Colorimetric Method for Estimation of Dissolved Oxygen in the Field

ABSTRACT The suitability of the Winkler method for the estimation of oxygen dissolved in water is well established (Standard Methods of Water Analysis, 1936; Fox & Wingfield, 1938). Its usefulness in the field, however, is limited by the fact that it is necessary either to titrate the iodine solutions in the field, or to carry back to the laboratory numerous samples of water. Moreover, the titration of iodine solutions necessitates the frequent standardization of the sodium thiosulphate solution. With the modification of the Winkler method described here, the oxygen content of water can be estimated quickly and easily in the field without bulky apparatus. As no standard solutions are required the method is particularly useful when estimations are made only occasionally.