the content of petroleum in domestic sewage is greater than that of animal and vegetable oil, when the oil content in water is 1. 15—11 mg/L, non-dispersive infrared spectrophotometry, infrared photometry and ultraviolet spectrophotometry can be used for determination. Among them, ultraviolet spectrophotometry mainly analyzes aromatic hydrocarbons with strong odor and toxicity, but does not include all petroleum. The extractant used in dispersion infrared spectrophotometry and infrared photometry is carbon tetrachloride or trichlorotrifluoroethane, and the extractant used in gravimetric method and ultraviolet bisection solubility method is petroleum ether. Westbank >

full-automatic infrared oil analyzer EP3111B

full-automatic ultraviolet oil analyzer UV3111B

2. chroma refers to the true color of water. It only refers to the color produced by dissolved substances in water samples, while the color of the same product of dissolved substances and insoluble suspended substances is the apparent color of water. The sewage treatment system usually determines the apparent color of treated sewage by dilution multiple method. There are three kinds of substances that form alkalinity, such as strong alkali (sodium hydroxide, potassium hydroxide) that can completely dissociate hydroxide, weak alkali (ammonia water, aniline) that partially dissociate hydroxide, and salts composed of strong alkali and weak acid (such as sodium carbonate, potassium phosphate, sodium sulfide). The alkalinity is determined by titration with a strong acid solution. When titrating, methyl orange ALK；alinity or total alkalinity alk is used; The alkalinity measured by phenolphthalein as an indicator is called phenolphthalein alkalinity, including the alkalinity formed by the first kind of strong alkali and the partial alkalinity formed by the third kind of strong alkali salt.

4. The acidity of water refers to the amount of substances contained in water that can neutralize strong alkali. There are three kinds of substances that form acidity: strong acid that can dissociate all hydrogen ions, weak acid (carbonic acid, organic acid) that partially dissociates hydrogen ions, and salts (ammonium chloride, ferrous sulfate, etc.) composed of strong acids and weak bases. Acidity is determined by titration with a strong alkali solution. The acidity measured by using methyl orange as indicator during titration is called methyl orange acidity, including the acidity formed by the first kind of strong acid and the third kind of strong acid salt; The acidity measured with phenolphthalein as indicator is called phenolphthalein acidity, which is the sum of the above three kinds of acidity, so it is also called total acidity.