Preparation and standardization of 0.1 N Potassium Thiocyanate USP Volumetric Solution
1. PREPARATION:
Weigh accurately about 9.72 g of Potassium thiocyanate, previously dried for 2 hours at 110°C, transfer to a 1 liter volumetric flask, dilute with water to volume, and mix well.
2. STANDARDISATION:
Transfer 40 mL of freshly standardized 0.1 N Silver nitrate VS to a 250 mL Erlenmeyer flasks, and add 100 mL of water, 1 mL of Nitric acid, and 2 mL of Ferric ammonium sulfate TS. Titrate with the Potassium thiocyanate solution, with agitation, to a permanent light pinkish-brown color of the supernant.
Calculation:
Normality = [mL x N AgNO3]/[mL KSCN]
Limit: 0.1 N ± 5 % (0.0950 N – 0.1050 N)
3. PREPARATION OF INDICATORS / REAGENTS:
a. Ferric Ammonium Sulfate TS :
Dissolve 8 g of ferric ammonium sulfate in water to make 100 ml.
b. 0.1 N Silver nitrate VS :
Preparation and standardization as per respective process.
4. STORAGE CONDITION:
Store in glass stoppered, amber coloured bottles.
