Analytical Determination of Some Elastomeric Components Aqueous Extracts KALMAN MARCALI
E. 1. d u Pont
de Nemours & Co., Inc., W i l m i n g t o n , De/.
The use of elastomers in the manufacture of specialty papers has stimulated the development of analytical methods for the determination of various elastomer components which may be extracted by contact with aqueous solutions. Analytical methods are described for the determination of trace quantities of zinc, phenothiazine, p-tert-butylcatechol, a disproportionated rosin (Resin 731 SA), and the sodium salts of condensed mononaphthalenesulfonic acid (Lomar PW), and 2anthraquinonesulfonic acid (Silver Salt) in aqueous mixtures. The first four components are measured colorimetrical1)-. The latter two components are determined by simultaneous ultraviolet spectrophotometry. The methods are capable of reliably detecting the above materials below 0.5 p.p.m. The synthesis and application of m- (p-dimethylaminopheny1azo)bcnzyltrimethylammonium chloride as a new reagent for the disproportionated rosin are described.
T
HE use of elastomers such as GR-S, natural rubber, neoprene, and butadiene-acrylonitrile polymers in the manufacture of specialty papers has become of increasing importance in recent years. Although natural rubber had been of interest for impregnating fibrous materials as early as 1824, it was not until the work of Kaye (29, SO) that serious consideration was directed toward the incorporation of synthetic latices into paper pulp to produce products in which cellulose is the continuous phase. Owens ( 4 1 ) studied the effect of styrene-butadiene ratio of Buns S latices. Walsh, A4bernathy, Pockman, Galloway, and Hartsfield ( 6 4 )found the addition of neoprene (polychloroprene) latex in the beater gave paper sheets of superior wet strength and other physical properties. This work with polychloroprene latex was favorably extended by Wheeler, Borders, Swanson, and Sears (65). Oliner and O’Keil ( 3 9 ) and Yost and Aiken (67, 6 8 ) compared properties and studied the effects of variables on beater addition of butadiene-acrylonitrile polymers. Since generally the addition of an appropriate elastomer or elastomer combination appreciably increases the tensile, burst, fold, and tear strength of paper, diversified applications have been found for these papers for many essential services such as food wrappers. This application required the development of analytical methods to obtain information on the extractability of elastomer components in various solvents, particularly for trace amounts of these components which are used in the manufacture of synthetic elastomers. This information would determine possible contamination of packaged products by the elastomer components and would aid in interpretation of changes in physical properties of treated papers or elastomer films on exposure to these solvents. Paper sheets treated m-ith one or more elastomers were individually extracted with six aqueous solvents. These extractaiits simulated component e and conditions of acidity and basicity present in many food mixtures. The final extracts were analyzed4or trace quantities of elastomer components by analytical methods described, The components of principal interest in this work included zinc, phenothiazine (thiodiphenylamine), p-tert-butylcatechol, a disproportionated rosin (Resin 731 SA), and the
sodium salts of a condensed mononaphthalenesulfonic acid (Lomar PIT) and 2-anthraquinonesulfonic acid (Silver Salt). GENERAL CONSIDERATION S
Extracts. The aqueous solvents employed for extraction included: water; Ringer’s solution (8.6 g r a m of sodium chloride, 0.3 gram of potassium chloride, and 0.33 gram of calcium chloride per liter of final solution) ( 6 1 ) ; sodium carbonate, p H 10; acetic acid, p H 3; lactic acid, 5%; and sucrose solution, 5%. These extractants simulated components and conditions of acidity and basicity present in many food mixtures. Extractions were carried out also with a dill pickle juice t o which the described procedures were applied successfully. The aqueous solutions were prepared for analysis by extracting approximately 900 grams of elastomer-treated paper with 1800 grams of the particular solvent. The extractions were performed in large glass-stoppered borosilicate glass tubes (23/4 X 55 inches) charged with the paper-solvent mixture by rotating