Caustic soda, solution

Aluminium is obtained on a large scale by the electrolysis of the oxide, dissolved in fused cryolite The oxide, occurring naturally as bauxite, AI2O3.2H2O, usually contains silica and iron(III) oxide as impurities. These must be removed first, since aluminium, once prepared, cannot be freed of other metals (which will be deposited on electrolysis) by refining it. The crude oxide is dissolved under pressure in caustic soda solution the aluminium oxide and silica dissolve and the ironflll) oxide is left ... 

The gas is passed through caustic soda solution to remove any sulphur dioxide or carbon dioxide produced in side reactions. Carbon monoxide is also obtained when an ethanedioate (oxalate) is heated with concentrated sulphuric acid ... 

Oxygen difluoride, OFj, is obtained when gaseous fluorine is passed through very dilute (27 ) caustic soda solution ... 

Caustic soda is classified as a corrosive material by the DOT and DOT regulations and specifications must be followed for handling, labeling, and transportation in containers. Warning labels are recommended for containers of caustic soda solutions and anhydrous caustic soda by the MCA (79). The DOT identification number is UN1824 for 50 or 73% Hquid, and UN1823 for anhydrous caustic. 

Caustic soda solutions are normally tested for general alkalinity and percentages of NaCl, Na2S04, and NaClO as weU as for Fe and Ni levels. The general methods are outlined in Table 22. Detailed analytical methodologies are available from the major caustic soda suppHers. 

Disposal of waste or spilled caustic soda must meet all federal, state, and local regulations and be carried out by properly trained personnel. Accidental spills of dry caustic are shoveled and flushed with water caustic soda solutions must be diluted and neutralized with acid before discharging into sewers. Dilute acetic acid may be used to neutralize final traces of caustic. 

Other Organic Processes. Solvent extraction has found appHcation in the coal-tar industry for many years, as for example in the recovery of phenols from coal-tar distillates by washing with caustic soda solution. Solvent extraction of fatty and resimic acid from tall oil has been reported (250). Dissociation extraction is used to separate y -cresol fromT -cresol (251) and 2,4-x5lenol from 2,5-x5lenol (252). Solvent extraction can play a role in the direct manufacture of chemicals from coal (253) (see Eeedstocks, coal chemicals). 

Alumina. A pure although not necessarily a refractory grade of alumina is obtained from bauxite by the Bayer process. In this process, the gibbsite from the bauxite is dissolved in a caustic soda solution and thus separated from the impurities. Alumina, calcined, sintered, or fused, is a stable and extremely versatile material used for a variety of heavy industrial, electronic, and technical appHcations. 

Commercial Products. Tellurium dioxide [7446-07-3] Te02 (79.9% Te theoretically), is made by heating an aqueous suspension of teUurous acid. The acid is purified, if necessary, by redissolving in caustic soda solution and neutralizing with sulfuric acid. 

Removal of Free Fatf Fields. Alkali treatment of the oil is accompHshed by the use of caustic soda solutions to neutralize the excess free fatty acids. Because castor oil readily forms emulsions with water and/or alkaline solutions, special techniques have been developed to neutralize the acids. A continuous counter-current process was developed using a stationary contact reactor (15). Treatment in the presence of a solvent is also utilized (16). 

In the known absence of bromoform, iodoform, chloral, and other halogenated methanes, the formation of phenyhsonitrile with aniline provides a simple and faidy sensitive but nonspecific test for the presence of chloroform, the carbylamine test. Phenyhsonitrile formation is the identification test given in the British Pharmacopoeia. A small quantity of resorcinol and caustic soda solution (10% concentration) added to chloroform results in the appearance of a yellowish red color, fluorescing yeUow-green. When 0.5 mL of a 5% thymol solution is boiled with a drop of chloroform and a small quantity of potassium hydroxide solution, a yellow color with a reddish sheen develops the addition of sulfuric acid causes a change to brilliant violet, which, diluted with water, finally changes to blue (33). 

Diphenyl carbonate, an alternative source of the carbonate group to phosgene, may be obtained by reacting phenol with phosgene in acqueous caustic soda solution, the reaction being accelerated by tertiary amines. The diphenyl carbonate can be purified by redistillation. 

The attractive possibility of dissolving the bis-phenol A in caustic soda solution and bubbling phosgene into it is not practical since the polymer is insoluble in the caustic soda and precipitates out at a low and variable molecular weight. 

