CONCENTRATION MEASURING METHOD AND FUEL BATTERY SYSTEM

PROBLEM TO BE SOLVED: To provide a concentration measuring method that can measure the concentration of hydrazine solution with high precision, and a fuel battery system having concentration measuring means adopting the concentration measuring method.SOLUTION: A method of electrochemically measuring the concentration of hydrazine in hydrazine solution containing alkali metal hydroxide comprises: bringing an action electrode 51, a counter electrode 52 and a reference electrode 53 of an electrochemical measuring device 50 into contact with the hydrazine solution (preparation step), sweeping the potential of the action electrode 51 in a positive potential direction and detecting the concentration of alkali metal hydroxide on the basis of a current value occurring at a predetermined potential (first detection step), further sweeping the potential of the action electrode 51 in the positive potential direction when the concentration of alkali metal hydroxide is equal to a predetermined value, and measuring the concentration of hydrazine by detecting variation of current (second detection step), and adjusting the concentration of alkali metal hydroxide when the concentration of alkali metal hydroxide is not equal to the predetermined value (concentration adjusting step). 【課題】ヒドラジン溶液の濃度を精度よく測定することができる濃度測定方法、および、その濃度測定方法が採用される濃度測定手段を備える燃料電池システムを提供すること。【解決手段】アルカリ金属水酸化物を含むヒドラジン溶液中のヒドラジン濃度を電気化学的に測定する方法において、ヒドラジン溶液に、電気化学測定装置５０の作用電極５１、カウンタ電極５２および参照電極５３を接触させ（準備工程）、作用電極５１の電位を正電位方向に掃引し、所定の電位において生じる電流値からアルカリ金属水酸化物の濃度を検知し（第１検知工程）、アルカリ金属水酸化物の濃度が所定値であるときに、作用電極５１の電位をさらに正電位方向に掃引し、電流変化を検出することによりヒドラジン濃度を測定し（第２検知工程）アルカリ金属水酸化物の濃度が所定値でないと検知されたときに、アルカリ金属水酸化物の濃度を調整する（濃度調整工程）。【選択図】図２