Table IV.
Effect of Organophosphorus Acids and Chloridates on Thorium-Alizarin Titration of Fluoride (pH 3)
Without Prior Treatment with Sodium Ethylate Interference Calcd. as Fluoride, so Added Found Methylphosphonic acid 2 6 0 8 5.5
Methylphosphonofluoridic acid (0.3% F - )
Diisopropyl phosphoric acid
10.0 15 0 20 0 5 0 10 0 20 0
Diisopropyl phosphorochloridate Ethyl methylphosphonochloridate Methylphosphonic dichloridate
30 5 5.5 15.6 10.6 20.3 2.5 10.2
Most of the studies of the fluorine methods were devoted to the analysis of phosphonofluoridates. The information presentred on results with diisopropyl phosphorofluoridate is also applicable to other esters of phosphorofluoridates.
1 7
3 0 0 0 0 0 0
2 3 3 3 0 1 0
0.0
0.0 0.0 0.1 0.6 3.1 6.3 0.0 0.1 0.0
LITERATURE CITED
(1) Armstrong, W. D., J . Am. Chem. SOC. 5 5 , 741 (1933). (2) Hoffman, J. I., Lundell, G. E. F., B u r . Standards J . Research 3, 581 (1929). (3) Hoskins, W. M., Ferris, C. A , , IND. ENG.CHEM.,ANAL.ED.8, 6 (1936). (4) Saunders, B. C., “Phosphorus and Fluorine,” pp. 206-11, Cambridge Univ. Press, Cambridge, Eng., 1957. (5), Stark, G., 2. anorg. Chem. 70, 173 - - - - ~ (IYII).
(6) Willard, H. H., Winter, 0. B., TND ENG.CHEM.,.SNAL.ED.5 , 7 (1933). RECEIVEDfor review April 29, 1959. Accepted August 17, 1959.
Separation of Zirconium from Titanium, Ferric Iron, Aluminum, and Other Cations by Cation Excha nge Chromatog raphy F. W. E. STRELOW National Chemical Research Laboratory, South African Council for Scientific and Industrial Research, Pretoria, South Africa
,A systematic study of the adsorbabilities of cations with A G 50WX8 resin in hydrochloric acid showed that a large difference exists between zirconium and most of the other cations. This fact is used to develop a cation exchange chromatographic procedure to separate zirconium from titanium, ferric iron, and aluminum. Other cations that are completely separated , C O + ~Mn+2, , Zn+2, include C U + ~Ni+?, Cd+’, Fe+2, Sn+2, Sn+4, Hg+2, UOZ+’, Be+’, Mg+2, Pbf2, Li+, Na+, K+, Rb+. The method should be especially useful for separation of small amounts of zirconium from large amounts of other elements.
A
of the partition of cations in hydrochloric acid media u i t h AG 50KX3 resins (5) revealed a large difference between the adsorbabilities of the strongly held zirconium ion and most of the other cations, as could be expected from the high affinity of zirconium for cation exchange resins of the sulfonated polyS Y s r m i A T I c STUDY
1974
ANALYTICAL CHEMISTRY
styrene type. These large differences indicated that good separation of zirconium from most other cations should be possible by cation exchange chromatography using hydrochloric acid as eluent. Brown and Rieman ( 2 ) separated zirconium and titanium by cation exchange chromatography on Dowex 50 resin using a 1% citric acid buffer a t a p H of 1.75 as eluent. Because large volumes of eluent are needed, and the presence of citric acid will tend to complicate the further ,analysis in many cases, it was felt that a separation with hydrochloric acid should have some advantages. Belyavskaya and Chmutova ( 1 ) developed a method to separate trivalent chromium and aluminum from zirconium by cation chromatography using hydrochloric acid as eluent. They reported that aluminum is hardly adsorbed from 1S hydrochloric acid by the Russian cationite KU-2. The AG 50WX8 resin used in the work described showed a stronger’ adsorption of aluminum, the distribution coefficient, D,
having a value of about 34 at a concentration of 1S acid, and the aluminum had to be eluted with 2N acid. Elution with 1 . 5 5 acid was not satisfactory. Freund and Miner (3) separated aluminum from zirconium by an anion exchange procedure using Dowex 1 resin and 0.06.T hydrochloric plus 0.8-V hydrofluoric acid as eluent for aluminum. EXPERIMENTAL
