简介:2.1 The distillations in Methods 9030 and/or 9031 are performed, except that the scrubber
solution is sulfide anti-oxidant buffer (SAOB), with ascorbic and salicylic acids added as oxygen
scavengers. The distillates ar简介:2.1 The distillations in Methods 9030 and/or 9031 are performed, except that the scrubber
solution is sulfide anti-oxidant buffer (SAOB), with ascorbic and salicylic acids added as oxygen
scavengers. The distillates are then analyzed potentiometrically using a sulfide ion-selective
electrode (ISE) in conjunction with a double-junction reference electrode and a pH meter with an
expanded millivolt scale or an ISE meter capable of being calibrated directly in terms of sulfide
concentration.
2.2 This method is an alternative to the iodometric titration procedure, where a solution
of thiosulfate is standardized against the thiosulfate solution, and the sulfide standard is standardized
against the iodine solution/thiosulfate solution (which requires daily calibration itself). This method
allows for standardizing the sulfide calibration standards by a potentiometric titration with
standardized silver nitrate using the sulfide ISE as the working electrode. Silver nitrate solutions are
stable when stored properly and are easily standardized against sodium chloride.
2.3 The key to acceptable recoveries is the use of the proper apparatus and careful
assembly of the distillation apparatus prior to distillation. If these steps are not taken, low recoveries
will result.详细>