Carbonate-bicarbonate solutions and

At the feed side of the membrane, carbon dioxide dissolves in the aqueous carbonate/bicarbonate solution and reacts with water and carbonate ions according to Equations (11.21) and (11.23). 

Benzoates. Dissolve 0-5 g. of the amino acid in 10 ml. of 10 per cent, sodium bicarbonate solution and add 1 g. of benzoyl chloride. Shake the mixture vigorously in a stoppered test-tube remove the stopper from time to time since carbon dioxide is evolved. When the odour of benzoyl chloride has disappeared, acidify with dilute hydrochloric acid to Congo red and filter. Extract the solid with a little cold ether to remove any benzoic acid which may be present. RecrystaUise the benzoyl derivative which remains from hot water or from dilute alcohol. 

Dissolve 0-5 g. of the phenol in 2 -5 ml. of pyridine, and add one equivalent of dlphenylcarbamyl chloride (or 0- 0-5 g. if the molecular weight is uncertain). Reflux the mixture for 30-60 minutes on a boiling water bath, and then pour into about 25 ml. of water. Filter the derivative, wash with a little sodium bicarbonate solution, and recrystallise from alcohol benzene, light petroleum (b.p. 60-80°) or carbon tetrachloride. 

Caustic soda is removed from the carbonate—bicarbonate solution by treating with a slight excess of hard-burned quicklime (or slaked lime) at 85—90°C in a stirred reactor. The regenerated caustic soda is separated from the calcium carbonate precipitate (lime mud) by centrifuging or rotary vacuum filtration. The lime mud retains 30—35% Hquid and, to avoid loss of caustic soda, must be weU-washed on the filter or centrifuge. Finally, the recovered caustic solution is adjusted to the 10% level for recycle by the addition of 40% makeup caustic soda. 

Fig. 5-12 Effect of external polarization (t/g) on potentials in the crevice between pipe surface and nonadherent PE coating, carbonate-bicarbonate solution at70 C.

Various workers have used equation 8.8, or some modified version thereof, to compare observed with calculated crack velocities as a function of strain rate, but Fig 8.8 shows results from tests on a ferritic steel exposed to a carbonate-bicarbonate solution. The calculated lines move nearer to the experimental data as the number of cracks in equation 8.9 is increased, while the numbers of cracks observed varied with the applied strain rate, being about 100 for 4pp 10 s , but larger at slower 4pp and smaller at higher 4pp. 

Fig. 8.21 Current density dilTerences between fast and slow sweep rate polarisation curves and stress corrosion cracking suspectiblity as a function of potential for a C-Mn steel in nitrate, hydroxide and carbonate-bicarbonate solutions...

The reaction mixture is cooled, 250 cc. of water is added, and mixture is made acid to litmus by addition of a cooled solu-koa of 100 g. of concentrated sulfuric acid in 200 cc. of water. Chipped ice is added if necessary to keep the mixture cool. The ui >er ester layer is separated, and the aqueous layer is extracted w% 200 cc. of ether. The combined ether and ester layers are ken with 350 cc. of a saturated sodium bicarbonate solution yr til no more carbon dioxide is evolved, and then the organic layer 1S fashed with 200 cc. of water. The water layer is combined with sodium bicarbonate solution and extracted with 400 cc. of e er. The combined ether and ester layers are dried over sodium Sl)lfate. The ether is removed by distillation on the steam bath, aiM the excess ethyl benzoate and acetoacetic ester (Note 3) are t removed by distillation under reduced pressure through a l tm. fractionating column. Finally, the ethyl benzoylacetate is tilled (Note 3) at 101-106°/1 mm. (130-135°/3 mm.). The y ld of ester boiling over a 5° range is 190-210 g. (50-55 per cent theoretical amount based on the ethyl acetoacetate). 

In a 1-1., round-bottomed flask is placed 72 g. of the crude oxazolidine in 600 ml. of water, and 201.6 g. (1.6 moles) of hydrated oxalic acid is added. The mixture is then heated under reflux for 1 hour, cooled, treated with 600 ml. of water to dissolve precipitated oxalic acid, and extracted with three 100-ml. portions of ether. The combined ethereal extracts are washed with 50 ml. saturated sodium bicarbonate solution and then dried over anhydrous potassium carbonate. Concentration of the ethereal solution gives 30-35 g. of crude aldehyde. Distillation of this material at 70-75° (1.5 mm.) gives pure o-anisaldehyde (22.8—26.3 g. 51-59%), m.p. 35.5-38° (Note 9). 

In a well-ventilated hood, behind a safety shield, to a stirred solution-of 523.6 mg (4.00 mmoles) of IV-acetyl-O-t-butylhydroxylamine and 0.48 ml of dry pyridine in 6 ml of carbon tetrachloride, cooled to — 10°C, is added drop-wise a saturated solution of nitrosyl chloride in 12 ml of carbon tetrachloride. After addition of the nitrosating agent has been completed, the reaction mixture is stirred for an additional hour at -10°C. Then, while maintaining the system at 0°C, the reaction mixture is washed in turn with 25 ml portions of water, a 10 % aqueous solution of hydrochloric acid, a 10 % solution of sodium bicarbonate solution, and finally with water again. The organic layer is separated and dried over anhydrous magnesium sulfate. 

Figure 11.23 Facilitated transport of carbon dioxide through an immobilized carbonate/bicarbonate solution [25]. Reprinted with permission from S.G. Kimura, S.L. Matson and W.J. Ward HI, Industrial Applications of Facilitated Transport, in Recent Developments in Separation Science, N.N. Li, J.S. Dranoff, J.S. Schultz and P. Somasundaran (eds) (1979). Copyright CRC Press, Boca Raton, FL...

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