Apparatus and methods used were similar to those reported (6). “Single element” elution curves were prepared for a large number of elements a t different hydrochloric acid concentrations. Those for zirconium and titanium are shown in Figures 1 and 2. The curves were used to evaluate the most favorable conditions for the separation. Composite elution curves were prepared using the hydrochloric acid concentration that promised the best separation. The curve for zirconiumtitanium is given in Figure 3. The curves for zirconium-iron and zir-
c
ML. ELUATE
Figure 1 . Single element elution curves for zirconium using hydrochloric acid of different concentrations and A G 50WX8, 100- to 200-mesh resin
A 5N HCl
0 4N HCI A 3N HCI With 2N HCI (0.2008 gram of ZrOs), the first trace of zirconium appeared after 600 mi. of eluent had been used
conium-aluminum were almost similar except that the aluminum showed more tailing than t'he iron and titanium. METHOD A N D APPLICATION SYNTHETIC SAMPLE
TO
As a result of this work, a method of separation u as developed and applied to synthetic solutions, prepared by measuring out and mixing amounts of the standardized solutions of the different cations. Thew were adsorbed on a column of AG 50WX8, 100- to 200-mesh resin of 22-cm. length and 1.15-cm. diameter. Titanium and ferric iron here eluted by 300 ml. of 21Y hydrochloric acid a t a flow rate of 2 to 2.5 ml. per minute. iiluniinum required 400 ml. of the same acid when present in large amounts as might be expected from the tailing effect. Zirconium was then eluted by 400 ml. of 5.2' hydrochloric acid a t the same flow rate. Flow rates of 3.5 to 4.0 nil. per minute using the same column size were applied to zirconium-iron separations. Thp elution curves showed only negligible differences from those for the lower flow rates. The amounts of zirconium, titanium, iron, and aluminum were determined by precipitation with ammonia after renioval of the excess hydrochloric acid by evaporation to a volume of a few milliliters. The precipitates mere ignited and weighed as the oxides. A correction amounting to some tenths of a milligram had to be applied to the zirconium result4 because the hydrochloric acid used contributed to the weight of the precipitate. The results of the separations are given in Table I.
Table
I.
used to convert zirconium pyrophosphate to the dioxide. The filtrate was neutralized to methyl red and tested for the presence of other cations. The results of the analysis aregiven in Table 11. As the results of the zirconium determination in flint clay KO. 97 did not agree well with the value given by the standard certificate, the zirconium was also determined by a n established method. Samples of 2 to 4 grams were used and two precipitations as zirconium phosphate in 3.5N sulfuric acid, in the presence of hydrogen peroxide with intermediate carbonate and bisulfate fusions, wcre employed to effect a complete separation from the large amount of aluminum and other metals. Triplicate results were 0.201, 0.198, and 0.20670 zirconium dioxide with a mean of 0.20275, and show a satisfactory agreement with the value of O.2O7YO arrived a t after the ion exchange separation. It is assumed that the given standard values are higher because, as a minor component, the zirconium dioxide was probably not determined with the special care exerted in the analyses described here. The certificate s h o w that
Results of Quantitative Separations of Synthetic Mixtures"
+
+
ZrOz Ti02 Fe203 A1203 TiOs Fen03 Taken, Taken, Taken, Taken, A1,03Found, ZrOn Found, Mg. Mg. Mg. Mg. Mg. Mg. 140.5 99.5 99.5 f 0 . 1 140.5 f 0 . 2 140.6 f 0 . 1 281.2 f 0 . 2 140.5 281 . 0 112.7 f 0 . 2 140.6 f 0 . 2 140.5 112.8 10.0 10.0 f 0 . 1 :322.1 f 0 . 2 322, I* 12.9 f 0 . 1 13.0 298.5 298 6 f 0 . 2 13.0 708.5 708.3 i 0 . 2 13.0 Z!= 0 1 13.0 225.6 225.4 f 0 . 2 1 3 l f O l 140.5 49.8 140.5 56.4 246.6 f 0 . 2 140 6 Z!= 0 2 6.5c 2810 S o t det,ermined 6.5 i0.1 All results are means of at least triplicate determinations. * Ti eluted by 300 ml. of l.5N hydrochloric acid. Iron plus zirconium w a s put through column in 1000 ml. of 0.5N hydrochloric acid.
