Determination of Moisture in Liquid Amine Mixture Propellant Fuel by Karl Fischer Titrimetry

The high alkalinity of the liquid amine mixture due to the presence of macro amount of triethylamine behaved to interfere with the determination of moisture in the amine mixture sample by the Karl Fischer titrimetry. It was proposed that a definite amount of acetic acid was added to the sample in the methanol titrating medium, keeping volumic ratio of the liquid sample to acetic acid less than or equal to 3 to 5, to control the acidity of the medium in the range of pH 5 to 6, which is optimal for the titration. The interference of high alkalinity due to triethylamin was thus eliminated. Precision of the method was tested by analyzing an amine mixture sample of known moisture content (w 0.58%) for 12 determinations, giving value of RSD 2.1%. Seven samples of amine mixture from different batches were analyzed by the proposed method, and checked with the standard gasometric method, giving values of relative deviation between results of the 2 methods in the range of -0.023% to 0.033%. No significant difference was found between the results of the 2 methods as shown by the results of t-test.