pH values of the Clark and Lubs buffer solutions at 25 C

The pH valucs of the well-known Clark and Lubs burrcr solutions havc been dctermined at 25 C on the convcntional activity pH scale dcfined by thc NBS standards. These solution s, which a rc useful for pH control in the rangc 1 to 10, a r c rca dily prcpared by combin ing portions of four stock solu tions with standard so lu t ions of hyd rochloric acid or sodium hydroxide. The fom stock solutions contain potassium chlo rid e, potassium hyd rogen phthalate potassium dihydrogen phosphate, or boric ac id and potassium chl or ide. The compositi~ns and buffcr values of the solu t ions are listed at interva ls of 0 .1 pH. Th e estimated accuracy is 0.02 pH unit.