Frequency properties of a piezoelectric quartz crystal in solutions and application to total salt determination

For an integrated circuit oscillator, the slope of the linear portion of the frequency shift/electrolyte concentration plot for a AT-cut quartz piezoelectric crystal immersed in a solution is dependent on the circuit capacitance, decreasing from positive to negative values with increasing capacitance. The slope does not vary significantly with the kind of salt. A method based on the frequency measurement is suggested for the rapid determination of the total salt content of natural waters.