Chemistry: physical processes – Physical processes – Crystallization
Patent
1978-09-28
1980-06-03
Turk, Arnold
Chemistry: physical processes
Physical processes
Crystallization
G01N 3122, G01N 3318
Patent
active
042059550
ABSTRACT:
A liquid sample is prepared for measurement of its calcium plus magnesium hardness by adding to the sample an aluminum chelate, preferably aluminum disodium (cyclohexylenedinitrilo) tetra-acetic acid, while maintaining the pH of the sample in the range between about 5 and 8. Interference by iron or copper ions is thereby substantially eliminated without using poisonous substances. The pH of the sample is then raised to between about 9.5 and 11 to insolubilize aluminum ions; a magnesium chelate is added to exchange calcium ions, releasing an equivalent number of magnesium ions; and a dye indicator that forms a colored complex with magnesium ions is added. The calcium plus magnesium hardness is then measured by titration or spectrophotometrically.
REFERENCES:
patent: 3368969 (1968-02-01), Palen
patent: 3496113 (1970-02-01), Platte et al.
patent: 3697224 (1972-10-01), Means
patent: 3895913 (1975-07-01), Bockowski et al.
Shimizu et al., "Determination of Mg, Fe, Ca, Cu, and Zn by EDTA and Their Application", Chemical Abstracts, No. 17767b, vol. 53, Nov. 1959.
Sherif et al., "Spectrophotometric Determination of Uranium (VI) by the Azide Reaction", _Analytica Chimica Acta, 26 (1962), pp. 235-241.
Hach Chemical Company
Turk Arnold
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