Dissolve 1.792 g of benzethonium chloride, previously dried to constant weight at 100° to 105°, in sufficient water to produce 1000 ml.
Dissolve 0.35 g of the dried substance in 30 ml of anhydrous acetic acid, add 6 ml of mercury(II) acetate solution and carry out potentiometric titration with 0.1M perchloric acid using 0.5ml of crystal violet solution as an indicator to the full colour change of indicator. Carry out a blank titration.
Each ml of 0.1M perchloric acid VS is equivalent to 44.81 mg of C27H42ClNO2.
MF = W/0.04481 x V
W = Weight of Benzethonium chloride in g.
V = Volume of perchloric acid consumed in ml.
1) Discard the solution after 30 days.
2) Restandardise before use
3) For storage and labeling follow the general procedure