end t o end for i days in a room conditioned to the temperature of extraction. .4t the end of the extraction, the solutions were filtered and analyzed for the various components mentioned. Apparatus. C.4RY RECORDING SPECTROPHOTOMETER, Model 11, Applied Physics Corp., Pasadena, Calif., fitted with appropriate 5-em. matched quartz cells. PHOTOELECTRIC COLORIMETER.rl Cenco-Sheard-Sanford phctelometer was used. The 5-cm. rectangular cells were held in position by two blocks of plywood (6 X 5 X 1.5 em.) so that they were transversed by light lengthwise in the conventional cell holder. During transmittance measurements, the usual diaphrKgm of the instrument was placed in position to transmit light through its standard rectangular aperture of 5 X 15 mm. .4ny good photoelectric colorimeter or spectrophotometer that can accommodate 5-cm. cells may be used. CELLS,absorption, rectangular, matched 55 X 50 X 10 mm., Will Corp., New York 12, S . Y. These cells were used only R ith the Cenco instrument. Reagents. -411 reagents used in this work were of analytical reagent grade. Solvents-e.g., chloroform and n-butyl alcoholw r e carefully distilled prior to use to eliminate impurities. Sample Calculations. The final concentrations of zinc, p-tertbutylcatechol, phenothiazine, and Resin i 3 1 SA are calculated as follows: A - B - part. per million
S
w h e r e 4 = component found in sample as read from standard curve, micrograms B = component found in blank as read from standard curve, micrograms S = sample weight, grams
.I. a coirective blank, the particular solvent used t o extract the elastonier film or elastomer-impregnated paper should be anal! zed simultaneously with the elastomer extract samples in 01 der to calculate the actual quantity of the particular neoprene component extracted from the film or impregnated paper. The calculations for condensed mononaphthalenesulfonic acid and 2-anthraquinonesulfonic acid are considered in their section. Statistical Treatment of Data. -4n analysis of variance (11) was performed on each set of data in order to detect variability due to solvent effects. I n this way a random standard deviation, s,, and confidence interval, L, were calculated for each table at the particular concentration level a t which the analytical methods were tested. The random standard deviation repre1586
V O L U M E 27, NO. 10, O C T O B E R 1955 sents the precision to be expected if any food solvent taken from among those represented by the various types studied were to be analyzed.
1587
it must be completely removed by thoroughly rinsing with zincfree distilled water. Also, all reagents should be carefully purified to be free of zinc contamination. Zinc-free distilled water and some organic reagents may be conveniently prepared by percolaZIhC tion through IR-120 or IR-410 resin columns (62). One hundred micrograms of copper, lead, mercury, bismuth, The determination of zinc in small quantities has been atcobalt, nickel, and tin ions do not interfere. When more than tempted by a number of techniques which include nephelometry 15 t o 25 y of cadmium are present high results are obtained. (16),turbidimetry (3),polarography (5, 5,17,36,45,58), spectrogMost ), elastomer extracts should not contain large concentrations raphy (36, 49, 63, 55), amperometry (37), coulometry (%I of the above metals. When large concentrations of interfering fluorometry (47), flame spectrophotometry ( Z ) , and colorimetry metals are present a mono-color method (51)should be considered. with reagents such as di-2-naphthylthiocarbazone ( 6 ) , &nitroIron and aluminum do not interfere. quinaldic acid (%) and dithizone (phenylazothionoformic acid phenylhydrazide) (9, 18, 24, 26, 48, 50, 51, 62). Colorimetric p-tert-BUTYLCATECHOL methods employing dithizone are extremely sensitive, and with appropriate control of pH and interfering ions very satisfactory Catechols may be added to elastomers to act as stabilizing results may be obtained. agents. 