1.1 This practice covers the procedures for preparation, testing and using the acidic aqueous ferrous ammonium sulfate solution dosimetry system to measure absorbed dose to water when exposed to ionizing radiation. The system consists of a dosimeter and appropriate analytical instrumentation. The system will be referred to as the Fricke system. It is classified as a reference-standard dosimetry system (see ISO/ASTM 51261). 1.2 The practice describes the spectrophotometric analysis procedures for the Fricke dosimeter. 1.3 This practice applies only to gamma rays, x-rays (bremsstrahlung), and high-energy electrons. 1.4 This practice applies provided the following are satisfied: 1.4.1 The absorbed dose range shall be from 20 to 400 Gy (1). 1.4.2 The absorbed-dose rate does not exceed 10 6 Gys1 (2). 1.4.3 For radioisotope gamma-ray sources, the initial photon energy is greater than 0.6 MeV. For x-rays (bremsstrahlung), the initial energy of the electrons used to produce the photons is equal to or greater than 2 MeV. For electron beams, the initial electron energy is 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 outside diameter. Corrections for dose gradients across an ampoule of that diameter or less are not required. 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.