VISOCOLOR® alpha Carbonate hardness • Titrimetric determination of carbonate hardness • The determination is preformed as titration with hydrochloric acid against a mixed indicator, which changes colour at pH 4.5. (Reaction principle analogous to APHA 2320, DIN EN ISO 9963-1 C23 & -2 C24) Type: titration test Range: 1 drop = 1 °d (corresp. to 18 mg/l CaCO3) Sufficient for about: 100 tests with an average hardness of 10 °d Shelf life at least: 1.5 years Sea water suitability: yes Detectable with PF-12: no • Carbonate hardness is that portion of calcium and magnesium ions which are present as carbonate or hydrogen carbonate.