4 number of methods are available for the determinaI n this investigation zinc was determined in aqueous extracts tion of phenolic derviatives in both high and low concentrations. by the mixed-color dithizone method (43, 50). As the details of In low concentrations the methods of Gibbs ( 2 1 ) and Snell this procedure are extensively discussed in the literature only the ( 5 7 ) using 2,6-dibromoquinone chloride have been widely apsample preparation is presented here. The liquid sample or displied. I n alkaline media 2,6-dibromoindophenols are formed with solved ash was extracted with a carbon tetrachloride solution of phenolic compounds having substituted para positions. Emerson dithizone-complexing metals. The extract was shaken with (14 j, Gottlieb (23), and Ettinger (15) used 4-aminoantipyrine, dilute hydrochloric acid to separate zinc, small quantities of lead This method has the disadvantage of being sensitive to p H variand cadmium into the aqueous phase from copper, cobalt, and ables, giving a test color in the absence of test material. The nickel which remained in the carbon tetrachloride. The acid sensitivity of this method is below 1 p.p.m. solution was finally extracted with a carbon tetrachloride solution Catechols in alkaline solution readily absorb oxygen m ith the of dithizone in the presence of diethyldithiocarbamate and amformation of colored compounds. p-tert-But>-lcatechol gives a monium citrate a t pH 8,5 to 9. I n this step, the red zinc dithizostable pink to blood-red coloration that is proportional to catechol nate was extracted into the carbon tetrachloride layer away from present at optimum concentrations. Color apparently is caused the dithizonates of lead, cadmium, and other metals and deterby the oxidation of the dihydroxy molecule to the quinoid. The mined colorimetrically. quinoid structure readily reverts to the hydroxy structure in acid media. Colors obtained by quinoid formation in basic media Sample Preparation. A. Extracts of water, sodium chloride were weak below 1 p.p.m. and lacked acceptable sensitivity. ( j L 6 )sodium carbonate (pH lo), acetic acid (pH 3). Weigh a 5-gram sample into a platinum dish. Add 10 ml. of h quantitative diazometric method for the determination of 1-Y hydrochloric acid (more if necessary) and heat on a steam phenolic aerivatives has been described by Theis (60) and Deichbath until all substances soluble in hydrochloric acid are brought man and others (12). I n this method the phenolic compound is into solution. Continue as directed under B with "Filter o f f any coupled in basic media to diazotized p-nitroaniline to give a red insoluble matter, etc." B. Extracts of sugar solution (5%), lactic acid is'%), and color, which may be measured spectrophotometrically. Because other solutions contacning organic matter. of the ready availability of reagents and apparent simplicity of .Ish a &gram sample in a platinum dish in an electric muffle the coupling reaction, this technique vias employed. furnace a t 500" to 550" C. Dilute solutions should be carefulljevaporated to prevent spattering until carbonization occurs. Reagents. Sodium acetate solution, 317,. Wet the cooled ash with 1 to 3 ml. of distilled water, then add Sodium carbonate, 2000. 10 ml. of 1-V hydrochloric acid (more if necessary) and heat on Hydrochloric acid 0.1S. a steam bath until all substances soluble in hydrochloric acid Acetic acid 0.1S. * are brought into solution. Add 5 ml. of hot water. Filter o f f any insoluble matter on a 7-cm. filter paper (Whatman S o . 42 or p-Nitroaniline solution. Dissolve 1.5 grams (Eastman Kodak equivalent) which has been washed with two 5-ml. portions of S o . 179, melting point = 147-148' C.) in 40 ml. of concentrated hot 112: hydrochloric acid, then washed with hot water until free hydrochloric acid and dilute to 500 ml. with water in a glassof hydrochloric acid. Collect the filtrate in a 100-ml. volumetric stoppered volumetric flask. flask, and wash the filter with hot water until washings are no Diazotized p-nitroaniline solution. Deliver 25 ml. of p-nitrolonger acid to methyl red. rldd a drop of methyl red indicator aniline solution into a 50-ml. Erlenmeyer flask. Cool the soluto the filtrate in the 100-ml. flask, next add la\r ammonium hytion in an ice bath for 10 to 15 minutes. Add 1 ml. of sodium droxide until neutral to methyl red, then add 4 ml. of 1N hydronitrite solution, and agitate the solution. It is suggested that this chloric acid. Allow the contents of the flask to cool, then adjust solution be prepared just before use and held in the ice bath. the volume to the 100-ml. mark with water. Bliquots of this p-fert-Butylcatechol. Purify this material to white crystals diluted sample are analyzed for zinc by a mixed-color (9, 60) or by vacuum sublimation. mono-color dithizone method ( 5 1 ) . Procedure. Into a 125-m1. Squibb separatory funnel carefully weigh a sample to contain approximately 50 y of p-tertDiscussion. Upon analysis of four known samples in 570 butylcatechol. Add 5 drops of 0 . 