Sulfite oxidation method

Measurement of the absorption rate of carbon dioxide in aqueous solutions of sodium hydroxide has been used in some of the more recent work on mass-transfer rate in gas-liquid dispersions (D6, N3, R4, R5, V5, W2, W4, Y3). Although this absorption has a disadvantage because of the high solubility of C02 as compared to 02, it has several advantages over the sulfite-oxidation method. For example, it is relatively insensitive to impurities, and the physical properties of the liquid can be altered by the addition of other liquids without appreciably affecting the chemical kinetics. Yoshida and... 

In 1960, Yoshida et al. (Y4), working with a geometrically similar system and with the sulfite-oxidation method, confirmed the results reported by Cooper et al. They also showed that the gas film does not offer any resistance to the mass transfer of oxygen from air to the sodium sulfite solution. In addition, they found that the mass-transfer coefficient per unit area was equal for water and for aqueous sodium sulfite. 

Sulfite Oxidation Method The sulfite oxidation method is a classical, but still useful, technique for measuring /cgfl (or [4]. The method is based on the air oxidation of an aqueous solution of sodium sulfite (Na SOg) to sodium sulfate (Na.,SO ) with a cupric ion (Cu " ") or cobaltous ion (Co ) catalyst. With appropriate concentrations of sodium sulfite (about 1 N) or cupric ions (>10 inolH ), the value of k for the rate of oxygen absorption into sulfite solution, which can be determined by chemical analysis, is practically equal to Zr, for the physical oxygen absorption into sulfate solution in other words, the enhancement factor E, as defined by Equation 6.20, is essentially equal to unity. 

It is a well-known fact that bubbles produced by mechanical force in electrolyte solutions are much smaller than those in pure water. This can be explained by reduction of the rate of bubble coalescence due to an electrostatic potential at the surface of aqueous electrolyte solutions. Thus, k a values in aerated stirred tanks obtained by the sulfite oxidation method are larger than those obtained by physical absorption into pure water, in the same apparatus, and at the same gas rate and stirrer speed [3]. Quantitative relationships between k a values and the ionic strength are available [4]. Recently published data on were obtained mostly by physical absorption or desorption with pure water. 

Culture media usually contain some electrolytes, and in this respect the values of A in these media might be closer to those obtained by the sulfite oxidation method than to those obtained by experiments with pure water. 

The sodium sulfite oxidation method (Cooper et al., 1944) is based on the oxidation of sodium sulfite to sodium sulfate in the presence of catalyst (Cu++ or Co++) as... 

Ver eich der fotografischen und der Sulfit-Oxidations-Methode zur Phasengrenzjldchen-Bestimmung in Blasensdulen, Chem.-Ing.-Tech. 52 (1980) 5, p. 468-469... 

Oxygen transfer rate (OTR) was determined using the sodium sulfite oxidation method [12]. OTRs were measured for standard Erlenmeyer flasks of 500-mL flask, 200-mL flask, 100-mL flask, 100-mL serum flask, and 100-mL serum flask filled with nitrogen, containing 100 mL of medium, respectively, shaken at 150 rpm at 37 °C. The OTRs of different oxygen-limited conditions were 12.6, 8.4, 5.1, 3.3, and 0 mmol/L h, respectively. 

This value corresponds to oxygen absorption rates which have been measured in shaken flasks and fermenters under optimum conditions. In our fermenters, a maximum oxygen absorption rate of 250 mmoles 02/hour/l was achieved when a strong stream of air was supplied and the solution was stirred at 2000 r.p.m. The determination of the oxygen transfer rates was made by the sulfite oxidation method. 

Unfortunately, neither the relative ratio of the absorption rates of hydrogen and oxygen is not known nor are practicable methods available to measure the absorption rate of hydrogen in aqueous solutions. A method for determining hydrogen absorption rates analogous to the sulfite-oxidation method for oxygen has still to be developed. 

Sulfite Oxidation Method. The sulfite oxidation method is based on the oxidation of sulfite to sulfate in the presence of a catalyst, where dissolved oxygen is consumed by the reaction... 

The reaction in Eq. (4.37) does not form ionic species therefore, the system hydrodynamics are not affected during the course of the test, unlike the sulfite oxidation method (Chisti, 1989). 

Carbon Dioxide Absorption Method. Another commonly employed chemical technique is the absorption of carbon dioxide into a mild alkahne or an appropriately buffered solution (Andre et al., 1981). The carbon dioxide method is similar in principle and procedure to the sulfite oxidation method. Chisti (Chisti, 1989) indicated that the limitations for this method were similar to those of the sulfite oxidation method. 

S interfacial area obtained by sulfite oxidation method ]. 

The sulfite oxidation method, however, can be expected to give approximately correct results even in rather heterogeneous dispersions because of the low gas phase conversions involved (8,9). Furthermore, the reaction kinetics is almost unaffected by CMC (10,11,12). The photographic method, on the other hand, has been shown to overestimate the interfacial area in sulfite solutions both with and without CMC (8,9). Therefore, in this study, the sulfite oxidation method is used for interfacial area determination. The influence of the added salt (0.8 mole l lNa2S03) is checked by additional kj a measurements in a CMC solution containing 0.8 mole l Na2S04. 

The effective area can be measured directly by the sodium sulfite oxidation method. 

---