Abstract: Manganese sulfate solutions of improved purity are prepared by digesting a combination of a reduced manganese ore with an aqueous acid solution in the presence of a particulate potassium-iron salt byproduct. The salt byproduct is the salt byproduct formed, in situ, by reaction of potassium impurity with ferric ion during digestion of a combination of a reduced manganese ore and an aqueous acid solution.

Abstract: A process for preparing manganese sulfate solutions having reduced concentrations of potassium impurity is disclosed wherein a digestion mixture of a reduced manganese ore, a source of water soluble aluminum ions, a source of water soluble ferric ions and an aqueous acid solution is prepared, having a solution pH ranging from about 0.5 to about 3.5. The mixture is then digested at a temperature sufficient to produce a mixed digestion product comprising a liquid phase of a manganese sulfate solution and a solid phase of digested ore residue and a particulate complex salt by-product. The liquid phase of manganese sulfate solution is then recovered from the mixed digestion product. An additional feature of this process involves conducting the digestion of the digestion mixture in the presence of at least one complex salt of the general formula:MFe.sub.n Al.sub.3-n (SO.sub.4).sub.2 (OH).sub.6where M is Na.sup.+, K.sup.+ or NH.sub.4.sup.+ and n is a number ranging from about 1 to about 3.

Abstract: The invention relates to a process for the recovery of valuable metals from sulfidic, silicate-containing raw materials by slurrying the raw material in water, by subjecting the slurry to a selective leach under atmospheric conditions and in an acidic milieu, and by separating the valuable-metal containing solution from the solid leach residue.When the leach is carried out by introducing an oxygen-bearing gas into the slurry which contains finely-divided sulfide and carbon, the acidity of the slurry drops in a controlled manner so that a high efficiency of oxygen, and a high selectivity of the leach as regards valuable metals, are obtained. Owing to the presence of carbon the oxygen is reduced very easily and so oxygen efficiency is high and the rate of dissolving of the valuable metals increases in the slurry mixture.

Abstract: A process for the preparation of manganese sulfate solutions having reduced levels of potassium impurity comprising blending a reduced manganese ore, an added source of water soluble aluminum ions and an aqueous acid solution to form a digestion mixture, digesting said mixture, preferably in the presence of crystals of a complex potassium-aluminum salt to form a mixed reaction product containing a liquid phase of manganese sulfate solution and recovering the liquid phase of manganese sulfate solution from said mixed reaction product.

Abstract: A process for recovering non-ferrous metal values from their ores, minerals, concentrates, oxidic roasting products, or slags by sulphating said starting material using a mixture comprising iron (III) sulphate and alkali metal- or ammonium sulphate as a reagent.

Abstract: Improvement in electrowinning manganese dioxide, or zinc in which the relative concentration of manganese or zinc ions to impurities is enhanced by selectively extracting manganese or zinc ions from a bleed taken from the electrowinning feed stream with an organic extractant, while rejecting impurities, stripping the loaded organics with spent electrolyte, and recycling loaded strip to the electrowinning feed. Stripped organic may be regenerated with an alkaline agent such as calcium oxide or magnesium oxide prior to recycle, and pH may be controlled during extraction by the same means.

Abstract: Metal constituents are recovered from the heavy bottoms produced during the liquefaction of coal and similar carbonaceous solids in the presence of a catalyst containing a metal capable of forming an acidic oxide by burning the heavy bottoms in a combustion zone at a temperature below the fusion temperature of the ash to convert insoluble metal-containing catalyst residues in the bottoms into soluble metal-containing oxides; contacting the oxidized solids formed in the combustion zone with an aqueous solution of a basic alkali metal salt to extract the soluble metal-containing oxides in the form of soluble alkali metal salts of the metal-containing oxides and recycling the soluble alkali metal salts to the liquefaction zone. In a preferred embodiment of the invention, the bottoms are subjected to partial oxidation, pyrolysis, coking, gasification, extraction or a similar treatment process to recover hydrocarbon liquids and/or gases prior to the burning or combustion step.

