Rapid methods for determining the sulphate, calcium, and magnesium content of brackish coastal waters are desired by geologists and biologists working in Mississippi Sound. They need daily, even hourly, analyses to correlate with other records. Investigators on other coasts have the
same need. Gravimetric and colorimetric methods are too slow and ponderous and are too difficult to use on shipboard. However, new titrants and new indicators permit titrating brackish water for sulphate, calcium, and magnesium ions in 5 to 10 minutes, each. Procedures are modifications of
recognized methods. The disodium dihydrogen dihydrate of Ethylene-diaminetetraacetic acid (EDTA) is used as a titrant to complex barium, calcium, and magnesium ions. Only three samples of brackish water are necessary; one to determine combined calcium, magnesium, and excess barium; one to
determine the amount of combined calcium and magnesium; and one to find the amount of calcium alone. Simple calculations show the amounts of sulphate, calcium, and magnesium ions.
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