m-Cresoxyacetic Acid, a Selective Reagent for Zirconium M. VENKATARAMANIAH
AND BH. S. V. RAGHAVA RAO Andhra University, Waltair, South India
EAGENTS for the determination of zirconium are many, but few are selective. The best known is mandelic acid, recommended by Kumins (e). To this may be added m-cresoxyacetic acid, ~ - O - C H z C O O H ,
Table 11.
(ZrOp taken, 0.0488 gram) Expt.
a reagent that is easily pre-
.
EXPERIMENTAL
Estimation of Zirconium. A stock solution of pure zirconyl chloride in 0.1 N hydrochloric acid was standardized by precipitation with cupferron (4). Aliquots of this solution were estimated with m-cresoxyacetic acid. The results are shown in Table I. Effect of Acid. The reagent precipitates thorium, ferric iron, titanium, and stannous tin as well as zirconium in neutral or slightly acid solution. In a study of the selective precipitation of zirconium in the presence of these elements, the solubility of zirconium m-cresoxyacetate in hydrochloric acid ww investigated by determining the zirconium oxide obtained from standard solutions in various acid concentrations. It has been observed that the precipitation of zirconium is quantitative in solutions up to 0.25 N in hydrochloric acid. Thus a convenient free acid concentration a t which separation can he attempted is 0.20 to 0.25 N . Composition of Precipitate. Ignition tests with the precipitate formed in solution 0.20 N in hydrochloric acid pointed to the association of one molecule of m-cresoxyacetic acid with each zirconium atom. These results, which showed variations of the order of 3% from sample to sample, conformed to the emOH pirical formula O=Z< , where R represents the m-cres-
a
b e
Sample 1
2 3
4 5 8 7 8 9 10
ZrO:
Difference,
MI.
.
65:06
m-Cresoxvacetic Acid Mkthod Sample, g. ZrOz, % 0.1016 65.08 0.0984 65.14 0.0972 65.01 hlean 65.08
A voluminous flocculent precipitate results. Continue to boil for 5 minutes and then set aside. Filter through a Whatman No. 42 filter, wash first with hot 0.1% solution of the precipitant in 0.20 N hydrochloric acid, then with water, ignite, and weigh es ZrOz. Double Precipitation. I n the presence of titanium, stannous tin, vanadyl or chromium ion, a double precipitation is necessary. Then do not attempt to wash the precipitate completely. Transfer the precipitate and the filter to the original beaker and dissolve by digesting with 1 t o 1 hydrochloric acid on a water bath. Dilute, then adjust the amount of free acid to about 0.20 N , and proceed as above.
Table 1. Determination of Zirconium i n Pure Solutions Gram
Cupferron Method Sample, g. ZrO, % 0.1034 65.02 0.1145 65.11 liein
R
Found,
I
Table 111. .inal>-sisof Zircon
oxyacetate radical. The precipitate is thus a basic salt of slightly varying composition which precludes its direct weighing.
ZrOt Taken, Gram 0.0976 0.0976 0,0732 0.0732 0.0488 0.0488 0.0244 0.0122 0.0041 0.0020
ZrOi Found, Difference, Gram Mg. Concentration of Free Acid = 0.20 X H C l 1 KO 0.8220 0 0487 -0.1 2 Be0 0.4330 0 0488 0 0488 0.8420 3 AlzOs 0.5110 4 0 0488 US08 ... 0.1894 5 hlnO 0 0488 6 0 0489 0.2548 CaO +o: 1 0.4100 7 0 0488 BaO ... 0,4330 0 0488 8 RzOaa 0 0489 0.8664 9 +o. 1 Fez03 10 A b 0 O49Zc 0.2110 +0.4 vi04 0.2110 10 9’; 0 0488 1’204 0 Od90C 0.4346 11 A +0:2 CrzOd 11 BtJ 0 0488 0.4346 CrzO3 12.4 SnO 0 0520 0.2380 +3:2 12 E d SnO 0 0-188 0,2380 ... 13 ‘rtIoz 0 0488 0,0980 0.1960 14 ThOz 0 0489 +c: 1 0 0514 0.1143 15Ab Ti02 +2.6 15 Bd 0 0489 +o. 1 0.1143 TiOz Concentration of free acid = 0.25 ’\i 11‘21 16 ThOi 0,1960 0.0487 -0.1 0,0486 17 0.1960 ThOz -0.2 0.0510 +2.2 18AL 0.1143 TiOz 0.0486 -0.2 0.1143 18 Bd Ti03 0.0515 +2.7 SnO 19 A b 0,2380 19 Bd 0,0186 -0.2 SnO 0.2380 Mixture of ceria, lanthana. praseodyrnia, a n d neodymia. Single precipitation, Residue is slightly colored. Double precipitation. Impurity Added, Gram
N O
CHa pared and purified ( 1 ) . From solutions 0.20 to 0.25 N in hydrcchloric acid, zirconium can be precipitated quantitatively in the presence of a number of elements, including thorium. This paper describea the use of this reagent for the selective precipitation of zirconium. The precipitate is voluminous and settles down quickly. As little as 2 mg. of zirconium oxide gives a precipitate large enough for convenient handling.
