James J. Auborn

Kinetics of octylphenyl polyoxyethylene alcohol micelle dissociation by a stopped-flow technique

Abstract The kinetics of dissociation of micelles of the nonionic detergent octylphenyl polyoxyethylene alcohol in aqueous solution and in 0.1 M KCl at 25° were studied by a stopped flow technique. The rate constant of dissociation of the first detergent molecule from the micelle, kn, n-1, was found equal to 510 sec−1. A value of 73 sec−1 for kn, n−1 had been found previously, using a temperature jump technique. These results suggest that the rate determining step seen in a temperature jump experiment is not the release of the first molecule of detergent from the micelle.

A Square Wave Dissociation Field Effect Pulse Generator for Use with Spectrophotometric Detection

A 50 kV square wave pulse generator and associated control circuitry for use in spectrophotometric dissociation field effect experiments has been constructed. The design differs from previous pulse generators in that cumbersome delay cables are not used. A 0.005 μF plastic capacitor is charged to a voltage adjustable from 30 to 52 kV. When the desired voltage is reached, a triggered spark gap is fired, connecting the capacitor to the chemical cell. At a preset delay time, continuously adjustable from 0 to 29 μsec, a second spark gap is fired, shorting the cell and causing the voltage remaining on the storage capacitor to be discharged through a 100 Ω resistor. This apparatus produces an exceptionally clean pulse with a rise‐ and fall‐time of less than 22 nsec and does not produce the troublesome reflections associated with devices using delay cables. This high voltage pulse perturbs the equilibrium between reacting species in the chemical cell, and the return to equilibrium is observed spectrophotometrically. Chemical relaxation times faster than 30 nsec have been reliably measured with this device.