Page 132 - Feed Lab

Suguna Management System Ver 1.0 / SOP / FQL / P2 - 43 Page 1 of 2

43. Estimation of sodium chlorite assay

FSodium Thiosulphate 0.1N: Dissolve 24.8 gm of
SCOPE
sodium thiosulphate in 1lit water. Add 0.5 ml of
Method is used to determine the content of sodium Chloroform as preservative, dilute to volume with
chlorite in commercial sodium chlorite and it is specific
water in a 1000 ml one-mark volumetric flask and
for these species.
mix thoroughly.

PRINCIPLE
FStandardization of Sodium thiosulphate:
Manual iodometric titration with an excess of sulphuric Accurately weigh 0.16-0.22 g dried, finely ground
acid. This method is based on the reducing action of K Cr O to nearest 0.0001g into 500ml flask,
7
2
2
the iodide ion on the chlorite species and on the dissolve in 25ml water, add 5 ml Hydrochloric acid
subsequent determination of iodine formed, by redox and 20ml potassium iodide and rotate to mix. Let
titration against sodium thiosulphate. stand for 5 minutes. Add 100ml water. Titrate with
sodium thiosulphate solution, shaking continuously
APPARATUS until yellow colour has almost disappeared. Add 1-
FOrdinary laboratory apparatus and glassware 2ml starch indicator solutions, and continue adding
thiosulphate solution until blue colour just
o
FDensimeter, temperature setting 20 C. disappears.
FAutomatic Pipette, range between 0.1 ml and 1 ml. PROCEDURE

1. Heat the Sodium chlorite laboratory sample to
REAGENTS
o
20 C and check the density in grams per milliliter
FPotassium Iodide Solution 10%: 10gm of with a densimeter set 20 C (V).
o
potassium iodide in 100 ml of dis.Water.
2. Take 0.2ml or 0.3 ml of the test sample to a 250ml
FSulphuric Acid Solution 1N: 2.7 ml of conical flask with tight fitting stopper.
con.sulphuric acid in 100 ml of dis.water.
3. Then add 50ml of dis.water + 20 ml of 10% KI
FStarch Indicator 1% : 1gm of starch in 100 ml of solution + 10ml of H SO .
hot dis.water. (This solution needs refrigeration to 2 4
avoid the decomposition of the starch with results 4. And put the stopper on the flask and leave in the
in a vague end point). dark room for 5 minutes.

Prepared by : Approved by :
120 Director - Technical