A potentiometric detector for hydrogen cyanide gas using silver dicyano complex

A sensitive method capable of detecting Hydrogen cyanide gas in atmosphere at its TLV is being presented. This method makes use of two silver electrodes kept in two separate compartments which are in contact with a solution of constant concentration of Silver dicyano complex at a pH 11.5. One of the electrodes used as reference is concealed and the other used for sensing is exposed to the incoming air. In the absence of Hydrogen cyanide gas the potential difference between the two electrodes is zero, but when hydrogen cyanide gas is passed into the cell, the activity of Ag(+) ions nearer to the sensing electrode changes, there by generating a potential difference between the two electrodes. The plot between the potential vs. log of Concentration of Hydrogen cyanide gas is linear, in the concentration range 0.66-42.3 mg/m(3) with a slope nearer to 120mV and regression coefficient around 0.997. The standard deviation is 6% (n=4). Minimum detectable limit is 0.66 mg/m(3). Various concentrations of Silver dicyano complex used gave similar plots.