Abstract: The solid oxalate of a catalytic metal such as cobalt, typically formed as an undesired and useless by-product during the liquid-phase oxidation of an organic compound, typically a hydrocarbon, in the presence of a homogeneous catalyst comprising said metal, is treated to convert the metal moiety to a reusable form by a process comprising leaching the metal oxalate with an aqueous solution of a soluble salt of ethylenediaminetetraacetic acid (EDTA). The resulting solution of EDTA-metal complex or chelate is then mixed with a soluble calcium salt to precipitate the oxalate moiety as insoluble calcium oxalate leaving the metal-EDTA complex in solution. After removing the resulting solid calcium oxalate, the remaining filtrate is acidified to convert the metal moiety to a simple salt which can be recycled to the liquid-phase oxidation, while the EDTA is precipitated as a solid which can also be recovered and re-used in the complexation step of the process.

Abstract: Crystalline transition metal aluminates conforming generally to the formulaMA.sub.a.sup.v Z.sub.b.sup.v.nAl(OH).sub.3.mH.sub.2 Owhere M is a transition metal having a valence charge of +2 selected from the group consisting of Cu, Zn, Mn, Fe, Co, and Ni, where AZ represents negative valence ions or radicals, v is a negative valence of 1, 2, or 3, n is a value to provide a mol ratio of Al/M of at least 1/1, preferably at least 1.5/1, and m is an integer of from zero to the maximum for waters of hydration, with (va)+(vb) equal to 2, are prepared in alkaline aqueous medium wherein transition metal compounds are caused to form adducts with amorphous hydrous alumina, Al(OH).sub.3, said adducts forming crystals when heated, said aluminates being useful, e.g., as ion exchangers and as spinel precursors among other things.

Abstract: Novel sequestering agents useful for the extraction of metal values and in various organic syntheses comprise a cross-linked organic polymeric substrate, said substrate having covalently coupled thereto a plurality of functional groups, the free valence of which having the structural formula: ##STR1## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.6 and R.sub.7, which are identical or different, each represents a hydrogen atom or an alkyl radical having 1 to 4 carbon atoms, R.sub.5 and R.sub.8, which are also identical or different, each represents a hydrogen atom, an alkyl or cycloalkyl radical having 1 to 12 carbon atoms, a phenyl radical, a --C.sub.g H.sub.2q --.phi. or C.sub.q H.sub.2+1 --.phi.-- radical, and further wherein q ranges from 1 to about 12, and n, m and p, which are also identical or different, range from 1 to 10, and .phi. is phenyl.

Abstract: Crystalline transition metal aluminates conforming generally to the formulaMA.sub.a.sup.v Z.sub.b.sup.v.nAl(OH).sub.3.mH.sub.2 Owhere M is a transition metal having a valence charge of +2 selected from the group consisting of Cu, Zn, Mn, Fe, Co, and Ni, where AZ represents negative valence ions or radicals, v is a negative valence of 1, 2, or 3, n is a value to provide a mol ratio of Al/M of at least 1/1, preferably at least 1.5/1, and m is an integer of from zero to the maximum for waters of hydration, with (va)+(vb) equal to 2, are prepared in alkaline aqueous medium wherein transition metal compounds are caused to form adducts with amorphous hydrous alumina, Al(OH).sub.3, said adducts forming crystals when heated, said aluminates being useful, e.g., as ion exchangers and as spinel precursors among other things.

Abstract: This disclosure concerns primarily the recovery of hydrogen-reduced metals from aqueous solutions of salts thereof, by hydrogen reduction at a porous hydrophobic catalytic barrier, at ordinary temperatures, in an apparatus provided with means to supply hydrogen to one face and aqueous solution to the other face of said barrier.

Abstract: A process for the recovery of molybdenum and rhenium from their sulfide ores which comprises subjecting the ores to microwave energy in the presence of oxygen to selectively heat the sulfides to convert them to oxides, and recovering the formed oxides. Alternatively, the sulfides in the ore are selectively heated with microwave energy in the presence of chlorine to convert them to the corresponding chlorides, and the metals recovered from the chlorides.

Abstract: A process for the recovery of nickel, cobalt or manganese from their oxides or silicates wherein such process, which requires the application of heat, is improved by utilizing microwave energy as the source of heat. The microwave energy may be utilized to cause the reduction of these values enabling such reduced values to then be recovered by conventional leaching processes. The microwave energy may also be used in conjunction with the chlorination of such values to produce their chlorides which are subsequently separated from the gangue and then processed by conventional means to obtain the metal values.

