Alkali concentration

It shows some amphoteric behaviour, since it dissolves in alkali (concentrated aqueous or fused) to give a ferrate(lll) the equation may be written as... 

PETP flakes produced from used soft drinks bottles were subjected to alkaline hydrolysis in aqueous sodium hydroxide. A phase transfer catalyst (trioctylmethylammonium bromide) was used to enable the depolymerisation reaction to take place at room temperature and under mild conditions. The effects of temperature, alkali concentration, PETP particle size, PETP concentration and catalyst to PETP ratio on the reaction kinetics were studied. The disodium terephthalate produced was treated with sulphuric to give terephthalic acid of high purity. A simple theoretical model was developed to describe the hydrolysis rate. 17 refs. 

In buffered surfactant-enhanced alkaline flooding, it was found that the minimum in interfacial tension and the region of spontaneous emulsification correspond to a particular pH range, so by buffering the aqueous pH against changes in alkali concentration, a low interfacial tension can be maintained when the amount of alkali decreases because of acids, rock consumption, and dispersion [1826]. 

Caustic Waterflooding. In caustic waterflooding, the interfacial rheologic properties of a model crude oil-water system were studied in the presence of sodium hydroxide. The interfacial viscosity, the non-Newtonian flow behavior, and the activation energy of viscous flow were determined as a function of shear rate, alkali concentration, and aging time. The interfacial viscosity drastically... 

The results of experiments with crude oil fractions in this study also suggest that several species were present in reaction interface. There are mainly long chain carboxylic acids. The difference in size and structure is expected to give them different pka values. As a result, different surface activity (i.e., IFT value) is obtained with different levels of alkali concentration. Crude oil fractions with lower surface activity only yield surface inactive salts that may appear as precipitates at the interface. 

Figure 5. Interfacial Tension versus Alkali Concentrations for the Acid (A1 to A3) Fractions of Crude Oil and Shale Oil.

The rate of reduction of a vat dye depends partly on the intrinsic chemical properties of the dye and partly on the size and physical form of the dispersed particles undergoing this reaction. The physical factors are much less important than the chemical aspects [26]. The vatting process entails conversion of the insoluble keto form into the soluble sodium enolate (section 1.6.1). The reaction takes place in two stages at ambient temperature. Extremely rapid reduction to the hydroquinone is followed by slower dissolution in the alkaline solution. At higher temperatures, however, the dissolution rate approximates more closely to the rate of reduction. Temperature and dithionite concentration are the important variables and the rate of reduction is much less dependent on dye or alkali concentration. 

This paper presents new data on dissolution kinetics. The effects of alkali concentration, size of the cation, and salt addition were studied. The influence of segmental mobility on dissolution was elucidated by measuring the temperature coefficients of the dissolution rates. Experiments were also carried out to study the relation between the chemical structure of a polymeric Inhibitor and Its effectiveness 1n retarding dissolution. Based on these results,... 

Dependence on Base Concentration. The dissolution rates of substituted PHHPs at different alkali concentrations are displayed 1n Figure 1 for seven different novolac resins. In each case, there appears to be a limiting concentration C0 below which the rate of dissolution 1s too slow to be measured 1n the experimental time scale. The ascending portion of the curve can be represented by a power law dependence of the rate on concentration C, eq.(1),... 

A careful examination of the data reveals that at least 1n some cases the rates deviate from the simple power law at low alkali concentrations. Such deviations are shown 1n Figure 2a for p-Cl-PHMP and PBPh-1. An excellent fit of the data over the entire concentration range was found by using (C - Cc) = Cs 1n eq.(2) instead of C, where C0 1s the limiting concentration,... 

In this sense, the underlying reason of the dependence on alkali concentration 1s similar to, yet different from, the concentration dependence of solvent diffusion in polymers. 

Prints containing Alkali Blue are not fast to the standard DIN 16524 solvent mixture, but they are fast to acid, paraffin, butter, and other materials. Tested in accordance with normative testing standards (Sec. 1.6.2.2), the prints unexpectedly also show fastness to alkali. It should be noted, however, that at higher alkali concentrations the tinctorial strength of the system declines and the shade becomes duller. This is a result of the fact that the pigment reacts with alkali. 

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... 

Figure 7. Effect of alkali concentration on conversion and product yields (logioR0 = 7.7).

The rearrangements of adrenochrome (1) and adrenochrome methyl ether (8) in water and alkali are first order with respect to amino-chrome concentration.106 However, no simple kinetic relationship between the rate of rearrangement and alkali concentration was found the rate of rearrangement in the presence of sodium hydroxide increased very rapidly with increasing alkali concentration.106... 

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