Direct or indirect titration?
When the titration reaction consumes the chemical of interest Eint we use the term direct titration (ν1T + ν2Eint = products): only one reaction occurs.
When the titration reaction consumes a chemical whose concentration is related to the chemical of interest Eint, we use the term indirect titration: several reactions may occur.
When two successive reactions take place, a chemical A in excess reacts with Eint in a total manner to create chemical B (νAA + νintEint = νBB + products).
Two types of titration may then be carried out:
1. The newly created chemical B is titrated (νTT + ν’BB= products).
2. Titration of the excess of chemical A that did not react with Eint (νTT + ν’1Aexc = products). In this case we speak of return titration.