The test is designed to determine the total hardness in water of approx. 1... 25 °dH without pre-dilution. Higher degrees of hardness can be determined by appropriate pre-dilution.

The determination of the total hardness is carried out by complexometric titration. Alkaline ions from the earth form a red-coloured complex with the indicator used. Titration with Na2-EDTA (Titriplex III) releases the indicator while the alkaline earth ions are complexed by EDTA. The free indicator turns the solution green. The titration is finished when the color changes from red to grey-green (shortly before the color change) to green.
By counting the drops, the total hardness of the water can be determined directly (1 drop corresponds to 1 °dH at 5 mL sample volume).

Kit contains 1x 15 ml reagent in a high quality dropper bottle for precise drop size (high accuracy) and a 10 ml sample vessel with graduation.