), only 18 per cent were violent, in comparison to 15 per cent violent agitations in 1987, 43 per cent in 1986 and 19 per cent in 1985. Further, 56 per cent agitations (in 1988) related to non-academic issues (within the campuses, like chang­ing the name of the university), 19 per cent to academic issues, and 25 per cent to some social issues (reducing bus-fare, communal tension).

Well-designed systems can approach perfectly mixed flow conditions in a single reactor, which help to optimize reaction kinetics and make the most of available leaching equipment.

Particle size.

The material to be leached is ground to a size that optimizes gold recovery and communition costs.

Children do curse their parents, when they learn through science how they have been robbed of their inheritance of health and strength. Yet, when women, who know of those terrible and almost unmentionable wrongs hidden in the marriage state, dare to expose and denounce them, men accuse them of want of refinement, of maternal instinct, and of true wifely affection.

In a few cases, whole ore is being ground to very less particle sizes for optimal processing, either by oxidative pre-treatment and/or leaching. Agitation leaching is rarely applied to material at greater coarse sizes because it becomes increasingly difficult to keep coarse solids in suspension, and abrasion rates increase.
By raising realistic propaganda in a period when mass agitation is not generally possible socialists are much more likely to be able to avoid both traps.

Increasingly, agitation leaching is being considered to treat very finely ground materials and, with the advances in ultrafine milling equipment have been ground to lesser particle sizes to liberate gold contained in refractory along with the sulphide mineral matrices prior to processing by agitation leaching and/or oxidative pre-treatment.
The difference between an agitation and a social movement is that social movement may take the form of agitation but every movement does not do so. Many movements are peaceful, for example, women’s liberty movement, the prohibition movement or the anti-nuclear move­ment. These peaceful movements are the result of cultural drift.

Slurry density.

Leaching is usually performed at slurry densities of between 35%and 50% solids, depending on the solids' specific gravity, particle size, and the presence of minerals that affect slurry viscosity (eg., clays).

Apart from encouraging the students to participate in the anti-British movement, the Society also made necessary arrangements for imparting education to the students who had been expelled by the government authorities. Satishchandra Mukherjee a\d his Dawn Society also made useful contributions in providing education to the expelled students.

Mass transport phenomena are maximized at low slurry densities; however, solids retention time in a fixed volume of leaching equipment increases as the density increases. In addition, reagent consumptions are minimized by maximizing slurry density, since optimal concentrations can be achieved at lower dosages, because of the smaller volume of solution per unit mass of material.
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Modification of pH

Alkali, required for slurry pH modification and control, must always be added before cyanide addition to provide protective alkalinity, which prevents excessive loss of cyanide by hydrolysis. Most leaching systems operate between pH 10 and 11. Staged addition of alkali may be required throughout the leaching circuit to maintain the desired operating pH, particularly when treating ores containing alkali-consuming materials.

In order to encourage the student participation in the political movement one Sachindra Prasad Basu organised the 'Anti-Circular Society' (1905).

pH control is achieved by manual or automatic (on-line) measurement at various stages in the process. Calcium hydroxide (slaked lime, Ca (OH),), or sodium hydroxide can be used for pH modification. Calcium hydroxide (slaked lime) is the cheaper of the two but is less soluble and produces solutions that are much more susceptible to salt precipitation and scale formation.
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Unslaked lime (CaO) is used occasionally because it is less costly than slaked lime, but it is less effective for pH modification.

For nonacidic- or non-alkali-consuming ores, calcium hydroxide concentrations of 0.15 to 0.25 g/L are typically required to achieve the desired pH range for leaching (ie., pH 10 to 11). This represents typical lime consumptions of 0.15 to 0.5 kg/tonne for non-acidic ores. Sodium hydroxide is known to be more effective than calcium hydroxide at dissolving a variety of minerals, particularly at high alkalinities, and it is a highly effective dispersant.

For example, students will agitate for removal of a particular vice-chancellor of a university but they will never fight for a change in the system of selecting vice-chancellors in universities in India. Similarly, they will fight to postpone examinations for a particular year but they will not agitate for restructuring the exami­nation system as such.

This may result in the dissolution of ore constituents, such as silicates, to produce various solution species, which can subsequently precipitate in a number of undesirable forms, potentially affecting downstream processes, including filtration, gold precipitation, or carbon adsorption.
Youth agitation is the behaviour of the youth whose goal is neither injury to a person nor destruction of public property but social protest. It is neither the result of innate destructive drive nor it is an inborn reaction to frustrations. It is a learned behaviour. Various forms of youth agita­tions are: demonstrations, slogan shouting, strikes, hunger strikes, road blocks (rasta roko), gheraos, and boycott of examinations.

Consequently, calcium hydroxide is generally the preferred method of pH control in agitated leaching systems.

Cyanide

Cyanide may be added to agitated leaching systems either prior to the leaching circuit, that is, during grinding, or in the first stage of leaching. Subsequent reagent additions can be made into later stages of leaching to maintain or boost cyanide concentrations to maximize gold dissolution.

The conception of boycott was mainly an economic one, though it had other aspects too.

