Coulometric titrimetry

A second approach to coulometry is to use a constant current in place of a constant potential (Figure 11.23). Controlled-current coulometry, also known as amperostatic coulometry or coulometric titrimetry, has two advantages over controlled-potential coulometry. First, using a constant current makes for a more rapid analysis since the current does not decrease over time. Thus, a typical analysis time for controlled-current coulometry is less than 10 min, as opposed to approximately 30-60 min for controlled-potential coulometry. Second, with a constant current the total charge is simply the product of current and time (equation 11.24). A method for integrating the current-time curve, therefore, is not necessary. 

Since a small quantity of electricity can be readily measured with a high degree of accuracy, the method has high sensitivity. Coulometric titrimetry has several important advantages. 

Total sulfur (TS), acid-volatile sulfide (AVS), Cr-reducible sulfur (CRS), and extractable sulfate in sediments were determined by coulometric titrimetry,106 a method that yielded improved data quality and increased laboratory throughput. 

Not all techniques that at one time showed promise eventually achieved widespread application. An example is coulometric titrimetry, whose history has been discussed.113 Reviews have also appeared of electroanalytical chemistry in molten salts114 and of the early years of the relatively new technique of spectroelectrochem-istry.115 The development of electrochemical instrumentation from its origins, through the electronic age to the computer age has been discussed.116... 

Titrimetry — A chemical analysis based on determining the quantity of - titrant that is required to react completely with the - analyte and that is performed by - titration. There are three common types of titrimetry -> volumetric titrimetry, -r gravimetric titrimetry, and -> coulometric titrimetry [i]. 

Coulometric titrimetry is a type of titrimetry in which the quantity of charge in coulombs required to complete a reaction with the analyte is the measured quantity. 

Two methods have been developed that are based on measuring the quantity of charge controlled-potential (potentiostatic) coulometry and controlled-cur-rent coulometry, often called coulometric titrimetry. Potentiostatic methods are performed in much the same way as controlled-potential gravimetric methods, with... 

Coulometric titrimetry Differential pulse polarography Flame atomic absorption (solvent extraction)... 

Terminology related to electroanalytical chemistry are chronoamperometry, voltammetry, coulometry, amperometric titrimetry, coulometric titrimetry, conductivity, con-ductimetry and high frequency titrimetry, electrometric titrimetry, electrogravimetry, electrodeposition, anodic stripping voltammetry (ASV), cathodic stripping voltammetry (CSV), polarography, differentia] pulse polarography (DPP), ion-selective electrode (ISE), ion-specific electrode (ISE), molecular selective electrode, potentiometry, potentio-metric titrimetry, and chronopotentiometric titrimetry. 

Coulometric titrimetry has been used for the determination of mercaptan, halide, and phosphorus compounds by using a silver electrode. The principle has also been used for... 

The use of dual intermediates was introduced into coulometric titrimetry by Buck and Swift (35) in 1952. They developed an improved method for the titrimetric bromination of organic compoxinds such as aniline that react slowly. Their method involved the electrical generation of an excess of bromine, the excess being back-titrated with electrically generated Cu(I). This constitutes another method of overcoming a sluggish end point. A dual-intermediate titrator with modern electronic instrximentation has been described recently (36). ... 

C. E. Champion, G. Marinenko, J. K. Taylor, and W. E. Schmidt, Determination of submicrogram amounts of chromium by coulometric titrimetry. Anal. Chem. 42, 1210-1213(1970). 

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