When testing Sulfite, remember testing should be carried out at room temperature! Hot boiler samples can have their Sulfite values overstated by as much as100%. Sulfite analysis with lodide-lodate is an Iodometric test procedure where you liberate Iodine during the test; Iodine is volatile when heated! Hot samples will have Iodine liberated as a gas with excess titrant added and Sulfite values can be overstated. Actual system Sulfite residuals will be correspondingly less with the boiler potentially under treated with oxygen scavenger and resultant corrosion cell formation from uncomplexed dissolved oxygen.