Sodium carbonate/hydroxide addition

Recovery of inorganic chemicals is crucial to the cost effectiveness of the Kraft process. The black liquor which is obtained from delignification is rich in solubilised lignin and carbohydrate degradation products and, after concentration, is combusted in a recovery furnace. The Carbon dioxide which is produced during combustion converts unused sodium hydroxide into sodium carbonate. In addition, the sodium sulfate is converted, under the reducing atmosphere of the furnace, to sodium sulfide. 

All water used in the analysis is deionized and polished with a Millipore Simplicity system, available from Millipore Corporation, Billerica, MA, USA. Two reagents are used in the sample boats to assist the combustion of organic materials. Additive B is a coarse aluminum oxide. Additive M is a 35 50 combination of calcium hydroxide and sodium carbonate. The additives, specially prepared by Wako Pure Chemical Industries, Ltd., Osaka, Japan, are available for purchase through NIC. The phosphate buffer in the scrubber vessel was prepared finm a powdered concentrate (Wako). 

On standing, gelatinous aluminium hydroxide, which may initially have even more water occluded than indicated above, is converted into a form insoluble in both acids and alkalis, which is probably a hydrated form of the oxide AI2O3. Both forms, however, have strong adsorptive power and will adsorb dyes, a property long used by the textile trade to dye rayon. The cloth is first impregnated with an aluminium salt (for example sulphate or acetate) when addition of a little alkali, such as sodium carbonate, causes aluminium hydroxide to deposit in the pores of the material. The presence of this aluminium hydroxide in the cloth helps the dye to bite by ad sorbing it—hence the name mordant (Latin mordere = to bite) dye process. 

Conduct the preparation in the fume cupboard. Dissolve 250 g. of redistilled chloroacetic acid (Section 111,125) in 350 ml. of water contained in a 2 -5 litre round-bottomed flask. Warm the solution to about 50°, neutralise it by the cautious addition of 145 g. of anhydrous sodium carbonate in small portions cool the resulting solution to the laboratory temperature. Dissolve 150 g. of sodium cyanide powder (97-98 per cent. NaCN) in 375 ml. of water at 50-55°, cool to room temperature and add it to the sodium chloroacetate solution mix the solutions rapidly and cool in running water to prevent an appreciable rise in temperature. When all the sodium cyanide solution has been introduced, allow the temperature to rise when it reaches 95°, add 100 ml. of ice water and repeat the addition, if necessary, until the temperature no longer rises (1). Heat the solution on a water bath for an hour in order to complete the reaction. Cool the solution again to room temperature and slowly dis solve 120 g. of solid sodium hydroxide in it. Heat the solution on a water bath for 4 hours. Evolution of ammonia commences at 60-70° and becomes more vigorous as the temperature rises (2). Slowly add a solution of 300 g. of anhydrous calcium chloride in 900 ml. of water at 40° to the hot sodium malonate solution mix the solutions well after each addition. Allow the mixture to stand for 24 hours in order to convert the initial cheese-Uke precipitate of calcium malonate into a coarsely crystalline form. Decant the supernatant solution and wash the solid by decantation four times with 250 ml. portions of cold water. Filter at the pump. 

Sodium iodide [7681-82-5] Nal, mol wt 149.92, mp 662°C, 84.66% I, forms colorless cubic crystals, which are soluble in water, ethanol, methanol, and acetone. It is used in photography, for the production of organic chemicals, and as an expectorant in cough medicines. Nal is separated by addition of sodium hydroxide or sodium carbonate to an acidic iodide solution (see also Expectorants, antitussives, and related agents). 

In the hot precipitation method, sodium carbonate solution is added slowly to a refluxing solution of mercuric chloride, followed by an additional reflux period of 1 to 2 h. The washed precipitate is then dried. A variation allows the substitution of mercuric nitrate for the chloride if substantial quantities of sodium chloride are used. Sodium hydroxide, ia the presence of sodium carbonate, is the precipitant. 

Chemical precipitation and solvent extraction are the main methods of purifying wet-process acid, although other techniques such as crystallisa tion (8) and ion exchange (qv) have also been used. In the production of sodium phosphates, almost all wet-process acid impurities can be induced to precipitate as the acid is neutralized with sodium carbonate or sodium hydroxide. The main exception, sulfate, can be precipitated as calcium or barium sulfate. Most fluorine and siUca can be removed with the sulfate filter cake as sodium fluorosiUcate, Na2SiFg, by the addition of sodium ion and control of the Si/F ratio in the process. 

Additional operations essential to commercial bauxite processing are steam and power generation, heat recovery to minimise energy consumption, process liquor evaporation to maintain a water balance, impurity removal from process liquor streams, classification and washing of ttihydrate, lime caustication of sodium carbonate [497-19-8] to sodium hydroxide [1310-73-2] repair and maintenance of equipment, rehabiUtation of mine and residue disposal sites, and quaUty and process control. Each operation in the process can be carried out in a variety of ways depending upon bauxite properties and optimum economic tradeoffs. 

