| 摘要 |
PROBLEM TO BE SOLVED: To provide a hardness indicator having good responsiveness to a minute amount of Ca2+ and deteriorating at a low speed in a high temperature environment of 50 deg.C or more. SOLUTION: This hardness indicator contains EBT, a pH buffer agent, a masking agent, Mg-EDTA prepared by removing water molecules from a hydrate of Mg-EDTA, and a non-aqueous solvent.
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