Polarographic analysis

The titration of ascorbic acid using coulometrically generated I2 and Br2 is described in this experiment. Details are also given for the polarographic analysis of ascorbic acid. 

Correct structure proofs were earlier difficult to obtain, usually involving several reaction steps, and the structures were, therefore, assigned by analogy in many cases. However, through Raney nickel desulfurization (cf. Section VII,C), through NMR spectroscopy,and through polarographic analysis such problems are now easily solved. 

The basic apparatus for polarographic analysis is depicted in Fig. 16.1. The dropping mercury electrode is here shown as the cathode (its most common function) it is sometimes referred to as the working or micro-electrode. The... 

The constant 607 is a combination of natural constants, including the Faraday constant it is slightly temperature-dependent and the value 607 is for 25 °C. The IlkoviC equation is important because it accounts quantitatively for the many factors which influence the diffusion current in particular, the linear dependence of the diffusion current upon n and C. Thus, with all the other factors remaining constant, the diffusion current is directly proportional to the concentration of the electro-active material — this is of great importance in quantitative polarographic analysis. 

The shift of the half-wave potentials of metal ions by complexation is of value in polarographic analysis to eliminate the interfering effect of one metal upon another, and to promote sufficient separation of the waves of metals in mixtures to make possible their simultaneous determination. Thus, in the analysis of copper-base alloys for nickel, lead, etc., the reduction wave of copper(II) ions in most supporting electrolytes precedes that of the other metals and swamps those of the other metals present by using a cyanide supporting electrolyte, the copper is converted into the difficultly reducible cyanocuprate(I) ion and, in such a medium, nickel, lead, etc., can be determined. 

General considerations. Conventional d.c. polarographic analysis is most conveniently carried out if the concentration of the electro-active substance is 10-4 — 10 3 molar and the volume of the solution is between 2 and 25 mL. It is, however, possible to deal with concentrations as high as 10 2 molar or as low as 10 5 molar and to employ volumes appreciably less than 1 mL. 

Polarographic analysis - continued Ukovic equation, 596 introduction to, 602 influence of dissolved oxygen, 602, 608 investigation of, 618 mercury, 608 principles of, 592 pulse, 611... 

In polarographic analysis it gives two breaks in the curve, indicating a two electron reduction probably by the eqn ClCH2N02+2e = CH2N02 +CJ- (Ref 5)... 

Dichloronitromethane. This article supplements the material in Vol 5, D1213-R under Dichloro-methane and Derivatives. In polarographic analysis it shows a complex curve indicating two 2-electron reductions giving finally NMe and two Cl ions (Ref 1). Its pKa at 25° was found to be 5.99 (Ref 2)... 

Bromonitromethane. This article supplements the material in Vol 2, B312-R under Bromo-rnethane and Derivatives CA Registry No 563-70-2. The IR and UV spectra are given in Ref 3. In polarographic analysis a two electron reduction to CH2N02 and Br is indicated (Ref 4). It can be quanty detd by treatment with coned sul-... 

Chelates in inorganic polarographic analysis applications. M. Kapanica, J. Dolezal and J. Zyka, Chelates Anal. Chem., 1967,1,179-264 (187). 

Describe clearly the use of polarographic analysis for obtaining the values of the formation constant and stoichiometric number of metal complexes. 

On the basis of the above, the advantages of polarographic analysis over other analytical methods can be summarized as follows ... 

Many handbooks like the CRC Handbook of Chemistry and Physics provide, on behalf of electrochemistry investigation, values of standard reduction potentials, listed either in alphabetical order and/or in potential order. These must be considered as potentials of completely reversible redox systems. In current analytical practice one is interested in half-wave potentials of voltammetric, mostly polarographic analysis in various specific media, also in the case of irreversible systems. Apart from data such as those recently provided by Rach and Seiler (Spurenanalyse mit Polarographischen und Voltammetrischen Methoden, Hiithig, Heidelberg, 1984), these half-wave potentials are given in the following table (Application Note N-l, EG G Princeton Applied Research, Princeton, NJ, 1980). 

The ac polarograms of the mixture at varying frequencies (Fig. 19) shows four ac summit peaks corresponding to reduction of T1(I), In(III), Cd(II), and Zn(II). The summit peaks for In(III) and Cd(II) are very close and so their ac waves are not very sharp. The first summit peak corresponding to T1(I) appears to be due to the combined reduction of lead and thallium ions, as is evident from the summit peak height. Hence, ac polarographic analysis only enables the identification of four metal ions out of seven and... 

Solutions for polarographic analysis should contain a surfactant in low concentration to act as a current maximum suppressor, and all traces of oxygen should be removed. 

Fhe polarographic analysis is obtained at a dropping mciiiiiry electrode with any conventional three-electrode polarograpb cin[)loying a saturated calomel electrode as the rcCercnco. 1 ho checkers added the 0.5-ml. aliquots of the... 

Polarographic Analysis of Primer Mixture for M60 Base -Detonating Fuze (Oct 1958)... 

The ESR data for several silaacenaphthene and silaphenalene radical anions (Table VI) obtained by electrolytic reduction (101), are similar to the results for trimethylsilyl-substituted naphthalenes (Table V) (49). The polarographic reduction potentials were 0.2-0.4 volt more positive than that of naphthalene (101). Similarly, some silaphenalene derivatives of the type X[R = H(R ,R = H,H H,Me Me,Me) and R = Ph R1 = R2 = Me] were shown by polarographic analysis to reduce more easily than silylnaphthalene or naphthalene and the unassigned ESR spectra of the radical anions were reported (99). 

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