Ramesh Chandra D. A. V. College Jullundur, Panjob, India
Detection of Barium, Strontium, and Calcium with Sodium Rhodizonate
Detection of barium and strontium in the presence of each other is well known. Calcium and magnesium do not interfere in neutral or slightly acidic solution. Feigll has based a test for calcium in medicinals on the observation that calcium reacts with sodium rhodizonate in alkaline medium, giving a violet precipitate, presumably of calcium rhodizonate. Feigl has further observed that while barium sulfate does not respond to the test, calcium sulfate, because of its higher solubility, does. It is this author's observation that strontium sulfate also does not respond to the test. The above observations render possible the rapid detection of Group I V cations with the same reagent. I FBIDII, F m , "Spot Tests in Organic Analysis," 5th ed., Elaevier Publishing Co., Amsterdam, 1956, pp. 50&09.
A neutral solution containing Ba+%,Sr+2, and CafZ is used. If properly diluted, Ba+%and Sr+%,but not Ca+%,will produce a brown spot when 0.2% solution of sodium rhodizonate is added to a drop of the group solution on a filter paper. When treated with dilute HC1, a Sr+2spot will disappear, and a Ba+%spot will persist and turn distinctly red. Strontium in the presence of barium must be detected after the interfering Ba+=has been removed by precipitation of the chromate. The test for calcium involves precipitating all three sulfates by adding saturated (NH&S04 and heating. The rhodizonate reagent can be added to the resulting suspension. A violet precipitate forms with Ca+= in the presence of diluted NaOH, and turns red-brown on standing.
Volume 39, Number 8, August 1962
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