1 s acetic acid and gently mix lactic acid solution a t the 10-p.p.m. level by the mixed-color the solution. Extract the test solution with two 10-ml. portions of ethyl ether. Deliver the ether extract into a 26-ml. glassdithizone method, the confidence interval for average of duplistoppered volumetric flask. Add 1 ml. of 9570 ethyl alcohol cate determinations was f 0 . 7 4 p.p.m. a t a 95% probability. and 1 ml. of 0.1-V hydrochloric acid. Immerse the bulb of the The accuracy was completely within the limits of the precision flask in a water bath a t 50" to 65' C. After the ethyl ether has of the method. .It the 50-p.p.m. level the confidence interval evaporated remove the flask from the a a t e r bath, and add 5 ml. of water and 1 nil. of sodium acetate solution. Cool the solufor duplicate determinations was +0.43 p.p.m. zinc as indicated tion for 10 minutes in the ice bath. .4dd 1 .ml. of diazotized by five analyses. The accuracy a t this level is approximately p-nitroaniline solution. I l i x the solution and add 2 ml. of 20% 98%. sodium carbonate. Agitate the solution for about 1 minute in For most accurate analyses, all glass apparatus used in the the ice bath. Remove the flask from the bath, cool the flask contents to room temperature, and dilute to the 25-ml. mark application of this method should be thoroughly cleaned. The with water. Determine the per cent light transmittance of the apparatus should be rinsed with sulfuric acid followed by four or solution with a photoelectric colorimeter equipped with 5-cm. five rinses with distilled water, and finally be given a rinse with cells and a 525-111~green filter. To standardize the instrument zinc-free water. If chromic acid is used for cleaning glassware, t o loo'% transmittance, prepare a reference blank solution by
ANALYTICAL CHEMISTRY
1588 performing all the steps of the analysis except the ether estraction. Read the micrograms of p-tert-butylcatechol corresponding to the per cent transmit,tance from a calibration curve. CALIBRATION. Weigh 50.0 mg. of pure p-tert-but?lcatechol into a 100-ml. glass-stoppered volumetric flask. Dissolve completely in 95% ethyl alcohol and dilute to the mark with the same alcohol. One milliliter of this solution contains 500 y of p-tertbutylcatechol. Dilute 10 ml. of this solution to 100 nil. with 95% ethyl alcohol in a glass-stoppered volumetric flask. This diluted standard (50 y of ptert-butylcatechol per ml.) is to be used in preparing the standard curve. These solutions should he protected from light by using amber-glass volumetric flasks. Employing a 1-nil. PIlohr calibrated pipet, put 0, 0.10,0.20,0.40, 0.60, 0.80, and 1.00 ml. of the diluted standard into 25-1111. glassstoppered flasks. SOKadd 1.00, 0.90, 0.80, 0.60, 0.40, 0.20, and 0.00 ml. of 95% ethyl alcohol, respectively. The flasks contain 0, 5, 10, 20, 30, 40, and 50 y of p-tert-butylcatechol, respectively. .4dd 1.0 ml. of 0.1N tiydrochloric acid, 5 ml. of water, and 1.0 nil. of sodium acetate solution. Continue as described in thz regular procedure starting ivith “cool the solution for 10 minutes. The st,andard curve (Figure 1) is constructed by plotting micrograms of p-tert-butylcatechol against per cent light tranemittance on semilogarithmic graph paper.
Table I. p-tert-Butylcatechol Determination in Various Solvents by Diazometry p-krl-Butylcatechol, P.P.M. __ Solvent
Present
Found
Present
1.2
1.0 1.2 1.2 1.2 0.9 1.2 1.4 1.4 1.2 1.2 1.2 0.16 i o .25 95%
25.0
Water Ringer’s solution Sodium carbonate, pH 10 Lactic acid, 5% Scetic acid, pH 3
-
x SI
L
P
x=
Found ‘3 . !I
27.5 29.0 31.5 27.5 26.0 31.5 33.9 27.5 33.9 29.2 3.45 *.5.38
.v
xi
=
mean
i-=__1
s
sr = standard randoin deviation (12)
L = i sr
confidence interval for average of duplicate determinations (,V = 2) at a probability level P P = probability level, 70, (Qp% used here) f l o o - P = “student’s 1” at a significance level 100 P (corresponding to a confidence interval of P = 9 5 R ) A’ = nuinher of determinations
.v
=
-
80706 0-
50-
40-
30-
20
I
6
Figure 1.
1 1 I l I I 12 18 24 30 36 42 40 54 P-TERTIARYBUTYLCATECHOL, MICROGRAMS PER 2 5 ML.
