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测定氯化钠含量的方法,中国药典和美国药典均系加一定量的硝酸银标准溶液使生成氯化银沉淀后,再用硫氰酸铵液反滴定剩余的硝酸银液。此法文献上称为弗尔哈德(Volhard)氏法。苏联药典和英国药典均系采用铬酸钾为指示剂,直接用硝酸银标准溶液滴定的方法,此法文献上称为摩尔(Mohr)氏法。近来在实际工作中发现,采用中国药典方法测定含量时,有数批检品其含量恰好在不合格的边缘,用中国药典法测定为99.40%;而用重量法或摩尔氏法测定,一般为99.80%左右,则合于中国药典规定。为此,我所曾对三种方法(重量法、摩尔氏法、弗尔哈德法)进行了比较试验,现将结果分述如后。试药:氯化钠:规格有 A.R.C.P.普通和注射四种。N/10 AgNO_3液:用 A.R.AgNO_3 按中国药典第二法配制和标定(用垂熔坩埚代替古氏坩埚)。N/10 NH_4SON 液:用 A.R.NH_4SCN,按中国药典
Determination of sodium chloride content of the Chinese Pharmacopoeia and the United States Pharmacopoeia are a certain amount of silver nitrate standard solution to generate silver chloride precipitation, and then ammonium thiocyanate anti-titration of the remaining solution of silver nitrate. This French document is called the Volhard method. Soviet Union Pharmacopoeia and British Pharmacopoeia are the use of potassium chromate as an indicator, the direct use of silver nitrate standard titration titration method, this method is called the Mohr’s law. Recently in the actual work found that the use of Chinese Pharmacopoeia method for the determination of content, there are several batches of seized its content just in the unqualified edge, with the Chinese Pharmacopoeia Determination of 99.40%; and by gravimetric method or the molar method, usually 99.80 % Or so, then the provisions of the Chinese Pharmacopoeia. To this end, I have conducted a comparative test of the three methods (gravimetric method, mole method, vorhad method), and the results are as follows. Reagents: Sodium chloride: A.R.C.P. specifications are common and four kinds of injection. N / 10 AgNO_3 solution: Prepare and calibrate with A.R.AgNO_3 according to the Chinese Pharmacopoeia second method (use the vertical melting crucible instead of the old crucible). N / 10 NH_4SON solution: A.R.NH_4SCN, according to Chinese Pharmacopoeia