and with sulfamic acid had the same average absorbancies (0.040). Table I1 shows the statistical analysis of the results of the chemical studies. An investigation of variance showed that the differences between average absorbancies are not significant. To determine the optimum concentration of sulfamic acid required to remove NOz interference without introducing complication to the original method, solutions containing 0.04 to 0.08% sulfamic acid in 0.1M sodium tetrachloromercurate (II) were prepared and used to determine sulfur dioxide in solutions containing 0.1 pg. SO2 and 10 fig. NOz per nil. Comparison was made with' the original method using Norfree SO1 solutions as the control. It was found that 0.06% sulfamic acid in 0.1M sodium tetrachloromercurate(I1) gave an absorbancy (0.025) nearest to that of the control (0.023). Using sulfamic acid in concentrations lower and higher than 0.06T0, absorbancies much lower than that of the control were obtained. Good results were obtained over normal concentration ranges of SO2 and a NO2 level of 10 p g . per ml. To ascertain the effect of sulfamic
acid on the stability of 0.1M sodium tetrachloromercurate(II), analyses of solutions containing O i l pg. sulfur dioxide per ml. were made using a solution of 0.1M sodium tetrachloromercurate(I1) which contained 0.06% sulfamic acid. No evidence of instability of the scrubbing solution was noted over a period of 21 days. A series of absorbing solutions (0.1M sodium tetrachloromercurate(I1) with 0.06y0 sulfamic acid) containing 0.01, 0.1, and 1.0 pg. per ml. of sulfur dioxide was prepared. To each solution 10 pg. per ml. of nitrogen dioxide, in the form of sodium nitrite, was added. Sulfur dioxide was then determined. At the hundredth microgram level of sulfur dioxide with 10 pg. of nitrogen dioxide, sulfamic acid still proved to be effective in preventing nitrogen dioxide from interfering in the colorimetric determination of sulfur dioxide, and the red-violet color of the test developed rapidly. Spectrophotometric measurements could be done within 30 minutes. At 560 mp the absorbancies of the samples followed the BeerLambert law. Sulfur dioxide can be quantitatively determined within 48 hours after col-
lection, with no loss of SO2 from the sample. Longer storage of sulfur dioxide in sodium tetrachloromercurate (11) with 0.06% sulfamic acid is not recommended because erratic results may occur. In this regard, the modified procedure suffers in comparison with the original method. The effective elimination of interference from the oxides of nitrogen makes possible the adaptation of this general method to the determination of sulfur in the micro- and ultramicroanalysis of organic substances and will be the subject of a later communication. LITERATURE CITED
(1) Altahuller, A. P., Schwab, S. M., Bare, M., ANAL.CHEM.31,1987 (1959). (2) Baumgarten, P., Marggrd, I., Ber. 63, 1019 (1930). (3) Marshall, E. K., Litchfield, J. T.,
Science 88, 85 (1938). (4) Ruchhoft, C. C., Placak, 0. R., Sewage Works J. 14, 638 (1942). ( 5 ) West, P. W., Gaeke, G. C., ANAL. CHEM.28, 1816 (1956).
RECEIVEDfor review March 12, 1962. Accepted July 19, 1962. Work BU ported by the National Institutes of Healti under Public Health Service research grant RG-7992.
Studies in Paper Chromatography of a Few Cations with Solvents Containing Chloroform R. P. BHATNAGAR' and N. S. POONIA Deparfment o f Chemistry, Holkar College, Indore, India
b Chloroform and chloroform mixtures were studied as possible solvents for the paper chromatographic separation of inorganic ions. R, values for C U + ~ ,Ni+z, Cof2, and Fe+3 are given for the various solvent compositions tested. Although chloroform itself is not an effective solvent for inorganic paper chromatography, chloroform mixtures containing alcohols, ketones, esters, or phenols give qualitative separations on paper disks and strips for the four inorganic ions studied.
