V O L U M E 2 4 , NO. 9, S E P T E M B E R 1 9 5 2
1449 a t least 12 separate steps are required by the U.S.P. method for amphetamine sulfate tablets, in addition t o the minimum six hand extractions necessary. The proposed method eliminates all but five of these steps and the extraction is performed automatically. A number of extractors can be set up siniultaneously and operated \)y one analyst. ACKNOWLEDGMENT
The authors wish t o express their appreciation t o E. G. E. Shafer for his helpful advice and t o Kelson 0. Klaner for suggesting the use of the baffle plate and modifications of the side arms. Frank J. Brandler constructed the eytract ors. LITER4TURE CITED
c.,
Figure 6 . Apparatus for Solvents Heavier than Water
(1) Craig, L. ASAL. CHEM.,22, 61 (1950); 23, 41 (1951); 24, 66 (1952). (2) Fritz, J. S., Ibid., 22, 578 (1950). (3) Ibid., p. 1028. (4) Ibid., 24, 306 (1952). (5) Fritz, J. S., and Keen, R. T., Zbid., 24, 808 (1952). (6) Fritz, J. S., and Lisicki, N.& Ibid., ‘I., 23, 589 (1951). ( 7 ) Golumbic, C., Zbid., 23, 1210 (1951). (8) Pifer, C. IT., and Wollish, E. G., ANAI.. CHEM.,24, 300 (1952). (9) U. S. Pharmacopoeia, XIVth rerision, 1950. (10) Vespe, V., and-Fritz, J. S., AWAL.CHEM.,in
press. ADV.ANT.4(; ES
~k~~ proposed has advantages Over conventional and U.S.1’. extraction methods for assay purposes. The labor savings are illustrated in Table IV. As can be seen,
RECEIVED for review April 4, 19.32. Accepted J u n e 9, 1952. Presentedat t h e Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy hlarch 6, 1952, and before the Division of Analytical Chemistry a t t h e 121st YIeetinp of t h e BIIERICAK C n ~ ~ r c a POCIRTY, r, Buffalo, N. I-.
Photometric Determination of Zirconium in Magnesium Alloys GLENN B. WENGERT The Doic Chemiral Co.,Midland, Mich.
I
N T H E search for high t~enq~erature alloys for use in jet aircraft, it was found that the addition of small amounts of eirconium t,o magnesium allo? Ilowed higher operating tempc’ratures and grain refinement without adversely affecting creep resistance (6). A new syptem of alloys was developed for which a fast’er,more accurate method for the determination of eirconiuni in low concentrations was desired. The gravimetric determination of zirronium by precipitation as the phosphate ( 3 )is subject to error in the low concentration range and requires a number of hours to compIet,e. Since the alizarin red S color complex har bec,n used for a number of years ap a qualitative spot test for zirconium (1, 2, E ) , it was decided t o investigate the possihility of dweloping a quantitative method using this reagent (4). APPARATUS AND REAGENTS
Transmittance measurements were made with a Beckman spectrophotometer, Model B, modified t o hold a 40-mm. Klett cell.
Zirconium Standard Solution. Dissolve approximately 0.356 gram of zirconyl chloride (ZrOCI2.8Hz0) in about 100 ml. of water. Add 100 nil. of concentrated hydrochloric acid and dilute to 1000 ml. One milliliter contains approximately 0.1 mg. of zirconium. Standardize by analyzing 100 ml. gravimetrically by the phosphate method. Alizarin Red S, 0.05% water solution (Sational Aniline and Chemical Co., Inc.). Potaspiurn Pyrosulfate (Ii2S?O7), ( .P., potassium bisulfate (fused powder). Ferric Chloride Solution. Dissolve 2.5 grams of iron wire in a minimum amount of hrdrochloric acid and nitric acid and dilute to 100 nil. with water. COLOR REACTION
Effect of pH. The effert of pH is shown in Figure I . The optimum color development is k)etween pH 0.6 and 1.5. Between pH 1.5 and 3.0 the oxychlorides of zirconium depress the color intmqity, while above pH 2.5 the lake formation occurs. Below
ANALYTICAL CHEMISTRY
1450
The development of a new system of magnesium-base alloys containing small amounts of zirconium led to the search for a faster and more accurate method for the determination of zirconium. The photometric alizarin red S method has been developed and found to give accuracy equal to or better than the gravimetric procedures. This has been applied to the analysis of a variety of magnesium alloys with zirconium contents ranging from 0.10 to 1 . 0 0 ~ ~A. significant sating of time has been accomplished.
