Volumetric titrimetry

Some method of signaling is required to indicate when the amount of titrant generated is equivalent to the amount of unknown present, and all of the endpoint detection methods used in volumetric titrimetry are, in principle, applicable to coulometric titrations. A list that covers most of the published coulo-metric titration procedures is given in Table 25.2. It is beyond our scope here to describe any of these in detail because each of these methods is a subject for discussion in its own right. Discussions of the equations for a number of types of titration curves are found in texts by Lingane [15], Butler [16], and Laitinen and Harris [17]. 

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]. 

Volumetric titrimetry — A - titration method in which the volume of -> titrant that is added to the -> titrand is measured [i]. 

Volumetric titrimetry is a type of titrimetry in which the volume of a standard reagent is the measured quantity. 

Write two equations that—along with the stoichiometric factor—form the basis for the calculation of volumetric titrimetry. 

As in any titration, a suitable method of detection of the equivalence point is necessary. In general, it can be said that any of the techniques that are useful in classical volumetric titrimetry are also applicable to coulometric titrations. As noted above, Szebelledy and Somogyi used traditional color-change indicators to determine their end points. 

Titrimetry, or quantitative analysis based on the amount of a standard solution consumed in a reaction, is another valuable technique for the analysis of both major and minor constituents. It is capable of high accuracy, especially when the amount of reagent consumed is determined by weight, and in such cases accuracies of 0.01 % have been obtained. Volumetric titrimetry can readily yield results of 0.1 % accuracy. 

In titrimetric analysis (often termed volumetric analysis in certain books), the substance to be determined is allowed to react with an appropriate reagent added as a standard solution, and the volume of solution needed for complete reaction is determined. The common types of reaction which are used in titrimetry are (a) neutralisation (acid-base) reactions (b) complex-forming reactions (c) precipitation reactions (d) oxidation-reduction reactions. 

Thus, most calculations in volumetric determinations (titrimetry) are enormously facilitated by using titer values, which may be seen in the following chapters related to various categories of volumetric titrations. 

A matter of practical importance in nonaqueous titrimetry is that, when volumetric equipment is used, errors should be prevented that arise from solvent volatility and from characteristics of viscosity and surface tension that differ from those of water. Temperature coefficients of expansion are often about six times that of water, so careful control of temperature is needed when volumes are being measured. Gravimetric titration techniques are recommended, since they avoid most of these volumetric problems. Details of a gravimetric technique using a syringe have been given. ... 

This chapter provides in troductory material that applies to all types of titrimetric methods of analysis, using precipitation titrimetry to illustrate the various theoretical aspects of the titration process. Chapters 14, 15, and 16 are devoted to the various types of neutralization titrations, in which the analyte and titrants undergo acid/base reactions. Chapter 17 provides information about titrations in which the analytical reactions involve complex formation. These methods are of particular importance for the determination of a variety of cations. Finally, Chapters 18 and 19 are devoted to volumetric methods, in which the analytical reactions involve electron transfer. These methods are often called redox titrations. Some additional titration methods are explored in later chapters. These methods include ampero-metric titration, in Section 23B-4, and spectrophotometric titrations, in Section 26A-4. 

Analytical chemistry began in the late eighteenth century with the work of French chemist Antoine-Laurent Lavoisier and others the discipline was further developed in the nineteenth century by Carl Fresenius and Karl Friedrich Mohr. As a pharmacist s apprentice in Frankfurt, Germany, Fresenius developed an extensive qualitative analysis scheme that, when it was later published, served as the first textbook of analytical chemistry. He built a laboratory at his house that opened in 1848. Here he trained students in gravimetric techniques that he had developed. Mohr developed laboratory devices such as the pinch clamp burette and the volumetric pipette. He also devised a colorimetric endpoint for silver titrations. It was his 1855 book on titrimetry, Lehrhuch der Chemisch-Analytischen Titromethode, that generated widespread interest in the technique. 

In volumetric cruilysis, the concentration of a Mlution is found by measuring the volume of solution that will react with a known volume of a standard solution. The procedure of adding one solution to another in a measured way until the reaction is complete is called rtrnttion. Volumetric analysis is often referred to as titrimetrie nnulysis or titrimetry. 

Convenience reagents also include ready-to-use buffers, bench reagents, and standard solutions and indicators for titrimetry. Buffers and standard volumetric solutions are also available in concentrated form so that a simple volumetric dilution of the contents of a container will produce the required reagent concentration. 

The amount of titrant added is usually measured by volume (by dispensing the solution from a burette), and in this case, titrimetry is an example of volumetric analysis. Occasionally, the titrant is measured by weight (especially if greater accuracy is required) or by amount of electricity (as in coulometric titrations). 

The first quantitative analytical fields to be developed were for quantitative elemental analysis, which revealed how much of each element was present in a sample. These early techniques were not instrumental methods, for the most part, but relied on chemical reactions, physical separations, and weighing of products (gravimetry), titrations (titrimetry or volumetric analysis), or production of colored products with visual estimation of the amount of color produced (colorimetry). Using these methods, it was found, for example, that dry sodium chloride, NaCl, always contained 39.33% Na and 60.67% Cl. The atomic theory was founded on early quantitative results such as this, as were the concept of valence and the determination of atomic weights. Today, quantitative inorganic elemental analysis is performed by atomic absorption spectrometry (AAS), AES of many sorts, inorganic MS (snch as ICP-MS), XRF, ion chromatography (1C), and other techniques discussed in detail in later chapters. 

The scientist who was responsible for the introduction of titrimetry into mainstream chemistry was Gay-Lussac. He further developed the apparatus used in volumetric analysis and was the first to use the word burette (Figure 14.3). In 1832 he introduced precipitation titrations for the estimation of silver. Sodium chloride solution was added to a solution of a silver salt until no further precipitation occurred. This was a time-consuming procedure as near the endpoint the precipitate had to be allowed to settle before each new portion of sodium chloride was added. 

The technique of volumetric analysis is the simplest type of titrimetry, and... 

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