Behaviour of piezoelectric quartz crystals in solutions with application to the determination of iodide

The frequency of oscillation of a piezoelectric quartz crystal immersed in solution changes with the temperature of the solution and with the ambient temperature of the oscillator, especially where the latter is transistorized. The frequency is also affected by the specific gravity, viscosity and specific conductivity of the solution. When all the properties are maintained constant, iodide present in the solution electrodeposits on the silver electrodes of a crystal to produce a reproducible change in frequency which allows iodide to be determined in the range 0.5–7 μM. Thiosulphate, cyanide, sulphide, Fe(III), Hg(II) and Ag interfere, but procedures for preventing their interference are given.