Abstract: A process for the wet calcination of sodium bicarbonate, sodium sesquicarbonate or mixtures thereof comprising forming a suspension of sodium bicarbonate, sodium sesquicarbonate or said mixture in a water-immiscible relative high boiling liquid, and heating the suspension to form sodium carbonate.

Abstract: Sodium carbonate having a high bulk density and pseudo-cubic crystal structure is prepared from impure trona purge liquors from the crystallizers containing high concentration of organics, silica and sulfate by a sequence of steps involving (1) treatment of the liquors with MgO; (2) separation of the treated liquor from the insoluble reaction products; (3) addition of Ca and Mg compounds to the liquor; (4) evaporating the solution to obtain sodium carbonate monohydrate crystals; (5) separating the crystals from the mother liquor; and (6) heating the crystals at temperature of about 150.degree.-200.degree. C. to convert to dense ash.

Abstract: Process for the production of sodium chlorate by the electrolysis of sodium chloride contaminated with sodium sulphate wherein the sulphate concentration in the system is kept below a pre-selected level. A portion of the mother liquor remaining after crystallizing out some of the sodium chlorate product is selectively further cooled to effect crystallization of some of the sodium sulphate present in the liquor. An acceptable "steady-state" concentration of sulphate ion is established which prevents the deleterious excess sulphate ion build-up in the electrolytic system.

Abstract: NaBrO.sub.2.3H.sub.2 O crystals with excellent storage stability which contain at least 30 wt. % of NaBrO.sub.2.3H.sub.2 O and 0.5-5.0 wt. % of NaOH. The crystals are produced by precipitation from NaBrO.sub.2 solutions containing NaOH and impurities and are very useful as oxidizing and brominating agents.

Abstract: Sodium and potassium chloride consolidated granular salt crystals are formed on a bed of granular salt by spraying, for example, the clarified brine of aluminum black dross upon the heated bed. The bed cascades in a revolving drum and is maintained at a temperature of about 250.degree.-350.degree. F. (121.degree.-177.degree. C.). That is, the bed is maintained at a temperature high enough to evaporate the water from the brine before the brine penetrates the bed and low enough to eliminate entrainment of salt in the evaporated water. An apparatus and process for the recovery of this salt product are claimed.

Abstract: Brine containing at least two salts, one or more of the salts having a higher hydrated form and a lower hydrated or anhydrous form, is fed to a non-convective solar pond and one of the salts having a higher hydrated form and a lower hydrated or anhydrous form is crystallized in a higher hydrated form, dehydrated to a lower hydrated form, and recovered from the bottom of the pond in solid, pure form essentially free from the other salts in the brine. To effect separation, the salt having a higher hydrated form and a lower hydrated or anhydrous form, which is to be recovered in pure form must be present in the pond in an essentially saturated concentration. The concentrations of any of the other salts must generally not exceed saturation concentration at the temperature in the top layer of the pond, and must not exceed saturation concentration at the conditions in the bottom layer of the pond. Concentrations of other salts in the pond must be controlled such that the required density gradient is maintained.

Abstract: Mined salt mixtures comprising sodium-carbonate, -bicarbonate, -chloride, -sulfate, and -double salts, such as trona and burkeite, are leached with a bicarbonate-saturated solution and added carbon dioxide to selectively dissolve the sodium chloride, sodium sulfate and burkeite and to precipitate additional trona, leaving a leach residue consisting essentially of trona. The trona is calcined and dissolved, and the carbonate solution is purified, crystallized and dehydrated in a non-convective solar pond yielding high purity sodium carbonate monohydrate which is converted into dense soda ash. The brine solution from the leach may be treated for the recovery of a further amount of trona.

Abstract: This invention is related to a process for the secondary obtention of sodium carbonate from a waste liquor (known as FLP waste liquor) containing principally sodium chloride, ammonium bicarbonate, ammonium chloride and carbon dioxide, which is obtained in the filtering section within the solvay process for the primary obtention of sodium carbonate, by adding a compound or a mixture of compounds sodium ions to the FLP waste liquor in the presence of carbon dioxide, in order to precipitate sodium bicarbonate therefrom, and treating the precipitation and sodium bicarbonate to obtain the secondary production of sodium carbonate.

