关键词: 电热恒温消解, 电位滴定, 土壤, 有机质, 测定

Abstract: A method for determining soil organic matter content using electric heating constant temperature digestion potentiometric titration was established. The soil sample was weighed and placed in a digestion tube. 10 mL of 0.4 mol/L K₂Cr₂O₇-H₂SO₄ solution was added, and the sample was digested using an electric digestion apparatus at 180 ℃ for 10 minutes. After the digestion solution cooled down, the remaining potassium dichromate was titrated using a fully automatic potentiometric titrator with 0.2 mol/L K₂Cr₂O₇-H₂SO₄ solution. The soil organic matter content was calculated based on the consumption of ferrous sulfate. The results showed that the relative standard deviation （RSD） of organic matter content in five field soil tillage samples ranged from 0.80% to 1.36%;the relative error of organic matter content in 5 soil standard samples[NST-4,GBW07414a（AsA-3a）,GBW07415a（AsA-4a）,GBW07460（AsA-9） and GBW07461（AsA-10）] ranged from 0.97% to 2.39%. The electric heating constant temperature digestion potentiometric titration method had good sensitivity and precision, which could achieve automatic titration control and data processing functions, improve detection efficiency, and was suitable for batch detection of organic matter in soil samples.

Key words: electric heating constant temperature digestion, potentiometric titration, soil, organic matter, determination