ABSTRACT
Various workers have discussed the determination of total alkalinity and carbonate [1-3] and the carbonate bicarbonate ratio [3] in sea water. A typical method utilises an autoanalyser. Total alkalinity (T m-equiv. per litre) is found by adding a known (excess) amount of hydrochloric acid and titrating back with sodium hydroxide solution; a pH meter that records directly and after differentiation is used to indicate the end point. Total carbon dioxide (C m-equiv. of bicarbonate per litre) is determined by mixing the sample with dilute sulphuric acid and segmenting it with carbon dioxide free air, so that the carbon dioxide in the sample is expelled into the air segments; the air is then separated from the sample and passed into buffered phenolphthalein solution, thereby lowering the pH and diminishing the colour of the phenolphthalein. The reduction in colour is measured colorimetrically (540 nm). The concentration of carbonate is given by 2 (T - C) m-equiv. L and the concentration of bicarbonate is 2C - T m-equiv. L _1.