Abstract: The invention relates to the treatment of brine and more particularly the treatment of the brine elutriate drawn off after evaporation of the brine at an elevated temperature to separate some of the sodium chloride thereon. The crude brine normally contains sodium sulphate and potassium chloride, sometimes to relatively high levels, and the invention is directed primarily at the separation out of these salts. To achieve this, the brine elutriate is cooled, in chamber (12) whereby an NaCl--/KCl--/Na.sub.2 SO.sub.4 -- salt mixture is separated off by crystallization. The remaining parent solution can be returned to the evaporation stage (10), without disturbing the equalized balance of the secondary salts in the brine to be processed. The NaCl present in the salt mixture can be recovered by deposition with refrigerated water and separation of the Na.sub.2 SO.sub.4.

Abstract: A method for enhancing the recovery of dense soda ash from Na.sub.2 SO.sub.4 - and NaCl-containing aqueous sodium carbonate solutions by first co-crystallizing anhydrous sodium carbonate and burkeite and next introducing the co-crystallized solids to an aqueous medium at elevated temperature to dissolve the burkeite and cause reversion of the anhydrous sodium carbonate solids to crystalline sodium carbonate monohydrate, which is then separated from the dissolved sulfate and recovered as product.

Abstract: A process for separating lead includes the steps of dissolving a water insoluble lead salt in an acetate solution and precipitating the lead by treating the acetate solution with a sulfite so as to form an insoluble lead sulfite. The acetate is recovered by concentrating the solution and precipitating the acetate therefrom, drying the acetate crystals and dissolving them in methanol. The methanol is then evaporated leaving purified acetate crystals. The process is shown as part of a precious metal recovery system in the treatment of tankhouse slime.

Abstract: In a treatment of carnallitic ores by treatment with a decomposition-brine containing amounts of MgCl.sub.2, KCl and NaCl suitable for precipitating artificial sylvinite in a solution of MgCl.sub.2 saturated in KCl and NaCl, the improvement of adding to said decomposition-brine a collector, e.g., a fatty amine acetate, for the flotation of KCl and a source of gas, preferably a gas-liberating additive such as H.sub.2 O.sub.2, so as to contact newly formed crystal nucleii of KCl selectively with said collector and to contact bubbles of said gas with said collector so as to form a froth enriched in KCl simultaneously with the decomposition of said carnallite, the process being particularly useful for treatment of underground carnallitic ore whereby the froth and brine are withdrawn at the surface, separated, and the brine, after make-up additions, is recycled to the ore formation.

Abstract: Separate deposits of trona or nahcolite ore are solution mined with two solvents, aqueous sodium hydroxide and aqueous hydrogen chloride. Aqueous sodium carbonate solution is withdrawn from the region of the NaOH-treated ore deposit, for recovery of soda ash. Aqueous sodium chloride brine is withdrawn from the region of the HCl-treated ore deposit and introduced to an electrodialysis cell to regenerate the two solvents and thereby continue the solution mining cycle.

Abstract: Method for the recovery of acidic effluent from pulp mill chlorine dioxide generators using the Mathieson or Solvay system. The spent generator acid is directed through a three-stage evaporation/crystallization process in which spent acid from the generator is evaporated and crystallized to produce stage 1 sodium bisulfate crystals. The first stage crystals are then redissolved to form a second solution which is crystallized in order to yield stage 2 sodium sesquisulfate crystals and, finally, the second stage crystals are redissolved in a third stage evaporation/crystallization stage to yield sodium sulfate crystals. Besides salt cake, the system also produces reusable sulfuric acid for the chlorine dioxide generator. No chemicals are added during the recovery steps.

