Electrical conductivity and UV measurements

The electrical conductivity of solutions is measured for at least three distinct purposes  

The example selected here shows the techniques developed by Szwarc s group (Bhattacharyya, Lee, Smid and Szwarc, 1965). They eschewed completely the use of taps and in each experiment the electrical conductivity and the optical absorption of the solution were measured this actually involves the same combination of devices as the Pask-Nuyken and Holdcroft-Plesch reactors described in Section 3.2.2. The description of the procedure is taken almost verbatim from the original publication, whose conciseness cannot be bettered. 

The apparatus is evacuated on a high vacuum line, flamed and sealed off at constriction i. The break-seal on ampoule B is crushed, and the whole unit is rinsed with the solution. The rinsing solution is then returned to B, and the unit is washed by condensing the solvent on the walls which are chilled in the usual way from outside. The required amount of solvent is distilled from 5 to a graduated cylinder, C, and then B is sealed off at P.  

The break-seal on A is then crushed, the sample to be investigated diluted with the solvent in C, and the optical density of the resulting solution determined in the appropriate optical cell. The solution is then transferred to conductivity cell H, and its resistance is measured. The optical density is redetermined, and thereafter about two thirds of the solution is transferred to C. The solvent from C is distilled into the chilled ampoule G and used to dilute the residual solutions left in H. The conductivity and the optical density of this solution are determined as described previously thereafter, two thirds is again transferred to C, and the remaining one third is diluted by the above-described procedure. In this way the conductivities are determined for decreasing concentrations of living polymer, so that the molar conductivity A can be calculated as a function of [living polymer] down to about 10 M. 

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