Spectrophotometric Determination of 0-Phenylphenol with Titanium Sulfate PATRICK H. CAULFIED AND REX J. ROBINSON Chemical Laboratories, University of Washington, Seattle 5, Wash. ples leaching with acetone or ether is satisfactory and more convenient. From acidified aqueous solutions o-phenylphenol may be extracted with ether. The volatile solvent is evaporated, and the solid o-phenylphenol is reacted directly with the titanium reagent. For 0.5 to 4.0 mg. of o-phenylphenol, 25 ml. of reagent are sufficient. The solution is stirred for 5 minutes to dissolve the sample and to fully develop the color. The optical density is measured a t 450 mp using a reference solution of concentrated sulfuric acid containing approximately the same concentration of phenol as the unknown sample. The concentration of o-phenylphenol is obtained from a suitable calibration curve.
Hall and Smith ( 2 )observed that there were color reacI tions ’1905between titanium(1V) and various phenols in concenN
trated sulfuric acid. Thymol was selected by Lenher and Crawford (3) as the most suitable reagent for the determination of titanium. The application of this reaction to the analysis of phenolic compounds, has, as yet, not been recorded in the literature. The present paper reports the investigation of the reaction between titanium(1T.’) and various phenols with special attention to the determination of o-phenylphenol. o-Phenylphenol has considerable industrial use as a preservative for casein paints, cosmetics, leather finishes, and sizing materials. Consequently, its rapid and accurate estimation is of importance.
EXPERIMENTAL
Absorption Spectrum of o-Phenylphenol-Titanium Complex. The absorption spectrum of the o-phenylphenol-titanium complex, for a solution containing 50 micrograms of o-phenylphenol per milliliter of reagent, is recorded in Figure 1. As shown in this figure, the region of maximum absorption is broad with the maximum optical density a t 450 mp. Effect of Time on Color Development. The rate of color development and the stability of the color complex hrere observed a t 450 mp for a solution containing 80 micrograms of o-phenylphenol per milliliter of reagent. Full color development was attained in 5 minutes, which is approximately the minimum time to dissolve the solid o-phenylphenol in the reagent solution. There v,-as no apparent change in optical density during the observation period of 2 hours. The sample was not protected from natural light between spectrophotometric readings. The constancy of optical density reading indicated that the complex was not affected by such exposure.
SOLUTIONS AND REAGEhTS
Titanium Sulfate Reagent. This reagent was prepaied by digesting 0.450 gram of J. T. Baker’s C.P. anhydrous titanium dioxide in 1 liter of concentrated sulfuric acid until a clear solution was obtained. This usually required heating for several hours a t a temperature of about 300” C. The solution was found to have a small and constant optical density throughout the visible spectrum.
t
t
m
z W
n J
a
0 I-
n
0 t 0.0
t
fn
2 W
WAVE LENGTH-my
,
n
Figure 1. Typical Absorption Spectrum of o-Phenylphenol-Titanium Complex in Sulfuric Acid
J
4
0 I-
n 0
Standard o-Phenylphenol Solution. -4diethyl ether solution was prepared to contain 0.100 gram of Eastman white label ophenylphenol per 100 ml. of solution. This solution did not discolor upon standing.
2
4
6
6
10
X ML 0-PHENYLPHENOL
EQUIPMENT
Figure 2. Composition of o-Phenylphenol-Titanium Complex by Method of Continuous Variation X = mi. of 0.0028 M o-phenylphenol; 10-5 = ml. of 0.0028 .If
The spectrophotometric measurements were made with a Cary Model 11, quartz recording spectrophotometer used a t slit selection zero. Fused quartz cells with a light path of 1.00 cm. were used throughout the investigation.
titanium reagent
PROCEDURE
Adherence of Beer’s Law. -4linear curve was obtained in the preparation of a calibration curve over the range of 4 to 160 niicrograms of o-phenylphenol per milliliter of titanium reagent. This indicates the applicability of Beer’s law for this range of concentrations of phenol. Composition of the o-Phenylphenol-Titanium Complex. The composition of the o-phenylphenol-titanium complex was studied using the method of continuous variation (4). Solutions of varying o-phenylphenol-titanium proportions in sulfuric acid w x e prepared from 0.0028 ;If solutions of phenol and reagent. The spectra of theee solutions had similar absorption characteristics. V i t h this method of color development, the wave length of maximum absorption occurred a t 430 mp, in contrast to 450
When necessary o-phenylphenol may be separated from interering materials by steam distillation. However, in certain sam-
Table I. Analysis of Vegetable-Tanned Sheepskin (Per cent o-phenylphenol by weight) Experimental
Deviation
1.41
1.40 1.40
0.01 0.01
1.80 2.00
1 77
0.03
1.95 1.95
0.05
Calculated
0.05
982
V O L U M E 25, N O . 6, J U N E 1 9 5 3 Table 11.
Spectrophotometric Data of Various PhenolTitanium Complexes
Name of Phenol m-Aniinophenol a-.4minophenola p-Aminophenol p-Bromophenol Catechol p-Chlorophenol a-Cresol 2,4-Dichlorophenol p-Ethylphenol Hydroquinone p-Hydroxybenzaldehyde p-Hydroxybeneoic acid 5-Hydroxy-l,3-dimethylpheno 1-Naphthol
Wave Length of Max. Absorption,
14p 417
...
2-Iiaphthol o-Nitrophenol" p-Nitrophenol Phenol o-Phenylphenol p-Phenylphenol Phenyl salicylate Phloronlucinol
Specific E x t . , Liter/(Gram Cm.) 12.6
...
