Dear Manoj,

This reagent can be prepared by the following procedure:

Preparation of Phenol (1, 3) - Disulphonic acid

Phenoldisulphonic acid was prepared by dissolving 25g of phenol in 150ml of conc. H2SO4. 35ml of fuming H2SO4 (30% SO3) was added and the solution was heated at 100ºC for 2 hours on water bath.

http://www.arpapress.com/volumes/vol7issue2/ijrras_7_2_15.pdf

Hoping this will be helpful,

Rafik

Dear Manoj,

This reagent can be prepared by the following procedure:

Preparation of Phenol (1, 3) - Disulphonic acid

Phenoldisulphonic acid was prepared by dissolving 25g of phenol in 150ml of conc. H2SO4. 35ml of fuming H2SO4 (30% SO3) was added and the solution was heated at 100ºC for 2 hours on water bath.

http://www.arpapress.com/volumes/vol7issue2/ijrras_7_2_15.pdf

Hoping this will be helpful,

Rafik

Please check the initial color of phenoldisulfonic acid (which is dependent on the purity and initial color of the reagents used for the manufacture of PDSA). To develop the characteristic color hue a strong alkali needs to be used anyway. Therefore, there should not be any problem to use acidic solution of PDSA for photometric analysis of nitrogen.

Kindly read The Determination of Nitrate in Wastewater from Nine Selected Areas of Coastal Guyana Via a Spectrophotometric method; link http://www.arpapress.com/volumes/vol7issue2/ijrras_7_2_15.pdf