ANALYTICAL CHEMISTRY
1792 Table VII. Saii:L4c 1
Sample 2
Jainlde 1
Sample Analyses of Certain Treated Ammonia Still Wastes Vntreated Lntreated L'ntreatcd Tre2ted with
500 p.p.rn. phenol-+amino antipyrine teat 509 p.p.m. phenol-bromine t.ut.i2i:netric rest 1100 p.p.rn. phenol-hron.ine t,irbi iirnetric tcit increasing ai?ioii1its oi a n o x i c l i z i i i ~agent
Phenol Found, P.P.31. 48 3.4 2.5
Sample 2
Units of Oxidizing Agents Used 2.5 5 0 8.4
1.3
10.0
9.4
Treated with active charcoal
author's experience indicates, however, that this will seldom be necessary. The time required for determining phenols by the described procedure varies from about 20 minutes for the bromine turbidimetric test t o about 2 hours for determining a 25 p.p.b. concentration by the 4-aminoantipyrine procedure. COiYCLUSION
h procedure has been developed for determination of any concentration of phenols likely to be met in aqueous wastes of I)y-product coke plants.
I t seems highly probable that the
method can be adapted for wide use. The adaptation must take into consideration both the type of phenolic bodies to be determined and the impurities to be removed. As might reasonably be expected, the results on the mixed tar acid solutions (Table 11)are noticeably lower than those on pure phenol (Table VI). This is presumably due in part to the p-cresol which, in isolated condition, a t least, gives no color with the 4-aminoantipyrine reagent, and to the difference in molecular weight of the alkylated phenols. The results given in Table VI1 on sample I, untreated, show the turbidimetric bromine test and the antipyrine test to be in good agreement, though the turbidimetric test is much quicker. The remainder of the figures illustrate the manner in which the effects of a progressive purification treatment of waste can be followed by meany of the proposed analytical method. LITER4TURE CITED
Baylis, J . Am. Wuter W o r k s Assoc., 19, 597-604 (1928). Emerson, J . O r g . Chem., 8, 417-19 (1943). Emerson and Kelly, Ibid., 13, 532-4 (1948). (4) Martin, ANAL.CHEM.,21, 1419 (1949). (5) Shaw, ISD. ENG.CHEM.,ASAL. ED.,1, 118 (1929). (6)Ibid., 3, 273 (1931). (7) Stevens, I n d . Eng. Chem.. 35, 655 (1943).
RECEIVED October 4, 1950. Contribution of the Fellowship o n Gas Purification sustained a t Mellon Institute by Koppers Co.. Inc.
Determination of Sodium Carboxymethylcellulose in Detergent Mixtures By the Anthrone Method HENRY C. BLACK, JR. Burnside Laboratory, E . I . du Pont de Nemours & Co., Inc., Penns Grove, A method was needed for determination of sodium carboxymethylcellulose in household detergents. The green color formed by reaction of anthrone with carbohydrate materials in sulfuric acid solution provided the basis for the present method. Color intensity is measured with a spectraphotometer. Controlled heating is necessary for reproducible results. Color intensity varies inversely with degree of substitution of the carboxymethylcellulose. The
I
S 1946, Dreywood ( 3 ) described a qualitative method for the
detection of carbohydrates by the use of anthrone (9,lOdihydro-9-ketoanthracene) in concentrated sulfuric acid. The formation of a green-colored complex indicated a positive test. Other investigators (6, 9) attempted to adapt the method to the quantitative estimation of carbohydrates. Viles and Silverman (9) described a procedure for the determination of cellulose in the dust of air samples collected in a textile mill. In this procedure, the dust was dissolved in 60% (by volume) sulfuric acid and a O.lyosolution of anthrone in 9570 sulfuric acid was added. The heat evolved on mixing developed the color. The solution was cooled after formation of the green color, and its transmittance at 625 mp was measured with a photometric instrument. The cellulose concentration was calculated from a calibration curve prepared in the same manner using known quantities of cellulose. Dreywood (3) demonstrated that positive results were obtained not only with carbohydrates but with certain carbohydrate