Expt. NO. 1 2 3
Separation of Zirconium from Other Elements
Separation of Other Impurities. All impurities added in the form of chlorides or nitrates are calculated to the oxides. Table I1 shows the results obtained.
...
-0.1
+o. 1 -0.2
...
OBSERVATIONS
+o:
1 +0.2 +O.l -0.2
Thorium 1s not precipitated by the reagent until the free acid concentration falls below 0.10 N . When present singly, titanium and stannous tin are not precipitated in acid solutions 0.10 N and stronger, but in the presence of zirconium small quantities are carried down even in 0.25 N free acid. The separation is, however, complete in a double precipitation. Vanadyl and chromium are not precipitated from neutral solutions, but contaminate the zirconium precipitate even a t 0.20 N acid concentration. The amount carried down is EO small that the weight of zirconia is not significantly higher,
PROCEDURE
Single precipitation. To the solution containing not more than 0.1 gram of zirconium oxide, add the calculated quantity of 2 N hydrochloric acid to give a free acid concentration of 0.20 N in a total volume of 200 ml. and 10 grams of solid ammonium nitrate, then dilute t o 100 ml. Boil. Add 2 grams of m-cresoxyacetic acid in 100 ml. of boiling water with continuous stirring.
539
ANALYTICAL CHEMISTRY
540
but the ignited residue is slightly colored. On a second precipitation the color disappears. Ferric iron is only partially precipitated in neutral solutions. Beryllium, aluminum, nickel, calcium, barium, uranyl, and trivalent rare earths (cerite group) are not precipitated. Sulfate interferes with the determination of zirconium.
( 3 ) and after removal of silica, zirconium was determined by double precipitation with m-cresoxyacetic acid in 0.20 iV hydrochloric acid. The results are shown in Table 111. For comparison, values obtained with the cupferron method ( 4 ) are included. LITERATURE CITED
ANALYSIS O F ZIRCOR
The method was checked by determining zirconia in a zircon ore from Travancore, India, which was found on qualitative analysis to contain silica, titania, and ferric oxide as well as zirconium. Thorium, aluminum, and the rare earths were not present in detectable amounts. The ore was fused with borax
(1) Koelsch, C. F., J . Am. Chem. Soc., 53,304 (1931). (2) Kumins, C. A., ANAL.CHEM.,19, 376 (1947). (3) Lundell, G. E. F., and Knowles, H. B., J . Am. Chem. Soc., 42, 1439 (1920). (4) U. S. Bur. Mines, BULL. 212 (1923). RECEIVED
April 4, 1950.
Fluorometric Determination of Benzil SAMUEL SASS AND JEROME GOLDENSON Chemical Corps, Technical Command, Army Chemical Center, Md.