P
solvents having donor properties have been used extensively in the paper chromatography of inorganics. However, little work has been reported with polar solvents which are not electron donors. Such a solvent is chloroform, which has been virtually neglected as a solvent for this type of chromatographic work. Lacourt, SomOLAR
Present address, Government Science College, Gwalior, India. 1
mereyns, DeGeyndt, arid Jacquet made an unsuccessful attempt to separate nickel, cobalt, and copper ions with chloroform (8). However, a 10% chloroform solution in acetone separated nickel from copper quantitatively (3). Laskowski and McCrone (4) successfully separated several ions using chloroform on paper impregnated with 8-quinolinol. But none of these studies can be regarded as a complete, systematic investigation of the usefulness of chloroform. The present work explores the possibility of using chloroform and chloroform mixtures for inorganic paper chromatography. Ion migration studies and R, measurements are included for some 35 mixed solvents. Separations are indicated in those cases for which the differences in R, values were reasonably large. EXPERIMENTAL
Apparatus. A glass chamber (20 X 20 x 50 cm.) and a cylindrical battery jar (12 cm. in o.d., and 35 cm. high)
with the usual accessories were used for descending and ascending paper chromatography, respectively. Disk chromatograms were prepared in air-tight glass chambers. The disks were supported over the rims of Petri dishes which held the solvent. Watch glasses were placed over the disks to keep them in position. Papers. Whatman No. 1 paper was used for all preliminary studies, while 3-mm. Whatman was used for the final strips (30 x 3 cm.); the disks were 11 cm. in diameter. Disks with wicks of about 3 cm. cut radially were used instead of disks with capillaries. The wicks were 2 to 3 cm. wide at the connecting end and about 1 mm. wide a t the free end. Reagents. Cobalt, nickel, copper (11), and iron(II1) solutions were prepared from their nitrates (E. Merck, pro-analysis quality). Solutions of 5 to 10 pg. of cation per 100 ml. were used for R, measurements; solutions of 20 to 50 pg. of cation per 100 ml. were used for the separations. All organic solvents were doubly distilled. Organic mixtures were prepared on a volume to volume basis, VOL 34, NO. 10, SEPTEMBER 1962
1325
Figure 2. Separation chromatogram
on
circular
Solvent 22, 4.30 hours
Figure 1. A. B. C.
Circulai' chromatograms
Solvent 2, 5 hours Solvent 5,4 hours Solvent 11,5 hours
with the exception of phenol solutions. Aqueous chloroform was prepared, by mturating absolute chloroform with an excess of deionized water. The nonaqueous layer was separated and served as aqueous chloroform. The aqueous layer was used to saturate the atmosphere in the chromatographic chamber.
D. Solvent 9,7.30 hours E. Solvent 15, 2 hours F. Sclvsnt 17, 2 houn
A 0.5% solution of dithio-oxamide in 90% alcohol and a 5% aqueous solution of potassium ferrocyanide were used as spray reagents. Procedure. RI measurements for Cu+*, Ni+', Cot*, and Fe+J were made on disks of Wbatman 3-mm. paper. The disks were spotted at the center
with the cation solutions using a micropipet. Outlines of the wet spots were marked with pencil. The disks were dried at room temperature (-25'' C.) and developed so as to obtain adequate migration. The solvent fronts were marked again, and the disks were dried and sprayed (dithiwxamide for copper, nickel, and cobalt; potassium ferrocyanide for iron). Chromatograms of copper, nickel, and cobalt were developed in a chamber saturated with ammonia vapor and then removed for drying. Successful separations (Figures 1 to 4) for the four cations were obtained with solvents 2, 5, 8, 9, 11, 15, 17, 22, 23, and 24 (see Table I for solvent composition). I n the separations, di-
Table I. R, Values for Individual Cations in Different Solvents
Time
NO.
Solvent ComDcmitiona
of Run, Hr.
1.
2.
0.87
0.93
0.22 0.00
0.29 0.24 0.39 0.00 0.00 0.11
0.66 0.00 0.00
3.
4. 5.
4.00 3.00 2.00 1.50 1.45 1.45 1.25 1.25 1.00
6.
7.
8.
9. 10.
0.00 0.00 0.00 0.00 0.05 0.00 0.00 0.00 0.06
0.70
0.09 0.00
0.35 0.63 0.11 0.00
0.03 0.00
0.00 0.00
0.00 0.00 0.02 0.00 0.00 0.00
0.57 0.69 0..51
0.31 0.14 0.00
0.00 @.IO 0.07 0.00
0.22 0.17 0.03 0.04 12. 0.00 0.00 13. 0.00 0.00 14. 0.19 0.09 0.10 1.00 15. 49 ml. A: 49 ml. G. 2 ml. K 0.35 0.66 0.90 1.00 2.40 16. 50 ml. A; 50 ml. H' 0.56 0.66 0.65 0.74 2.40 17. 49 ml. A, 49 ml. H, 2 ml. K 0.00 0.81 0.00 0.28 1.25 18. 100 ml. A, 3.47 grams I 0.74 0.81 0.78 0.85 2.00 19. 100 ml. A, 3.47 grams I, 10 ml. L(2N) 0.00 0.07 0.00 0.00 2.25 20. 100 ml. A, 100 grams I, satd. with L(2N) 0.54 0.61 0.50 0.54 2.10 21. 50 ml. A, 50 ml. B, 6.0 grams I 0.09 0.33 0.29 0.39 2.15 22. 46 ml. A, 23 ml. F, 23 ml. B, 8 ml. K 0.40 0.52 0.07 0.17 23. 49 ml. A, 24.4 ml. F, 24.4 ml. G, 0.2 ml. K 1.30 0.10 0.32 0.00 0.08 3.25 24. 43.2 ml. A, 46.1 ml. F, 10.7 ml. K, 2 grmle 1. 25. 45 ml. A, 22.6 ml. J, 23.4 ml. D, 9 ml. L 1.30 0.84 L00 Slight diffusion 0.00 0.09 (glacial) A Chloroform, B methanol, C ethmal, D-2-propanol, E butanol, F amyl alcohol, G acetone, H Zbutanone, I tetrmhlaride, K coned. hydrochloric acid, L acetic axid. 11.