Abstract: A method for thermally decomposing manganese nitrate in an aqueous solution containing alkali and/or alkaline earth nitrates including splashing said aqueous solution containing manganese nitrate to form droplets or sheets of solution, heating said droplets or sheets of solution to partially decompose each droplet or sheet of solution to form manganese dioxide and nitrogen dioxide, and reuniting said droplets or sheets of solution containing manganese dioxide with said aqueous solution containing manganese nitrate; and/or spraying said aqueous solution containing manganese nitrate to form droplets of solution, heating said droplets of solution to fully decompose each droplet to form nonstoichiometric manganese dioxide, and nitrogen dioxide, and recovering said nonstoichiometric manganese dioxide.

Abstract: Recovery of cobalt and manganese metal oxidation catalysts from residue of trimellitic acid manufacture and separation of recovered cobalt from recovered manganese can be accomplished by a novel method involving dissolving the residue in water, displacing dissolved cobalt as cobalt metal by manganese metal added to the solution whose pH has been adjusted to pH of 6 and then using magnetic means for separating metallic cobalt from the cobalt-free solution.

Abstract: Cobalt and manganese are recovered from incineration ash obtained by combustion of residue from the manufacture of trimellitic acid and its recovery as 4-carboxyphthalic anhydride and then the recovered cobalt is separated from the recovered manganese by magnetic separation. The foregoing is accomplished by extraction of the ash with an aqueous solution of hydrogen bromide or chloride, recovery of the extract solution, and the upward adjustment of its pH while adding powdered manganese to precipitate metallic cobalt for its separation by magnetic means.

Abstract: A unique method of separating cobalt and manganese from residue obtained from the manufacture of trimellitic acid by the oxidation of pseudocumene in the presence of cobalt and manganese as metal oxidation catalysts and from each other without contributing to the problem of solids disposal. Said unique method comprises extracting the residues with water, removing cobalt and mangangese from the extract solution with a cation exchanger thereby producing a metal-free solution of trimellitic acid, regenerating the cation exchanger with a strong inorganic acid, adjusting the pH of the spent regenerating acid to pH of 3 to 4 if iron is present to precipitate it as its hydroxide but at least to pH of 6 while also adding powdered manganese to precipitate metallic cobalt.

Abstract: Large proportion of available manganese ores contain high proportions of potassium. Electrolytic manganese dioxide (EMD) is manufactured from manganous sulphate obtained from naturally occuring manganese ores. Crystallographically EMD has to be essentially gamma phase and other phases, alpha and beta should be the bare minimum. High potassium content is, however, an obstruction in the way of getting gamma phase EMD. The present invention describes a method of making manganous sulphate solution with low level impurity of potassium from high potassium ores which comprises adding the reduced ore to spent electrolyte containing ferric ions and digesting same at pH 1-2 and temperature of 60.degree.-90.degree. C. for 1-4 hours, and thereafter again adding reduced ore to the digested product till pH is raised to 4-6.

Abstract: A process for separating metal values from sea nodules by sulfating the nodule ore under substantially dry conditions, followed by leaching of the sulfated ore; separation of the leaching solution from water-insoluble residue and recovery of the metal values from the leaching solution.

Abstract: Rhenium and tungsten are recovered from a rhenium tungsten alloy by electrochemically dissolving the alloy in substantially 4 to 5 normal sodium hydroxide to form a rhenium-containing solution, solvent extracting the rhenium-containing solution with an organic heteroatom-containing solvent (e.g. pyridine) or acetone to form a second solution of the solvent containing rhenium, distilling the solvent from the second solution to form a raffinate containing rhenium, adding sulfuric acid to the raffinate to adjust the pH thereof to about 1, extracting tungsten from the raffinate with a solution of trioctylamine in kerosene containing octyl alcohol, and subjecting the raffinate containing sodium perrhenate to ion exchange to eventually convert it to ammonium perrhenate.

Abstract: A homogeneous manganese dioxide composition having on a microscopic scale domains of alpha and delta manganese dioxide is manufactured by reacting a manganese-oxygen containing composition with a sodium containing composition at elevated temperature followed by acid treatment.

Abstract: A process for preparing manganese nitrate solution by leaching manganese ore containing manganese dioxide in an aqueous slurry containing dissolved nitrogen dioxide gas. The reaction is controlled by monitoring the pH of the aqueous slurry, and adjusting the relative concentration of the manganese ore containing manganese dioxide and/or the rate of addition of nitrogen dioxide containing gas, to establish and maintain the leaching reaction.

