Why this reaction occasionally produce conglomerates instead of the nice purple color we use to quantify parabenzoic acid?
1. Sample containing parabenzoic acid as analyte + NaOH; boiling; + HCl to pH 2
2. + sodium nitrate - to form the azo bonds
3. + sulfanilamide - to react extra nitrite
4. + azo-dye: (N-(1-Naphthyl)ethylenediamine dihydrochloride (NED))
the more analyte in the sample the faster the sediment shows up in the sample, the color is pinkish when sediments present