论文部分内容阅读
现行的硝酸钠国家标准(GB4553—84)中规定测定硝酸钠含量,采用定氮合金在强酸性介质中还原硝态氮,用蒸馏法蒸馏还原出来的氨,并用定量的硫酸溶液吸收,再以氢氧化钠标准滴定溶液回滴。这个方法的原理是经典的。但是,在测定空白值时,由于滴定终点的化学环境和样品测定终点时的化学环境不同,如果按标准规定采用同一种指示剂(甲基红-亚甲基蓝混合指示剂),就产生了一个系统误差,导致实际测定结果偏低3‰左右。
The current sodium nitrate national standard (GB4553-84) provides for the determination of sodium nitrate content, the use of fixed-nitrogen alloy in strong acid medium reduction of nitrate nitrogen, distilled by distillation to recover the ammonia, and quantitative sulfuric acid solution to absorb, and then Sodium hydroxide standard titration solution back drop. The principle of this method is classic. However, when measuring the blank value, a systematic error is generated if the same indicator (methyl red-methylene blue mixed indicator) is used as standard because the chemical environment at the end of the titration differs from the chemical environment at the end of the sample measurement , Resulting in the actual measurement of low 3 ‰ or so.