This is direct titration in which halide is titrated with silver nitrate.
This is indirect or back titration, in which halide is first precipitated with silver nitrate (excess) and the remaining amount of silver nitrate is titrated with ammonium or potassium thiocyanate.
2.
Potassium chromate or eosin is used as an indicator.
Ferric nitrate or ferric ammonium sulphate is used as an indicator.
3.
The endpoint was observed with a red colour precipitate of silver chromate (K2CrO4 as an indicator).
The endpoint was observed with a red colour solution of ferric thiocyanate.
4.
Determination of halides carried out at neutral to slightly alkaline pH (pH 6.5−9.0) as in acidic condition chromic acid is formed and in basic condition silver hydroxide is formed.
Determination of halides carried out at acidic pH.
5.
Titrations of I− and SCN− are not possible as AgI and AgSCN strongly absorb chromate ions and interfere in end-point detection.
Titration can be used for the determination of Cl−, Br− and I−.
6.
As the solubility of Ag2CrO4 increases with rising temperature, it is recommended to carry out titration at room temperature.
As the colour of the ferric thiocyanate complex fades above 25°C, it is recommended to carry out titration below 20°C.
