Determination of the endpoint of the titration buffer solution in the measurement of boiler water hardness
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I measure the hardness of boiler water; when preparing the ammonia-ammonium chloride buffer solution, I add sodium magnesium EDTA. Then, the buffer solution is titrated with 0.001 mol/l EDTA, using Eriochrome Black T as an indicator, but the end point of the titration cannot be determined. What could be the problem? Our boilers require water hardness to be less than 0.03 mmol/L
Add EDTA disodium magnesium salt? Is this included in the standard method?
GB/T1576, take a look at it
I took a look at GB/T 6909; its scope specifies that chromotropic blue T is used for the determination of concentrations ranging from 0.1 to 5 mmol/L. Since the concentration you are measuring is less than 0.03 mol/L, acidic chrome blue K should be used as an indicator