Manufacture. Aqueous sodium hydroxide, sodium bicarbonate, sodium carbonate, or sodium sulfite solution are treated with sulfur dioxide to produce sodium metabisulfite solution. In one operation, the mother Hquor from the previous batch is reinforced with additional sodium carbonate, which need not be totally in solution, and then is treated with sulfur dioxide (341,342). In some plants, the reaction is conducted in a series of two or more stainless steel vessels or columns in which the sulfur dioxide is passed countercurrent to the alkaH. The solution is cooled and the sodium metabisulfite is removed by centrifuging or filtration. Rapid drying, eg, in a stream-heated shelf dryer or a flash dryer, avoids excessive decomposition or oxidation to which moist sodium metabisulfite is susceptible. 

Carbonate leaching under ambient conditions is extremely slow with poor recoveries. Therefore, the ore is typically leached in an autoclave with air providing most of the needed oxygen. The leach Hquor is separated from the soHd in a countercurrent—decantation system of thickeners, and the uranium is precipitated from the clarified sodium carbonate solution with addition of sodium hydroxide (eq. 9) (23). 

Brine Preparation. Rock salt and solar salt (see Chemicals frombrine) can be used for preparing sodium chloride solution for electrolysis. These salts contain Ca, Mg, and other impurities that must be removed prior to electrolysis. Otherwise these impurities are deposited on electrodes and increase the energy requirements. The raw brine can be treated by addition of sodium carbonate and hydroxide to reduce calcium and magnesium levels to below 10 ppm. If further reduction in hardness is required, an ion-exchange resin can be used. A typical brine specification for the Huron chlorate ceU design is given in Table 6. 

Other options for the purification of CA include dissolution in hot water, aqueous ammonia, aqueous formaldehyde, or hot dimethylformamide followed by filtration to remove most of the impurities. The CA is recoverable by cooling the aqueous solution (84), acidifying the ammonium hydroxide solution (85), or cooling the dimethylform amide solution with further precipitation of CA by addition of carbon tetrachloride (86). Sodium hydroxide addition precipitates monosodium cyanurate from the formaldehyde solution (87). 

After the addition of 2 1. of water, the mixture is steam-distilled as long as any oil comes over. The crude, heavy, yellow oil is separated and washed with two 200-cc. portions of 10 per cent sodium hydroxide, once with 100 cc. of water, twice with 150-cc. portions of concentrated sulfuric acid, and finally with 100 cc. of 5 per cent, sodium carbonate solution. It is dried with about 5 g. of calcium chloride, filtered through glass wool, and distilled using a long air condenser. Most of the product boils at i8o-i83°/75o mm. The yield of pure colorless material, b.p. i83°/76o mm., is 125-135 g. (36-39 per cent of the theoretical amount, based on the amount of -toluidine originally used, or 54-59 per cent based on the amount of 3-bromo-4-amino-toluene). 

Carbonates and bicarbonates are used as lower alkalinity adjuncts or substitutes for hydroxide. It has been suggested that hydroxide/carbonate systems are more resistant to carbonation during spraying than hydroxide-only solutions. Powder products blended with light sodium carbonate are much less hygroscopic, and the carbonate can be a useful carrier for liquid additives, such as surfactants and solvents. 

Bacterial activity is least when the pH lies between 9 and 10. The addition of a small amount, 0.1 g L 1, of sodium carbonate is advantageous to ensure the correct pH. In general, alkali hydroxides, sodium carbonate ( > 0.1 g L 1), and sodium tetraborate should not be added, since they tend to accelerate the decomposition ... 

Further addition of lime converts soluble magnesium or sodium carbonate into the insoluble hydroxide and further insoluble calcium carbonate. In theory it is possible to limit the lime addition to maintain the magnesium salt as soluble carbonate, but in practice some magnesium hydroxide is always formed (say, 10%), so it necessary to compensate for this by the addition of more lime ... 

The diazo transfer reaction between p-toluenesulfonyl azide and active methylene compounds is a useful synthetic method for the preparation of a-diazo carbonyl compounds. However, the reaction of di-tert-butyl malonate and p-toluenesulfonyl azide to form di-tert-butyl diazomalonate proceeded to the extent of only 47% after 4 weeks with the usual procedure." The present procedure, which utilizes a two-phase medium and methyltri-n-octylammonium chloride (Aliquat 336) as phase-transfer catalyst, effects this same diazo transfer in 2 hours and has the additional advantage of avoiding the use of anhydrous solvents. This procedure has been employed for the preparation of diazoacetoacetates, diazoacetates, and diazomalonates (Table I). Ethyl and ten-butyl acetoacetate are converted to the corresponding a-diazoacetoacetates with saturated sodium carbonate as the aqueous phase. When aqueous sodium hydroxide is used with the acetoace-tates, the initially formed a-diazoacetoacetates undergo deacylation to the diazoacetates. Methyl esters are not suitable substrates, since they are too easily saponified under these conditions. 

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