Titration methods high frequency

J)Other analytical methods which include, among many, a thermometric method (104), a high frequency titration (105), and a colored indicator method (106). 

Titration Curves. Generally it can be expected that if a low-frequency conductance titration can be performed, a high-frequency one can also. However, the cell size, ionic strength of the solution, and frequency needed to give a good endpoint are variables that must be determined by trial and error. Even after the best conditions are found, the curves obtained may be nonlinear and show little response. However, if an endpoint can be found, there is a definite advantage to a method in which no... 

The high frequency titration (h.f.t.) (1,2) as a method for complexing study in solution was used by R.HARA and P.WEST (3) for the first time. This method is based on the determination of the molar ratio of the metal to the addend from an inflection point in the titration curve due to a change in conductivity in the moment of completion of complex formation, especially with complexing agent, which will liberate hydrogen ions, such as EDTA. 

Most methods for the determination of carboxyl groups in polymers are based on titration techniques including, for example, the following copolymers acrylic acid-itaconic acid [16], acrylic acid-ethyl acrylate [17] and maleic acid-styrene [18]. High-frequency titration has been applied [19] to the analysis of itaconic acid-styrene and maleic acid-styrene copolymers. The method can also be used to detect traces of acidic impurities in polymers, and in the identification of mixtures of similar acidic copolymers. Titration indicates that the acid segments in the copolymers of itaconic acid-styrene, and maleic acid-styrene, and the homopolymer polyitaconic acid, act as dibasic acids. The method has a sensitivity that permits identification and approximate resolution of two carboxylate species in the same polymer, for example ... 

High-frequency titration gives a precise location of the inflection points related to the polymer carboxyl groups, and is a sensitive method for the determination of the freedom of the copolymer samples from monobasic acid impurities (comonomer acids). This is because mixtures of copolymer acids with monobasic and dibasic acids show definite inflection points that can be related to the individual carboxylate species present. 

Like zinc ions, cadmium ions can be titrated in buffered solutions with EDTA but the end-point is more easily located by high frequency titration than by an indicator. Among the instrumental methods suitable for the determination of cadmium in dilute solutions, atomic absorption is ideal and polarography is also suitable. Gravimetrically, cadmium can be precipitated as the oxinate similar to zinc. In addition, it can be precipitated as molybdate. 

It must be realized that the constant current (-1) chosen virtually determines a constant titration velocity during the entire operation hence a high current shortens the titration time, which is acceptable at the start, but may endanger the establishment of equilibrium of the electrode potentials near the titration end-point in an automated potentiometric titration the latter is usually avoided by making the titration velocity inversely proportional to the first derivative, dE/dt. Now, as automation of coulometric titrations is an obvious step, preferably with computerization (see Part C), such a procedure can be achieved either by such an inversely proportional adjustment of the current value or by a corresponding proportional adjustment of an interruption frequency of the constant current once chosen. In this mode the method can be characterized as a potentiometric controlled-current coulometric titration. 

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