液体推进剂混胺燃料中作为主要组分存在的三乙胺使其显示较高的碱性,对用卡尔费休滴定法测定其水分含量时产生干扰。提出了在试样的甲醇滴定介质中加入一定量的乙酸,保持液体混胺试样和乙酸的体积比小于或等于3比5,达到使滴定介质的酸度控制在最佳pH范围5~6之间。经此操作,由三乙胺的高碱度引起的干扰可消除。对已知水分含量的混胺试样按方法进行分析,算得其水分测定值的相对标准偏差(n=12)为2.1%。取不同批号的混胺试样7件,按方法进行分析并用标准气量法对结果进行校核。两种方法测定结果的相对偏差在-0.023%~0.033%之间。又根据t-检验法的结果认定,两方法所得测定值之间不存在显著差异。

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.