Differential test: Benzoate test (IT-5) was positive. Or adding ferric chloride test solution (TS-101) to 10% sample solution, light yellow precipitation should be generated. Potassium test (IT-27) was positive. Or acidify 10% sample solution with dilute hydrochloric acid test solution (TS-117) and filter. Adjust the filtrate to neutral with sodium hydroxide test solution (TS-224), add 1 part (volume) saturated sodium bitartrate solution and 1 part (volume) ethanol, then shake. There should be white crystalline precipitate formation. 

Content analysis: Sample pre-dried by 105% to constant weight 2.5-3G (accurate to 0.1mg), dissolved in 50ml water. After neutralization with 0.1mol/L hydrochloric acid [phenolphthalein test solution (TS-167) as an indicator]. Add 50 ml of ether and several drops of bromophenol blue solution (TS-53), and titrate with 0.5mol/L hydrochloric acid under constant shaking until the color begins to change. Separate the lower water layer, wash the ether layer with 10 ml water, and add the lotion and another 20ml ether into the separated water layer. Titrate with 0.5 mol/L hydrochloric acid under constant shaking. Each ml0.5mol/L hydrochloric acid is equivalent to potassium benzoate (C7H5KO2)80.1 lmg.