ANALYSIS OF STANDARD SAMPLE
One standard analyzed sample (National Bureau of Standards) was used to test the zirconium separation.
Method. About 2 grams of sample were weighed out and fused with sodium carbonate. T h e product n as dissolved in hydrochloric acid and silica removed in t h e usual way. T h e resulting hydrochloric acid solution was diluted t o a volume of 500 t o 600 ml. and passed through a column of AG 50WX8 resin, 100- to 200-mesh particle size, 22 cm. long and 1.15 cm. in diameter. Aluminum, iron, titanium, and other cations were eluted with 400 ml. of 2 s hydrochloric acid; zirconium was eluted a i t h 400 ml. of 5,V hydrochloric acid. After the hydrochloric acid had been removed from the zjrconjum fraction b y evaporation, zirconium was precipitated as the phosphate from about 3 . 5 s sulfuric acid solution. The precipitate was separated, ignited, and weighed as zirconium pyrophosphate. The factor 0.467 was
Table II. Determination of Zirconium in National Bureau of Standards Analyzed Sample Flint Clay No. 97
Standard Value, ZrOt, 7" 0 25a
Zr02 Found,
70
a Reports from 6 analysts ranging from 0.23 to 0.30.
some analysts did not determine it at all, but probably included i t in the aluminum oxide. DISCUSSION
The foregoing method provides a simple means for the complete separation of zirconium from titanium, ferric iron, and aluminum. Other cations t h a t are completely eluted with 300 ml. of 2 5 hydrochloric acid include Cu+*, Ki+2, Pb+2, Co+2, Mn+2, Zn+2, Cd+2, VOL. 31, NO. 12, DECEMBER 1959
1975
. 30
C
E n e w 0 N
9Q
20
-'
e c;
r
10 -
i M:
- -2N
ELbA'E
I 100
-
~
- 1 -
200
'-5y
HC
YL
Figure 2. Single element elution curves for 'titanium using hydrochloric acid of different concentrations and AG 30'WX8, 100- to 200-mesh resin 0
2N
HCl
A 1.5N HCI
Fe+2, Snf2, Sn+4, Hgt2, UOZ+2, Be+2, N&+, Li+, "a+, K+, and Rb+. The elution of large amounts of calcium is complete only after elution with 500 ml. of 2&' acid. Strontium, barium, trivalent rare earths, and thorium cannot be separated from zirconium by the method as described here, but special methods can be envisaged where these cations are present. Thorium can be separated by using a column of AG 50WX12 resin of 200- t o 400-mesh particle size (6). The rates of elution are considerably lower, but the cations listed above can be eluted first by 2N hydrochloric acid, and then the zirconium can be eluted by 4N acid, leaving the thorium on the column. As regards the cation exchange separation of calcium, strontium, barium, and the rare earths from zirconium, a possible variation of the method described here is to follow the elution with 2-V hydrochloric acid by elution with 0.2N oxalic acid instead of 5N hydrochloric acid. As shown by Lister ( 4 ) , oxalic acid is a n effective eluent for zirconium. As calcium, strontium, barium, and rare earths do not form stable oxalate complexes but give insoluble oxalates, it might be expected t h a t they will not move on the column. This modification of the method is under investigation at present. Conditions for separation of zirconium from trivalent chromium were also studied. The elution curves of the chromium showed three separate bands of different colors, probably due t o the ions [Cr(H20)ClzIf, green; [Cr(H20)2Cl] +2, blue-green; and [Cr(HzO)a] f3, red-violet. The green band was eluted very rap-
1976
0
ANALYTICAL CHEMISTRY
0 1.ON HCI
I
I
303
LO0
1 500
603
HC: ELUATE
Figure 3. Composite elution curve for zirconium-titanium with an AG 50WX8, 100- to 200-meshI resin column 2 2 cm. long and 1 .I 5 cm. in diameter Flow speed, 2.0 to 2.5 ml./minute Zirconium, 0.2395 gram as ZrOz Titanium, 0.2286 gram as Ti02
