Allegedly Pure Solvents

Alumina and titania in different solvents were studied in [822]. MgO and ZnO in seven organic liquids were studied in [1686]. Silica in a series of nonaqueous solvents and in acetonitrile-water and methanol-water mixtures was studied in [3139,3140]. Only positive potentials are reported, probably by mistake. Silica in decane was studied in [3141]. ZnO in absolute methanol, ethanol, and propanol was studied in [3142]. Montmorillonite in 2-propanol was studied in [3143]. Silicon in a 99% l-butanol-1% water mixture was studied in [3145]. In [3146], 11 solids (oxides and inorganic salts) in 9 solvents were studied. 

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Studies of surface charging in nonaqueous solvents can be divided into three categories. Many studies were carried out in allegedly pure solvents without the addition of any solutes. In several studies, a possible correlation between the value of the potential and the parameters characterizing the acid-base properties and the polarity of the solvent was investigated. Detailed discussion of these solvent scales can be found elsewhere [3133-3135], Basically, the solvent scales apply to pure solvents, but the effect of solutes has also been studied [3136]. In fact, the... 

In 1956, my brief from Archer Martin was to invent a more sensitive detector for gas chromatography. When a low voltage was applied to an ionization detector so that only thermal electrons are collected, a 1 mg sample of an allegedly pure sample of methyl caproate gave a never ceasing range of off scale peaks. I shall never forget the of amazement on Tony James face. There were two problems with the detector, it was too sensitive and it was erratic. When I tried a mixture made up in the solvent CCLt the current fell to zero and there remained. 

Certain organic molecules, e.g. 7,7,8,8,-tetracyanoquinodimethane TCNQ can accept electrons and form free anion radicals stable at room temperature. Concentrations of TCNQ and TCNQ radical can be determined using ESR, or even assessed on the basis of coloration. Meguro and Esumi [345] proposed a method to determine acid base properties of solid surfaces from radical concentration in the surface layer for a series of electron acceptors having different electron affinities. In this method a tacit assumption is made that except for the studied absorbent and TCNQ/TCNQ radical there are no other electron acceptors or donors in the system, which is not necessarily correct. This problem is analogous to assessment of acid base properties of materials based on their electrokinetic potentials in allegedly pure organic solvents (Section V). 

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