Abstract
An accessory circuit modification to correct automatically for zero drift was developed for use with the Titrilog with increased sensitivity. Correction relative to a preset baseline is accurate within ± 2% of full scale. The sensitivity was increased by a factor of 15 to give a calibration sensitivity of one pphm of S02 per recorder chart division. The sensitivity and time response of the modified system permit operation of the Titrilog as a continuous, unattended monitor of SO2 in the ambient atmosphere. The instrument responds to low concentrations in the pphm range and to transient peak concentrations of several minutes duration.