[MartynYarrow]

Explain briefly with chemical equation why glacial acetic acid is used instead of dilute sulphuric acid in the estimation of available chlorine experiment.

THANK YOU!

[AWK]

Show details of your method.
Usually bleach is titrated in a procedure with addition of an excess of NaI or (KI), then iodine formed is titrated with thiosulfate. Sometimes a small amount of acid is added to iodide solution.  In any case acid cannot be added to bleach before titration.

[MartynYarrow]

The procedure is :

1)pipette 10ml of bleach solution and diluted to 250 ml
2)pipette 25ml of dil bleach solution , add about 15ml potassium iodide
solution followed by 10ml glacial acetic acid
3)Titrate the liberated iodine w/ standardized thiosulphate
when the mixture has reached to pale lemon yellow and add 0.5 ml of 1%
starch indicator and cotinue the titration until colorless

[AWK]

It seems to be a quite normal procedure. Since bleach is hardly alkaline, and iodine can react with alkali, solution should be neutralized. In many procedures of bleach determination a small amount of H2SO4 is added to KI before mixing with bleach. H2SO4 decompose thiosulfate and cannot be use in an excess. But I do not understand, why to a water solution of the reaction mixture a glacial acetic acid should be added. In my opinion a diluted acetic acid will be absolutely sufficient.  I think, your procedure comes from other methods of determination, eg spectrophometrical in which a very narrow pH range is needed.