AS 3550.2-1990

Sets out a titrimetric method for determining the carbon dioxide content of waters in concentration range 1 to 100mg/L.

This Standard sets out a titrimetric method for the determination of free carbon dioxide in waters using either a coloured or potentiometric end-point.As carbon dioxide may be present in the free form or chemically combined as carbonates or bicarbonates, a means for determining the total carbon dioxide from the concentration in all forms is provided in Appendix A. The method is applicable to waters containing free carbon dioxide in the concentration range 1 mg/L to 100 mg/L.Interferences: Cations and anions that quantitatively disturb the normal carbon dioxide-carbonate equilibrium interfere with the determination. Aluminium, chromium, copper and iron are some of the metals whose salts contribute to high results. The iron(II) concentration should not exceed 1.0 mg/L. Positive errors are caused by amines, ammonia, borate, nitrite, phosphate, silicate and sulfide. Mineral solids and salts of strong acids and weak bases affect the determination and therefore should be absent. Negative errors may be introduced by high total dissolved solids, such as those encountered in seawater, or by adding excess indicator.

Reconfirmed 2016. First published as AS 2448-1981. Revised and redesignated AS 3550.2-1990.