1.1 This practice covers the preparation, testing and procedure for using the acidic aqueous ferrous ammonium sulfate solution dosimetry system to measure absorbed dose in water when exposed to ionizing radiation. The system consists of a dosimeter and appropriate analytical instrumentation. For simplicity, the system will be referred to as the Fricke system. It is classified as a reference standard dosimeter (see Guide E1261). 1.2 The practice describes the spectrophotometric analysis procedures for the Fricke dosimeter. 1.3 This practice applies only to [gamma] rays, x rays, and high-energy electrons. 1.4 This practice applies provided the following are satisfied: 1.4.1 The absorbed dose range shall be from 40 to 400 Gy (1). 1.4.2 The absorbed dose rate shall not exceed 106 Gy[dot]s -1 (2). 1.4.3 For radioisotope gamma-ray sources, the initial photon energy shall be greater than 0.6 MeV. For bremsstrahlung photons, the initial energy of the electrons used to produce the bremsstrahlung photons shall be equal to or greater than 2 MeV. For electron beams, the initial electron energy shall be greater than 8 MeV (see ICRU Reports 34 and 35). Note 1-The lower energy limits given are appropriate for a cylindrical dosimeter ampoule of 12 mm diameter. Corrections for dose gradients across an ampoule of that diameter or less are not required. The Fricke system may be used at lower energies by employing thinner (in the beam direction) dosimeter containers (see ICRU Report 35). 1.4.4 The irradiation temperature of the dosimeter should be within the range of 10 to 60°C. 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.