Higher Concentrations Of Sodium Hydroxide Research Articles

Mechanisms of loading of metal cyanides by weak-base resins

The behaviour of some weak-base resins in gold cyanide solutions was unexpected under certain conditions. At pH values where the resins should have been in their free-base form and not functioning as anion exchangers, they sorbed gold cyanide. Titrations of various resins were carried out in the presence of gold cyanide and in its absence. The effect of high concentrations of sodium hydroxide on the extraction of metal cyanides by certain resins was investigated. From the results of the experiments it was proposed that in addition to the conventional mechanism of ion-pair formation with the protonated functional group, metal cyanides could be loaded by another mechanism which probably involves sorption of an ion pair formed between the cyanide anion and a sodium cation. In order to substantiate this proposal, the effect on loading by different alkali metal cations and their concentration in metal cyanide solutions was investigated. The effect of pH value and potassium ion concentration on co-sorption of potassium and metal cyanide, and the effect of temperature on sorption of gold and nickel cyanides provided convincing evidence for the proposed mechanisms.

Mechanism of proton removal from 2-phenylazoresorcinol monoanion by hydroxide ion in 95%(v/v) dimethyl sulphoxide–water

Dissociation of the hydrogen-bonded proton from 2-phenylazoresorcinol monoanion requires high concentrations of sodium hydroxide in aqueous solution but occurs at low hydroxide ion concentrations in 95%(v/v) Me2SO–H2O. Kinetic studies in 95%(v/v) Me2SO–H2O show that proton removal takes place by single-step attack of hydroxide ion on the hydrogen-bonded proton and by a two-step process through a non-hydrogen-bonded open form, with half-lives for the reaction in the range 8–20 µs.

Photochemical analysis studies—III: A fluorimetric and ultraviolet spectrophotometric study of the photolysis of chloroquine on silica-gel thin layers, and its analytical application

The photolysis of chloroquine on silica-gel thin layers has been studied by ultraviolet spectrophotometry and fluorimetry. It has been shown that a reversible photoisomerization of chloroquine takes place and yields a fluorescent photoproduct. The effect of pH, alkali-metal halides, and the eluent system on the fluorescence intensity of chloroquine and its photoproduct was investigated. The fluorescence on silica-gel thin layers is quenched by high concentrations of sodium hydroxide; this is explained in terms of interference of sodium ions in the hydrogen-bonded adsorption of chloroquine on the silica gel. The results have been used to develop a method for determination and separation of chloroquine at the nanogram level. Linear calibration plots are obtained, covering the range between 4 and 10 4 ng.

Modification of Lowry's protein assay for the determination of protein in high concentrations of sodium hydroxide

Modification of Lowry's protein assay for the determination of protein in high concentrations of sodium hydroxide

KINETICS AND MECHANISM OF THE OXIDATION OF 1-PROPANETHIOL AND 2-PROPANETHIOL BY 2,6-DICHLOROPHENOLINDOPHENOL IN METHANOL-WATER MEDIUM

Abstract The oxidative cleavage of 1-propanethiol and 2-propanethiol (1-PT and 2-PT respectively) by 2,6-dichloro-phenolindophenol have been studied in methanol-water medium and the thiol-disulphide conversion has been studied kinetically in presence of hydroxyl ion at 30°C. The reaction follows a second order kinetics in indophenol in both cases. The order of reaction is one in 1-propanethiol while in 2-propanethiol, the order shows a transition from zero to one at higher concentrations of alkali. The rate constant shows a direct proportionality with [OH−] in case of 1-propanethiol but in the oxidation of 2-propanethiol, an inverse linear proportionality has been noticed. Again in the oxidation of 2-PT, the rate is indifferent to [OH−] at higher concentrations of sodium hydroxide (ca. < 2.5 × 10−4M). The rate of oxidation of 1-PT increases on increasing the dielectric constant of the medium while a decrease in the rate of oxidation of 2-PT has been observed in these studies. Variation of ionic strength a...

Catalysis and inhibition of the alkaline hydrolysis of benzocaine and analogs by a cationic surfactant.

The first-order rate constants for the alkaline hydrolysis of ethyl benzoate and ethyl p-nitro- and p-aminobenzoates (benzocaine), catalyzed by CTAB, a cationic surfactant, were measured at 25°in the presence of sodium hydroxide and sodium bromide. Although the alkaline hydrolysis of esters is generally accelerated by cationic micelles, that of the three benzoates tended to be inhibited by CTAB micelles under the following conditions : (i) at high CTAB concentrations, (ii) at high concentrations of sodium hydroxide, (iii) at high concentrations of an added salt (including buffer components), (iv) at high ester concentrations, and (v) for compounds possessing a small value of the Hammett substituent constant. These effects were explained quantitatively on the basis of a theory in which the total counterion concentration is assumed to remain constant regardless of the concentrations of CTAB, sodium bromide, and sodium hydroxide, and in which the association constant for a CTAB micelle and an ester, the degree of counterion binding to CTAB micelles, the ion-exchange constant, and a relative rate constant are taken as parameters.

AN IMPROVED SAKAGUCHI REACTION FOR MICROSPECTROPHOTOMETRIC USE

1. The Sakaguchi reaction for arginine has been modified to provide a technique suitable for the quantitative microspectrophotometric estimation of protein arginine. The reagent consists of 2,4-dichloro-α-naphthol, sodium hypochlorite and barium hydroxide. Previous Sakaguchi reagents containing high concentrations of sodium or potassium hydroxide caused extensive damage to the tissue; substitution of barium hydroxide has eliminated this problem. In addition, it appears that barium ions stabilize the resulting Sakaguchi color. 2. Conditions were found for making intensely stained, stable and reproducible preparations which can be dehydrated and mounted to match their index of refraction without loss of colour, and which do not fade significantly for at least two weeks. 3. Intensive acetylation and formalinization, which are thought to block the guanidyl group of arginine, considerably decrease the intensity of the Sakaguchi reaction. 4. The ratio between the amount of Sakaguchi color in bull sperm and in trout sperm, as determined from the results of microspectrophotometric examination, is in rather close agreement with the ratio derived from the amounts of arginine in these cells estimated biochemcially. This supports the concept that the Sakaguchi reaction described here represents a stoichiometric reaction with arginine.