Abstract: A method for continuously controlling the formation of crystal fines in a continuous crystallizing process in which product crystals are produced in a crystallizing zone from crystallizable material in a mother liquor, and in which product crystals are thereafter recovered. The invention is practiced by adding a flocculant, specific to the crystallizable material, to the mother liquor at a rate effective to cause flocculation of particles of crystallizable material in the mother liquor. One embodiment of the invention is practiced in a process for producing sodium bicarbonate crystals by adding anionic polyacrylate and/or polyacrylamide polymers to a sodium carbonate-containing feed brine received in a carbonator.

Abstract: A liquid melt becomes converted to crystalline form at a particular temperature either spontaneously or when artificially nucleated. The liquid releases heat at crystallization. If the liquid is in a supercooled state when it begins to crystallize, its temperature will rise from the particular temperature at which it is nucleated.Another liquid material is mixed with the liquid to be crystallized. The liquid additive has properties of forming a metastable solid together with the crystallizing material. When the liquid additive exsolves, the crystalline aggregate is weakened and is easily decomposed into fragments of small size. The liquid additive materials may include monohydric alcohols, diols and triols. The liquid additive material may be included in the liquid to be crystallized, in small amounts, amounts to two percent (2%) to five percent (5%) being typical.

Abstract: A process for producing particles of a non-friable eutectic mixture of sodium nitrate and potassium nitrate for solar power station use is disclosed. In one embodiment of the invention, the particles are produced by shock chilling a molten stream of mixed nitrate material and crushing the resulting flakes to a size range of between about -5 mesh and about +30 mesh. In a second embodiment, particles of this size are produced by spray granulation of a concentrated solution of mixed nitrate salts onto a fluidized bed to produce dry, free-flowing, solid spheres. In both embodiments, the particles are extremely hard, resistant to moisture pickup and adaptable to being readily shipped by bulk containers.

Abstract: An anhydrous sodium carbonate crystal is produced by crystallizing an anhydrous sodium carbonate crystal from an aqueous solution of sodium carbonate in the presence of 0.5 to 10 wt. % of sodium chloride and 0.3 to 20 wt. % of sodium hydroxide and separating the crystal from a mother liquor.

Abstract: A method for recovering alkali values from subterranean deposits of trona ore associated with sodium chloride by contacting the trona with an aqueous mining solution containing sodium hydroxide and subsequently utilizing the alkali values contained in the resultant salt- and sodium carbonate-containing solution. The alkali values are preferably crystallized as substantially salt-free sodium carbonate monohydrate, which is dried to recover soda ash. The mother liquor containing all of the salt is then treated to prepare a dilute sodium hydroxide solution, which may be employed as aqueous mining solution in a cyclic method to recover additional alkali values from trona.

Abstract: Calcined trona and/or nahcolite bearing ore particles are separated into a plurality of fractions of relatively uniform particle size. Those calcined particles smaller than about 6.7 mm in size and larger than about 0.2 mm in size are passed through an electrostatic separator to obtain an ore concentrate containing a greater percentage of soda ash and a lesser percentage of insoluble impurities than were present in the ore; a middling fraction and an ore tailing fraction containing a lesser percentage of soda ash and a greater percentage of insoluble impurities than were present in the ore. The middling fraction may be recycled to increase the yield of ore concentrate. Calcined particles smaller than about 0.2 mm may be combined with the ore concentrate. The combined ore concentrate fraction may be marked as technical grade soda ash or used as a high grade feed to a monohydrate refining process.

Abstract: Poly N,N-dimethylaminomethyl acrylamide, when added to clarified trona solutions, improves the crystals subsequently formed from these solutions. Preferably, the poly N,N,-dimethylamino methyl acrylamide crystal modifier is used in conjunction with a water-soluble cationically charged coagulant.

