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本文在改进铜的碘量法分析的基础上,建立起无铬木质素中铜的分析方法,对于研究和改进无铬木质素的性能有重要作用。其方法是:在酸性条件下,先以(NH_4)_2S_2O_8氧化分解木质素,再以NaCl除尽多余的(NH_4)_2S_2O_8,适度浓缩驱赶HAc。尔后调整PH,以NaF+K_2[CH(OH)COO)_2为掩蔽剂兼缓冲剂,KSCN为沉淀剂,倾入准确的过量Na_2S_2O_3标准溶液,淀粉为指示剂,用标准I_2液滴定之。该法抗干拢性强,终点鲜明,重现性好,检出下限达1mg铜,完全满足无铬木质素中铜分析的要求。
In this paper, based on the improvement of copper iodometry, the analytical method of copper in chromium-free lignin is established, which plays an important role in the research and improvement of the properties of chromium-free lignin. The method comprises the following steps of: oxidating lignin with (NH_4) _2S_2O_8 under acidic conditions, and then removing (NH_4) _2S_2O_8 with excess NaCl to moderately drive the HAc. The pH was then adjusted to NaF + K 2 [CH (OH) COO) 2 as a masking agent and buffer. KSCN was used as a precipitating agent and poured into an accurate excess of Na 2 S 2 O 3 standard solution. Starch was used as an indicator and calibrated with a standard I 2 droplet. The method is strong anti-dry, clear end, good reproducibility, the detection limit of 1mg of copper, fully meet the chromium-free lignin in the analysis of copper requirements.