Page 128 - Feed Lab

Suguna Management System Ver 1.0 / SOP / FQL / P2 - 39 Page 1 of 1

39. Estimation of Formaldehyde Assay

FStandard Hydrochloric Acid - 0.1 N and 1N
PRINCIPLE
The method is based on the quantitative liberation of PROCEDURE
sodium hydroxide when Formaldehyde reacts with
1. Weigh accurately a glass stoppered conical flask
Sodium Sulphite to form the Formaldehyde bi sulphite
addition product. containing 10 ml of distilled water. Add to it about
3ml of the Formaldehyde solution and reweigh.
Add two drops of ( approximately 0.1 ml ) of the
APPARATUS
Thymalphthalein indicator solution followed by 0.1
FConical Flask 250ml
N sodium hydroxide solution drop by drop until a
FGraduate Pipette 5ml, 10ml faint blue colour is just perceptible.

FBurette 10ml 2. Measure 75 ml of freshly prepared sodium sulphite
solution into a second 250 ml conical flask. To it
add two drops (approximately 0.1 ml) of the
REAGENTS
Thymalphthalein indicator solution followed by 0.1
FSodium Sulphite Solution : Dissolve 126 gm of
anhydrous Sodium sulphite, or 252 gm of the N HCl acid solutions until the blue colour just
disappears. Add this solution to the neutralized
hydrated salt, in water and dilute for 1000ml
formaldehyde solution previously prepared.
FThymalphthalein Indicator solution : Dissolve 0.1
3. Mix the two solutions by swirling for two minutes
gm of Thymalphthalein in 100ml of 80 percent
rectified spirit. and then titrate with 1N Hcl acid until the blue colour
just disappears.

CALCULATION
3.003 X TV X N. of Hcl
Aldehyde content (as HCHO) Percent by mass = -------------------------------------------------

M
Where,
TV = Volume in ml of standard 1N Hcl acid.
N = Normality of Standard 1N Hcl acid.
M = Mass of the material taken for the test.

Prepared by : Approved by :
116 Director - Technical