For rapid determination of nitrate ion activity or concentration in aqueous solutions. Typical applications include fertilizers, sewage, water supplies, erosion, limnographic studies, dissolved plant ash and other biological analyses, explosives, pharmaceuticals and photographic manufacturing. Electrode is an ionplus Sure-Flow, plastic membrane, combination electrode. Range is 1.0 to 7 x 10-6M (14,000 to 0.1 ppm as N). Temperature range is 0 to 40°C.