Abstract: In a potentiometric system for measuring low levels of ion activity, a method of adjusting the pH in a sample stream by the passive addition of low molecular weight acid or base reagent, without dilution of the sample stream, and without introduction of any interfering, reactive or test ions into the sample stream. A membrane is provided, permeable to the acid or base reagent used to adjust sample stream pH, and impermeable to ionic species. The membrane is placed between a reagent reservoir and the sample stream. Constant flow of the sample stream by the membrane maintains the reagent partial pressure differential between the reservoir and the stream, causing diffusion of reagent through the membrane into said stream.

Abstract: An improved electrochemical reference electrode for use in potentiometric determinations of species in solution. The body of the electrode is composed of a material substantially permeable to liquid water whose exterior surface, excepting a comparatively small area, is covered by a membrane through which water may pass only by diffusion and which is also ion impermeable. The small area which is not covered forms an opening through the membrane to the body. The body contains a saturated salt slurry. When the electrode is immersed in an aqueous sample solution, water diffuses through the membrane and is transported in bulk across the body. Upon entry into the slurry, the water dissolves the solid salt in the slurry to produce an electrolyte which in turn flows outward through the small area of the body which is not covered by the membrane, whereby a liquid junction is provided between the electrolyte and the sample solution.

Abstract: In a potentiometric system for measuring low levels of ion activity, a method of adjusting the pH in a sample stream by the passive addition of low molecular weight acid or base reagent, without dilution of the sample stream, and without introduction of any interfering, reactive or test ions into the sample stream. A membrane is provided, permeable to the acid or base reagent used to adjust sample stream pH, and impermeable to ionic species. The membrane is placed between a reagent reservoir and the sample stream. Constant flow of the sample stream by the membrane maintains the reagent partial pressure differential between the reservoir and the stream, causing diffusion of reagent through the membrane into said stream.