microtest® Test Kit Specifications

microtest Calcium 10

Titrimetric Test for


1 drop = 10 mg/L Ca2+

Product Code602300
ContentsKOH Solution, 15 mL
Indicator, 6 mL
Titration Solution, 15 mL
Test Tube, 10 mL
Instructions for Use
Analytical MethodComplexometric Titration: At pH >12, calcium forms a pink coloured complex with certain indicator dyes (e.g. calconcarboxylic acid, hydroxynaphthol blue). Because of the high pH, magnesium is precipitated as Mg(OH)2 and does not interfere. On adding EDTA (ethylenediamine tetraacetic acid), calcium prefers to complex with EDTA, and releases the indicator dye. As the uncomplexed dye exhibits a blue colour, the titration endpoint is indicated by a sudden colour change from pink to pure blue. The amount of EDTA added is directly proportional to the concentration of Ca2+ ions.
Number of Tests50 – 80
InterferencesUnder conditions of the test, the following concentrations of ions do not cause interferences: copper < 2mg/L; iron < 20 mg/L; manganese < 10 mg/L. Phosphate interferes by precipitating calcium. Strontium and barium give a positive interference. Alkalinity in excess of 300 mg/L may cause an indistinct end point in hard waters. If magnesium is present, a precipitate of magnesium hydroxide will form during the titration, which will adsorb some if the indicator dye. This has no effect on the result of the test. In waters low in magnesium, the indicator will exhibit a dull red colour instead of a bright red at the beginning of the titration.
Measuring RangeThe recommended measuring range is 20 to 200 mg/L (2 – 20 drops @ 10 mg/L) for 5 mL of sample volume. This range can be extended by taking a smaller or larger water sample. For a 2.5 mL sample the measuring range is 40 to 400 mg/L and for a 10 mL sample the range is 10 to 100 mg/L.
Shelf Life2 years
ApplicationsDetermination and monitoring of calcium levels in industrial water treatment (boiler feed water), swimming pools.