Titration blank ($V_{\mathrm{blank}}$)

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] 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.