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水杨酸钠碘化钠注射液的含量测定,部颁标准(1963年版)采用乙醚-水双相滴定中和法测定水杨酸钠的含量。滴定中,因生成的水杨酸难溶于水(1∶460),易溶于乙醚,水杨酸被不断的萃取到醚层中,从而使反应进行完全。本法用甲基橙作指示剂,用盐酸标准溶液滴定至水层显红色为终点。实验中发现,若乙醚中含有过氧化物,则水-醚两层均染色(醚层显橙黄色,水层显橙红色),无法确定终点。经分取醚层后,分取两份。一份中滴加淀粉指示液数滴显兰紫色,另一份中滴加硫代硫酸钠试液,橙黄色退去,
Sodium salicylate sodium iodide injection determination, the ministerial standard (1963 Edition) Determination of sodium salicylate by ether-water two-phase titration and neutralization. Titration, salicylic acid generated due to insoluble in water (1: 460), soluble in ether, salicylic acid is continuously extracted into the ether layer, so that the reaction was complete. Methyl orange as an indicator of this Act, with hydrochloric acid standard solution titration to the water layer was red as the end point. The experiment found that if the ether contains peroxide, the water - ether were stained both layers (ether layer was orange yellow, aqueous layer was orange red), can not determine the end. Divided by the ether layer, two points. A drop of starch indicator solution drops blue purple, the other in the drop of sodium thiosulfate test solution, the orange-yellow receded,