Determination of ammonia-nitrogen used indophenol method (method phenate). This method of giving out a good result for the waters of the pool water. reagent used is phenate (phenol), chlorox (oxidizing solution) and manganese sulphate. phenol and hypochlorit (chlorox) action in the solution is alkaline-forming phenylquinone monoimine which would then be reacted with ammonia to indophenol blue. blue color density comparable to existing levels of ammonia.