The resultant yellow sodium cellulose xanthate is dispersed in an aqueous caustic soda solution, where some hydrolysis occurs. This process is referred to as ripening and the solution as viscose . When the hydrolysis has proceeded sufficiently the solution it transferred to a hopper from which it emerges through a small slit on to a roller immersed in a tank of 10-15% sulphuric acid and 10-20% sodium sulphate at 35-40°C. The viscose is coagulated and by completion of the hydrolysis the cellulose is regenerated. The foil is subsequently washed, bleached, plasticised with ethylene glycol or glycerol and then dried. 

To produce a moulding composition, aniline is first treated with hydrochloric acid to produce water-soluble aniline hydrochloride. The aniline hydrochloride solution is then run into a large wooden vat and formaldehyde solution is run in at a slow but uniform rate, the whole mix being subject to continuous agitation. Reaction occurs immediately to give a deep orange-red product. The resin is still a water-soluble material and so it is fed into a 10% caustic soda solution to react with the hydrochloride, thus releasing the resin as a creamy yellow slurry. The slurry is washed with a counter-current of fresh water, dried and ball-milled. 

CAUSTIC SODA, DRY, SOLID CAUSTIC SODA, SOLUTION CDEC see SULFALLATE... 

Chemical Reactivity - Reactivity with Water Decomposes, but not vigorously Reactivity with Common Materials No reaction Stability During Transport Stable Neutralizing Agents for Acids and Caustics Can be absorbed in caustic soda solution. One ton of phosgene requires 2,480 lbs. of caustic soda dissolved in 1(X)0 gal. of water Polymerization Not pertinent Inhibitor of Polymerization Not pertinent. 

The first vessel in the blowdown system is therefore an acid-hydrocarbon separator. This drum is provided with a pump to transfer disengaged acid to the spent acid tank. Disengaged liquid hydrocarbon is preferably pumped back to the process, or to slop storage or a regular non-condensible lowdown drum. The vented vapor stream from the acid-hydrocarbon separator is bubbled through a layer of caustic soda solution in a neutralizing drum and is then routed to the flare header. To avoid corrosion in the special acid blowdown system, no releases which may contain water or alkaline solutions are routed into it. 

Aqueous plant effluent and drawoff streams such as steam condensate, sour water, or spent caustic soda solution may require disposal to a disengaging drum. 

Consider an aqueous caustic soda solution whose molarity mi = 5.0 kmol/m (20 wt.% NaOH). This solution is to be used in >scH(t>ing H2S from a gaseous waste. The operating range of interest is 0.0 < xi kmoUn ) < 5.0. Derive an equilibrium relation for this chemical absorption over the operating range of interest. 

A process lean stream and an external MSA are considered for removing H2S. The process lean stream, S1, is a caustic soda solution which can be used as a solvent for the reactive separation of H2S. An added bonus for using the process MSA is the conversion of a portion of the absorbed H2S into Na2S, which is needed for white-liquor makeup. In other words, H2S pollutant is converted into a valuable chemical which is needed in the process. The external MSA, S2, is a polym ic adsorbent. The data for the candidate MSAs are given in Table 8.2. The equilibrium... 

The chemical absorption of HjS into caustic-soda solution (Astarita and Gioia, 1964) involves the following two reactions ... 

Dipping solution Dissolve 100 mg of 8-anilinonaphthalene-l-sulfonic acid ammonium salt in a mixture of 40 ml caustic soda solution (c = 0.1 mol/1) and 57 ml of an aqueous solution containing 21 g citric acid monohydrate and 8 g sodium hydroxide per hter. 

Citrate buffer solution Dissolve 210 g citric acid in 400 ml caustic soda solution (c = 5 mol/1) and make up to 11 with water. Mix 530 ml of this solution with 470 ml caustic soda solution (c = 1 mol/1) and adjust to pH 6.6 with caustic soda solution or citric acid [1]. 

Fast Blue Salt B Reagent 289 Spray solution II Caustic soda solution (c = 0.1 mol/1)... 

Note The detection is not affected if the dipping solution exhibits a slight opalescent turbidity. Fast blue salt BB [18] or fast blue salt RR [18,19] can be employed in the reagent in place of fast blue salt B. It is occasionally preferable not to apply spray solutions I and II separately but to work directly with a 0.1% solution of fast blue salt B in caustic soda solution (c=l—2mol/l) [13, 15] or in 0.5% methanolic caustic potash [3]. 

Dissolve 1.9 g di-sodium tetraborate decahydrate in 100 ml water and adjust the pH to 10.5 with caustic soda solution. 

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