In the absence of cyanide-consuming minerals in the ore or concentrate to be leached, cyanide concentrations used in practice range from 0.05 to 0.5 g/L NaCN, and typically between 0.15 to 0.30 g/L NaCN. Typical cyanide consumptions observed in agitated leaching systems for free-milling ores vary from about 0.25 to 0.75 kg/t. In cases where the feed material contains significant amounts of cyanide consumers and/or high silver content (ie., >20 g/tonne), higher cyanide concentrations may be applied, that is, 2 to 10 g/L NaCN.
In regard to the liquor business, he says: We need something more than votes to suppress the business. What we want is a moral power that will demand prohibitory laws and insist on their enforcement." Where, is that "moral power" to come from? Not from the men, and not from women in their present condition. Woman has tried, persuaded, pleaded and labored; she must become something more than she has been ere she can do more.

In such cases, cyanide consumptions may vary from 1 to 2 kg/t, and in some cases much higher, depending on the nature and amount of cyanide-consuming minerals. Cyanide concentrations are usually monitored by manual titration techniques or less commonly by on-line cyanide analyzers, based on titrimetric, colorimetric, potentiometric, and ion-specific electrode techniques.

Oxygen Content

Oxygen is typically introduced into leaching systems as air, either sparged into tanks as the primary method of agitation, or supplied purely for aeration. In either case, crude sparging systems are usually sufficient to provide satisfactory bubble dispersion and to ensure that adequate dissolved oxygen concentrations are maintained.

The oft-repeated war-cry "We must agitate," must also be ours. The masses of women need to be aroused from the torpid state engendered by continual dwarfing,--need to be awakened to what they might and should be,--need to be taught the wants of their natures,--need to be elevated to the highest, purest womanhood. The torpidity of woman balks her progress.

Typically, the amount of dissolved oxygen concentrations can be maintained at, or even slightly above, calculated saturation levels with air sparging. The optimum sparging system depends on the geometry of the leach tanks.
The new spirit of nationalism that had been aroused among the people of our country found its expression in the formation of the national education system. When the idea of boycott assumed a wider meaning it also included the boycott of foreign education and the course of study prescribed by the British.

For example, conical-bottomed Pachuca tanks with single sparging points (common South African practice prior to about 1980) and flat-bottomed leach tanks with multiple sparging points, or simple down-the-agitator-shaft addition, have all been used.
In August and September 1990, many universities/colleges in North India faced the problem of students’ agitations on the reservation issue and re­mained closed for about two months. Similar agitations took place in 1994 took in some parts of the country.

In a few cases, particularly when treating ores that contain oxygen-consuming minerals, pure oxygen [5] or hydrogen peroxide [4] have been added to increase dissolved oxygen concentrations above those attainable with simple air sparging systems.
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Residence time. Residence time requirements vary depending on the leaching characteristics of the material treated and must be determined by test work. Leaching times applied in practice vary from a few hours to several days. Leaching is usually performed in 4 to 10 stages, with the individual stage volume and number of stages dependent on the slurry flow rate, required residence time, and efficiency of mixing equipment used.

Every brainless fop, every ignorant boor, and every foul-mouthed roue cracks his jokes upon the "impending crisis," as some of them term it. Every speaker and writer expresses his opinion concerning it. The question is discussed on the street corners, in the legal and medical offices, in the lyceum halls and in the pulpit. It is well, it shows the movement is gaining ground. Our modesty may shrink from the publicity, but great wrongs have to be publicly probed. The oppositionists | | 173 fight doggedly, but if the onward march and attack be continued faithfully, they must retreat or surrender.

Counter-current leaching.

Leaching efficiency can be enhanced by the application of Le Chatelier's principle. In summary, the lower the concentration of gold in solution, the greater the driving force for gold dissolution to occur, although in a mass transport controlled reaction it is debatable what role this plays in gold leaching. An alternative explanation for this phenomenon is the reversible adsorption of gold cyanide onto the ore constituents. The gold adsorption is reversed when the solution is exchanged for a lower grade solution or when a material (such as activated carbon or suitable ion exchange resin) is introduced into the slurry, which actively competes for the Aurum cyanide species. This effect can be exploited in practice by performing intermediate solid-liquid separation steps during leaching to remove high-grade gold solutions, and rediluting the solids in the remaining slurry with lower-grade leach solution and/or with freshwater plus reagents. Successful applications of this principle have been used at the Pinson and Chimney Creek, Nevada (United States), and East Driefontein (South Africa) plants, and at other operations [6, 7].

At many operating gold plants, an increase in gold extraction is observed when a leach slurry can be transferred from one type of process equipment to another (ie., between leach tanks, thickeners, filters, pumps, and pipelines).

An extensive programme was chalked out to observe the 16 October, 1905, the day fixed for the Partition of Bengal, as the day of mourning.

This can be explained by the different mixing mechanisms in the different equipment, coupled with other factors, such as changes in slurry percent solids, changes in solution composition, and the effects of pumping transfer (ie., plug flow mixing).Likewise, the benefits of the carbon-in-leach (CIL) process compared with leaching and carbon-in-pulp (CIP) have been clearly demonstrated both experimentally and in practice, even without the presence of interfering constituents in the ore[8]. The CIL process results in improved conditions for gold dissolution[3].

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