418 473 460 465 455 490 473 503 420 390 453 440 655 435
17.6 20.6 27.4 18.4 16.2 16.8 34.4 63.2
451 455 450 482 435 415 460 405 469 438
5.0 15.6 12.2 28.8 15,7 4.7 22.4
...
...
a
983
1.5
4.3 17.7 33.6 35.2 28.4
...
6.8
16.8 20.4
No visible absorption spectrum. Failed t o dissolve in titanium sulfate reagent.
nip obtained with the earlier method when reacting the reagent with the solid phenol. There was no indication of secondary absorption maxima. &4color complex with a 1 to 1 molar ratio of o-phenylphenol to titanium is indicated by Figure 2. A study of catechol-titanium and hydroquinone-titanium complexes Pholved that they also formed in a 1 to 1 molar ratio. Griel and Robinson ( 1 ) reported the thymol-titanium complex formed with a 1 to 1 molar ratio. Appreciable dissociation is indicated with all four of these complexes. Testing the Method of Analysis. The following example illus-
trates the accuracy of the procedure. Samples of vegetabletanned sheepskin were prepared containing between 1.0 and 2.0% of o-phenylphenol by weight. These samples were leached by ether and reacted with titanium reagent as described in the procedure. The experimental results, presented in Table I, indicate an error of about 1.5%. Sublimation of o-Phenylphenol. B sample of 0.3144 grams of o-phenylphenol with a surface area of 2.46 sq. cm. lost about 0.2% by weight when heated for 12 hours a t 37' C. This emphapizes the importance of reacting the solid o-phenylphenol with the titanium reagent immediately after evaporation of the volatile solvent. Reaction of the Titanium Reagent with Other Phenols. The color-forming characteristics of the complexes formed in the reaction of the titanium sulfate reagent with 27 phenols have been recorded in Table 11. Included are the wave lengths of maximum absorption and the specific extinction coefficients, which have been calculated on the basis of 100% association of the phenol. These data indicate both the relative interference of the various phenols with the estimation of o-phenylphenol and the utility of the titanium sulfate reagent in the estimation of the various phenols. 4ChNOWLEDGMENT
Part of the spectrophotometric measurements in this investigation were made by the first author on the Cary spectrophotometer of the United States Air Force, Materials Laboratory, Kright .4ir Development Center, Dayton, Ohio. LITER4TURE CITED
(1) Griel, J. V., and Robinson, R. J., h . 4 ~ CHEW, . 23, 1871 (1951). (2) Hall, J., and Smith, J., Proc. Phil. Soc., 44, 196 (1905). (3) Lenher, V.,and Crawford, W.G., J . Am. Chem. Soc., 35, 138 (1913). (4) T-oshurgh, I T , C., and Cooper, G. R., Ibid., 63,437 (1941). R E C E I ~ for E Dreview Soyember 24, 1953. Accepted March 2, 1953.
Polarographic Characteristics of Metallic Cations in Acetate Media MICHAEL A. DESESA AND D.47lD Y. HUME Massachusetts Institute of Technology, Cambridge 39, AMass.
ARTHUR C. GLAJIM, JR.,
AND
DONALD D . DEFORD
.Vorthu.estern University, Ecanston, I l l . XCIDEPZTAL to
a study of complex formation in acetate medium
I ( 2 ) and the development of a polarographic method for the
determination of indium ( 1 ), observations have been made of the polarographic characteristics of 29 metal ions in various acetatecontaining supporting electrolytes. The measurements were made with Model X X I Sargent visible recording polarographs. The initial and final span voltages were measured to 1 0 . 1 mv. with an auxiliary potentiometer when very precise determinations of half-wave potentials were required. All measurements were made a t 25 + 0.1" C., and corrections were applied for zR drop in the cell unless negligible. Potentials were measured directly against the saturated calomel electrode. In the 1I.I.T. aork, the supporting electrolyte was always a mixture 2 -l4in ammonium acetate and 2 *If in acetic acid with 0.01% of gelatin added as a maximum suppressor. The workers at Sorthwestern University employed a mixture 1 -11each in sodium acetate and acetic acid, unless otherwise indicated, with 0.001%gelatin added. All reagents were made up from c.P., or better, grade chemicals. Most of the metallic constituents were used as solutions of the nitrates in dilute nitric acid. Reagent grade disodium acid arsenite, sodium molybdate, thallous acetate, stannous chloride, gallium sesquioxide, ferrous sulfate, tungstic acid, vanadium
pentoxide, gold chloride, and indium metal were used in the preparation of the corresponding stock solutions. The palladium stock solution was obtained by dissolving the metal in aqua regia. Where complex-forming anions such as chloride could not be excluded in the preparation of the stock solution, care was taken to keep their concentration low enough in the final acetate mixture so that they exerted no appreciable influence. Polarograms were taken with the various metallic constituents present a t a concentration of 0.001 M. The data are summarized in Table I. The half-wave potentials in the two media were found to be similar but not identical, values in the more concentrated buffer invariably being slightly more negative. Experiments with a number of the elements showed the half-wave potentials to be quite dependent on acetate ion concentration, as would be expected in view of the fact that most of the elements form moderately stable acetate complexes. Copper, although showing a single wave in acetate buffers of moderate concentration, developed a clearly defined double wave in 4 -21ammonium acetate, indicating stabilization of the cuprous state. The double wave obtained with antimony was not inveatigated further but is probably attributable to sluggish equilibrium between different complex formfi. Uranyl ion in 1M am-
