Sodium hydroxide concentration, effect

In a first set of experiments, the impact of the sodium hydroxide concentration (0.1, 1.0, 2.0 M) and gas-flow direction (co-current, counter-flow) was analysed (50 ml h liquid flow, 65 pm film thickness) [5]. The higher the base concentration, the higher is the conversion of carbon dioxide. For aU concentrations, complete absorption is achieved, but at different carbon dioxide contents in the gas mixture. The higher the carbon dioxide content, the higher is the gas flow velocity and the larger must be the sodium hydroxide concentration for complete absorption. The gas flow direction had no significant effect on carbon dioxide absorption as the gas velocities were still low, so that no pronounced co- or counter-flow operation was realized. 

In the former case the sodion is the precipitating ion, in the latter the chloride, it is evident however that the hydroxyl ion is more readily adsorded by the platinum than the chloride necessitating a greatly increased concentration of the sodium hydroxide to effect precipitation. 

Effect of Alkali Concentration. Figure 7A depicts that the variation of the conversion of glycol lignin with sodium hydroxide concentration reaches a plateau at about 60%. Also, the ether soluble material remains constant... 

The addition of hydroxide ions to substituted benzaldehydes (ArCHO + OH <=> ArCH(0H)0 ) is used to establish J-acidity scales in water-ethanol and water-DMSO mixtures containing sodium hydroxide as a base. The pK-values in such mixtures are linearly correlated with Hammett substituent constants. The independence of reaction constant p of solvent composition confirms that substituted benzaldehydes are suitable J- indicators for hydroxide solutions in water-ethanol and water-DMSO mixtures. Dependence of J- values on sodium hydroxide concentration is only slightly affected by ethanol up to 90 % and at a constant sodium hydroxide concentration shows only small increase between 90 and 98 % ethanol. J- increases more with increasing DMSO concentration, but the effect is much smaller than that of DMSO on H- values based on proton abstraction from aniline. 

Comparison of Aqueous and Water-Ethanol Solutions. The effect of the presence of ethanol in aqueous solutions of sodium hydroxide is usually small. This is shown by the similar shape of the dependence of J- on sodium hydroxide concentration (Figure 1) and by the small differences m J values obtained at the different constant ethanol concentrations up to 90 vol % (Table III). Even when the concentration of sodium hydroxide was kept constant (e.g., 0.1 M), the difference between J values in 90 vol % ethanol and 98 vol % ethanol was only 0.16 J- units (Figure 2). In this range of ethanol concentrations, it is necessary to consider the competitive influence of ethoxide ions, the addition of which would result in a decrease of the C6H5CO— absorbance indistinguishable from the decrease caused by hydroxide ion addition. In 90 vol % ethanol, the ratio of hydroxide and ethoxide concentrations is about 1 1, while in 98 vol % ethanol, it is possible to extrapolate (30) that about 90% of the base will be present as the ethoxide ion. 

Figure 15 Effect of sodium hydroxide concentrations as a pretreatment for benzyla-tion on the thermoplasticity of Sugi surfaces. Note pretreatment time was 1 h. Benzyla-tion conditions were at 120°C for 1 h. Sugi Cryptomeria japonica D. Don). Angle of glossiness was 60°.

Stone et al. (S29) developed by a mathematical analysis the functional relationship between the rate of extraction of silica from pure quartz in sodium hydroxide solution and time, temperature, sodium hydroxide concentration, and particle size. With the use of response surface methodology, a comprehensive picture of this dissolution process was obtained from a few well-chosen experiments. The fractional extraction of silica can be expressed by a second-order equation. The effect of quartz particle size and temperature are predicted to be about equal and greater than the influence of sodium hydroxide concentration and reaction time. The reaction rate is controlled by the surface area of the quartz. An increase in sodium hydroxide concentration increases the activation energy for the reactions and is found to be independent of quartz size. 

