Standardization of solutions used in argentometry

0.1M silver nitrate standardization against sodium chloride

Silver nitrate solutions of known concentration can be prepared from known mass of dried AgNO₃. However, if we don't have access to the high purity reagent, or if we have a solution of unknown concentration, we can easily standardize it against sodium chloride.

Reaction taking place during titration is

AgNO₃ + NaCl → AgCl↓ + NaNO₃

Procedure to follow:

• Weight exactly about 0.15-0.20 g of dried sodium chloride into 250 mL erlenmayer flask.
• Add about 100 mL of distilled water, dissolve.
• Add 1 mL 5% w/w potassium chromate solution.
• Titrate with AgNO₃ solution till the first color change.

0.1M potassium thiocyanate standardization against silver nitrate solution

Potassium thiocyanate solution has to be standardized, as it is not possible to prepare and dry KSCN pure enough so that it can be used as a standard substance for solution preparation. The easiest method if the standardization require standardized solution of silver nitrate. As KSCN solution is used for back titration of the excess of AgNO₃, when we need to standardzie KSCN solution we usually have standardized silver nitrate solution ready.

Reaction taking place is

AgNO₃ + KSCN → AgSCN↓ + KNO₃

Procedure to follow:

• Pipette 25 mL aliquot of about 0.1M AgNO₃ solution into 250mL erlenmayer flask.
• Add 50 mL of distilled water.
• Add 1 mL of 10% FeNH₄(SO₄)₂ solution.
• Titrate with potassium thiocyanate till the first visible color change.