Electrometric titration curves

The procedure described in the preceding paragraph will of course measure the number of hydrogen ions bound to or dissociated from all substances which are present in the solution under study. The accuracy of an experimental electrometric titration curve depends to a considerable degree on the absence of buffers, carbon dioxide, and any other substance, other than the protein of interest, which is capable of acting as an acid or base. 

For other kinds of groups, where the electrometric titration curve must be used, we pick a region of pH within which only one of the of Eq. (10) is an unknown function of Z. In the acid region for example we may tentatively assume that the pKjnt of the usually small number of a-carboxyl groups is known. Side-chain carboxyl groups are the only other groups which are titrated in this range, so that Eq. (10) becomes... 

The very first electrometric titration curve of a protein to be reported in the literature is a study of ovalbumin (Bugarszky and Liebermann, 1898). 

Fig. 5. Theoretical Electrometric Titration Curves of Organic Substances, Showing Two-stage Oxidation Resulting from Presence of Semiquinones.

Fig. 2. Electrometric Titration Curves for Mono-basic Acids, Referred to the Saturated Calomel Electrode.

Fig. 6, Electrometric Titration Curves of Some Typical Acids by the Differential Method.

The acid constants were determined from the pJCa values obtained from 0.05N NaOH electrometric titration curves (hydrogen electrode). Experimentally it was impossible to measure all the compounds by this method, since some were extremely insoluble (sic) in water, and because of their high molecular wei ts, the pJC values were not significant. For the very insoluble (sic)... 

Fia. 79.—The Electrometric Titration Curves of Chromic Sulphate Solutions. 

Fig. 4. Change in Slope of the EMF-Volume Curves for the Electrometric Titrations of Fig. 2.

Bates RG, Siegel GL and Acree SF, Dissociation constants and titration curves at constant ionic strengdi from electrometric titrations in cells without liquid junction, /. Res. Nat. Bur. Stand., 30,... 

J. A. Atanasiu 1-2 found that in the electrometric titration of soln. of mercurous nitrate and potassium chromate the curve shows a break corresponding with... 

X 10" respectively. When pilocarpine is dissolved in excess of acid and back titrated with sodium hydroxide, a sharp break in the titration curve is observed at pH 4.31 (99). The pH of a solution of pilocarpine hydrochloride, measured electrometrically, is 4.44 at 18° (100). The influence of pilocarpine on the electrocapillarity curve of mercury has been determined by M. Gouy (101). 

Potentiometric titrations were one of the techniques that benefitted. Although the concept of electrometric titrations was exploited as early as 1893 by Behrend C2) the first instruments to enable the automatic recording of titration curves were electromechanical systems developed in the early 1920 s. 

Figure 1-4. Electrometric titration of samples of gastric juice obtained from human subjects after stimulation of secretion by a histamine analog. Intersections of the curves with the dashed line on the left represent that would be obtained by titration to the Topfer indicator endpoint (pH 3.5), and the intersections with the dashed line on the right represent titratable acidity determined by titration to the phenol-phthalein endpoint (pH 9.4). (From Moore EW, Scarlata RW. The determination of gastric acidity by the glass electrode. Castroentero/ogy 49 178-188, 1965.)...

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