If you're interested in forensic toxicology and are trying to determine the presence of salicylate by using a visual colorimetry, then look no further. This indepth and compelling video takes you into world of salicylate determination.
Salicylate determination with visual colorimetry, Part I
Using iron(III) nitrate to determine salicylate concentration in standardized salicylate solutions and urine.
You can actually use any iron(III) salt, such as ferric chloride, ferric ammonium sulfate, and so on. Concentration is not critical