TOTAL HARDNESS INDICATOR TABLETS
tablets are dissolved in 100 ml of the water sample to be tested, which has been buffered at pH 10 with 1 ml of Ammonia/ Ammonium chloride buffer solution, and then titrated with EDTA solution (0,01 M) till the sample turns from red to blue. Total hardness in mg/l = 10×ml of titrant used
The total hardness test can be used to measure water hardness. Water hardness is caused by the presence of alkaline earths, primarily calcium and magnesium. Total hardness is measured as the sum of all calcium and magnesium ions