Mix Sodium phosphate monobasic (SPM) and dibasic (SPD) solutions in the proportions

indicated and adjust the final volume to 200 ml with deionized water. Adjust the

final pH using a sensitive pH meter.

ml of SPM 92.0   81.5   73.5   62.5   51.0    39.0     28.0    19.0    13.0       8.5       5.3

ml of SPD 8.0    18.5    26.5   37.5   49.0     61.0   72.0      81.0     87.0     91.5     94.7

pH              5.8     6.2     6.4      6. 6     6.8       7.0      7.2        7.4       7.6        7.8      8.0