Alkaline vitreous solution

Thus, for most of the reactions of etr in water-alkaline matrices at reasonable values of the parameters v0, ae, and a, eqn. (7) of Chap. 5 describes with good accuracy the kinetics of the process over a broad interval of observation time. At the same time, for a small number of acceptors [Os02(OH)4 and Br03 ] in water-alkaline matrices the experimentally observed kinetic curves were found to deviate markedly from eqn. (7) of Chap. 5 or values of IV, were obtained that are unreasonable from the viewpoint of the theory of an elementary act of electron tunneling. The reasons for these deviations have not yet been finally made clear. It will only be noted here that they may be connected, for example, with possible errors in measuring the concentration of et r by the optical method in the presence of reaction products that can perhaps have absorption bands in the same spectral region as etr, with the simultaneous presence of several forms of an acceptor in vitreous solutions [104], as well as with deviations of the dependence of the probability VT(R) of tunneling on the distance, R, from a simple exponent of the form of eqn. (3) of Chap. 5 for the reasons discussed in Chap. 3. 

Vitreous silica is susceptible to attack by alkaline solutions, especially at higher concentrations and temperatures. For 5% NaOH at 95°C, although craving may be evident, surface corrosion is only 10 p.m after 24 h (87). For 45 wt % NaOH at 200°C, dissolution proceeds at 0.54 mm /h (88). The corrosion rates in other alkaline solutions are Hsted in Table 3. Alkaline-earth ions inhibit alkaline solution attack on vitreous siUca. Their presence leads to the formation of hydrated metal siUcate films which protect the glass surface (90). 

The first process for which, by direct experiment, the electron donor and the electron acceptor particles were proved to be at a large distance from each other at the moment of reaction and for which, in addition, any possibility of a diffusion channel for the decay of the reagents was excluded, appeared to be the reaction between the trapped electron, et , and the anion radical, O, in a vitreous 10 M NaOH water-alkaline solution. Let us examine the results of research on this reaction in more detail. 

Fig. 27. Kinetic curves for the decay of et, in a vitreous water-alkaline solution (6M NaOH) containing 0.025 M of CrO2- at 178 K. The points represent the experimentally observed values [43] the lines are the curves drawn from calculations using eqn. (35) of Chap. 4 (curve 1) and eqn. (27) (curve 2) i D = 3lA and D = 2.2 x 10 12cm2s-1.

Rate constants of the reactions of eaq with various acceptors in liquid water at 298 K and the characteristic times, t, for the reactions of et with the same acceptors in vitreous water-alkaline solutions at 77 K... 

An elongated excrescence, or line of such excrescences, in vitreous enamelware the fault is usually a manifestation of swelling in the metal. Lamotte Comparator. A pH meter of a type recommended by the US Porcelain Enamel Institute for use in the determination of the acidity or alkalinity of PICKLING (q.v.) solutions. (Lamotte Chemical Products Co., Baltimore,... 

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