Abstract: An improved hydrazine analyzer is disclosed wherein sample and electrolyte solutions are supplied from constant flow rate sources into a mixing chamber where they are premixed. The premixed combination of electrolyte and sample is then passed through a sensing chamber having a sensing thimble disposed therein. The thimble is of a porous material having a platinum wire electrode wound about the outside thereof and having a silver wire inserted into silver chloride salt on the inside thereof to form a reference half cell. As the electrolyte-sample mixture passes through the sensing chamber, a portion of the fluid passes from the outside of the thimble to the inside of the thimble wetting the silver chloride salt to establish electrical contact and provide the internal filling solution of the reference half cell.