This document describes methods for determining the amount of carbon dioxide in water samples. It discusses how surface waters typically contain less than 10 ppm of free carbon dioxide while ground waters often exceed this level. The classical buret titration method and improved evolution method are described for determining carbon dioxide concentration. An instrumental coulometry method is also mentioned. The document provides details on reagents, procedures, and precautions for the buret titration method, which involves titrating a water sample with sodium hydroxide and measuring the amount of carbon dioxide absorbed.

1. DETERMINATION
OF
CARBON DIOXIDE
IN WATER
SAIMA ALEEM
M.PHIL
ENVIRONMENTAL CHEMISTRY

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

3. Classical method
Buret titration method.
Improved evolution method.
Instrumental method
Coulometry method.

4. 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

5. precaution
Sample must be fresh.
performed immediately after collection of
water sample.

6. 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.

7. 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.

8. 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.

9. DETERMINATION OF CARBON DIOXIDE IN
WATER BY COULOMETRY
Collection of sample
 Sample are drawn into 12 individually borosilicate
glass bottles.

10. 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.

11. “ THANK YOU”