I
60
~
~
66
Calibration curve for p-tert-butylcatechol determination
Experimental. For accurate analyses the p H of the solution during extraction of the sample and the ethyl alcohol concentration present during the coupling reaction should he controlled. To obtain quantitative extraction of p-tert-butylcatechol the solution must be acidic (< p H 5). Above pH 7, the catechol recovery may be as much as 60% low. The presence of acidifipd aqueous ethyl alcohol was found necessary to prevent the loss of catechol after the ethyl ether had evaporated. If more than 5 ml. of 95% ethyl alcohol vere present during the coupling reaction, a white precipitate formed together with an estraneous hroivnish color which erratically affected both sample and blank. Good results were obtained when 1 to 2 ml. of %yo ethyl alcohol were used. The addition of 5 ml. of water was necessary before adding diazotized p-nitroaniline to prevent insoluble salt formation after the addition of sodium acetate. More reproducible colors were obtained with sodium carbonate than with an alkali metal hydroxide. Figure 2 contains the spectrum of a solution resulting from the coupling of p-tert-butylcatechol with diazotized p-nitroaniline. It may he seen that the absorption maximum is a t 466 mp. Figure 1 indicates that a good standard curve may be obtained with the above procedure at 525 mp for p-terl-hutylcatechol when present in concentrations of 0 to 2 y per nil. C v w higher sensitivity would be attained at 466 zk 5 nip. Results. The method was evaluated a t two levels of concentration. A4nalyse’swere run with each solvent after the addition of known quantities of p-tert-butylcatechol. The results are piesented in Table I. Discussion. Table I indicates that accurate recovery of p-tert-butylcatechol may be obtained a t both 1- and 25-p.p.m. levels. Statistical variance analysis of the data piesented in Table I indicated no systematic errors.
I I I I I 400 500 600 700 WAVE LENGTH, Mp Figure 2. Absorption spectrum of p-tert-butylcatechol coupled to diazotized p-nitroaniline
300
1.9 p.p.m. p-tert-butylcatechol i n sodium carbonate solution 5-cm. cells
If aromatic amines or phenols other than p-tert-butylcatechol are present which form colors with diazotized p-nitroaniline under the conditions of the analysis, the spectral characteristics of the final solution should be investigated. Thus, suspected aromatic amines or phenols may be detected and determined together with p-terl-butj-lcatechol after appropriate spectral standardization. PHENOTHIAZINE
Phenothiazine (thiodiphenylamine) is usually utilized in coinpounding elastomers as a stabilizing agent. Methods availahle for the determination of phenothiazine include the work of Smith ( 5 6 ) , Eddy ( I S ) , and Cupples (IO), who employed the osidation of phenothiazine to red 3,i-dihydroxyphenazathionium hromide ( 6 3 ) . Kniaseff (SI) suggested the use of cuprous chloride in alcoholic media to give a purple red color. Since white cuprous chloride on expowre to air changes its composition to green basic cupric chloride, CiiCI3.3Cu0.3H~0(35), the exact composition of the active ingredient has not been determined. This method required approximately 52 hours for complete color formation. Two papers had employed precious metal salts for pheno-
V O L U M E 2 7 , NO. 10, O C T O B E R 1 9 5 5
1583
thiazine analysis. The gravimetric procedure of Payfer and Marshall (42) involving a precipitation of platinum phenothiazine tetrachloride Pt( CI2HSNS)&l,,was not considered here. Overholser and Yoe (40) suggested the use of palladous chloride to form a dark blue complex with phenothiazine having the formula Pd(CltH9XS)C1*. Difficulties were encountered with this method because of the instability of the colored solutions. The oxidation of phenothiazine to the red phenothiazine derivative initially described by Smith (66) formed readily in ethanolic media with bromine. This reaction was emplol-ed in this investigation.
1.01
1
Figure 3.