N. J .
accuracy is 2% relative, provided the degree of substitution is known. Other carbohydrates, carbohydrate derivatives, furfural, 5-hydroxymethylfurfural, and certain polyoxyethylene derivatives of fatty acids and phenols are the only known interfering substances. The method should be useful for determination of carboxymethylcellulose in other mixtures and, with appropriate modification, of other carbohydrates and carbohydrate derivatives. derivatives as well. Samsel and DeLap ( 7 ) applied the anthrone reaction to the determination of methylcellulose. Initial attempts to apply the procedure developed by Viles and Silverman to the determination of sodium carboxymethylcellulose (NaCMC) in detergent mixtures were unsuccessful. Reproducible results were very difficult to obtain, primarily because of the lack of control of the heat evolved on mixing the sample and the anthrone reagent. In order to improve the reproducibility, it was necessary to eliminate the heat evolved on mixing and then develop the color by heating under controlled conditions. APPARATUS AND MATERIALS
All transmittance measurements were made with a Beckman Model DU spectrophotometer with 1.00-cm. Corex cells. Samples of sodium carboxymethylcellulose of low (0.1 t o 0.8) degree of substitution, manufactured as technical grade by
1793
V O L U M E 23, N O . 1 2 , D E C E M B E R 1 9 5 1 the Du Pont Co., were purified by precipitating the free acid carboxymethylcellulose with strong mineral acid and washing with water. The purity of the free acid carboxymethylcellulose after washing and drying was assumed to be lOOy,. Refined sodium carboxymethylcelluloses of high degrees of substitution (greater than 1.0) were specially prepared by R. W. Sommers and M. F. Fuller a t the Burnside Laboratory and were used without further purification. Purity of refined sodium carboxymethylcellulose was determined by ash and by the copper salt precipitation method ( 2 ) . 100
1
BLANK
1
I
solution is cooled immediately and diluted to the mark with 60% sulfuric acid. The transmittance a t 625 mF is measured with a Beckman spectrophotometer or other photometric instrument. A calibration curve is prepared by dissolving 0.1 gram of sodium carboxymethylcellulose, of the same degree of substitution as the sodium carboxymethylcellulose in the detergent, in 100 ml. of 607, sulfuric acid, and repeating the procedure on 0.2-, 0.5-, and 1.0-ml. aliquots of this solution. A plot of transmittance against concentration is made on one-cycle semilog aper and the best straight line is drawn through the points. TRe concentration of sodium carboxymethylcellulose in the sample solution is read from this curve. If the degree of substitution of the sodium carboxymethyl cellulose in the sample is unknoiin, an estimate must be made on the basis of experience or other information. EXPERIMENT4L
Q U A N T I T Y OF ' M A T E R I A L ' . I m g / 5 0 m l
I 200
450
500
I 550 W A V E LENGTH
Figure 1.
600 IN
650
700
750
my
Spectral Transmittance of Complexes of Anthrone with Cellulose and with Carboxymethylcellulose
The anthrone (melting point 154-155" C.) was obtained from The Matheson Co., East Rutherford, N. J., and was used without further purification. The anthrone-sulfuric acid solution was prepared by dissolving 1 gram of anthrone in 1 liter of 95% sulfuric acid. The solution was allowed to stand for a t least 4-hours before using and was discarded after it was 24 hours old. Just before use, the concentrated acid reagent solution was diluted with water to 60y0 (by volume) sulfuric acid, and cooled to room temperature.
