V O L U M E 27, NO. 12, D E C E M B E R 1 9 5 5 urement; carbon tetrachloride pore volume values determined a t a p / p o of 0.950 are both reliable and easy to measure. ACKNOWLEDGMENT
The authors should like to thank their colleagues, R G. Meisenheimer and E. E. Roper, for their generous cooperation and constructive criticism. LITERATURE CITED
(1) Bachmann, IT.,Z . anorg. Chem., 79, 2020 (1912). (2) Brunauer, S.,Emmett, P. H., and Teller, E., J. Am. Chem. SOC., 60, 309 (1938).
1965 (3) Harkins, W., and Cheng, Y. C., Ibid., 43, 35 (1921). (4) Hildebrand, J. H., and Scott, R. L., “Solubility of Sonelectrolytes,” 3rd ed., pp. 109, 131, 345, Reinhold, Kew York, 1950. (5) Holmes, J., and Emmett, P. H., J . Phus. & Colloid Chem., 51, 1262 (1947). (6) Ries. H. E., “Advances in Catalysis,” vol. 4, p. 88, Academic Press, Kew York, 1952. (7) Ries, H. E., Van Nordstrand, R. A., Johnson, 11. F. L., and Bauermeister, H. O., J . Am. Chem. SOC.,6 7 , 1242 (1945). ( 8 ) Rossini, F. D., hlair, B. J., and Streif, A. J., “Hydrocarbons from Petroleum,” pp. 135, 142, Reinhold, New York, 1953. (9) Van Kordstrand, R. A., Kreger, W.E., and Ries, H. E., Division of Petroleum Chemistry, 112th Meeting, ACS, Xew York, September 1947. R E C E I V E for D review J u n e 20, 1955.
Accepted August 27, 1955.
Determination of Zinc in Presence of Iron and Nickel JACK LOWEN and ALICE L. CARNEY Lincoln Laboratory, Massachusetts lnstitute of Technology, Lexington, Mass.
The analjsis of ferrites requires the determination of zinc, iron, and nickel to a high degree of accuracy, and although standard methods meet this requirement for iron and nickel, the accurate determination of zinc requires separation bj methods that are usually tedious and erratic. Ion exchange offers a rapid and convenient method of separation, and subsequent precipitation of the zinc with quinaldic acid yields accurate results.
M
OST analvtical chemists are aware of the value of ion exchange as a tool for the separation of elements, but hesitate to apply the method to specific problems. By nature, zinc is one of the elements difficult to determine in the presence of iron and nickel, and recommended methods for its separation (1) are tedious and often erratic. Honever, separation by ion &change ( 2 ) on Amberlite IRA-400 or Donex-1 (a quaternary amine, polystyrene-divinylbenzene) is comparatively simple and can be made almost automatic by commercial ion exchange columns. Sickel is not retained even in 1 2 5 hldrochloric acid, iron is eluted by 0 . 5 S hydrochloric acid, and zinc by 0.005LV hydrochloric acid. Once separated, the zinc can be accuiately determined by precipitation with quinsldic acid (3). The separation of zinc from other elements, as well as its determination in the gamma range, has been discussed (2-5). EXPERIMENTAL PROCEDURE
Preparation of Ion Exchange. The ion exchange column can be a simple glass tube with the resin supported by glass wool resting on a one-hole rubber stopper, through which a glass tube is inserted to provide the outlet. rubber tube and a screw clamp are used as the valve. More convenient models, which have the advantages of a reservoir and a design that does not let the column run dry, are available commercially (Microcheniical Specialties Co., Berkeley 3, Calif. ). The height of resin should be about 30 em. and its diameter 1 to 2 em., as the total volume of resin determines the volume of solution needed to elute the ions. Amberlite IRA4-400 or Dowex-1, 60 mesh, is suspended in distilled water. After the slurry is allowed to settle for a few minutes the cloudy, supernatant liquor is poured off, removing very fine particles and allowing a reasonable flow through the resin. To free the slurry of organic contaminants (a visible cloudy layer) it is poured into the column and washed T\ith methanol. Then the resin is rinsed with distilled water to remove the methanol. The column can be stored with water for indefinite periods of time; however, it cannot remain for extended periods-Le., overnight or weekendsin concentrated hydrochloric acid. Just before using, the column is equilibrated with 121V hydrochloric acid. Separation of Elements. A solution of the chlorides of iron (as ferric), nickel, and zinc in concentrated hydrochloric acid is evaporated to 1 to 2 ml., is allowed to cool, and is transferred to
Table I.
Determination of Zinc after Separation by Ion Exchange
Zn Added, 1Ig.
Fe + i. Added,
48.8
Mg. 201.3
29.2
201.3
Ni +
.4dded, 11g.
+
Zn Found, 1Ig.
53.1
A v . = 48.7 2= 0.20 (std. d e r . ) 31.86
Av. = 29.0 i 0.3 (std. dev.)
48.5 48.7 48.9 48.7 48.4 48.7 48.9 48.7 48.6 49.1 29 2 28.6 29.3 28.9
the ion exchange column (previously equilibrated with 12X hydrochloric acid) with additional 12N hydrochloric acid. The column is eluted with 25 to 50 ml. of the same acid or until all the nickel has been washed through. The resin is then eluted with about 100 ml. of 0 . 5 s hydrochloric acid to separate the iron fraction. The zinc fraction is eluted with about 150 to 200 ml. of 0.005N hydrochloric acid. The exact amounts should be checked for each column. -4lthough the flox rates are not critical, they should be 0.5 to 1.0 ml. per minute. Determination. Iron and nickel can be determined on separate samples. A trace of iron seems to persist in the zinc fraction and can be complexed with tartrate. To the solution of about 200 ml., 3 to 4 grams of ammonium chloride and 7 to 8 grams of potassium sodium tartrate are added. The amount of zinc should not exceed 0.1 gram. The solution is then neutralized to p H 7 with ammonium hydroxide and heated to boiling, and 15 nil. of 3yo quinaldic acid (prepared by solution in hot water) is added with vigorous stirring and heating until precipitation is complete. The solution is cooled, filtered through a porous porcelain (Selas) crucible, and washed n-ith cold water. The gravimetric fact,or, F = 0.1529, is weighed as zinc quinaldate, Zn(CloH6O?S)2.H20. The results obtained are shown in Table I. LITERATURE CITED
(1) Hillebrand, K, F., Lundell, G. E. F., Bright. H. A , . and Hoffman, J. I.. “Applied Inorganic Analysis,” 2nd ed., p. 426,
Wiley. New T o r k . 1953. (2) Kraus, K. 8 . . and Moore, G. E., J . Am. Chem. SOC.,75, 1460 (1953). (3) Miller. C. C., and Hunter, J. A., Analyst, 79, 483 (1951). . 26, 1345 (1954). (4) Rush, K.&I., and Yoe. J. H., A s . 4 ~ CHEY., ( 5 ) Vogel. A. I., “Quantitative Inorganic Analysis.” 2nd ed., p. 466, Longmans, Green, London, 1951. RECEIVEDfor review M a y 11, 1966. Accepted August 22, 1955. Research supported jointly b y the Army, Navy, and A i r Force under contract with Massachusetts Institute of Technology.
