N. S. Poonia V. P. Bakre and M. s. h i Vikram Universiity Uijain, India
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Detection of iron with Llblimine
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While reporting on the use of salicylimine and its derivatives as precipitants for copper and nickel, Duke1 pointed out that a red precipitate and a red color forms when iron(I1) and (111), respectively, are treated with salicylimine. The authors in the present investigation have found the sensitivity of the reaction and also investigated the reactions of this reagent with other cations at and above pH 3.0. It was found that the sensitivities for the iron(I1) and (111) tests are practically comparable and that no other ion formed colored products like those of iron. However, the test is no more sensitive (1.5 7 in the dilution 1 : 100,000) than the conventional ones.= An improved procedure which promises appreciable sensitivity is presented below. Reagent. One tenth of a milliliter of salicylaldehyde is ground with about 25 ml of 20% ammonia until the yellow particles of salicylimine disappear. The excess of ammonia is neutralized with dilute acetic acid. If the last drop of the acid decolorizes the yellow color of the reagent, a little ammonia is added to restore it. Test. The acidic solution of iron is treated with sodium bicarbonate solution to raise the pH to 3.0. A few drops of this solution are treated with 1 ml of the
reagent. On shaking the contents wlth 2-3 drops of isopentanol, a red to orange color is imparted to the alcoholic layer (when identification limit 0.001 r in the dilution 1:20,000,000). When detecting iron at the limiting concentration, a blank run is helpful. Effect of Diverse Ions. None of the noble, rare, or the common metals interfere except cerium(IV), which oxidizes the reagent to a brown color, and titanium, which precipitates as a light yellow precipitate. The latter neither permits the extraction of the iron complex into isopentanol nor allows it to be visible. The light colorations due to copper and nickel a t concentrations up to 100 times the amount of iron du not obscure the test. Phosphate and fluoride mask iron, and the test fails. Organic hydroxy acids tend to decrease the sensitivity of the reaction, but they can be removed in an acid solution of iron with potassium pern~anganate.~ The pH of the oxidized solution is adjusted to 3.0 before applying the test. DUKE,F H., Ind.Eng. hem. Anal. Ed., 16,750 (1944). IFEIGL,F., "Spot Tests in Inorganic Analy~is," Elsevier Publishing Co., 1958, p. 161. POONIA, N. S., BHAGIVAT, W. V., J. CHEM.EDCC.,43, 424 (1966).
Volume 44, Number 8, August 1967
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