Figure 1 shows the curve obtained Fvhen transmittance of the green comples is plotted against wave length, for cellulose and carboxymethylcellulose. Maximum absorption occurs a t 625 mp. The concentrations of cellulose and carboxyniethyIreIlulose were identical. Figure 2 shows the adherence to Beer's law when the logarithm of the transmittance is plotted against concentration. I t can be seen from Figures 1 and 2 that at a given concentration the transmittances obtained u-ith cellulose and with carbosymethylcellulose are very different. This difference is discussed below. Effect of Temperature. I t had been recognized by previous investigators that an elevated temperature was necessary to develop the color and that the heating time had a critical effect on the intensity of the color produced. Several determinations were made using the same conditions throughout, except for the time of heating. I t was found that minimum transmittance occurred a t about 15 minutes (Figure 3).
PROCEDURE
The sample, usually about 1 gram of a typical powdered household detergent, is dissolved (2 to 3 hours) in 607, (by volume) sulfuric acid and made up to volume with 60% sulfuric acid in a 100-ml. volumetric flask. If the solution is not clear, it is filtered through a dry medium porosity sintered-glass crucible into a dry container. An ali uot containing not more than 1.0 mg. of sodium carbox~me%~lcellulose is placed in a 50-ml. volumetric flask, 30 ml. of the diluted anthrone reagent are added, and the flask is placed in a boiling water bath for 15 minutes. The
-
0o
IO
20
30
40
50
TIME I N MINUTES
Figure 3.
C O N C E N T R A T I O N I N rng
50ml.
Figure 2. Transmittance of Anthrone Complex us. Cellulose or Carboxymethylcellulose Concentration
Effect of Heating Time on Color Development
Effect of Aging Reagents and Solutions. One of the main disadvantages of the method is the instability of the anthronesulfuric acid reagent. Variable results are obtained if the reagent is used before it is about 4 hours old. Progressively diminishing color intensities are produced as the age of the reagent increases beyond 24 hours. Likewise, color intensity decreases as the age of the sulfuric acid solution of cellulose material increases. Table I illustrates the effect of the age of the reagent, and Table 11, the effect of the age of the sample solution. After the green complex has been formed, the color is stable for several hours. The transmittance increases only about 1% in 24 hours. I t is not necessary to prepare a calibration curve for each determination if sample solution and reagent are aged
*
1794
ANALYTICAL CHEMISTRY Table I.
Effect of iging Reagent
Age of .4nthrone Sollition
% Tof Complex a t 623 nip
24 hours 2 days 6 days 9 days
29 31.5 39.5 37
Table 11.
Effect of Aging Sample Solution 7a T o f Complex a t 623 nip
Age of dsriiple Solution
3 hours
29
9 da$s
33 36
44 hoiirs 6 days
29
properly. It is convenient to prepare the anthrone reagent in the Iate afternoon of the day before it is needed. The sample is dissolved the next day and the color developed as soon as the sample is completely dibsolved. Less than 2% error occurred when the same calibration curve was used for 2 to 3 weeks. If an error of more than about 2% was obtained, it could usually be traced to improper aging or operator error.
> D E G R E E OF S U B S T I T U T I O N
Figure 5 .
e o v o H Z 5 0 4 - i o m g . CELLULOSE / 5 0 m i .
0
0
5
IO
I5
20
I
Effect of Degree of Substitution of Carboxymethylcellulose
stitution ranging from 0 to 2.2 were analyzed in 60% sulfuric acid. It was found that the color intensity decreased as degree of substitution increased. By calculating the extinction coefficient a t 625 mg, and plotting this value against degree of substitution, the curve shown in Figure 5 was obtained. The value of 285 a t a degree of substitution of 0 was obtained on the starting material before etherification. From a value of 285 the extinction coefficient drops rapidly until a degree of substitution of about 1.0 is reached. The rate of decrease in extinction coefficient diminishes as the degree of substitution increases beyond 1.0. Therefore, it is necessary to use a calibration curve which has been pi epared from sodium carboxymethylcellulose of the same
25
T I M E IN.MINUTE5
Figure 4.
