Concentration     β (NO₂⁻): 990 - 1010 mg/l
Determination method: Cerimetric titration.
The content of this solution was determined by back-titration with Ammonium(II) ferrous sulfate (article number 1.03792) standardized by Cerium(IV) sulfate (article number 1.09092) against volumetric standard Iron(II)ethylendiammonium sulfate (article number 1.02402). The expanded measurement uncertainty is ± 0.7 % (k=2 coverage factor for 95% coverage probability). The certified value is traceable to primary standard NIST SRM 8040 (NIST: National Institute of Standards and Technology, USA) by means of volumetric standard Iron(II)ethylendiammonium sulfate measured in the accredited calibration laboratory of Merck KGaA, Darmstadt, Germany in accordance to DIN EN ISO/IEC 17025.