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一、前言铵态氮的测定最常采用的方法有甲醛法及蒸馏法。在硫酸铵与硝酸铵中测定氮时,一般认为甲醛法是标准法,但甲醛法只适合于纯硫酸铵或硝酸铵的分析。如系混合肥料,其中掺入了其他成分,则甲醛法不能应用。因为PO_4~≡、Ca~(++)、Fe~(+++)、Al~(+++)等都有干扰,即在两终点间H_2PO_4~-变成HPO_4~≡,影响滴定,并且Ca~(++)、Al~(+++)、Fe~(+++)能生成沉淀,使结果不明确。蒸馏法需要一套完整的蒸馏装置,测定时间较长,蒸馏装置必须严密,否则结果偏低。我们采用氧化还原法测定铵态氮,只要样品中不含有Fe~(++)、Cu~(++),分析结果与甲醛法、蒸馏法相符合,
I. Introduction Determination of ammonium nitrogen is the most commonly used method for formaldehyde and distillation. The determination of nitrogen in ammonium sulfate and ammonium nitrate, the formaldehyde method is generally considered the standard method, but the formaldehyde method is only suitable for pure ammonium sulfate or ammonium nitrate analysis. If the compost, which incorporates other ingredients, the formaldehyde method can not be applied. Because PO 4 ~ ≡, Ca ~ (++), Fe ~ (+++), Al ~ (+++) and so on have interference, that is between the two end points H 2 PO 4 ~ - becomes HPO 4 ~ ≡, affecting titration, and Ca ~ (++), Al ~ (+++), Fe ~ (+++) can precipitate, making the result unclear. Distillation requires a complete set of distillation apparatus, the determination of a longer time, the distillation unit must be tight, otherwise the result is low. We use the redox method for the determination of ammonium nitrogen, as long as the sample does not contain Fe ~ (++), Cu ~ (++), the analytical results with the formaldehyde method, distillation method consistent,