Abstract
Colorimetric determination of ethoxybenzamide in mixed anti-cold pharmaceutical preparations was studied, and a new method with high accuracy and selectivity has been established. Hofmann rearrangement was carried out for ethoxybenzamide to yield o-phenetidine, which gave orange red coloration by diazotizing with sodium nitrite, followed by diazo-coupling with β-naphthol. The coloration shows its absorption maximum at 510mμ. Optimal conditions for Hofmann rearrangement and diazo-coupling were investigated and it was found that Hofmann rearrangement had to be carried out under cooling in ice-water. At the ordinary temperature and above, the calibration curve of ethoxybenzamide does not go through the origin, probably because some amount of the o-phenetidine produced would be decomposed further.
