Sodium hydroxide concentrations

Above a pH of about 10 near room temperature, surface alkalinity increases and corrosion rates fall sharply. When sodium-hydroxide concentration rises to several percent, the corrosion rate drops to almost zero. Even at very high sodium-hydroxide concentrations, the corrosion rate increases only slightly. 

The thus yielded active fraction, about 200 ml, was neutralized with sodium hydroxide, concentrated to about 15 ml in vacuo, separating the precipitated inorganic salts therefrom. After decolorization with active carbon, 150 ml of methanol was added, the mixture was allowed to stand overnight at 5°C and the precipitate was collected by filtration. The precipitate was washed with methanol and dried in vacuo to yield crude tuberactinomycin-N hydrochloride (yield, 3.07 g purity, 71 S% recovery, 62%). 

Restraining the sodium hydroxide concentration held in the bulk boiler water. 

Influence of OH concentration on the reaction rate constant. From the dependence of the observed first order rate constant on the sodium hydroxide concentration, shown in Table 3, it can be established that equation (2) holds, where ko represents the contribution due to the unimolecular decomposition process and koH is the contribution due to the base-catalysed process in alkaline medium. 

From the results of experiment 2.1, we confirmed decomposition reaction is pseudo first-order, and calculated pseudo first-order decomposition rate constants. Then fixnn relationship between each first-order reaction rate constant and sodium hydroxide concentration, we confirmed that the reaction is expressed by second-order with expression first-orders for both of sodium hydroxide and fenitrothion. 

Almost same relationships were also found for other two organophosphorus insecticides, parathion and diazinon. So second-order decomposition rate constants were used to evaluate all of the organophosphorus insecticides, where the second-order decomposition rate constants were calculated by dividing the first-order doiomposition rate constants by the sodium hydroxide concentration. Rate constants of malathion and phenthoate could not be obtained, because these rmetion rates were too fast to analyze. 

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. 

Non-sulfonated lignins such as those from alkaline pulping processes are insoluble in water but easily soluble in sodium hydroxide solutions. When dissolved in and eluted with a sodium hydroxide solution, they show polyelectrolyte properties, i.e., the molecular species interact. As revealed by Figure 9, the fractionation result is strongly dependent on the sodium hydroxide concentration up to a concentration of 0.4M. A 0.5M sodium hydroxide solution is thus an appropriate eluent for fractionation on Sephadex G-50 (3). 

Figure 9. Influence of sodium hydroxide concentrations in the eluent on fractionation of lignins in draft black liquor. Column Sephadex G-50. (Reprinted with permission from ref. 3. Copyright 1976 Wiley.)...

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... 

For the data of Table IV, the values of k calculated from Equation 10 agree with the observed k within about 3%. Equation 10 further predicts that at constant sodium hydroxide concentration (T > NaOH), an increase in T would be accompanied by a decrease in k, and this has been experimentally observed. 

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. 

Values of CArcH(OH)cr/CArCHO f°r eac benzaldehyde derivative were measured at 10-15 different sodium hydroxide concentrations in solutions containing fixed ethanol or DMSO concentrations ranging from 1 to 90 vol %. Since spectra obtained in the presence of 1% ethanol were indistinguishable from spectra recorded in purely aqueous solutions, it was possible to use absorbancies obtained in 1% ethanolic solutions for the calculation of pX2(H20) values. Ionization ratios were also determined in benzaldehyde solutions containing a constant concentration of sodium hydroxide (0.01M) and an ethanol or DMSO content which was varied between 1 and 98 vol %. 

Calculated values (Table III) of J- in ethanol-water mixtures show a dependence on sodium hydroxide concentration (Figure 1) resembling that in water. 

Figure 1. Dependence of the J- acidity function on sodium hydroxide concentration in water-ethanol mixtures of different composition. Curve 1 (O) J vol % EtOH curve 2 ( ) 10 vol % EtOH curve 3 (O) 50 vol % EtOH curve 4 (9) 90 vol % EtOH.

J for Hydroxide Solutions in Aqueous DMSO. J values for solutions containing fixed amounts of DMSO and varying sodium hydroxide concentrations were determined (Table IV) using Equation 1. These show a similar trend for all DMSO concentrations investigated (Figure 3). 

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. 

D. L. Trimm We have found no evidence of such attack on the alkyl and aryl disulfides produced in our study, even at a sodium hydroxide concentration of 5M. Such reactions would be expected to occur more easily, however, with substituted disulfides such as 3,3 -dithiodipropionic acid or 2,2 -dithiodiethylamine. 

In the alkaline solvolysie of AT-j9-bromoethylajailineJ the rate of appearance of bromide ion was dependent on sodium hydroxide concentration and satisfied Eq. (15). The second-order component of this... 

A modified biuret reagent was formulated (sodium tartrate replaces sodium potassium tartrate, the sodium hydroxide concentration is reduced, and potassium iodide was deleted). When the modified biuret reagent was mixed with samples containing 2% detergent (SDS or sodium cholate or Triton X-I00), it resulted in less protein-to-protein variation among six proteins. 

Bassam Z. Shakhashiri, "Hydrolysis of 2-chloro-2-methylpropane," Chemical Demonstrations, A Handbook for Teachers of Chemistry, Vol. 4 (The University of Wisconsin Press, Madison, 1992), pp. 56-64. The time required for the color change in this reaction is shown to increase with increasing sodium hydroxide concentration, decrease with increasing 2-chloro-2-methylpropane concentration, and increase as the ratio of water/acetone increases. These observations are related to the mechanism of 2-chloro-2-methyl-propane hydrolysis. 

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