Abstract: This invention relates to the preparation of sodium metasilicate. More particularly, this invention relates to a process for the preparation of solid, crystalline, substantially anhydrous sodium metasilicate which comprises the steps of:(a) reacting an SiO.sub.2 -containing material with a concentrated aqueous solution of sodium hydroxide in an SiO.sub.2 to Na.sub.2 O molar ratio of from about 1.2:1 to 1:1.2 under elevated pressure and at an elevated temperature, to form a sodium metasilicate suspension;(b) filtering the suspension from step (a) to obtain a filter cake and filtrate;(c) crushing the filter cake from step (b) at elevated temperature;(d) removing water from the crushed filter cake to recover substantially anhydrous sodium metasilicate;(e) concentrating the filtrate from step (b); and(f) returning the concentrated filtrate from step (e) to the reaction mixture of step (a).

Abstract: This invention relates to a method of producing articles which generate heat at a substantially constant temperature for an extended period of time and which are able to remain in a stable state until such time as the generation of heat is desired. The method also relates to supercooled fluids produced by such methods. The method involves the processing of supercooled fluids such as hypo to produce this stable state. As a first step, a suitable material such as ethylene glycol may be added to the supercooled fluid to stabilize the supercooled fluid and to decrease the generation of heat in the supercooled fluid to obtain a desired temperature. The mixture is then heated to a relatively high temperature considerably above the melting temperature of the supercooled fluid. With the mixture at the high temperature, water is added to provide a particular specific gravity and an alkali is added to provide a particular pH.

Abstract: Soda ash is produced from crude trona ore in a novel process which comprises(a) reducing the ore particle size to a maximum of about 4.0 millimeters in diameter,(b) removing fines from the ore to produce a minimum particle size of about 0.1 millimeter in diameter,(c) differentially electrifying the ore particles according to differences in conductance,(d) segregating the ore particles by electrostatic separation into at least two fractions according to the differences in electrical charge resulting from the electrification of step (c), and(e) calcining the fraction of least conductance to convert the trona contained therein to soda ash,steps (a) through (d) occurring at a temperature not to exceed about 100.degree. C.

Abstract: A method of changing the salt content of a solution is described by including the salt in a nonconvective solar pond heated by solar radiation and having stable salt-concentration and temperature gradients increasing from the top to the bottom of the pond, the bottom layer of the pond being a substantially saturated solution at a predetermined temperature. A feed solution containing the salt is introduced directly into the bottom layer and is circulated through the bottom layer. The predetermined temperature of the bottom layer is different from the initial temperature of the feed solution when introduced into the pond bottom layer and is selected to effect a change in solubility, and thereby a change in the salt content, of the feed solution by causing salt in the feed solution to be precipitated therefrom, or additional salt to be dissolved therein.

Abstract: The improved production of sodium sulfate, potassium sulfate and other valuable salts from salt plant bitterns or the like wherein initial reduction in sulfate ion concentration yields salt cake and greatly facilitates the selective recovery of potassium and other valuable by-product salts. The process includes cooling the bitterns while below a certain concentration to produce glauber salt, followed by successive solar evaporation steps to yield harvestable potash salts. The salts are selectively treated and then refined by flotation. The flotation overflow is converted to potassium sulfate product by decomposition and crystallization steps and the underflow provides a recycle salt mixture for converting the glauber salt to salt cake.

Abstract: Disclosed is a process for preparing a salt hydrate composition having a phase transition heat greater than the heat capacity of water at a corresponding temperature, for charging a latent heat storage device. The process comprises the steps of providing an acid component of the salt hydrate; providing a base component of the salt hydrate, wherein at least one of the acid or base components comprises a liquid; and mixing the acid component and the base component together to cause a neutralization reaction. The acid and base components are mixed in a ratio and in respective concentrations to produce a salt hydrate solution saturated at the desired phase transition point.

Abstract: Improved process for preparing sodium carbonate from crude trona without carbon column scaling by evaporating a portion of water from a clarified sodium carbonate solution to crystallize sodium carbonate crystals therefrom, separating the sodium carbonate crystals from the crystallizer liquor, passing only the crystallizer liquor which contains organic impurities through a carbon column to reduce the organic impurity concentration therein, and evaporating a portion of water from the carbon treated crystallizer liquor to crystallize additional sodium carbonate crystals.