Effect of -4cid Concentration on Color Development
Effect of Acid Concentration. To determine the effect of acid concentration on color intensity and on the time required for the development of maximum intensity, the procedure as described tvas followed, using solutions containing, respectively, 60, 70, 80, and 90", sulfuric acid. It was found (Figure 4) that the time required for maximum color development decreases with increasing acid concentration until the acid concentration reaches about 80%. At 90To acid concentration the course of the reaction appears to be altered. Another effect of higher acid concentrations is to increase the intensity of the color produced. Approximatelr the same transmittance is obtained Rith 0 . 5 mg. of cellulose in 80% sulfuric acid as with 1.0 mg. of cellulose in 6070 sulfuric acid. Therefore, smaller quantities of cellulose can be determined by increasing the acid concentration. Effect of Degree of Substitution. As the calibration curves for cellulose and carboxymethylcellulose did not coincide, i t was necessary to determine the effect of the degree of substitution of the carbox3.methylcellulose on color intensity. Several samples of sodium carbo.;yrnethJ.lcellulose with degree of sub-
I
a00
Figure 6. 1.
2. 3.
I
240 280 W A V E LENGTH I N .
I
I
320
360
IO
mp
Spectral Transmittance
Hydroxymethylfurfural Solution of cellulose in 60% sulfuric acid Solution of carboxymethylcellulose in 60 70sulfuric acid
V O L U M E 23, NO. 12, D E C E M B E R 1 9 5 1
1795
degree 01' FulBxtitution as sodiun~carboxymethylcellulose in the material to be analyzed. Probable Mechanism of Color Formation. The mechanism of the i,eartiori betn-een cellulose, and anthrone is not fully understood. .\?cording to Karrer ( 5 ) .anthrone reacts with aldehyde 01' ketone group.. Sattler and Zerban (8) postulated that the waction with sugars involves conversion of the sugar to furfural or a furt'ural derivative by deb>-dration and ring formation. \\~olfroni.Schuetz, and Cavalieri ( I O ) demonstrated the formation of j-h?-tlroxymethylful.Eural from glucose by refluxing in neutral or. acid aqueous solution. Heuser ( 4 ) stated that t,he \.ield of gluco~cfrom the sulfuric acid hydrol>-sis of c-?llulow is R I I O U t '36';.
Table 111.
Determination of Sodium Carbox\methjlcellulose in Detergents and Soaps Original KaChlC Contenta,
%
Detergent Detergent Detergent Detergent
A
1.25
IiaCJIC Added
%
0.W 0.68 0.68
NaCh'lC Present,
%
NaCMC Found,
%
1.94 1.9; B 0.85 0.86 0.17 C 0.42 1.10 1.12 1.21 D 0.53 0.68 1.23 0.69 Soap E 0.69 0.00 0.6Y Soap F 0.69 0.00 0.69 0.6Y * Ry a n t t r o n e method, sample size 0,1000 gram (in aliquot)
Diffrrrncr c7
/c
io.01
n oo
f0.02
t o , 02 0.00 0.00
furfural than did the cellulose solution. I t may be that substituents in the 2 and/or 3 positions interfere with the formation of 5-hydroxymethylfurfural. Applications. Several commercial household detergents and soaps were analyzed for sodium carboxymethylcellulose by the method. A weighed amount of sodium carboxymethylcellulose TT-as added and the analysis repeated. The results, shown in Table 111, indicated substantially quantitative recovery of the added sodium carboxymethylcellulose. Interferences. Phosphates, silicates, and fatty acids appeared not to interfere with the determination of sodium carboxymethylcellulose in detergents and soaps. Carbohydrates, carbohydrate derivatives, furfural, and 5-hydroxymethylfuI.iural all give tolored complexes, anti each would interfere in the determination of another member of the group. S o other int,erferences were found here. Certain polyoxyethylene derivatives of fatt5- acids and phenols have been reported to depress color formation ( 1 ) . Sucah compounds can usually be removed from dry mixtures by extraction with anhydrous alcohol. Although the method was developed primarily for the determination of sodium carhox?.meth!.l(~ellulose in detergent mixtures. it is believed that it will be found useful for the determination of sodium carboxymethylcellulose in other mixtures and for the determination of other cellulose derivatives. LITERATURE CITED
