The aim of this standard is to describe two different procedures for the determination of water-soluble chloride ion content in soil samples, expressed in mg/kg.
The first method is based on Mohr´s procedure to determine the chloride ion with silver nitrate. The chloride reacts with the silver ion before silver chromate is formed, due to the lower solubility of silver chloride. The potassium chromate indicator reacts with excess silver ions to form a red silver chromate precipitate to the end point with permanent orange coloring. This method is suitable for analyzing solutions with a pH between 6.0 and 8.5. If necessary, the pH can be raised and the hydroxides of several metals, including iron, can be filtered off. Iron, barium, lead, and bismuth precipitate with the chromate indicator.
The second method utilizes a pH/mV meter equipped with a chloride ion electrode to determinate the water-soluble chloride ion content of soils by the use by comparing the mV readings to the electrode calibration curve, previously obtained. Samples containing from 10 to 1000 mg/kg of chloride can be analyzed by this test method.
Sulfide, bromide, iodide, thiocyanate, cyanide, phosphate, sulfite, carbonate, hydroxide, and iron interfere in the two methods described in this standard. Sulfide, sulfite, and thiosulfate can be removed with a peroxide treatment, but usually no attempt is made to remove bromide and iodide because they are usually present in insignificant quantities compared to chloride.
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Apr 8, 2025