(1
1326
ANALYTICAL CHEMISTRY
0.10 0.70
0.22 0.77
0.00 0.43 0.00
0.37 0.51 0.14
0.00
0.00
0.00
0.38 0.23 0.00 0.19
0.06
0.52 0.57 . 0.30 0.35 0.00 0.15 0.00 0.03 Slight diffusion 0.10 0.20 0.22 0.40 0.75 0.85 0.00 0.70 0.61 0.84
0.00
0.18
0.22 0.40 0.55 0.32
0.26
0.74 0.49
0.00
0.08
0.56
phencl, J carbon
Figure 3. Separation on chromatogram
circular
Solvent 24,7 hours
thic-oxamide was applied and the copper, nickel, and cobalt rings were covered with a thick paper stencil. Potassium ferrocyanide was then sprayed. This avoided diszguration of the copper rings by the spray. Strips of Whatman 3-mm. paper were used for separations with solvents that had given good sqarations. The strips were spotted 3 cm. from the edge which dipped into the solvent. Ascending and descending techniques were used to achieve sharp separations. The strips were removed from the chambers after the solvents had traveled 20 to 25 em. and sprayed as in circular chromatography. Good separations were obtained for copper and iron with solvents 1, 2, 5, 8, and 9. The nickel and cobalt spots did not separate well (Figure 5). RJ Measurements. All RJ measurements tiere made with respect t o inner as n-ell as outer edge& of the rings. Each RJ value represents the mean of about 12 measurements a t different point,s on a particular ring. RESULTS AND DISCUSSION
Preliminary studies with absolute chloroform gave no migration for the cations, contrary to the observations of Lacourt et al. ($). Aqueous chloro-
Figure 5. Strip chromatograms A. Solvent 2,36 hours B. Solrent 8.48 h o w C. Solvent 9,48 hovn
form resulted in tailing in the strip stndes Lederer Pollard, Elbeith, and McOmie (7), and Harasawa (1) have shown that the solvent must he polar for effective separation of inorganic species. Chloroform alone is unable to dissolve inorganic salts or form complexes with them. However, the
(a,
32.I...
Figure 4. Separation chromatoarom
on circular
Solvent 23, 8.30 hours
present study indicates that when chloroform is mixed with alcohols, ketones, esters, or phenols, inorganic paper chromatography is feasible and successful. Results in Table I illustrate that the addition of chloroform to polar solvents having donor properties increases the polarity of the system, thus aiding movement and separation. VOL 34, NO. 10, SEPTEMBER 1962
1327
With solvent mixtures containing alcohols (Table I), Rf values d e c m with increase in the molecular weight of the alcohol added (4, 8). No movement of the ions occurred with pentanolchloroform mixtures. Butanol and %propanol aided in the slight movement of cobalt and iron only (Table I). Solvent mixtures 14 and 16 containing ketones gave better movement for the cations. Acetone mixtures gave a reasonable Rf value for iron(II1) only. However, the presence of %butanone aided in the migration of all four cations. With this solvent, cobalt and nickel gave greater Rf values than iron and copper, because the nitrates of cobalt and nickel form complexes with 2butanone (8). The presence of hydrochloric acid modified the migration tendencies of the ions in each case (Table I), and helped to give constant and reproducible R, values. When hydrochloric acid was used, iron had an Rf value of 1.0 in all cases. The Rf values decreased in the following sequence when acid-containing solvents were employed : Fe > Cu > Co > Mi. (Chloroformmethanol and chloroform-acetone systems were exceptions.)