1
I
I
.4bsorption speetruni of 3,T-dihydroxyphenanathionium bromide
3.6 p.p.m. phenothiazine in ethyl alcohol .%ern. cells
approxiniately 10 minutes. Sow continue as described in the above procedure beginning with "Add 5 ml. of saturated bromine water." Construct a calibration curve to relate per cent transmittance a t 525 mp and micrograms of phenothiazine per 25 nil. Experimental. A number of variables were investigated during method development. Each variable is discussed briefly. MISCELLANEOUS OXIDIZIXG ~ ~ G E N T S .A number of oxidizing agents were investigated as possible color formers for phenothiazine. Potassium perborate, sodium vanadate, and lead peroxide had very weak color-forming tendencies in ethyl alcohol or ethyl alcohol-water mixtures with phenothiazine even when heated to 70" C. Ferric chloride readily converted phenothiazine to a colored compound in aqueous media acidified with hj-drochloric acid. However, when a hydroxylic solvent such as ethyl alcohol was added, color development decreased by as niiich as 50%. When hydrogen peroxide is added to an acidified ethyl alcohol solution of phenothiazine and heated to about 80" C., the phenothiazine is converted to a highly colored conipound which is believed to be 9-hydroxyphenothiazoneJ ako known as thionol. For quantitative analysis, however, a close adjustment of the amounts of acid, ethyl alcohol, and hydrogen peroxide relative to the quantity of phenothiazine was found necessary. Therefore, this method of producing the highly colored thionol from an unknown quantity of phenothiazine cannot conveniently be made the basis of an accurate colorinietric method for estimating phenothiazine. BROWSE AS AN OXIDAST. lT7hen phenothiazine is treated with saturated bromine water, under appropriate conditions, a red alcohol-soluble compound is formed. This compound is believed to be 3,7-dihydroxyphenazathionium bromide with the following possible formula (66).
N Reagents. Bromine, saturat,ed aqueous solution. Phenothiazine, recrystallized (54). Dissolve phenothiazine in 10 parts of C . P . toluene with the aid of heat. Add 0.2 gram of activated charcoal for each 4 grams of phenothiazine. Boil 10 minutes under reflux and filter while hot through a heated filter. Cool solution and collect phenothiazine crystals on a suction filter. Dry crystals in oven a t 100' C. and then in vacuum desiccator containing paraffin chips. Repeat recrystallization process, if necessary, until product melts a t 184-185' C. Procedure. Into a 125-ml. separatory funnel weigh a sample to contain approximately 50 y of phenothiazine. Extract wit,h two 10-nil. portions of ethyl ether. Deliver the ether ext,racts into a 23-ml. glass-stoppered volumetric flask. Immerse the bulb of the volumetric flask in a water bath a t 60" to 70" C. to evaporate ether. After the evaporation is complete, add 10 nil. of '35% ethyl alcohol and allow the solution to heat approxiniately 10 minutes. Add 5 ml. of saturated bromine water and gently agitate the solution. Allow the solution to stand in the water bath for 15 to 20 minutes. Add a second portion of 1)roniine water, agitate, and allow the solution to stand another 15 to 20 minutes in the water bath until all traces of free hroniiiie are eliminated. At this point the presence of phenothiazine is indicated bj- a red color. Remove the flask from the water bath, cool to room temperature, and adjust the volume to the 25-1111. mark with 95% ethyl alcohol. Agitate the solution well. Determine the per cent transmittance of the solution in a k i n . cell at 525 mp. Ninety-five per cent ethyl alcohol phould he used to adjust the instrument to 100% transmittance. Read the micrograms of phenothiazine corresponding to the per cent transmittance from a calibration curve. Run a blank on reagents and solvents used and correct the results accordingly. CALIBRATION. Standard phenothiazine solution A. Dissolve 100 nig. of pure phenothiazine in 95% ethyl alcohol and dilute to 100 nil. in a glass-stoppered volumetric flask. Standard phenothiazine solution B. Dilute 5.0 nil. of aolution h to 500 ml. with 95% ethyl alcohol in a glass-stoppered of volumetric flask. This solution contains 0.010 nig. (10 phenothiazine per 1111. Into glass-stoppered 25-ml. volumetric flasks put 0.50, 1.00. 2.30, 3.50, 5.00, 7.50, and 10.00 ml. of solution B, respectively. These solutions contain 5, 10, 25, 35, 50, 75, and 100 y of phenothiazine. To each flask add 9.5, 9.0, 7.5, 6.5, 5.0, 2.5, and 0.0 ml. of 95% ethyl alcohol, respectively. Immerse the flasks in a water bath a,djusted to 60' to 70" C., and allow the solutions to heat mi)
I
Br
z
2
40-
IO
Figure 4.
30 4 0 50 60 70 80 90 100 P H E N O T H I A Z I N E , MICROGRAMS PER 25 ML.
