【国外标准】 Standard Test Methods for Iron in Water

4.1 Iron is the second most abundant metallic element in the earth's crust and is essential in the metabolism of plants and animals. If presented in excessive amounts, however, it forms oxyhydroxide precipitates that stain laundry and porcelain. As a result, the recommended limit for iron in domestic water supplies is 0.3 mg/L. These test methods are useful for determining iron in many natural waters.1.1 These test methods cover the determination of iron in water. Procedures are given for determining total iron, dissolved iron, and ferrous iron. Undissolved iron may be calculated from the total iron and dissolved iron determinations. The test methods are given as follows:  Range SectionsTest Method A—Atomic Absorption, Direct  0.1 to 5.0 mg/L  7 to 16Test Method B—Atomic Absorption,  Graphite Furnace  5 to 100 μg/L 17 to 26Test Method C—Photometric Bathophenanthroline μg/L 40 to 1000 μg/L 27 to 381.2 It is the user's responsibility to ensure the validity of these test methods to waters of untested matrices.1.3 The chelation-extraction and two former photometric test methods were discontinued. See Appendix X2 for historical information.1.4 The values stated in SI units are to be regarded as standard. The values given in parentheses are mathematical conversions to inch-pound units that are provided for information only and are not considered standard.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. Specific hazards statements are given in Note 4, 11.7.1, and X1.1.2.