抄録
In determining pH of water having a small buffer capacity divergent values for pH were obtained by the ordinary method, whereas by Tomiyama's method2) a consistent value was obtained irrespectively of the values for the buffer capacity of sample waters. Experiments have been carried out to see an extent of error in the measurement of pH of waters having small buffer capacity. The magnitude of error was found to be of valiance not only with buffer capacity but also with pH value of a sample water. This phenomenon has been elucidated by taking into account the variation in buffer capacity with pH value of the water.
A mathematical treatment has been made to find out a formula which enables us to calculate the magnitude of the deviation by knowing values for pH and the buffer capacities of a sample water and an indicator. It has clearly been shown that the values for the deviation calculated by use of the present formula were in good agreement within the experimental error with those obtained in the present experiments.