Abstract: A method for enhancing recovery of sodium carbonate from sodium carbonate solutions which contain sodium chloride. Anhydrous sodium carbonate is recovered in good yields from aqueous sodium carbonate solutions containing sodium chloride by evaporative crystallization at superatmospheric pressure and at a temperature of at least about 120.degree. C.

Abstract: A process for the production of low organic, low silica, anhydrous sodium carbonate comprising (a) calcining raw trona ore to produce crude sodium carbonate containing soluble and insoluble impurities, (b) admixing said crude sodium carbonate with a substantially saturated sodium carbonate solution to produce sodium carbonate monohydrate crystals containing insolubles and an impure sodium carbonate solution; (c) separating these monohydrate crystals and impurities; (d) dissolving the monohydrate crystals to produce a substantially saturated sodium carbonate solution and insolubles; (e) separating said solution from the insolubles; (f) evaporative crystallization of the separated saturated sodium carbonate solution to produce pure sodium carbonate monohydrate crystals; (g) optionally, subjecting the crystals recovered in step (f) to steps (d-f) once, but no more than once; (h) heating said monohydrate crystals to obtain low organic, low silica, anhydrous sodium carbonate product particles; and (i) optionally,

Abstract: Alkali values are recovered in a cyclic method from mechanically mined trona ore or from trona deposits by a solution mining technique utilizing a solvent comprising an aqueous solution of sodium sulfide. The ore is solubilized as sodium carbonate which is precipitated as sodium sesquicarbonate and/or sodium bicarbonate by treating the solution with hydrogen sulfide and the precipitated salt separated from the mother liquor. In the process, sodium sulfide and hydrogen sulfide become converted into sodium hydrosulfide which is contained in the mother liquor. Heat treatment of the mother liquor converts the sodium hydrosulfide into sodium sulfide thereby regenerating a solution of sodium sulfide which is recycled to the trona ore and into hydrogen sulfide which is evolved and recycled to the sodium carbonate solution.

Abstract: A method for recovering alkali value from sodium bicarbonate-containing ore by utilizing an aqueous solvent containing ammonia. The aqueous ammonia solvent is contacted with the ore to solubilize the sodium bicarbonate-containing ore. The alkali values in the resulting solution are crystallized, preferably as sodium carbonate monohydrate or as sodium sesquicarbonate, which may be processed to recover soda ash. Aqueous ammonia solvent is preferably regenerated from the mother liquor remaining after recovery of the solids, the ammonia solvent then being employed in a cyclic method to recover additional alkali values from the ore.

Abstract: Sodium oxalate is supersaturated solution in Bayer spent liquor stabilized by the presence of humic material is precipitated by the treatment with an adsorbent which adsorbs the humic material to give an insoluble product, thus removing it from solution and destabilizing the solution with respect to precipitation of sodium oxalate. The preferred adsorbent is activated carbon. The activated carbon can be dispersed in the spent liquor as a fine powder or the spent liquor can be passed through a column of particulate carbon. Precipitation of sodium oxalate can be expidited by addition to seed crystals and/or addition of sodium oxalate solution which is supersaturated at a temperature higher than that of the spent liquor.

Abstract: Sodium oxalate in supersaturated solution in Bayer spent liquor stabilized by the presence of humic material is precipitated by the treatment with cationic sequestrants which interact with the humic material to give an insoluble product, thus removing it from solution and destabilizing the solution with respect to precipitation of sodium oxalate. Preferred cationic sequestrants are quaternary nitrogen compounds including medium or long chain alkyl groups. Precipitation of sodium oxalate can be expidited by addition of seed crystals and/or addition of sodium oxalate solution which is supersaturated at a temperature higher than that of the spent liquor.

