Inorganic analysis acid-base titrations

If a gas is soluble in a suitable solvent, and the concentration of the solution can be determined by a simple analytical technique, then accurately measured quantities of the gas can be dispensed by using the appropriate volume of the solution. For example solutions of the hydrogen halides in various solvents can be determined by simple acid/base titration and solutions of chlorine in carbon tetrachloride can be determined by addition of excess potassium iodide and back titration with sodium thiosulphate. Refer to textbooks of inorganic analysis for details of these methods. 

Several important elements that occur in organic and biological systems are conveniently determined by methods that involve an acid/base titration as the final step. Generally, the elements susceptible to this type of analysis are nonmetallic and include carbon, nitrogen, chlorine, bromine, and fluorine, as well as a few other less common species. Pretreatment converts the element to an inorganic acid or base that is then titrated. A few examples follow. 

Titrations based on oxidation-reduction reactions enjoy wide use. Permanganate, dichromate, and iodine and iron(II), tin(II), thiosulfate, and oxalate are commonly used oxidizing and reducing titrants, have been employed to determine components in both inorganic and organic analysis. As we saw in Chapter 7, solvent water does not play as central a role as in acid-base titrations. Oxidants or reductants strong enough to decompose water are not practical as titrants. 

An acid-base titration is a quick and convenient method for the quantitative analysis of substances with acidic or basic properties. Many inorganic and organic acids and bases can be titrated in aqueous media, but others, mainly organic, are insoluble in water. Fortunately, most of them are soluble in organic solvents hence they are conveniently determined by nonaqueous acid-base titrimetry. Although acid-base titrations can usually be followed potentio-metrically, visual endpoint detection is quicker and can be very precise and accurate if the appropriate indicator is chosen. 

Controlled-current coulometry (coulometric titration) can be utilized to determine not-easily oxidizable (or reducible) analytes of different applications via acid-base, precipitation, com-plexation titrations, etc. Furthermore, it benefits short analysis time and small amount determination [2]. Dzudovic et al. [21] reviewed some studies employing acid-base titrations for the determinations of non-aqueous or water-insoluble compounds (organic and inorganic). Typically, acidimetric titrations were undertaken coulometrically based on the EF liberated by the oxidation of the introduced H2O. Coulometric titrations of bases in nonaqueous solvent were performed using anodic depolarizers (titrants) to generate as a source. On the other hand, coulometrically atkalimetric... 

Kojima Y, Hayashi A, Tachi I (1960) Studies on lignosulphonic acid (VI) Conductometric titration with weak base 7pn Tappi 14 831-834 Kolthoff IM, Sandell EB (1952) Textbook of quantitative inorganic analysis Macmillan, New York, 759pp... 

USE As acid-base indicator in 0.2% soln in alcohol. pH 4.4 red 6.4 blue. Satisfactory for titrating mineral acids, strong bases, many alkaloids determining alkalinity and temporary hardness in water analysis. Biological stain dye for wool, silk- Not adapted for carbonates, weak inorganic and organic acids, weak bases. Lacmoid is more sensitive than litmus, particularly in form of test paper. 

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