Chemical Equilibria in Mineral Water

Mineral waters stimulate the appetite, improve the bowel functions, promote digestion, act as diuretics and, naturally, still thirst these are real wonder drugs which are produced in the depths of the earth. They contain bicarbonates and valuable trace elements and are normally freed from iron and treated with carbon dioxide before being put on the market. A well-chilled mineral water works wonders on the morning after  

Full bottle of mineral water (no natural or artificial colorings ) with screw top, dropping pipette, 0.1 % alcoholic solution of bromocresol green, safety glasses. 

Bromocresol green is an indicator acid with a pK/ of 4.7 it colors solutions yellow below pH 3.8. This is due to the bicarbonate formed when carbon dioxide dissolves in water on cooling and at a sufficient pressure this affords a sufficient quantity of H3O ions (eqns. 1 and 2)  

A considerable amount of the carbon dioxide can escape when the bottle is opened, so that the pH lies between 3.8 and 5.4 and a green color is formed. The remaining gas can be displaced by vigorous heating of the contents of the bottle the pH value increases further and the color of the indicator changes to an intense blue.  

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As mentioned in the introduction to this section, there is a second class of programs that solve for chemical equilibrium in pre-defined systems. These contain built-in equilibrium constants, reactions, and sets of species. Many such programs are currently available and a good many of these have been summarized by Nordstrom and Ball (1984). Most of these programs describe chemical equilibria in mineral-water systems. 

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