Chemical titrations

The widely used —COOH and —OH endgroup chemical titrations are detailed below. 

Carboxy-hydroxy reactions, 63 Carboxyl endgroup chemical titration, 94 Carboxylic acid-aryl acetate interchange reactions, 62, 63... 

Hydroxybenzylamine intermediates, 392 Hydroxybenzylamines, 389, 391, 416 thermal decomposition of, 392 Hydroxy-ester interchange reactions, 62, 65, 69-74, 84, 111 Hydroxy-functional crosslinkers, 214 Hydroxyl endgroup chemical titration, 94-95... 

All existing techniques of EEP detection may be divided into several groups spectral, calorimetric, chemical titration, electrical methods, and also a method of sensor detection. 

Common chemical titrations include acid-base, oxidation-reduction, precipitation, and complexometric analysis. The basic concepts underlying all titration are illustrated by classic acid-base titrations. A known amount of acid is placed in a flask and an indicator added. The indicator is a compound whose color depends on the pH of its environment. A solution of base of precisely known concentration (referred to as the titrant) is then added to the acid until all of the acid has just been reacted, causing the pH of the solution to increase and the color of the indicator to change. The volume of the base required to get to this point in the titration is known as the end point of the titration. The concentration of the acid present in the original solution can be calculated from the volume of base needed to reach the end point and the known concentration of the base. 

Energy transfer to photoreactive acceptors has also been widely utilized for excitation quantum yield determination (chemical titration), mainly in the decomposition of dioxetanes ° . The quantum yields are calculated from the photoproduct yield obtained at infinite energy acceptor concentrations ( = 1.0) by extrapolation of the double-reciprocal relationship between the photochemically active energy acceptor concentration and the photoproduct yield ( Lp ). H the quantum yield of the photochemical reaction (excitation quantum yield (< > ) can be calculated (equation 8) . ... 

Calibration methods I modified luminol standard II absolute calibration HI Hastings-Weber light standard IV luminol standard V mean value obtained by different determination methods, including chemical titrations VI triplet yield of 0.3 E mol for TMD, obtained with DBA. 

Tetramethylammonium ozonide, 736 Tetramethyl-l,2-dioxetane (TMD) chemical titration, 1224 chemiluminescence, 1221, 1234 quantum yield standard, 1224, 1226 N,N, N, A -Tetramethyl-p-phenylenediamine hydrogen peroxide determination, 735, 631, 633... 

Chlorine and bromine atoms have been monitored in flow discharge systems by measuring the heat liberated on a probe when a pair of atoms recombine on the surface.43-51,52 Ogryzlo51 has employed a moveable nickel calorimeter for both Cl and Br atoms. Chemical titration of the chlorine atoms may then be developed by comparing the effect of the addition of a material that rapidly removes the atoms observed with the calorimetric probe. Ogryzlo51 has found that NOC1 may be used for titration of the Cl atoms as the reaction... 

The concentration of hydroperoxides can often be determined by infrared analysis or by chemical titration. Diperoxides are more difficult to detect experimentally. If both substituents of the peroxide are polymeric radicals, P, the corresponding peroxide POOP can actually be considered as an oxygen bridge between two macromolecules and should therefore behave like a crosslink ... 

In considering photoactivity on metal oxide and metal chalcogenide semiconductor surfaces, we must be aware that multiple sites for adsorption are accessible. On titanium dioxide, for example, there exist acidic, basic, and surface defect sites for adsorption. Adsorption isotherms will differ at each site, so that selective activation on a particular material may indeed depend on photocatalyst preparation, since this may in turn Influence the relative fraction of each type of adsorption site. The number of basic sites can be determined by titration but the total number of acidic sites is difficult to establish because of competitive water adsorption. A rough ratio of acidic to basic binding sites on several commercially available titania samples has been shown by combined surface ir and chemical titration methods to be about 2.4, with a combined acid/base site concentration of about 0.5 mmol/g . 

Disadvantages. Further study may reveal possible positive or negative interferences in the chemical titration and ion generation reactions. 

The reaction between toluene 2,4-diisocyanate and carboxylated MWCNTs afforded amido-functionalized nanotubes containing highly reactive isocyanate groups on their surface (Scheme 1.4). The amount of the isocyanate groups was determined by chemical titration and thermogravimetric analysis (TGA) [105]. The modified tubes may constitute promising components to prepare polymer-nanotube composites and coatings [106]. 

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