How can the pH of a non-aqueous liquid be measured?
The pH scale is defined in terms of hydrogen ion activity in aqueous solution and is not therefore strictly applicable to pH measurement in non-aqueous systems. If measurements are to be performed in non-aqueous liquids, there are several problems which may be encountered. The low ionic strength and low conductivity of some non-aqueous solvents may result in high noise or drift. In addition, the glass membrane of the pH electrode may become dehydrated from immersion in the non-aqueous solvent and thus lose its ability to respond to H+ ions. The ideal way to minimize these effects is to use a separate reference and measuring electrode with an auxiliary salt bridge containing a non-aqueous electrolyte filling solution .If this is not available a standard pH electrode may be used providing the following steps are performed: • Select an electrode with a low resistance membrane and a free flowing diaphragm such as the Schott Blueline 13. • Use an electrode containing a non-aqueous filling s
