Abstract:Abstract: Purpose: To evaluate the uncertainty of measuring 65% aqueous nitric acid solution oxidation with liquid oxidizing test. Methods: The method of liquid oxidizing test was adopted to measure 65% aqueous nitric acid solution oxidation, and the mathematical model thereof built. According to relevant rules and standards of the evaluation of uncertainty, uncertainty factors in the test including repetitive operation, moisture content of cellulose fiber, resistance of heating wire, pressure sensor, etc. were evaluated. Results: When the test time of 65% aqueous nitric acid solution oxidation was 2.534 s, its expanded uncertainty was 0.162 s (P=95%, k=2). Conclusion: Uncertainty of 65% aqueous nitric acid solution oxidation mainly comes from repetitive measurement, solubility of the standard solution, and length and resistance of the heating wire.