A Simple and Fast Method of pH Measurement for Wood

The pH of freshly cut red oak heartwood exposed to steaming at atmospheric pressure for periods of 0, 1-l/2, 3, 6, 12, 24, 48, and 96 hours was determined using three different methods. One method was that developed by the U. S. Forest Products Laboratory on wood meal suspended in distilled water. The second method involved suspension of wood meal in unbuffered HCl solution for periods of 5 and 30 minutes. The third method involved extraction of wood fluids by a hydraulic press and measurement of pH, of, the press-extracted liquid. Wood pH ranged from 2.85 to 3.69; pH decreasing with increasing steaming time. Results showed that pH of wood obtained from measurements on press-extracted fluids was slightly lower than the values obtained by conventional methods. This was attributed to the lower liquid-to-wood ratio when the extraction method was used. Increasing relative water content of the distilled water suspension increased pH values. HCl suspensions gave increasing pH values with increasing wood meal content. It was concluded that the new method involving pH measurements on press-extracted wood fluids is simpler and faster than either of the two conventional methods examined when the experimental material has a high moisture content. In addition, pH values obtained from these extracts better correspond to those of the actual moisture in wood and less influenced by experimental conditions.

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