pH 0.6 the curve fall. off sharply, indicating destruction of tlic complex. Effect of Zirconium Concentration. In Figure 2 transmittance is plotted against wave length, for various concentrations of thc zirconium alizarin red S complex. Llinimum transmittancr (maximum optical density) occurs between 510 and 520 1131. A calibration curve Phow that a straight line i R obtainrd u p to maximuni density for the volumes and conditions statcd FIG ?I .L I R F-
EFFECT OF p H ON AESORPTION BY THE ZIRCONIUM %IZA,RIN
50(p’
I
0
1
0
05
IS
IO
20
25
30
many metals, but these colors arr all destroyed by strong mineral acids except those due to zirconium or hafnium.” DETERMINATIOY OF ZIRCOSIUM IN \IIC;YESTCI\I
ALLOY 5
Preparation of Standard Curve. In 100-ml. volumetric flask.c prcymre a series of standards ranging in concentration from 0.1 to 0.3 mg. of zirconium. Add 5 ml. of 0.05% alizarin red S and dilute to about 90 ml. Calculate and add hydrochloric acid to give approximately an 0.1 solution and dilute to volume. Shake and allow to stand for 15 minutes. Place the blank in a 40-mm. cell. At a wave length of 510 mg set the instrument a t aero optical density. Read the optical density of each standard concentration and plot on cross-section paper. Preparation of Sample. Weigh 1.500 to 2.000 granls of alloy into a beaker. A4dd25 ml. of water and sufficient hydrochloric acid to dissolve the sample. Filter through No. 42 Whatman
J
35
Stability of Color. Optimum color dtw~lopxnr~ritrequires about 15 minutea. After this, transmittance does not change over a pexiod of 2 to 3 davs in diffuse light a t a temperature from 25O to 3 5 O Diverse Ions. Table I 11sts those ions Fhich up to the given concentrations have no effect upon the color development. Potassium bisulfate, phosphates, and sulfates all interfere ( 7 ) in the same manner. As shown in Figure 3, potassium bisulfate up to a concentration of 0.08 gram per 100 mi. inhibits the formation of the complex. The solution requires an hour to reach maximum color intensity. dbove that concentration, maximum color does not develop. The interference of bisulfate can be removed by precipitation of zirconium aa the hydroxide, using iron as a carrier. Fluorides interfere quantitatively in concentrations greater than 0.01 mg. per 100 ml. Very high neodymium could interfere a t 510 mp, though a t 500 m9 the interference would be less. Thorium is the only element investigated ~5 hich interferes by increasing the color intensity. Between pH 1.1 and 1.5 this increase varies with the concentration and the pII. From pH 0.6 to 1.0 thorium does not interfere. The effect of varying amounts of hafnium in zirconium upon the accuracy of the determination k not known. However, Hopkins (.$) stated that “alizarin-tsulfonir ,+(.id (alizarin-S) gives a rrci-violet color with
c.
I 0 400 20
1
1 I : 1 i ,
40
60
500 20 40 60 80 600 20 W l V E L E N G T H IN M I L L I M I C R O N S
80
FIGURE
40
60
80
7W
3
EFFECT OF KHS04 ON ABSORPTION I 60
8 z Y
Table I.
Noninterfering Concentrations of Diverse Ions ME./ Mg./ 100 M I .
Aluminum Copper Iron
Lead
Magnesium
4
4 5 10 500
Manganese Nickel Rare earths Thorium
Zinc
100 ml. 5 12 9 40 18
50
+
2
c ).
