Based on the catalytic effect of nitrite on the color fading reaction of oxidation of thymol blue by potassium bromate in dilute phosphoric acid solution , a catalytic kinetic photometric method for the determination of trace amounts of nitrite was developed .
Control methyl violet dipstick methods , through determination of 50 non-acid free samples with thymol blue grass phenol methods , determination found that the results easy to produce false-positive and false-positive rate was 80 % .