iX AX investigation of miticides for use in clothing, a method Iimpregnated was required for the determination of small amounts of benzil in cloth. Attempts to find suitable colorimetric n
method for this new effective miticide ( 1 , 2, 7 ) were unsuccessful ( 4 ) . An adaptation of a gravimetric method (6) was found to be accurate for larger quantities of benzil in pure finish cloth ( 4 ) ,but impurities which are soluble in ethyl alcohol and insoluble in dilute hydrochloric acid interfered and the method was not suitable for trace amounts. Application of ultraviolet absorption measurements a t the strong absorption band of b e n d (260 mp) wap limited because of marked interferences in cloth containing ultraviolet-absorbing material such as certain sizing preservatives The condensation reaction ( 3 )of diketones such as benzil and nitrobends with alkylated aminophenols to form blue-red dyestuffs with yellow-red fluorescence was utilized in the method described here. In the procedure developed, benzil is determined photofluorometrically as a eondensation product with m-diethylaminophenol. It was also observed that very small amounts of alkylated aminophenols can be detected by condensation with an escess of benzil. APPARATUS
Klett photofluorometer, Model 2070, with matched tubes and filters 597 and 351. Beckman quartz spectrophotometer, Model CUV, range 220 to 1000 mp, with interchangeable hydrogen discharge lamp in housing! power supply unit, and a pair of fused silica absorption cells with borosilicate glass covers. REAGENTS
Benzil, technical grade material, purified by recrystallization from 95% ethyl alcohol. Analysis: C, 79.9%; H, 4.77% (calculated for benzil, CllH1002: C, 79.98%; H, 4.79%). Reagents for fluorometric method. m-Diethylaminophenol, recrystallized from 95% ethyl alcohol. Reference solution, 0.0004 gram of fluorescein in 1 liter of water. Reagents for gravimetric determination. 2,CDinitrophenylhydrazine solution made by saturating 2 N hydrochloric acid with 2,4dinitrophenyIhydrazine, 2 S hydrochloric acid, and 95% ethyl alcohol. DEVELOPMENT 0F FLUOROMETRIC METHOD
Investigations were conducted to determine whether the condensation reaction ( 3 )could be adapted as a quantitative method for the estimation of benzil. Exploratory work with several aminophenols indicated that a compound melting below 100" C. would give the best results. m-Diethylaminophenol (melting point 78" C.) was found to be a satisfactory reagent !Then condensed with benzil a t 100" C. for 90 minutes. Two to 4 moles of the aminophenol are required for each mole of benzil ( 3 ) . Re-
coveries of 98% and better were obtained on purified samples of benail by this method. Unsized, undyed cotton pure-finish herringbone twill cloth was impregnated with known quantities of b e n d . The miticide w a i then extracted with ethyl alcohol and determined by the fluorometric method. Recoveries of 97% or better were obtained. With b e n d which had not been impregnated in cloth recoveries of 98% or better were obtained.
Table I. Comparison of Fluorometric with Gravimetric and Ultraviolet Absorption Methods for Determination of Benzil i n Cloth Benzil, % Sample NO.
Fixative Chlorinated paraffin Chlorinated paraffin Chlorinated paraffin Chlorinated paraffin Chlorinated uaraffin None None None None
Fluorometric 5.17 5.20 2.16
Gravimetric 5.10 LO2
2.07
0.07
0.01 7.66 0.17 0.25
0.76
7:47 0.19
0.27 0.80
Cltraviolet absorption measurement 5.35
5.29 2.08 0.07 0.01 7.61 0.18 0.25
0.78
The results given in Table I were obtained by application of the follo~-ingfluorometric method t o samples of pilot plant impregnated cloth. As this cloth did not contain material that would interfere in the gravimetric or ultraviolet absorption methods, these methods were used for comparison purposes and are also described below. Cut the cloth sample into 1-cm. squares and mix to make more homogeneous. Place a 3.000- to 5.000-gram sample of cloth (enough to contain a t least 1 mg. of benzil) in the thimble of a Soxhlet extraction apparatus. Extract with 95% ethyl alcohol for 2 hours. If the extract is turbid, let it stand overnight and filter. Make up the extract to a known volume in a volumetric flask with 95% ethyl alcohol, so that a concentration of 0.01 to 0.04 mg. of benzil per ml. is obtained. Using a pipet or microburet, accurately measure 1 ml. of the solution into a test tube. To the same test tube add from a microburet 1ml. of a 95% ethyl alcohol solution containing 50 mg. per ml. of m-diethylaminophenol. Place the test tube over a hot water bath maintained a t 100' C. and heat for 90 minutes. (A 3-liter beaker covered by a Transite board a i t h holes large enough to support a test tube by the flare serves as an escellent bath when heated on a hot plate. The water level should be just below the bottom of the tube.) Wash the melt from the test tube into a 100-ml. volumetric flask and make up to volume with 95% ethyl alcohol. Make measurements on a Klett photofluorometer using filter? 597 and 351 with a reference solution of 0.0004 gram per liter of fluorescein. Prepare a curve relating fluorometer reading with