5
40
0 0 Q
!i 30 0
0
02
04
06
08
G R A M OF K H S 0 4 PER l O O m l
IO
12
I4
1451
V O L U M E 2 4 , NO. 9, S E P T E M B E R 1 9 5 2
comtituents with several other elements as minor constituents. % ’ Total Zirconium Aluminum, iron, hydrogen, Gravi- ColoriVariamanganese, nickel, and silicon tion metric metric decrease the proportion of acid0.62 -0.02 0.64 0.63 0.64 -0.01 soluble zirconium present in 0.63 0.65 +0.02 the magnesium (6). An investi0 . 6 4 0 . 6 3 -0.01 gation of the effect of various 0.64 0.64 0.00 0.64 0.63 -0.01 acids upon the separation of 0.39 0.39 0.00 the soluble from the insoluble 0.41 0.38 -0.03 0.41 0.39 -0.02 zirconium waa necessary. In 0.41 0.41 0.00 Table 11, dilute hydrochloric 0.36 0.39 -0.03 acid was used in the photo0.37 0.36 +0.01 0.84 0.86 -0.02 metric determinations and 0.84 0.86 t O 02 dilute sulfuric acid in the gravi0.85 0.8.5 0.00 metric tests. 0.84 0.8i t0.03 In another ssries of esperi-.. ments, dilute nitric w a ~compared to dilute sulfuric acid (9). The conclusion was reached that dilute nitric, hydrochloric, and sulfuric acids are equally effective in separating soluble from insoluble zirconium. Data of Taylor (8) on the corrosion of zirconium by these dilute acids confirm that none of them attacks the unalloyed metal appreciably.
Table 11. Comparison of Colorimetric with Gravimetric Results % Insoluble Zirconium Gravi- ColoriVariametric metric tion
Sample
% Soluble Zirconium Gravimetric
Colorimetric
Variation
iO.02 f0.02
‘0.01
0.60 0.60 0.60
0.57 0.59 0.60
-0.03 -0.01 0.00 0.00 -0.02 0.00 -0.03 -0.02
67333
Rar;
-3
0.04 0.03 0.03
0.05 0.05 0.05
67333
Rod1
0.04 0.04 0.04 0.06 0.07 0.06
0.04 0.04 0.05 0.06 0.07 0.06
0.00 0.00 +0.01
0.60 0.60
0.00 0.00 0.00
0.33 0.34 0.35
0.59 0.60 0 58 0.33 0.31 0.33
0.07 0.03 0.04 0.06 0 04 0 04 0 03
0.06 0.06 0.06
-0.01 t0.03 +0.02
0.07 0 05
iO.01 +O 01 TO 02 -0 02
0.34 0.33 0.33 0.78 0 80 0 81 0 81
0.33 0.33 0.32 0.79 0 81 0 79 0 81
67365
2 3
Bar 1 2 3
67365
Rod1 2 3
Bar 67366 Rod 1 2 67366
3
0 06 0 05
0.60
-0.01
+0.01 0.00
-0.01 f O 01 -0 01 -0 02 LO 01
~
paper into a 500-ml. volumetric flask and add 10 ml. of concentrated hydrochloric acid. Make to volume and save. Place the paper containing the insoluble zirconium in a porcelain crucible and char slowly. Heat at 950’ C. for 30 minutes. .4dd about a gram of potassium bisulfate and fuse. Cool and dissolve the melt in 100 ml. of water containing 1 ml. of concentrated hydrochloric acid and 1 ml. of ferric chloride solution. Add ammonium hydroxide until all of the iron and zirconium are precipitated. Filter through No. 40 Whatman paper and wash with warm water. Dissolve the hydroxides from the filter paper with 10 ml. of hot 1 to 1 hydrochloric acid. Transfer to a 250ml. volumetric flask and make to volume. Procedure. Pipet an aliquot from each flask to contain from 0.1 to 0.3 mg. of zirconium and place in 100-mI. volumetric flasks. Add 5 ml. of 0.05y0 alizarin red S solution; measure in enough hydrochloric acid t o give approximately an 0.1 A‘ solution and make t o volume. Prepare a blank containing all of the reagents used. Shake and dlow t o stand for 15 minutes. Determine the optical density at a wave length of 510 mp, using a 40-mm. cell. From the standard curve determine the amount of zirconium present. Results. Table I1 shows a comparison of results obtained by the gravimetric phosphate method and the photometric alizarin red S method. The samples used are magnesium alloy standards which contain varying amounts of zinc and rare earths as major
