Carbon dioxide see also Chapter 1 and Section

Carbon dioxide dissolved in water (so-called free, dissolved carbonic acid) represents a significant factor in the chemical and biochemical make-up of 

The designation free, dissolved carbon dioxide stems from the ratio 

CO2 H2CO3 = 99 % i % in water. It is free in contrast to bonded hydrogen carbonate and carbonate, and dissolved differentiates it from the gaseous carbon dioxide frequently occurring in spring waters. 

dissolved carbon dioxide is determined acidimetrically by titration 

The determination of free, dissolved carbon dioxide in mineral waters containing particularly large quantities of carbonic acid (more than 1 g of CO2/I) can be carried out gravimetrically. The CO2 is fixed with sodium hydroxide solution or calcium oxide at the sampling point, distilled off in the laboratory, bonded to soda-asbestos and weighed. The result obtained is the total carbonic acid content of the water. The content of free, dissolved carbon dioxide can be calculated by subtracting the separately determined hydrogen carbonate content. 

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