idly by 2'V and even b y l . 5 N acid, and the blue-green band could be eluted by 400 ml. of 2N acid as well. But the redviolet ion was fairly strongly adsorbed and could not be separated from zirconium. Because all the hydrochloric acid solutions of trivalent chromium tried out thus far have shown the presence of a t least a small quantity of the red-violet trivalent chromium cation, the attempt to work out a separation by this method was unsuccessful. Nitrates and perchlorates do not interfere with the separation, but anions that form very stable complexes n i t h zirconium, such as fluorides and oxalates, should be removed. Sulfates can be tolerated up to a concentration of about O.lNJwhen u p to 0.3N hydrochloric acid is present. When sulfuric acid is the only acid present, a sulfate concentration up to 0.3N is safe for accurate work. When 176.1 mg. of zirconium dioxide were put onto the column and were eluted with 0.3N sulfuric acid, no zirconium could be detected in the first 300 ml. of eluatg, while the first 25 ml. of eluate already showed a trace of zirconium when 0.5N sulfuric acid was used as eluent. When the sample is adsorbed on the column from sulfuric acid-sulfate solution of a concentration higher than 0.1N in sulfate, i t is advisable t o remove the sulfate by washing the column with about 30 ml. of distilled water before starting the elution with 2N hydrochloric acid. Otherwise, small amounts of zirconium may be eluted at the beginning. Concentrations of phosphate, low
enough not to interfere by precipitate formation, may also be present. The total zirconium handled by a column of the given measurements should not amount to more than 200 nig. of zirconium dioxide. With this amount the first traces of zirconium will appear when 600 to 650 ml. of 2N hydrochloric acid have been passed through the column. If larger amounts of zirconium have to be handled, the column should be made longer, keeping the same diameter When only small amounts of zirconium are present (1 to 10 nip.), the amount of other cations can be considerably increased. It is, for instance, possible to separate 5 mg. of zirconium quantitatively from a n amount of iron that is many times in excess of the total column capacity, when the iron is added in a solution that is less than 0.2N in iron and less than 0.5N in hydrochloric acid, by using a column about 20 em. long. Thus, the described method should be especially useful for the separation of small amounts of zirconium from large amounts of other elements. Instead of using 400 ml. of 4X or 5N hydrochloric acid, zirconium can be eluted completely with 250 ml. of 3N sulfuric acid. Because i t is impractical to remove this acid by evaporation, a eorrection must be applied to the final result for the nonvolatile matter (mostly silicon dioxide) that is contributed by the ammonia, if ammonia is used for the precipitation. This correction is of the order of 0.5 mg. for analytical reagent grade ammonia solution and up to
LITERATURE CITED
more than 2 mg. for laboratory reagent grade. ACKNOWLEDGMENT
The author expresses his gratitude to P. C. Carman of the National Chemical Research Laboratory, Pretoria, for his correction of the paper and to W. E. Schilz of the University of Pretoria for his advice and interest in the work.
(1) Belyavskaya, T. A., Chmutova, M, K., Nauch. Doklady Vysshei Shkoly, Khim. i Khim. Tekhnol. 1958, No. 2, 305-7. (2) Brown, W. E., Rieman, W., 111, J. Am. Chem. SOC.74, 1278 (1952). (3) Freund, H. F., Miner, F. J., ANAL. CHEM.24, 1229 (1952); 25, 564 (1953). (4) Lister, B. A. J., J. Chem. SOC.1951, 3123.
(5) Strelow, F. W. E., ANAL. CHEM.31, 1201 (1959). RECEIVEDfor review May 22, 1959. Accepted September 1, 1959. Published by permission of the South African Council for Scientific and Industrial Research. Abstracted from work done for a D.Sc. thesis at the Department of Inorganic and Analytical Chemistry, University of Pretoria.
Co Io r
Reaction for Determination of Some Meta-Dinitro Aromatic Compounds JAMES P. HEOTIS’ and JESSE W. CAVETT Research Division, Dr. Salsbury’s laboratories, Charles City, Iowa
b During the development of a colorimetric method for the determination of 3,5dinitrobenramide it was observed that 3,5dinitrobenzoic acid did not develop color with the reagents. This led to a study of the scope of the reaction. A theory of the color reaction is presented.