The addition of phenol to an organic solvent enhanced the polarity and acidity simultaneously. Hence, Rf values for the cations increased in its presence. Addition of acetic acid modified the Rf values still more. However, increasing the percentage of phenol to 10% had no useful effect. Separations with ternary or polynary mixtures were better than those with binary combinations. The solvents containing hydrochloric acid were generally more successful and gave h e r separations (see Figure 1). Separations with mixtures containing alcohols and acids were successful (Figure 1,A to D), although separations with ketone-containing mixtures were better (Figure 1,E and F). Linstead, Burstall, and Wells (6) have shown that solvents containing low molecular weight ketones, water, and acid are satisfactory for iron, cobalt, nickel, and manganese separations. Results of our separations are in agreement with those of Linstead et $. (6). However, our studies with solvents containing aliphatic alcohols and hydrochloric acid were successful, contrary to previous findings (6). Solvents 22 and 24 gave a good separation (Figures 2 and 3), while solvent 23
gave nearly quantitative separation for the ions under study (Figure 4). Time required for separations is much more than shown in Table I for R, studies of single cations. This is partly due to the interfering effect of cations on the movement of each other and partly due to other adjustments xade t o ensure good separations. LITERATURE CITED
(1)Harasawa, S.H., J . Chem. Soc. Japan, Pure Chem. Sed. 72, 107, 236, 423 (1951). (2)Lacourt, A., Sommereyns, H. G., DeGeyndt, E., Jacquet, O., Mikrochic 36, 117 (1951). (3) Lacourt, A., Sommereyns, G., Jac uet, o., Wantier, G., B ~ U .h e . d i m . France 1951, 873. (4) Laekowski, D. E.,McCrone, W. C., ANAL.CHEM. 23, 1579 (1951). (5) Lederer, M., A d . Chim. Acta 4, 629 (1950); 5, 185 (1951). (6) Linstead, R. P., Burstall, F. H., Wells, R. A., J . Chem. Soc. 1950, 516. (7) Pollard, F. H.,Elbeith, M., McOmie, J. F. W . , Discussions Faraday SOC.7 , 183 (1949). ( 8 ) Pollard, F. H., McOmie, J. F. W., “Chromatographic Methods of Inorganic Analysis,” Butterworths, London, 1953. RECEIVED for review December 18, 1961. Accepted June 27, 1962.
Spectrophotometric Determination of Hydroperoxide in Diethyl Ether WINTHROP C. WOLFE Building Research Division, National Bureau of Standards, Washington 25, D. C. ,An improved acidic titanium reagent for determining hydroperoxide is described. The reagent is used to determine hydrogen peroxide, terf-butyl hydroperoxide, 1 -ethoxyethyl hydroperoxide, and the unknown peroxide resulting from the oxidation of diethyl ether on storage or on exposure to ultraviolet radiation. 1 -Ethoxyethyl hydroperoxide has been postulated as a product of the oxidation of diethyl ether in air. Samples of diethyl ether, which had been oxidized in storage or by exposure to ultraviolet radiation, are analyzed by the acidic titanium method, using the improved reagent, and by an iodometric method, and the results are compared. Residues from the evaporation of oxidized ether are analyzed in an attempt to identify the oxidation products.
R
Ecent publications (7, 10) show a renewed interest in the acidic titanium method (6, 9) for hydrogen peroxide and various organic and 1328
ANALYTICAL CHEMISTRY
inorganic hydroperoxides which can be converted to hydrogen peroxide. Unlike iodometric methods (2, 6, 8, 12), often used for hydrogen peroxide and hydroperoxides, the acidic titanium method is not affected by air or oxidbing agents and does not require titration. The titanium method is extremely sensitive and uncertainties due to blank determination can be eliminated by using an optical spectrometer or filter photometer, with the reagent as the blank. With the development of pure, colorless titanium tetrachloride and a technique for preparing stable sdutions in water or in aqueous hydrochloric acid solution ( I ) , acidic titanium reagent can be prepared from any desired concentration of acid and of titanium. This is impossible by means of the methods used to prepare acidic titanium sulfate solution. EXPERIMENTAL
Preparation of Acidic Titanium Tetrachloride Reagent. A 10-ml. portion of 6 N hydrochloric acid and
a 10-ml. portion of water-white titanium tetrachloride (1) were cooled separately in beakers surrounded with crushed ice. The chilled titanium tetrachloride was added dropwise to the chilled acid solution. (Foaming may occur if the acid solution is added to the titanium tetrachloride.) The mixture was allowed to stand at ice temperature until the yellow solid dissolved and was then diluted to 1 liter with 6N hydrochloric acid. Solutions prepared in this way contain about 4 mg. of Ti per ml. and are stable; the titanium tetrachloride did not hydrolyze when the reagent was allowed to stand at room temperature for 18 months. However, solutions prepared in the same manner from titanium tetrachloride and distilled water or less concentrated hydrochloric acid solutions became turbid on standing at room temperature-i.e., a solution prepared from 20 ml. of titanium tetrachloride and 2 liters of 1N hydrochloric acid formed a white precipitate of TiOz on standing at room temperature for one month. Analysis of Aqueous Hydrogen Peroxide Solutions. Aliquots of aqueous hydrogen peroxide solutions were