Abstract: A process in which manganese is recovered from manganese nodules after the nodules have been treated to recover base metals such as copper, nickel, cobalt, and molybdenum. The process includes the steps of reacting the manganese in the nodules to yield a carbonate and subjecting the manganese carbonate to flotation. The manganese carbonate froth is collected from the top of a flotation cell, is dried to produce a manganese concentrate, and is sintered to produce a synthetic manganese oxide. Sintering of such concentrates at 1000.degree. C. yields a product containing greater than 50% manganese.The effect of reagent dosage, pH control, and temperature control on the yield of the synthetic manganese oxide is also disclosed.

Abstract: Metal values of ferromanganese nodules harvested from ocean floors are placed in aqueous solution suitable for partition as by selective extraction with chelating agents by treating the nodules with aqueous solutions which contain oxalic acid or mixture of oxalic acid with a strong acid. These unique reagents may be used alone or in combination with other reducing, complexing or acidic treating agents.

Abstract: Metals in oxide, carbonate and/or hydroxide form in ores or ore concentrates are converted to the corresponding carbide by a solid state reaction with carbon. The carbide then is separated in substantially pure form from the gangue constituents and may be converted to the metal.

Abstract: A method for thermally decomposing manganese nitrate in an aqueous solution containing alkali and/or alkaline earth nitrates including splashing said aqueous solution containing manganese nitrate to form droplets or sheets of solution, heating said droplets or sheets of solution to partially decompose each droplet or sheet of solution to form manganese dioxide and nitrogen dioxide, and reuniting said droplets or sheets of solution containing manganese dioxide with said aqueous solution containing manganese nitrate; and/or spraying said aqueous solution containing manganese nitrate to form droplets of solution, heating said droplets of solution to fully decompose each droplet to form nonstoichiometric manganese dioxide, and nitrogen dioxide, and recovering said nonstoichiometric manganese dioxide.

Abstract: A process for recovering heavy metal ions or heavy metal ions and halogen values from a solution comprising a lower aliphatic monocarboxylic acid, which comprises the steps of:(1) contacting a lower aliphatic carboxylic acid solution containing heavy metal ions or heavy metal ions and halogen values with an anion exchange resin, at least 60% of the ion-exchange groups of said anion exchange resin being in the bromide or chloride state, while the water concentration in the lower aliphatic monocarboxylic acid solution has been adjusted to a level lower than 20% by weight, thereby to adsorb the heavy metal ions or the heavy metal ions and the halogen values on the anion exchange resin; and(2) desorbing the adsorbed heavy metal ions or the adsorbed heavy metal ions and the adsorbed halogen values from the anion exchange resin by elution with an eluent.

Abstract: A method is provided for extracting at least one of the trivalent ions Fe and Al from an acid solution. The method comprises uniformly mixing the acid solution with a liquid organic extractant comprising an organophosphorus compound and an alkylaromatic sulfonic acid dissolved in a water-immiscible organic solvent, the extractant being selective to the solvent extraction of said trivalent ions under acidic conditions. The molar ratio of the sulfonic acid to the organophosphorus compound is controlled over a range of about 1:4 to 10:1 and the mixing carried out for a time sufficient to effect solvent extraction of said trivalent ions and provide a raffinate substantially impoverished in said trivalent ions and a loaded extractant containing said trivalent ions, following which the loaded extractant is separated from the raffinate.

Abstract: A process for separating molybdenum values from sea nodules which includes sulfation of the sea nodules, volatilization of the molybdenum values from the sea nodules and collection of the volatile molybdenum values.

Abstract: A liquid-liquid extraction process is disclosed, in which an aqueous solution, containing metal ions, is contacted with an organic liquid substantially insoluble in water. The organic liquid contains two water-insoluble reagents, viz. a diester of dithiophosphoric acid and an organic phosphate, in a preferred volume ratio of between 1:10 and 2:1. The organic liquid may also contain a diluent for the reagents.

Abstract: Coal hydrogenation catalyst is recovered from coal hydrogenation residues containing carbonaceous matter, coal ash and catalyst by contacting such residues with oxygen and steam under conditions to provide H.sub.2 and CO containing gases and fused ash which contains catalyst, contacting the fused ash with a reactant which will react with the catalyst to form a catalyst compound which is volatile at the temperature of the fused ash and withdrawing vaporized catalyst compound from the fused ash. The vaporized catalyst may be condensed and dissolved in a solvent liquid to form a solution of catalyst for application to coal to be hydrogenated.