Catalytic Effects in the Alkaline Oxidation of Cellulose

Michie and Neale1 have reported results which suggest that copper has an unexpectedly high catalytic effect in the reaction of cellulose with oxygen in the presence of low concentrations of alkali. By comparing their observed rate of reaction for copper-treated cotton containing fully carbonated sodium hydroxide with a value calculated from Davidson's2 results for the uncatalysed reaction at high sodium hydroxide concentration, they deduced that the copper increased the rate by a factor of 80 or more. Very much smaller increases, namely, less than tenfold, had been found by other workers, concerned with alkali concentrations of 5 N or higher, on addition of metallic catalysts.

Visible and Ultraviolet Absorption Spectra of 1,3,5-Trinitrobenzene in Water in the Presence of Sodium Hydroxide

Abstract (1) Absorption spectra of the colored solutions of 1,3,5-trinitrobenzene and various concentrations of sodium hydroxide in water have been measured at 25°C. The colored solution shows absorption bands at 260, 300 and 440∼500mμ. The absorbances of the visible absorption bands increase below the sodium hydroxide concentration, about 0.6 n, but decrease above the sodium hydroxide concentration, as the concentration of sodium hydroxide increases. On the other hand, the 260 and 300 mμ bands, observed above the sodium hydroxide concentration, about 0.4 n, increase their absorbances with an increase in concentration of sodium hydroxide. These lead to the suggestion that the visible absorption bands are due to [Trinitrobenzene·OH]− and the 260 and 300 mμ bands are due to [Trinitrobenzene·2OH]2−. (2) Below the sodium hydroxide concentration, about 0.6 n, Benesi and Hildebrand’s equation holds for the colored solutions, giving an equilibrium constant of 2.7 for the reaction between trinitrobenzene and hydroxyl ion in water at 25°C. (3) On keeping the colored solution to stand for long hours, the 260 and 300 mμ bands and the visible absorption bands decrease their absorbances, while an absorption band appears at about 350 mμ. (4) When an aqueous solution of hydrochloric acid is added into the colored solution with a high concentration of sodium hydroxide, the absorbances of the visible absorption bands increase. The 260 mμ band and the visible absorption bands disappear by adding a solution of hydrochloric acid, enough to neutralize the sodium hydroxide contained in the solution. By the addition of acids, [Trinitrobenzene·OH]− and [Trinitrobenzene·2OH] 2− seem to change into trinitrobenzne reversibly.

The Kinetics of the Electroreduction of Acetone

The electrolytic reduction of acetone in alkaline aqueous solutions at a mercury surface has been studied with the object of determining the kinetics of the formation of isopropyl alcohol and pinacol. The reduction rate has been studied at various acetone concentrations, in varying concentrations of sodium hydroxide, in solutions of sodium sulfate, sodium chloride, barium hydroxide, and potassium hydroxide. During electrolysis the rates of formation of isopropyl alcohol and pinacol were followed continuously. It is found that at low acetone concentrations the rate of formation of isopropyl alcohol is proportional to the acetone concentration, while the rate of formation of pinacol is proportional to the square of the acetone concentration. At somewhat higher acetone concentrations the pinacol rate becomes linear in acetone concentration, and near saturation the isopropyl alcohol rate becomes practically independent of acetone concentration. At constant current density, increasing the sodium hydroxide concentration decreases the yield of isopropyl alcohol and increases the yield of pinacol (except at high concentrations of acetone and sodium hydroxide). Substitution of chloride or sulfate for hydroxide causes an increase in the alcohol rate but lowers the pinacol rate. Substitution of barium for sodium stops the reduction completely. Substitution of potassium for sodium increases both yields. Increasing the current density is accompanied by a decrease in the fraction of the current which goes into isopropyl alcohol formation and pinacol formation. It is shown that these experimental results can be explained by a modification of the mechanism proposed by Müller. The acetone is first adsorbed on the mercury with the formation of a covalent bond. The product of the adsorption may dissociate from the surface as a free radical, in which case pinacol is the final product, or it may first add on a proton and then dissociate from the surface as an ion which adds a second proton to become isopropyl alcohol.

Effect of Concentrated Sodium Hydroxide on Boiler Steel Under Tension

Abstract The study reported in this paper was undertaken primarily for the purpose of developing failures in typical boiler plate under tension and in contact with high concentrations of sodium hydroxide in water solution. The failures occurring were examined carefully for evidence commonly considered indicative of caustic embrittlement. Photomicrographs are presented showing the presence of both intercrystalline and transcrystalline cracks. The author also includes a discussion of riveting pressures inasmuch as such pressures tend to affect the stresses in the fabricated unit. Impurites in the metal used for rivets and plates are also considered. As a result of these studies it is concluded that whereas the stresses in the fabricated unit and the concentration of caustic in solution may be primary causes for the development of the phenomenon of caustic embrittlement, other factors contributing to metal stress and perfection of the fabricated unit may logically be considered in arriving at the fundamental cause of embrittlement. Typical of these factors are (a) riveting pressures, and (b) purity and uniformity of rivet and plate metal. A more conscientious consideration of the nature of the resulting cracks in boiler failure will indicate the presence of both transcrystalline and intercrystalline cracks; and finally it is pointed out that intercrystalline cracks may not always be associated with caustic attack.