M
compounds react with acetone and alkali to produce quinoid ions of limited stability (1-4, 6, 8, 1 0 ) . Lewis and Seaborg (9) demonstrated that ammonia and primary amines reacted with them to forni orthoquinoid structures which were stabilized by double chelation. Porter (11) reported on the use of tetraethylammonium hydroxide and N,N-dimethylformamide in the determination of mono- and dinitro aromatic compounds. Most of the assays were dependent on a rather strict control of time of assay after the reagents were added. I n experiments designed to stabilize the color development of amines with 3,5dinitrobenzamide sufficiently for routine feed control, diethylamine and dimethyl sulfoxide appeared to be the solvent mixture possessing this property ( 5 ) . During the development of the assay method the free acid failed to produce color with the reagents used and this unexpected development led to a study of the scope of the reaction with other mets-dinitro compounds. ETA-DINITRO
EXPERIMENTAL
The reaction was carried out b y adding 2 ml. of diethylamine reagent to a solution containing 0.10 mg. of comPresent address, Research Division, Eaton Laboratories, Norwich, N. Y.
Table I.
Color Reactions of Various Meta-Dinitro Compounds
Color after DiethylCompound amine m-Dinitrobenzene Purple 3,5-Dinitrobenzamide Purple 3,5-Dinitrobenzoic acid, methyl ester Purple N-Methyl-3,5-dinitrobenzamide Purple 3,5-Dinitrobenzhydrazide Blue 3,5-Dinitrobenzoic acid, n-butyl ester Purple 3,5-Dinitrobenzoic acid, isopropyl ester Purple 3,5-Dinitrohippuric acid Purple 3,5-Dinitrobenzoyl-p-nitroaniline -4mber N,N-Di-( 2-hydrosyethyl)-3,5-dinitrobenzamide Purple 2,4Dinitrophenylhydrazine Red-orange 2,4-Dinitrophetiylacctic acid Green 2,4Dinitrotoluene Green 2,CDinitrophenyl thiocyanate Yellow-green 2,2’,4,4‘-Tetranitrophenyl Pink Bis-(2,4-dinitropheiiyl)disiilfide 3,7-Dinitrophenothinzine sulfoxide N1-(2,PDinitrophenyl )-N*-
Orange
Red
Klett Readings,‘ Minutes 20 60 120 38 4.5 45 656 700 700 600 680 670 780 780 780 500 700 770
Beckman DU Readings at 45-75 Minutes Wave length of max. absorp- Atisorption, mp tivity 57.5 78.i 570 16,065 555 16,960 566 15,410 575 14,610
650 660 630
..
650 650 610 520 530 550 145 250 290
555 565 555
14,610 14,150 5,810
...
...
180 550 17 19 95 220 28 243
295 550 19 24 79 258 28 250
350 560 25 30 65 280 26 275
--r rn
695 .-.
695 430 640 650 ...
89.i 12,530 26,370 36,850 ...
phthaloyl Amber 103 122 136 ... 2,7-Dinitroanthraquinone Purple 23 43 65 535 i,ow a Readings taken a t times specified after addition of reagents, using No. 56 filter.
pound i n 8 ml. of dimethyl sulfoxide (Stepan Chemical Co., Chicago 6, Ill.). Measurements were made on the Beckman DU spectrophotometer throughout the maximum absorption range, and the Klett-Summerson photoelectric colorimeter u i t h the KO.56 filter. The age of the diethylamine played a n important part in the development of color. The first diethylamine used was a 9-year-old sample. A new reagent from the same company gave readings which were one third of the earlier value. The reagent could be artificially aged b y refluxing a suspension of 40 grams of sodium or potassium fluosilicate per liter of dry diethylamine for 48 to 72 hours. Fluosilicate acted as a n
inhibitor of the destruction of the quinoid ion. RESULTS
The data in Table I show that the magnitude of the absorbance of certain of the compounds was sufficient for the method to serve as a means of assay. The following compounds did not develop color or absorb light in the visible spectrum. 3.5dinitrobenzoic acid; 2,6-dinitro-4.-chloroaniline; 2,6dinitrohydroquinone-4-monoacetate;3,5-dinitrosslicylic acid; 3,&dinitrosalicylic acid, methyl ester; 3,Sdinitrosalicylamide; 2,4dinitroaniIine; 2,4VOL. 31, NO. 12, DECEMBER 1959
0
1977