Abstract: The average size of Glauber's salt crystals formed by crystallization of Na.sub.2 SO.sub.4 from aqueous solution in systems comprising Na.sub.2 SO.sub.4, H.sub.2 O and Glauber's salt is decreased by including a fluorine-containing surfactant in the system.

Abstract: Method for the manufacture of crystals of sodium carbonate monohydrate, comprises crystallizing sodium carbonate monohydrate from a carbonated aqueous liquor of sodium hydroxide above 35.degree. C. and separating the crystals of sodium carbonate monohydrate and a mother liquor. The sodium carbonate monohydrate is crystallized on crystalline seeds of sodium carbonate monohydrate obtained by evaporation, between 35.degree. and 107.5.degree. C., of a solution of sodium carbonate free from sodium hydroxide.

Abstract: Sodium sulfate crystals, also known as salt cake, are obtained as a side stream in the manufacture of chlorine dioxide by the reduction of sodium chlorate with chloride ions in an aqueous, acidic medium containing sulfate ions. The sodium sulfate crystals are contained in a mother liquor saturated with sodium sulfate and contaminated with chloride ions. The process provided by the present invention purifies the salt cake crystals by separating the crystals from the mother liquor without evaporation of the mother liquor until a critical dryness level is achieved and then the remaining mother liquor is evaporated to result in purified salt cake crystals having substantially reduced chloride ion content.

Abstract: Sodium nitrite in liquid form is deposited on a substrate and allowed to crystallize thereby forming a thin layer on the substrate. The substrate is either dipped into a solution containing sodium nitrite or into sodium nitrite in the molten state and then pulled out again. Subsequent drying or cooling of the wetted substrate top surface causes the crystalline film to form. Alternatively, sodium nitrite in a liquid state is applied to the top surface of the substrate and the substrate is rotated to assure an even distribution of the sodium nitrite. Again, drying or cooling causes the crystalline layer to form. The so manufactured unit is shown as part of a pyroelectric radiation detector, as image receiver in a television camera tube and as the storage element in a field effect transistor arrangement.

Abstract: A modular chlorine dioxide generating unit (10) is disclosed wherein recycled reaction mixture passes along a flow path (18) internally of the generator vessel (12) out of direct fluid flow communication with the reaction medium (13) from the lower end (16) of the vessel (12) to a discharge point in the vapor phase (15 ) above the liquid level (13) in the generator vessel (12).

Abstract: The formation of large crystals during the cooling and crystallization of Glauber's salt is prevented by the addition of ferric ions to the system.

Abstract: An improved process for the production of soda ash from trona including the steps of sizing the trona, heating the trona to eliminate water and carbon dioxide therefrom, dissolving the trona in an aqueous medium to obtain a solution thereof, removing insoluble solid materials from the solution, crystallizing sodium carbonate monohydrate from the solution, and heating the crystallized sodium carbonate monohydrate to produce soda ash. The improvement of the invention comprises the step of removing insoluble solid materials from the solution of trona by classifying the insoluble solid materials in a plurality of hydroclones.

Abstract: Enhanced recovery of ammonium perchlorate from waste solid rocket propellant is effected by leaching shredded particles of the propellant with an aqueous leach solution containing a low concentration of surface active agent while stirring the suspension.

Abstract: Anhydrous sodium carbonate is crystallized from saturated aqueous sodium carbonate solutions at temperatures in the range of 104.degree. to below 109.degree. C. by adding to the solution very small proportions of additives which function to reduce the transition temperature of monohydrate to anhydrous sodium carbonate.

