DETERMINATION OF CARBON DIOXIDE

IN WATER

SAIMA ALEEM

M.PHIL ENVIRONMENTAL CHEMISTRY

DETERMINATION OF CARBON DIOXIDE IN WATER

Introduction Surface waters• Surface waters normally contain less than 10 ppm free carbon dioxide. Ground water• Ground waters may easily exceed that

concentration.

DETERMINATION OF CARBON DIOXIDE IN WATER

Classical method • Buret titration method.

• Improved evolution method.

Instrumental method• Coulometry method.

DETERMINATION OF CARBON DIOXIDE IN WATER BY Buret

titration method

• Fill the burette with standarized sodium hydroxide.

• Take a 100 ml of sample in a conical flask .• Add 10 drops of Phenolpthalein indicator.

CO2 + NaOH NaHCO3 + Na+ + H2O

DETERMINATION OF CARBON DIOXIDE IN WATER BY Buret

titration method

precaution

• Sample must be fresh.• performed immediately after collection of

water sample.

DETERMINATION OF CARBON DIOXIDE IN WATER BY IMPROVED EVOLUTION METHOD

REAGENTS • 1.5 N sulfuric acid (for acidifying the sample).• 0.03N barium hydroxide (for absorbing carbon

dioxide).• Standard 0.04N hydrochloric acid( for titrating

the barium hydroxide).• Phenolphthalein indicator.

DETERMINATION OF CARBON DIOXIDE IN WATER BY IMPROVED EVOLUTION METHOD

Blank determinations• Transfer 200 ml boiled dislled water

in flask “A”.• Introduce 40 ml. of barium hydroxide

solution into the absorption tube, C. • Add 0.2 ml. of phenolphthalein

indicator.• Acidify the sample by the addition of

25 ml. of 1.5 N sulfuric acid from buret “I”.

• Apply heat to it by means of the 300-watt hot plate.

• After 15 minute of recirculation barium hydroxide is titrated with

standrized hydrochloric acid.

DETERMINATION OF CARBON DIOXIDE IN WATER BY IMPROVED EVOLUTION METHOD

Sample determination• Transfer 200 ml water sample in a flask

“A”.• Introduce 40 ml. of barium hydroxide

solution into the absorption tube, C. • Add 0.2 ml. of phenolphthalein

indicator.• Acidify the sample by the addition of 25

ml of 1.5 N sulfuric acid from buret “I”.

• Apply heat to it by means of the 300-watt hot plate.

• After 15 minute of recirculation barium hydroxide is titrated with

standrized hydrochloric acid.

DETERMINATION OF CARBON DIOXIDE IN WATER BY INSTRUMENTAL METHOD

DETERMINATION OF CARBON DIOXIDE IN WATER BY COULOMETRY

Collection of sample

• Sample are drawn into 12 individually borosilicate glass bottles.

DETERMINATION OF CARBON DIOXIDE IN WATER BY COULOMETRY

Procedure• First the back ground level and calibration

factor have been determined.• Dispense the sample (30 cm3) into the stripping

chamber.• Acidify it with phosphoric acid (1.5 cm3).• Record the final coulometer reading.• when the coulometer titration rate returns to the

background level ,system is ready to analyze next sample.

“ THANK YOU”