Abstract: Nickel, cobalt and manganese are selectively recovered from Atlantic deep sea nodules by means of a preliminary treatment with acetic acid, followed by leaching with sulfurous acid.

Abstract: Heavy metal values are recovered from mother liquors remaining from oxidations to mono- or poly- carboxylic acids in aliphatic monocarboxylic acids in presence of catalyst heavy metals and bromides by (1) concentrating, (2) precipitating and (3) separating heavy metals as sulphates and (4) recovering aliphatic monocarboxylic acid and H Br by distillation, (5) dissolving sulphates in water, (6) adsorbing heavy metals on a cation exchange resin and (7) desorbing them, preferably with the solution from Step 4.

Abstract: A process is disclosed wherein essentially all of the rhenium can be removed from an aqueous solution of molybdenum without the extraction of molybdenum using a particular solvent extraction solution. The extraction solution consists essentially of quaternary ammonium compound and at least about 50 percent by volume of a highly aromatic solvent which dissolves a quaternary ammonium-rhenium complex to the extent of at least 0.1 percent by volume selected from the group consisting of benzene and an aromatic solvent containing primarily lower alkyl benzenes having molecular weights of either 106, 120, 134 or 148 with minor amounts of relatively long chain aliphatic hydrocarbons containing greater than 8 carbon atoms and minor amounts of napthalene.

Abstract: The radioactive concentration of technetium-99m contained as pertechnetate ion in aqueous solution is increased by(1) acidifying the solution,(2) contacting the acid solution with a bifunctional ion-exchange material which is an anion-exchanger under acid conditions and a cation-exchanger under alkaline conditions, so that pertechnetate ion is retained thereon, and(3) eluting the pertechnetate ion with a small amount of aqueous alkaline liquid.

Abstract: A system for treating waste gas in which the waste gas is contacted with an absorbent which contains manganese dioxide; thereafter contacting the absorbent with water to solubilize salts of manganese with an acidic ion exchange resin that retains manganese and passes acids formed from manganese salts; contacting the ion exchange resin and contained manganese with dilute nitric acid to obtain Mn(NO.sub.3).sub.2 solution; and precipitating MnO.sub.2 from the Mn(NO.sub.3).sub.2 solution.

Abstract: A chromatographic process of producing high purity and high yield radioactive Technetium-99m. A solution containing Molybdenum-99 and Technetium-99m is placed on a chromatographic column and eluted with a neutral solvent system comprising an organic solvent and from about 0.1 to less than about 10% of water or from about 1 to less than about 70% of a solvent selected from the group consisting of aliphatic alcohols having 1-6 carbon atoms. The eluted solvent system containing the Technetium-99m is then removed leaving the Technetium-99m as a dry, particulate residue.

Abstract: A process for recovering the metals manganese, nickel, and cobalt from their oxides and silicates in which the metal oxide or silicate is heated with ferric chloride in the absence of air and in the presence of a volatility depressant salt which is preferably an alkaline metal chloride or ammonium chloride to form the soluble chloride of the metal followed by dissolving the metal chloride from the residue and recovering the metal from the chloride solution by electrolysis, cementation or other standard recovery procedure.

Abstract: Nickel, cobalt and manganese are recovered from deep sea nodules by leaching with sulfurous acid. In addition, selective extraction of nickel and cobalt from copper is achieved by suitable adjustment of process variables such as leaching time and volume and concentration of acid.

Abstract: A method for selectively extracting metal values from manganese bearing ores such as marine nodules. The ore is initially leached to solubilize manganese and other desirable metals as nitrates. The resulting solution is then treated with manganous hydroxide to selectively precipitate metals such as copper, nickel and cobalt. The enriched mixture of metal hydroxides is separated from the manganese nitrate solution, which is decomposed to recover high purity MnO.sub.2.

Abstract: The invention provides a method and apparatus for preparing aqueous solutions of technetium-99m pertechnetate. In a preferred embodiment, the eluate from a technetium-99m generator is contacted with a cation-exchange resin having adsorbed thereon a cation which forms an insoluble salt with the anion of the generator eluate, whereby there is obtained an aqueous solution of the pertechnetate in water. The solution may be concentrated by adsorption of the pertechnetate on alumina, followed by desorption using a smaller volume of aqueous electrolyte.