Surfactant Mixing Rules. The petroleum soaps produced in alkaline flooding have an extremely low optimal salinity. For instance, most acidic crude oils will have optimal phase behavior at a sodium hydroxide concentration of approximately 0.05 wt% in distilled water. At that concentration (about pH 12) essentially all of the acidic components in the oil have reacted, and type HI phase behavior occurs. An increase in sodium hydroxide concentration increases the ionic strength and is equivalent to an increase in salinity because more petroleum soap is not produced. As salinity increases, the petroleum soaps become much less soluble in the aqueous phase than in the oil phase, and a shift to over-optimum or type H(+) behavior occurs. The water in most oil reservoirs contains significant quantities of dissolved solids, resulting in increased IFT. Interfacial tension is also increased because high concentrations of alkali are required to counter the effect of losses due to alkali-rock interactions. 

Crude 10% sodium hydroxide containing sodium chloride is purified in a similar manner to the product of the causticization process. The water is evaporated in nickel or nickel-clad steel (to reduce corrosion) multiple-effect evaporators to about 50% sodium hydroxide concentration. At this concentration, sodium chloride is only about 1% soluble (2%, on a dry basis) in the more concentrated caustic so that the bulk of it crystallizes out and is filtered off. This quite pure sodium chloride is recycled to the cells. Lor many purposes, such as for pulp and paper production, this purity of 50% sodium hydroxide is quite acceptable. If higher purities are required, sodium hydroxide may be separated from residual water and salt by chilling to the double hydrate crystals NaOH 2HiO, m.p. about 6°C, or as NaOH 3.5HiO, with a m.p. of about 3°C, or by counter-current extraction [9]. The sodium hydroxide obtained after these steps contains 2-3 ppm sodium chloride, equivalent to the purity of the mercury cell product ( rayon grade ) [10]. Concentrations of 73% and 100% sodium hydroxide (see details, Section 7.5) are also marketed. 

For pulping purposes, the effective alkali present is higher than the actual sodium hydroxide concentration in the white liquor because of the existence of an hydrolytic equilibrium between sodium sulfide and sodium hydrogen sulfide (Eq. 15.14). 

In Fig. 204, results composed from literature data [522] are shown for 3 and 5% aqueous solutions of agarose specimens that were obtained by alkali treatment with 2,3 or 10% sodium hydroxide solution. Treatment with solutions of increasing sodium hydroxide concentration yields agaroses with increasing tendencies to form gels that, in addition, ate more stable. Stress relaxation measurements at temperatures varying from 25 to 75 C over nearly 4 decades in time (0.01 to 30 h) have been published. The authors tried to make use of a kind of time-temperature superposition principle to obtain str relaxation curves over a larger time scale they shifted their curves over the time axis (horizontally) in order to obtain one mastercurve. However, results obtained in this way are questionable, because the normal (WLF) time-temperature superposition is allowed only if the structure of the system is independent of temperature. Nevertheless, it appears (also from Fig. 204) that the effect of... 

To examine the effect of alkalis on the viscosity of HPAM, the viscosity of polymer solutions was measured as a function of shear rate at various alkali concentrations. Viscosity measurements were repeated on the same solutions after two weeks (336 h) and four weeks (696 h) from initial mixing. Figure 13 depicts the variation of the low-shear relative viscosity with sodium hydroxide concentration at polymer concentration = 1,000 ppm and a temperature of 20°C. After approximately one hour from initial mixing, the low-shear relative viscosity decreased with sodium hydroxide concentration to a limiting value. This result is similar to the trend previously observed with sodium chloride and is due to the shielding effect of the sodium ion. The influence of sodium hydroxide on the low-shear viscosity measured two weeks (336 h) from initial mixing was more dramatic where higher viscosities were obtained at low alkali concentrations. Low-shear viscosity measurements after four weeks (696 h) were very similar to those obtained after two weeks. 

Figure 20. Effect of sodium hydroxide concentration on the lovr-shear Newtonian viscosity of a polymer solution having 0.5 wt% Neodol 25-3S and 1,000 ppm polymer.

