Acid indicator

Indicator Acid Color Base Color pH Range P/Ca... 

Chemical analysis of surfaces within crevices often reveals high concentrations of chloride. Chemical spot tests can indicate acidic pH. 

As a result of the concentration of acidic species, such as chloride and sulfate, material scraped from the inside of tubercles is virtually always acidic when mixed with water. Acidity varies not only from tubercle to tubercle but also from place to place in a given tubercle. Acidity is greatest near the corroded metal surface. The size of the fluid-filled cavity can indicate acidity. The larger the cavity, the more acidic the internal environment. 

Examples include hydrochloric acid, nitric acid, and sulphuric acid. These are strong acids which are almost completely dissociated in water. Weak acids, such as hydrogen sulphide, are poorly dissociated producing low concentrations of hydrogen ions. Acids tend to be coiTosive with a sharp, sour taste and turn litmus paper red they give distinctive colour changes with other indicators. Acids dissolve metals such as copper and liberate hydrogen gas. They also react with carbonates to liberate carbon dioxide ... 

Acid-base indicator Acid (or base). Neutralization is complete as determined by color change of indicator. 

The proton pump inhibitors are used for treatment or symptomatic relief of various gastric disorders, including gastric and duodenal ulcers, GERD, or pathological hypersecretory conditions. Painful, persistent heartburn 2 or more days a week may indicate acid reflux disease which can erode the delicate lining of the esophagus,... 

For analysis in solutions, the most frequently used CL reaction is alkaline oxidation of luminol and lucigenin in the presence of hydrogen peroxide as oxidant, although sodium hypochlorite, sodium perborate, or potassium ferricyanide may also be used. CL reactions involving alkaline oxidation have been used to indicate acid-base, precipitation, redox, or complexometric titration endpoints either by the appearance or the quenching of CL when an excess of titrant is present [114, 134], An example of these mechanisms is shown in Figure 14. 

Another problem is that different workers make their calculations of second-order rate constants in the micelle in different ways. For example, the surface potential of a micelle may be specifically included in the calculation in order to estimate ion binding, but there is a circularity in this argument because surface potentials are often estimated from micellar effects upon indicator acid-base equilibria which themselves depend upon ion-binding to micelles (Fernandez and Fromherz, 1977). 

Figure 10.17 H NMR spectra of spent acid samples spanning operational range of sulfuric acid concentrations. Shift of sulfuric acid peak with change in acid strength is indicated. Acid soluble oils and micellar water are readily quantified.

Interpretation. The optimum pFH is 3.8-4.2. Vaiues of pFH < 7.0 indicate acidity, in this case mainiy from the iactic acid produced by the fermentation of weii preserved siiage. ... 

Deuterium exchange studies on decaborane and other boranes indicate acidic character of bridge hydrogens. They react with bases undergoing proton abstraction reactions ... 

Figure 3.1. Gas-phase A//add values (kcal/mol) for carbon acids that give aromatic or antiaromatic carbanions. Acyclic analogues are included for comparison. Arrow indicates acidic hydrogen.

Note whether the material has undergone decompn or is markedly volatile, as indicated by 1) Discoloration 2) Appearance of colored fumes above the sample 3) Development of an odor indicating acidity and 4) Loss... 

In organic solvents the acidity functions H corresponding to hydrogen dissociation from neutral indicator acids were reported for solutions of alkali metal alkoxides in various alcohols (2), using nitroanilines (21), aminobenzenecarboxylic acids (22), or indols (23) as indicators. For addition reactions of methoxide and ethoxide ions to neutral indicator acids, acidity functions J (also denoted as Hr) based on use of nitrobenzenes (21) and a-cyanostilbenes (18) as indicators in methanol and dimethylsulfoxide-methanol and -ethanol mixtures were reported. Recently (24) the acidity function J- (denoted as Jm) was derived for methoxide ion solutions in methanol using substituted benzaldehydes as indicators. These scales involve arbitrary choice of water as the solvent for determination of the dissociation constant of the anchoring acid. 

If it is assumed, in a first approximation, that the activity coefficient ratios /ha/ /a- and /ArCHo//ArCH(OH)o do not differ very much, the difference between H and J for a given solution would be expressed by H- — J = —log flH2o-However a calculation of the difference by the latter formula, using the only available information (33) about the activity of water in water-DMSO mixtures, leads to values much smaller than those found in practice. This would indicate that the ratio /ha//a-> for the H indicator acids, is considerably larger than the ratio of /ArCHo//ArCH(OH)o- for the benzaldehydes used as J indicators. Probably this difference in activity coefficient ratios is caused by a larger extent of charge delocalization in the A anion compared to the geminal diol anion, which causes an extra stabilization of A- (manifested by a decrease in f ) by dispersion interaction with DMSO. 

K. Spectrophotometry with indicators Acid-base indicators are themselves acids or bases. Consider an indicator, Hln, which dissociates according to the equation... 

Sweetsur, A. W. M. and White, J. C. D. 1975. Studies on the heat stability of milk protein. III. Effect of heat-indicated acidity on milk. J. Dairy Res. 42, 73-88. 

Evaluations of tile chemical properties of a soil could he perplexing if an attempt were made to include all components that affect plant growth. Methods ill use today rely on indicators for judging the interaction of many factors at one time. Soil reaction or hydrogen ion concentration (expressed as pH) is the most widely used indicator. Acidity alone may or... 

FIGURE J. 1 The acidities of various household products can be demonstrated by adding an indicator (an extract of red cabbage, in this case) and noting the resulting color. Red indicates acidic, blue basic. From left to right, the household products are (a) lemon juice, (b) soda water, (c) 7-Up , (d) vinegar,... 

The non-linear plot in Fig. 11.2A indicates acid-base catalysis (i.e. when both acid and base are involved in the same catalytic mechanism with rate = 1cha.b[HA] [B] [HS]), and the Icha.b parameter can be determined from the slope of a plot of k0bs/(l - FB)( [acid] + [base])2 versus FB (not shown). 

A pH indicator molecule exhibits an equilibrium between the indicator acid InA and the indicator base InB [Eq. (1)]. 

Hammett (on quantitative study of very weak bases,409 reaction rates and indicator acidities,410 and rate-equilibrium relationships411) Hey and Waters (on free radicals) 412 Mayo and Walling (on free radicals) 413 and Dippy (on the strengths of organic acids)414... 

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