what s residue ignition methodein water analysis?

Question

what does residue ignition figure show in the sample of water?

Answer 1

This is a guess, but I'm comfortable with it: if you evaporate all the water from a sample, leaving only the salts that were dissolved in it, weigh them, heat them, and weigh them again, the difference will represent the carbon dioxide that was driven off from calcium and magnesium carbonate. The resulting material will contain the metallic oxides, as well as phosphates and sulfates which are less volatile. Re-hydration and subsequent evaporation will convert the oxides back to hydroxides, which can be weighed to give another hit as to how much of these were present.