Active ingredient content in malathion

ESTIMATION OF ACTIVE INGREDIENT CONTENT IN MALATHION

Principle

         When malathion is reacted with alkali dimethyl dithiophosphate is formed. The product formed is reacted with in the presence of starch.

Materials required

i)                    Iodine (0.1N), ii) Hydrochloric acid (2N), iii) Sodium thiosulphate, iv) Sodium hydroxide, v) freshly prepared starch solution, vi) Reflux condenser, vii) Burette, viii) Balance.

Procedure

v  Transfer exactly 0.1g of malathion into a 250 ml conical flask and add 30 ml of sodium hydroxide.

v  Attach a condenser and reflux gently for about 15-20min till the malathion completely dissolves.

v  Cool the content and add 50 ml of 0.1N iodine solution.

v  Set aside for 10min and add about 25ml of 2N HCL to acidify the mixture.

v  Titrate immediately against 0.1N sodium thiosulphate in the presence of starch indicator (V1). Disappearance of dark blue colour is the end point.

v  Simultaneously run a blank titration (Vb). Volume of 0.1N sodium thiosulphate consumed for blank that consumed for the sample titration (Vb-V1) will give the actual volume of sodium thiosulphate consumed.

Calculation

Malathion content 

=

V1 =Volume of sodium thiosulphate consumed for the titration

VB =volume of sodium thiosulphate consumed for blank titration

N = Normality of sodium thiosulphate

W =Weight of the sample taken for the determination