~
LITERATURE CITED
( 1 ) Boer, J . H. de, Chem. Weekblad, 21,404 (1924,. (2) Feigl, F., ”Qualitative Analysis by Spot Test,” pp. 124-9, Xew
York, Nordemann Publishing Co., 1939. (3) Hillebrand, W. F., and Lundell, G. E. F., ”hpplied Inorganic Analysis,” pp. 442-61, New York, John Wiley & Sons, 1929. (4) Hopkins, B. S., ”Chapters in the Chemistry of Less Familiar Elements,” Vol. 11, Chap. 12. p. 16. Champaign. Ill., Stipes
Publishing Co., 1939. ( 5 ) Selson. X. E., and Strieter, F. P., Trrrna. .4174. Foiclulrynnan’s SOC.,58, 400 (1950). (6) Pavelka. F., Mikrochemie, 8, 345 (1930). (7) Smith, L., and West, P. W., IND.ENG.(:HEX.. A s a ~ .ED,, . 13. 271 11941).
(8) Taylor. D. F., Iizd. Eng. Chern., 42, 639 (1950). (9) TVinn. D. M.,Dow Chemical (“o,, unpublished experiments, April 15, 1949. R E C E I ~ Efor D rei4erv .Januarx 17, 1952.
lccepted July 9, 1952.
Calcium Acid Malate Hexahydrate A Suggested Versatile Primary Standard A . C . SHEAD, D e p a r t m e n t of C h e m i s t r y , Ziniiqersity of Okluhomtr. V o r m a n . Okla.
C
ALCIUM acid malate hexahydrate, CaH2CsHsO1&H20, with a molecular weight of 414.286 and a remarkably high equivalent weight of 207.143, offers exceptional advantages as a versatile primary standard of multiple applications. It can be directly applied in alkalimetry, calcium chelatometry, and the calibration of pH meters. Indirectly, by calcining in platinum to calcium oxide with subsequent solution in excess acid and residual titration with base having a k n o m ratio to the acid, it can be employed to standardize both solutions.
1x1 dried at 100” C’.> and this is its only drawback from the standpoint of conventional procedure. However, the accompanying analyses show that when i t is properly prepared and stored, the adsorbed moisture content is almost undetectable. Aspiration of dry air over the crystals for a brief period will remove evcn this trace of moisture. Chalking would immediately reveal any decomposition. This phenomenon has never heen detected in these laboratories. PREPARATION OF MATERIALS
PROPERTIES
Calcium acid malate hexahydrate is readily prepared chemically pure from abundant “sugar sand,” a by-product from the sap skimmings of the maple sugar industry. It is pure white, free flowing with no tendency to cake on storage, and, properly bottled, has proved stable to high atmospheric temperatures and low humidities for the 5-year period over which i t has been observed in these laboratories. At no time has any change been observed during weighing directly on a watch glass. I t cannot
Calcium acid malate hexahydrate ili not regularly on thr market. Crude sugar sand, calcium malate, is sieved to remove leaves, twigs, and other gross trash. The calcium content is determined. The amount of sulfuric acid to react with this is calculated for a given desired charge and the acid diluted two or three times with water to prevent charring of the charge. After the acid and charge sufficient to form malic acid and calcium sulfate have been mixed, an equal portion of the crude sugar sand is addpd to form acid calcium malate from the malic acid formed in the first reaction. After thorough mixing, enough