Abstract: A continuous process for the recovery of chemicals in saline water including the steps of converting the sulfates in the saline water feed to sodium sulfate; separating and recovering in the oxide forms essentially all of the magnesium and calcium from the saline water feed; then preparing a sodium chloride fortified solution by mixing the feed with recycled sodium chloride; crystallizing and re-crystallizing and then separating sodium chloride crystals, preferably in two evaporative crystallization processes; stripping bromine from the sodium chloride depleted solution; crystallizing and then separating sodium chloride and sodium sulfate crystals from each other and then from solution; recycling the separated sodium chloride to the first sodium chloride crystallization step; separating residual sulfates from the solution; crystallizing and then separating sodium chloride crystals; recycling the separated sodium chloride to the first sodium chloride crystallization step; crystallizing and then separating pota

Abstract: Disclosed is a process for the production of partially dehydrated or anhydrous salts from higher hydrates of the same salt, utilizing solar energy. Hydrated salts which have an increasing solubility with an increase of temperature, possessing a transition temperature from the existing high hydrated form to the desired one in the range of between about 30.degree. C. to about 100.degree. C. are partially or completely dehydrated in a solar pond having a non-convecting characteristic. Examples of salts produced according to the present invention are: anhydrous sodium sulfate from sodium sulfate decahydrate, magnesium sulfate monohydrate from magnesium sulfate heptahydrate, sodium carbonate monohydrate from sodium carbonate decahydrate and sodium borate pentahydrate from sodium borate decahydrate.

Abstract: A process for selectively recovering coarse crystalline K.sub.2 SO.sub.4 from a crystallizer is disclosed. A classifier comprising an elongated cylindrical vessel which is located separate from the crystallizer is employed in the process. Crystallization is effected in the crystallizer and supernatant liquor recovered as overflow during crystallization is passed from the crystallizer into the lower portion of the elongated cylindrical vessel. Slurry is recovered from the bottom of the crystallizer and introduced into a middle portion of the elongated cylindrical vessel. Coarse crystalline K.sub.2 SO.sub.4 falls to the bottom of the elongated cylindrical vessel and is recovered therefrom. Fine crystalline K.sub.2 SO.sub.4 is entrained in the upwardly flowing liquor and passed upwardly therewith. The upwardly flowing liquor and fine crystalline K.sub.2 SO.sub.4 are withdrawn from the top of the elongated cylindrical vessel and recycled to the crystallizer.

Abstract: Sodium carbonate is crystallized in multi-stage evaporative crystallizers from a pregnant liquor process solution typically obtained by dissolving calcined crude trona in water, separating insoluble impurities, and removing the majority of organic matter with activated carbon. After separation from the sodium carbonate crystals, a portion of the mother liquor usually is recycled to the crystallizers, and the remainder is purged to prevent buildup of impurities. Product quality is improved, and the amount of purged mother liquor is reduced by feeding the pregnant liquor predominantly to the initial stage crystallizers, directing the majority of the recycled mother liquor to a final stage crystallizer, recovering sodium carbonate crystals from slurries from at least the initial stages, and withdrawing purge liquor only from the slurry from the final stage crystallizer.

Abstract: Described herein is a process for producing soda ash (sodium carbonate) from natural ores such as trona in which separate soda ash products are produced having differing purities. According to the invention, a substantially purified and saturated solution of sodium carbonate is divided into at least two separate process streams, one of which is subjected to crystallization in the absence of recycled mother liquor to form high purity sodium carbonate-containing crystals, while the other stream is subjected to crystallization in the presence of recycled mother liquor to form lower purity crystals. The crystals are thereafter separately processed to obtain soda ash products of differing grades.

Abstract: A method for the storage and retrieval of thermal energy is disclosed, which in a two phase, two component system is able to utilize both the sensible heat of water (always one of the components) and the heat of fusion of the second component (a salt which forms a hydrate). The system to be employed must be graphically definable in a phase diagram including a liquidus, the compositional range of the system being selected so as to lie within the compositional range of the liquidus along which the system is to operate during both the heating and cooling cycles.

Abstract: An aqueous solution of sodium hydroxide containing soluble impurities such as a concentrated catholyte produced by a diaphragm electrolysis is cooled by a coolant or a heat-exchanger to form a slurry containing sodium hydroxide hydrate crystals and fine impurity crystals. The fine impurity crystals are adsorbed on bubbles which are formed by vaporizing a dissolved coolant or introducing a gas in the slurry and separated from the slurry.