5. Precision and Accuracy
A synthetic ujiknown sample containing 241 mg/1 chloride, 108 mg/1 Ca, 82 mg/1 Mg, 3.1. mg/1 K, 19.9 mg/1 Na, 1.1 mg/1 nitrate N, 250 ug/l nitrite N, 259 mg/1 sulfate, and 42.5 mg/1 total alkalinity (contributed by NaHC03) in distilled water was determined by the mercurimetric method, with a relative standard deviation of 3.3% and a relative error of 2.9% in 10 laboratories.