Avoid reaction when using ph meter
How to avoid the measured solution and salt bridge component reaction?
If the test solution contains soluble silver salts, monovalent mercury salts, or thallium salts, potassium chloride should not be used in the salt bridge. Saturated potassium nitrate or ammonium nitrate should be used to obtain satisfactory results. The non-aqueous solution is the application of sodium iodide in methanol and potassium thiocyanate in ethanol as the intermediate solution.
In short, the composition of salt bridge solution can not be precipitated with the measured solution, redox reaction phenomenon, otherwise it will interfere with the determination of electromotive force.