Studies on Chemical Extraction in Liquid-liquid System
1958 Volume 22 Issue 2 Pages 93-96
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1958 Volume 22 Issue 2 Pages 93-96
In the previous paper3), we reported that the rate of extraction in liquid-liquid system, where a rapid chemical reaction was taking place, might be given by Eqs. (1) and (2). We thought perhaps this would also hold true in the case of chemical gas absorption, due to the concentration of the substance reacting with the solute in water layer, q.
But, to chemical gas absorption, these equations were said to be inapplicable. For instance, Sherwood and Pigford6) compared the rate of absorption of NH3 in water with the rate of chemical absorption of CO2 in NaOH solutions above 1N, where KB was constant, (and this KB, according to Eq. (2), should be kB) and found that the former was much larger than the latter, so that the theory based on the infinitely rapid reaction failed to explain these results.
Considering these points, Eqs. (1) and (2) were re-investigated concerning liquid-lipuid extraction, using a vessel whose contents were gently stirred just as in our previous experiment. Results obtained may be summarized as follows:
1) Chemical extraction rates are constant, in the range above some critical value of q, for the systems of NH3 (benzene)-H2SO4 (water), some organic amines (benzene)-H2SO4 (water), organic acids (b.)-NaOH (w.) or KOH (w.), and I2 (b.)-Na2S2O3 (w.) as shown in Table 1.
2) In the physical extraction, where KB=kB, kB in the solute may be determined by physical extraction, when the distribution coefflcient m is very large with formic acid, monochloroacetic acid or ammonia in benzene-water system, as shown in Fig. 1. kB obtained from chemical extraction and from Eq. (2) were plotted versus D, and these coincided approximately on the same line of kB∝ D2/3-0.7, as physical extraction for the system of large m (Fig. 1).
3) Gordon and Sherwood4) suggested the method of determining the film coefflcients by plotting the left-hand side of Eq. (5) versus m, or the left-hand side of Eq. (4) versus l/m. By this method kB of butyric acid (for instance) was determined at 4.17 and 4.12 from Fig. s. 2-3, and 4, respectively, and these values agreed with the kB of chemical extraction in Table 1.
