Abstract
Since the nitrite ion has absorption maximum at 355mμ, photometric titration was carried out with the spectrophotometer set at 355mμ. It was found that sulfanilamide and sulfacetamide could be determined with good accuracy without being affected by the absorption of their own diazonium salts at 355mμ. In the case of sulfaguanidine, sulfathiazole, sulfadiazine, and sulfamerazine, the absorption of the respective diazonium salts formed affects absorption at 355mμ. Absorption spectra of these sulfonamides were therefore measured over the whole range of ultraviolet region before, during, equivalence point, and excess of titration. The spectrophotometer was then set at the determined wave length and determination was carried out, by which it was found that the determination of these sulfonamides was possible, as in the case of sulfanilamide and sulfacetamide. This kind of photometric titration has smaller individual difference than the existing method using zinc iodide-starch solution as an indicator. Consequently, determination of sulfanilamides by photometric titration makes it possible to calculate the amount of sulfanilamides from the crossing of two straight lines and the determination can be made with a minute amount of sample.
