(17) Ibid., 18, 576 (1941). (18) Salutsky, RI. L., Kirby, H. W., AN~L. CHEW27, 567 (1955). (19) Salutsky, h l . L., Stites, J. G., Martin, Ibid., 2 5 , 1677 (1953). A. W., (20) Smith, G. F., “Periodic Acid and Iodic Acid and Their Salts,” p. 5, G. F. Smith Chemical Co., Columbus, Ohio, 1950.
private communica(21) Stoenner, R. W,, tion. (22) Wahl, 4.C., Bonner, N. A., “Radio. activity Applied to Chemistry,” DD. 106 ff.. Wilev, Sew York, 1951. (23) JTeaver, B., ANAL. CHEX. 26, 477 (1954). (24) Ibid., p. 479. (25) Willard, H. H., Ibid.,22, 1372 (1950). -
(26) Willard, H. H., hlerritt, L. L., Dean, J. A., “1,ytrumental hfethods of Analysis, 2nd ed., p. 182, Van Xostrand, New York, 1951.
1
RECEIVED for review January 13, 1956. Accepted August 30, 1956. Division of Analytical Chemistry, 128th Meeting, ACS, Minneapolis, Ninn,, September, 1955
Separation of Iron from Aluminum by Precipitation of Ferric Periodate from Homogeneous Solution LEONARD GINSBURG, KAY MILLAR, and LOUIS GORDON Department o f Chemistry, Syracuse University, Syracuse 7 0, N. Y Iron(ll1) can b e quantitatively precipitated from homogeneous solution as the periodate in very dilute nitric or sulfuric acid. The precipitate is dense, easily filtered and washed, and can be quantitatively converted to ferric oxide by slow ignition. Iron can b e separated from aluminum by the method described, more effectively in nitric than in sulfuric acid. By a single precipitation in nitric acid, 85 mg. of iron can b e separated from 10 mg. of aluminum; with twostage precipitation, as much as 100 rng. of aluminum can be present. IRON PRECIPITATES have poor analytical properties because they are voluminous and difficult to filter and wash. One notable euception is basic ferric fo1,mate precipitated by the urea method of Willard and Sheldon (4). These investigators proposed the use of this dense precipitate for the removal of iron preparatory to the determination of bivalent metals. The separation of iron from aluminum by this method was not satisfactory ( 2 ) . Gordon and Ginsburg (1)have shoIvn that ferric periodate can be precipitated from homogeneous solution. Aluminum alone does not precipitate under the conditions usrd to precipitate iron as the periodate. Thcse procedures ( f ) have been modified for the separation of iron and aluminum. The present study describes experimental results obtained by precipitating iron as the periodate in the presence of aluminum and determining the efficiency of the separation by determining aluminum in the precipitate and iron in the filtrate.
MAX’
REAGENTS A N D APPARATUS
Unless otherwise specified, all cheniicals were reagent grade. Ferric Sulfate Solution. Approximately 8 grams of electrolytic iron (Standard Sample Co., Ames, Iowa) was dissolved in about 100 ml. of 46
0
ANALYTICAL CHEMISTRY
1 to 1 hydrochloric acid b y heating. The resulting solution was evaporated t o dense fumes with sulfuric acid and t h e residue was taken u p with distilled water. This solution, free of chloride and ferrous ion, was filtered and diluted to approximately 6 liters. The resulting solution was standardized by precipitation of hydrous ferric oxide, followed by ignition to the oxide. The solution mas found to contain 35.4 mg. of iron per 25 ml. Ferric Nitrate Solution. Approximately 17 grams of t h e electrolytic iron was dissolved in approximately 100 ml. of hot 1 t o 4 nitric acid. T h e resulting solution was boiled t o expel ovides of nitrogen. After filtration, t h e solution was diluted t o approximately 2 liters and standardized as above. The ferric nitrate solution was found t o contain 85.4 mg. of iron per 10 ml. All other solutions were prepared as previously described (1). All pH measurements were made on a Beckman Model H-2 DHmeter.
copious evolution of nitrogen during the reduction of the periodate. The solution was cooled and then analyzed for iron (1). Aluminum in Precipitates. Aluminum was determined in t h e ferric periodate and in t h e ignited residues of ferric oxide. For t h e determination of aluminum in ferric periodate concentrated hydrochloric acid was added t o t h e filtering crucible containing t h e precipitate, which readily dissolves. Ignited residues had t o be warmed gently for several minutes with a few milliliters of concentrated hydrochloric acid to effect solution. In both cases the resulting solution was diluted to volume in a 50-ml. volumetric flask and then a suitable aliquot was withdrawn for aluminum determination Usually 20 ml. of the hydrochloric acid solution was taken and neutralized to a p H of approximately 1. Aluminum was then determined (1). PRECIPITATION OF IRON I N SULFURIC ACID SOLUTION
ANALYTICAL METHODS
I r o n in Filtrates.
The filtrates and washings obtained from each precipitation experiment were evaporated t o about 50 ml. The resulting solution was acidified with a few milliliters of sulfuric acid and then treated cautiously with 85% hydrazine solution, which was added dropiyisc until t h e iodine color produced n’as completely discharged. T h e hydrazine m a added slowly because of the
Table
I.
Find PH
1.9
1.95 2.05 2.1 2.2
Procedure. I n a n unscratched 400ml. beaker place a solution containing no more than 50 mg. of iron(II1) and 5 ml. of 1 to 1 sulfuric acid. Add 2.5 grams of paraperiodic acid. Dilute t o about 100 ml., dissolve all solids, add 9.5 grams of acetamide, dilute t h e solution t o 150 ml., and adjust t h e p H to 0.8. Cover t h e beaker n i t h a watch glass and maintain the solution a t 95” C. for approximately 3.5 hours. Then filter
Iron Remaining in Solution a t Various pH Values after Precipitation from Sulfuric Acid Solutions Iron in Filtrate Iron in Filtrate
and Washings,
Final
hfg.
PH
and Washings, Mg.
0.6
2.3 2.35 2.4 2.5 2.6
0.1,0.03,0.2 0.1 0.1 0.05, 0.07
