Mohr's method titration - Introduction - Reactions - Principle - Applications

1. Hygia Institute of Pharmacy
Ghaila Road, Gazipur Balram Rd, near IIM Road, Prabandh Nagar, Lucknow,
Uttar Pradesh 226020
Prepared by
1. Richa Yadav
Under guidance
Pharmaceutical Chemistry (Lecturer)
Mr. Kartik Tiwari
Head of Department
Diploma in Pharmacy
Mrs. Richa Tripathi
Precipitation Titration
Precipitation titration is a quantitative analytical technique in chemistry where the reaction
between the analyte (substance being analyzed) and a titrant (solution of known
concentration) results in the formation of a solid precipitate. The formation of this insoluble
substance is used as an indicator to determine the endpoint of the titration.
• Analyte: Chloride ions (Cl⁻).
• Titrant: Silver nitrate (AgNO₃).
• Indicator: Potassium chromate (K₂CrO₄).
• Endpoint: Formation of a red-brown precipitate of silver chromate (Ag₂CrO₄).
1. Mohr's Method:
AgNO
3
--------
-- --
-- --
--------
--------
--------
--------
NaCl
-------------------------------
------------------------------
--------------------------
AgCl
White ppt.
K2CrO4
Ag2CrO4
Red orange colour
Figure – Mohr’s Method
Principle:
Reaction between Titrant and Analyte sample
AgNO3 + NaCl AgCl + NaNO3
When AgNO3 is titrated with the analyte sample containing
chloride it will form silver chloride which form white
precipitate in the conical flask.
Silver chloride
(White ppt.)
Reaction between Titrant and Indicator at the endpoint
AgNO3 + K2CrO4 Ag2CrO4 + KNO3
Silver chromate
(Red brown ppt.)
When AgNO3 is at the end point with an indicator of K2CrO4
it will form red brown precipitate which indicate the end point
and the titration should be stop and note the burette reading
(amount of titrant used).
• Mohr's method is commonly used in
analytical chemistry laboratories for routine
analysis of chloride content in various
samples, such as water, food, and
pharmaceuticals.
• It provides a reliable and straightforward
technique for quantitative analysis of chloride
ions.
Applications: