利用GRIESS反应做重氮化法含量测定内指示剂的研究

(一)按Griess反应芳香族胺类的重氮化鹽,如对氨基苯磺醯胺类药物等,在酸性溶液中皆能与α-萘胺或二苯胺分别偶合成偶氮色素而显紅色,过多之亞硝酸可与氮色素再作用使紅色消失而呈棕黄色。二苯胺为較好的内指示剂。(二)本法仅用于無色溶液。滴定至全量的三分之二以后加入指示剂較适宜。(三)本反应宜在溴化鉀存在下进行。

APPLICATION OF THE GRIESS REACTION IN THE STUDY OF INTERNAL INDICATOR FOR DIAZOTIZATION DETERMINATION

(1) According to Griess reaction, diazonium-salts formed from aromatic amines such as sulfonamides etc., react with NaNO₂ in acid medium and may be coupled with α-naphthylamine or diphenylamine to produce red colored compounds. In presence of excess NaNO₂, these red colored compounds will further Change to brownish yellow. For diazotization titration, diphenylamine is used as a good internal indicator. (2) Internal indicator may be used only in colorless solution and the end point is not sharp. (3) KBr should be added as a catalyst not only to accelerate the velocity of diazotization, but also to decrease the interaction between azo dyes and nitrous acid. (4) The indicator should be added after the addition of two-third of the amount of NaNO₂ required (the total quantities of NaNO₂ used amounted to 30ml) or before the addition of the last 5ml of NANO₂. The results thus obtained show practically no difference from these obtained by external indicator method.