An Interlaboratory Test of pH Measurements in Rainwater.

An interlaboratory test of pH measurements in rainwater has been conducted. Various types of electrodes and junction materials were used in this test. The results of this exercise verify that there are significant differences in the pH values of low ionic strength solutions reported by various laboratories. Other work suggests that these differences are due to residual liquid junction potentials. Furthermore, this test confirms the efficacy of using dilute solutions of a strong acid as working standards for pH measurements in acid deposition studies.