Solutions of cellulose and of rarboxymethylcellulose in 60% sulfuric acid were heated in the boiling water bath for 15 minutes and cooled as in the analytical procedure. The ultraviolet absorption curves of these solutions were similar in shape t o that of ~-h~tlroxyniethylfurfural!with an absorption maximum a t 290 mM (Figure 6). Although the indicated yields of b-h>-droxymethylfurfural ~ w r e much below theoretical, this evidence tends t o confirm the formation of 5-hydroxymethylfurfural as an intermediate in the color-forming reaction. I t seems prob&le that ceilulose is hydrolyzed to glucose by sulfuric acid in the cold, the glucose yields 5-h-droxymethylfurfural by deb!-dration and ring formation on heating, and the 5-hydroxymethylfurfural then wa(,t.swith anthrone to give the color. The carboxymethylolutioii gavr a loiver apparent yield of 5-h>-droxyinrth>-l-
(1) C'oiiner, -4.Z.. private communication. ( 2 ) Conner, &4.Z.,and Eyler, R. TV., AN-AL.CHEM.,22, 1129 (1950). (3) Dreywood, R., ISD.Eso. CHEM.,Asar. ED.,18, 499 (1946). (4) Heuser, Emil, "Cellulose Chemistry," p. 520, Xew York, John Wiley & Sons, 1944. (5) Karrei., Paul, "Organic Chemistry," p. 405, ?;em T o r k . Nordeman Publishing Co., 1938. (6) Morse. E. E., ASAL. CHEY..19, 1012 (1947). (7) Samsel, E. P., and DeLap, R. A . , I b i d . . 23, 1795 (1951). (8) Rattler. L.. and Zerban. F. IT., Science, 108, 207 (1948). (9) Viles, F. .J.. ,Jr., arid Silrerman, L.. - 4 s . k ~ . CHEZI.,21, 950 (1949). (10) TTolfrom, 11. L.. Schuetz. R. D., and Caralieti, L. F., J . Am. C'hem. Soc., 70, 514 (1948). RECEIVED M a y 19, 1931. Presentpd before the Analytical Chemistry Division of the Third Delaware Chemistry Symposiuni. Delaware Section, AMERICANC H E M I C A L SOCIETI-.University of Delawnrr, S e w a r k . Del., J o n r u r v 13, 1951.
Colorimetric Determination of Methylcellulose with Anthrone E. P. S.IMSEL AUD R. A. DEL-IP The Dow Chemical Co., Midland, Mich.
T
HE rapidly increasing commercial importance of methyl-
cellulose ( 3 ) makes desirable the development of a colorimetric method to be used in conjunction with the well-known alkoxy1 determination ( 1 , 7 ) . Methods have been developed for the identification of this paiticular cellulose ether when it is found incorporated with other mnteiiale such as starch, gums, emulsions, and suspensions. Methocel ( D o x meth: lcellulose) is an ether of cellulose formed by interaction of methyl rhloride and cellulose n hich has been saollen by treatment with a strong base. TWOtypes are available, a water-soluble material and an alkali-soluble material; the latter has a lower degree of substitution. The tests described herein are applicable to both types, but unless specifically mentioned, the water-soluble type is meant. The Tvater-soluhle ma-
terial is a white, odorless, tasteless powder n-hich is soluble in cold water, but soluble to only a very slight degree in hot water, an interesting and unusual property. The solubility of the several viscosity grades in hot 1%-aterwas studied. Methocel is insoluble in most saturated salt solutions and most organic solvents. Methylcellulose (6) can be separated from starches and gums by first dissolving in water and then adding alcohol to throw out these materials. T e a k acids or alkalies may be added to remove interfering substances. Water-soluble impurities may be separated from methglcellulose by hot water extraction. Sodium carboxymethylcellulose, being soluble in hot water, can be extracted from methylcellulose in this manner. The use of anthrone as a qualitative and quantitative test for
