The A15/66 Monitor takes a unique approach to the measurement of sulfite ion concentration. In operation, a small amount of sample is pumped into the system and mixed with acid. In the acidic solution, the sulfite ion is converted to sulfur dioxide. The mixed sample flows into a special chamber where the sulfur dioxide is stripped from the sample. A sensor located in the gas stream measures the released SO2 concentration and displays the results is terms of equivalent sulfite ion concentration.