Figure 29 depicts the effect of sodium hydroxide concentration (up to 10 wt%) on the flow curves of polymer solutions having 3,000 ppm Flocon 4800 at 20°C. The effect of sodium hydroxide on the polymer flow curve depended on the shear... 

The effect of sodium hydroxide concentration on xanthan flow curves also was examined at various polymer concentrations from 500 to 3,000 ppm. Figure 30 shows the low-shear relative viscosity as a function of sodium hydroxide concentration. Increasing sodium hydroxide concentration up to 10 wt% caused a dramatic drop in the low-shear relative viscosity (up to 90%). Most of this drop occurred during the addition of the first I wt% sodium hydroxide. Increasing sodium hydroxide further caused only a gradual decrease in the low-shear relative viscosity. This gradual drop was very noticeable at a polymer concentration of 3,000 ppm. 

Wang et al. [54] studied the effect of WG on the degumming process of jute fiber in order to improve the fiber properties. It was found that the WG concentration, sodium hydroxide concentration, and treatment time were the three most important parameters for the degumming process. The authors concluded that the degumming process was an effective method for ranoving hemicellulose, lignin, pectin, and certain other noncellulose materials. WG or alkali treatments depend on several variables such as the concentration of the alkaline solution, temperature, and the duration of the treatment. These variables directly affect the adhesion between the fiber and the matrix, and consequently, they also affect the mechanical and thermal properties of the fiber-reinforced composites. 

Figixre 2 shows the effect of sodium hydroxide concentration in the aqueous phase on the polycondensation. High sodium hydroxide concentration of 50 wt%, which was conveniently used for the general phase transfer catalyzed alkylation,was necessary to prepare polymer XVII of high molecular weight. 

Tepe and Dodge found Kca to be essentially independent of gas rate, a condition which would normally indicate that the liquid film was controlling absorption. However, the exponent relating the effect of liquid rate is not as high as would be expected in a simple liquid-film-controlled absorption. As shown in the figure, the absorption coefficient increases with increased sodium hydroxide concentrations up to about 2 N and then decreases. The decrease is presumably due to the higher viscosity of more concentrated solutions—a phenomenon also observed for alkanolanune solutions. 

A very effective universal filling for vacuum desiccators is obtained by having concentrated sulphuric acid C in the bottom of the desiccator, and flake sodium hydroxide D in the inverted glass collar supported on the shoulders of the desiccator, the collar then being covered... 

To obtain a maximum yield of the acid it is necessary to hydrolyse the by-product, iaoamyl iaovalerate this is most economically effected with methyl alcoholic sodium hydroxide. Place a mixture of 20 g. of sodium hydroxide pellets, 25 ml. of water and 225 ml. of methyl alcohol in a 500 ml. round-bottomed flask fitted with a reflux (double surface) condenser, warm until the sodium hydroxide dissolves, add the ester layer and reflux the mixture for a period of 15 minutes. Rearrange the flask for distillation (Fig. II, 13, 3) and distil off the methyl alcohol until the residue becomes pasty. Then add about 200 ml. of water and continue the distfllation until the temperature reaches 98-100°. Pour the residue in the flask, consisting of an aqueous solution of sodium iaovalerate, into a 600 ml. beaker and add sufficient water to dissolve any solid which separates. Add slowly, with stirring, a solution of 15 ml. of concentrated sulphuric acid in 50 ml. of water, and extract the hberated acid with 25 ml. of carbon tetrachloride. Combine this extract with extract (A), dry with a httle anhydrous magnesium or calcium sulphate, and distil off the carbon tetrachloride (Fig. II, 13, 4 150 ml. distiUing or Claisen flask), and then distil the residue. Collect the wovaleric acid 172-176°. The yield is 56 g. 

Attention is directed to the fact that if only minute amounts of material are available or if the substance is expensive, considerable economy may be effected by treating, e.g., the aqueous solution or suspension with the necessary quantity of concentrated sodium hydroxide solution or concentrated hydrochloric acid. 

---