Semi-micro-titrations

The yield of radioactive D.F.P. from 32P is necessarily small on the semi-micro scale (p. 75) it is better therefore to titrate the fluoride (obtained after the decomposition of D.F.P.) with thorium nitrate, sodium alizarin sulphonate being used as indicator.2 It is necessary, however, first of all, to remove the fluoride by distillation (p. 211). This method gives an accuracy of +1 per cent with 50 mg. of D.F.P. This degree of accuracy on a semi-micro scale3 may be considered fairly satisfactory. 

S) Bishop, E., and R. G. Dhaneshwar Differential Electrolytic Potentiometry. VIII. The Behaviour and Energetics of Current-Carrying Silver and Silver Halide Electrodes in the Semi-Micro Scale Titration of Nanogram Amounts of Halides at Extreme Dilution. Analyst 87, 845 (1962). 

By analogy, the anion exchangers like Amberlite IR-4 should bind preferentially the dicarboxylic acids. This is also the case. A mixture of amino acids and hydrochloric acid, which is stirred for 1 to 3 hours with sufficient resin IR-4 to give a final pH of 6 to 7, will adsorb completely the acidic amino acids and leave the neutral and basic amino acids unaffected (Cannan 1944, Cleaver et al., 1945). On the pure fraction eluted with HCl from the resin, Cannan determined the aspartic and glutamic acids separately by a combination of electrometric titrations in water and formaldehyde solutions and a gasometric ninhydrin estimation—a method well suited for work on a semi-micro scale. 

D3339 Test Method for Acid Number of Petroleum Products by Semi-Micro Color Indicator Titration ... 

Cool the solution and add 100 mL of acetone. Titrate the solution potentiometrically with standard 0.01 M silver nitrate, using glass versus silver-silver chloride electrodes. If an automatic titrator, such as a Metrohm, is available, use the semi-micro 5-mL piston buret. If the titration is carried out with a manually-operated pH meter, use a 5-mL semi-micro buret which can be estimated to three decimal places in millilitres. 

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