Procedure given is applicable to the direct analysis of potable and raw water, but is particularly intended for polluted waters and saline waters. The range covers a nitrat nitrogen concentration up to 45 mg/l using a 5 ml test portion, and a cell of path length 10 mm. A concentration of 0,22 mg/l can be detected. Potential interferences from nitrite and chloride are removed, certain substances may distil over and colour the distillate.