1977 Volume 24 Issue 3 Pages 136-141
An apparatus for measuring the organic acid content was designed and constructed. The apparatus was equipped with constant current unit. The impedance signal measured was converted from analoguetodigital and represented as acid content(%), i.e. as citric acid content for Satsuma mandarin juice, after arithmetrically computed with the corresponding equation. Compensation for the error resulted from the circuit was carried out automatically with the internal standard resistance at every measurement. The error of measurement was within 0.1% as conductance value.
A special temperature correction method was developed by a combination of a standard potassium chloride solution and the temperature coefficient of organic acid. In using the method, the acid content could be determined at the temperature range 5-35°C and the deviation was less than O.04% as citric acid.
The devised correction method was independent of the kind of organic acid, regardless of the variety of pK1. The correction of the empirical errors, introduced by the measuring cell and contaminants in measuring water, and the check of reading would be simultaneously achieved by the temperature correction.
