The Determination of Chloride in Milk

Abstract

The direct titration of chloride in milk by modifications of Mohr's method, with silver nitrate and with potassium chromate indicator, yields results which are so erroneously high and variable that this method, even with a correction factor, is not considered suitable for the accurate determination of chloride in milk. The direct titration method with dichlorofluorescein indicator yields somewhat lower results, but results which are still considered too high and erratic to be relied upon. Indistinct endpoints with either indicator, and the adsorption of silver by protein, are pointed out as important sources of error. An easy and quantitatively precise modification of the Volhard method is proposed for determining chloride in milk. One combined reagent, containing standardized silver nitrate, nitric acid, and ferric alum indicator, is added to the sample and the percentage of chloride is determined by titrating with standardized potassium sulfocyanate. Sources of error and methods of improvement in other methods, as well as conditions necessary for accurate Volhard titrations, are described. © 1939, American Dairy Science Association. All rights reserved.