ASTM D511-08

Calcium and magnesium salts in water are the primary components of water hardness which can cause pipe or tube scaling.

1.1 These test methods cover the determination of calcium and magnesium in water by complexometric titration and atomic absorption spectrometric procedures. Two test methods are included, as follows:

1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.3 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 hazard statements are given in 12.2.6 and 20.6.

7.1 This test method is applicable to most waters in a range from 1 to 1000 mg/L of calcium plus magnesium expressed as calcium, but may fail in the analysis of highly colored waters, brines, or waters that contain excessive amounts of metals. The upper and lower limits may be extended by either dilution or use of micro apparatus.

7.2 Data are not available to determine which matrices were used to obtain the precision and bias data, and it is the responsibility of the analyst to determine the acceptability of this test method for the matrix being analyzed.

16.1 This test method can be used to determine the concentration of calcium and magnesium in water. The determination of these ions in brackish water, sea water, and brines requires the use of the method of additions described in Section 22.

16.2 This test method is applicable for calcium concentrations in the range from 1.0 to 15 mg/L and magnesium concentrations from 0.25 to 3.5 mg/L. The upper limits can be increased to 1500 mg/L calcium and 350 mg/L magnesium by proper single dilution technique. Serial dilution technique should be used to further extend the limit.

16.3 The precision and bias were obtained on reagent water (1 % HCl). It is the responsibility of the analyst to determine the acceptability of this test method when analyzing untested matrices.