Abstract: Process for quantitatively converting non-ferrous metals chosen from the group consisting of copper, nickel, cobalt, vanadium, and manganese in an ore concentrate to soluble sulfates and simultaneously convert the ferrous values in the ore to insoluble oxides. The process comprises roasting finely divided ore particles at a temperature in excess of 650.degree. C. in the presence of a roaster gas comprising at least a stoichiometric amount of oxygen and at least 1% SO.sub.2. The roasting is performed in the presence of a sufficient amount of a mixture of salts to allow the formation of a liquid coating on the ore particles. In a preferred embodiment, the mixed salt which forms the liquid coating comprises Na.sub.2 SO.sub.4 and K.sub.2 SO.sub.4 with the ratio of sodium to potassium being between 1.0 and 2.0.

Abstract: A process in which copper, nickel, cobalt and molybdenum are recovered by reducing comminuted raw manganese nodules with an aqueous solution containing cuprous ions. An improvement is disclosed in which copper is oxidized to provide a starting solution of cuprous ions for the process. In one important embodiment of the invention wet copper cement is added to a solution of carbon dioxide and ammonia and ground manganese nodules are then added to the mixture. As a result, a starting solution containing cuprous ions is produced. A major advantage gained from utilizing manganese nodules as an oxidizing agent is that the manganese nodule is itself reduced and its metal values are added to the reaction solution.

Abstract: Activated manganese (IV) oxide is used as a curing and vulcanizing agent for polysulfide polymers. By adjusting the following parameters the properties as a curing and vulcanizing agent can be influenced in a predictable way: (a) alkali metal content or foreign metal content; (b) water content; (c) specific surface. A process is described to adjust these parameters.

Abstract: An active natural manganese dioxide mineral for use in dry battery cells is produced from a natural manganese dioxide ore by reacting the ore or a preconcentrate thereof with a solution of an acid. The acid reacts with the carbonates, such as calcium carbonate, to produce water-soluble salts which are then washed away. The resultant mineral can have an MnO.sub.2 content of 80% by weight or more.

Abstract: After the non-cobalt values are stripped from the co-loaded organic, the cobalt ions on the organic are reduced to the divalent state. The organic loaded with divalent cobalt ions is easily stripped with a dilute acid to render the organic recyclable.In another embodiment of the invention simultaneous reduction and "crowding" is utilized to strip cobalt from the organic. In this embodiment, a convenient source of both reductant Cu.sup.+ and of copper and/or nickel such as pregnant leach liquor is used to crowd the reduced cobalt from the organic.

Abstract: Production of titanium dioxide which is characterized by recovery of reusable H.sub.2 SO.sub.4, highly pure Fe oxide and hydroxide and fractional recovery of Mn, V and Cr, etc., from FeSO.sub.4. nH.sub.2 O and waste acid of 20 - 40% H.sub.2 SO.sub.4 containing abundant heavy metallic ions, which are by-produced in the production of TiO.sub.2 by dissolution of Ti raw materials such as ilmenite, steel production slag, such as electric furnace slag, convertor slag with H.sub.2 SO.sub.4.

Abstract: A method of treating raw materials containing components of metals of the group IVb of the Periodic Table, which comprises heat-treating a raw material of a component of a metal of the group IVb of the Periodic Table containing coloring poisonous metal components such as Mn, V and Cr components in the presence of a flux composed mainly of an alkali metal nitrate or an alkali metal peroxide which is a thermal decomposition product of the alkali metal nitrate in an amount 2 to 5 times the amount of the raw material on the weight basis in a non-reducing atmosphere to thereby effect fluxing reaction, and subjecting the resulting fluxing reaction product to a leaching treatment of at least one stage in an aqueous medium to separate the fluxing reaction product into said coloring metal components and a concentrate of the component of the group IVb of the Periodic Table which is acid-soluble and substantially free of said coloring poisonous metal components.

Abstract: In the hydrometallurgical recovery of metal values from ores and the like in which a metal bearing source is reduced in the presence of at least one additive at temperatures ranging from about 500.degree. to about 900.degree. C. and thereafter extracted, the improvement of said process comprises pretreating a portion of process tails from a preceding run with the additive prior to the reducing roast. The additive which is used to pretreat the minor portion of the feed stock may comprise that which is recovered from the roaster offgas and admixed with a portion of the tail stream from the extraction step.