Before revision: By means of mixing different chemical (The standard solutions are made with distilled water, ammonia, copper sulphate, potassium-chromate and cobalt-sulphate) a color palette is produced in a series of numerically designated vials (1-21) which is compared with the color of the water body.
After revision: By means of mixing different chemical (The standard solutions are made with distilled water, ammonia, copper sulphate, potassium-chromate and cobalt-sulphate) a standard color scale is produced in a series of numerically designated vials (1-21) which is compared with the color of the water body.