A titration blank runs the background procedure without the intended reacting sample, matching relevant water, indicator quantity and titration endpoint conditions. Its titrant demand estimates a background contribution to subtract. The inspected EPA procedure uses such a phenolphthalein blank; this is a distinct control, rather than an instruction present in Columbia's Part 3.[ref]
Process Measurement Procedures: Sulfuric Acid Emissions by R. Maddalone and N. Garner. Printed pp. 26–27, §1.4.4.2, indicator-blank paragraph and steps 1–3: water replaces acid, indicator quantity matches, blank volume is subtracted
A blank must match the relevant background to justify subtraction; it does not remove sample-specific side reactions or a mismatch between titration endpoint and equivalence point. New to topics? Read the docs here!