20
Calibration curve for phenothiazine determination
The absorption spectruni is given in Figure 3. Distinct absorption maxima are present at 384 and 520 mp. REPRODUCIBLE COLORFORMATION.It has been found that i n alcoholic media dropwise additions of bromine (IO,66) may cause a greenish purple hue. Three experimentally controllable factors have been found to favor the formation of normal red color^: rapid addition of bromine water; two additions of excess bromine; and maintenance of the temperature of the solution during the addition of oxidant between 60" and 70" C. With the aid of theqe conditions it is possible to obtain consistent color formation. .4 standard curve is shown in Figure 4.
1590
ANALYTICAL CHEMISTRY
Table 11. Phenothiazine Determination in Various Solvents by Oxidation with Bromine Solvent
Present 2.0
Water Ringer's solution Sodium carbonate, pH 10 Lactic acid, 5% Acetic acid, pH 3 Sucrose solution, 5%
3? 8,
L
P
Phenothiazine, P.P.M. Found Present 1.9 50.0 2.0 2.0 1.9 1.8 2.2 1.8 1.8 2.0 2.0 2.1 2.0 2.0 0.12 io.19 95%
Found 49.2 46.6 46.2 46.7 45.2 49.9 49.8 53.4 49.8 47.3
...
...
49.2 2.49 1.3.88
Results. The reliability of the method was tested a t the 2- and 50-p.p.m. levels. Known quantities of phenothiazine were added to the respective solvents and analyzed by the above procedure. The data are given in Table 11. Discussion. Table I1 shows that the method gives very good recovery of phenothiazine from the various solvents. Statistical variance analysis of the data presented in Table I1 showed no significant solvent effects. p-tert-Butylcatecho1, Resin 731 SA (disproportionated rosin), Lomar PW, and 2-anthraquinonesulfonic acid in 50-p.p.m. level did not interfere. Generally, the method may be applied where aqueous bromine does not oxidize or brominate components to produce interfering side products. The method detects 0.2 p.p.m. of phenothiazine. In a single experiment with lactic acid a turbidity developed in the final solution after adjusting the volume to 25 ml. The solution was filtered through 12.5-cm. Whatman KO.12 folded filter and the per cent transmittance obtained. The filtration affected the results by less than 0.1 p.p.in. RESIR 731 SA
Many colored reactions for the detection of various resins either in their natural state or in admixtures have been proposed from time to time. Some of these include the Liebermann-Storch reaction ( 3 3 ) and variations of the Halphen test (19) 26). These ieactions are not specific since other compounds such as terpenoids give similar colors. Recently Swann (59) has suggested a colorimetric method for determining free rosin and rosin esters by a modified Liebermann reaction employing 18N sulfuric acid and acetic anhydride. The red to violet colors were measured colorimetrically. While this method gave fairly good colors with rosin in relatively concentrated solutions, it was not sufficiently sensitive for use with a disproportionated rosin. il modification by Sandermann (62) of the Liebermann-Storch reaction to allow a sulfonation of the resin for 12 hours followed by neutralization of the excess acid with concentrated sodium hydroxide was ineffective for quantitative application. Various other suggested reagents such as chlorosulfonic acid ( 7 ) or phloroglucinol (1,3,5benzenetriol) ( 4 6 ) were useless for trace analysis. A disproportionated rosin does not have favorable fluorescent characteristics such as rosin ( 6 6 ) to make this property attractive for quantitative trace analysis. -4s no adequate method was available in the literature for the determination of Resin 731 SA in trace quantities, the development of a sensitive method was undertaken. Paraffin chain cation-active compounds have been shown by Auerbach ( 1 ) to react with bromophenol blue to form colored complexes, which may be extracted with benzene and the active compound measured colorimetrically. A similar technique was utilized by others (27, 28, 4S, 44)to determine relatively complex molecules. Following preliminary work by Campbell (4),a method was de-
veloped which is based on the formation of a colored compound by Resin 731 SA and a specially synthesized new cationic azo dye, m(p-dimethylaminophenylazo)benzyltrimethylammonium chloride, in an organic solvent, extraction of excess dye into aqueous alkali, followed by colorimetric or spectrophotometric measurement of the yellow resin-dye compound preferentially retained in the organic phase.
Reagents. Sodium hydroxide, 0.51Y. Prepare this reagent from 50 weight yo sodium hydroxide. Hydrochloric acid, 1 to 1. Resin 731 SA. This material is a commercial product purchased from Hercules Powder Co. Three samples obtained from different containers indicated excellent uniformity. m-(p-Dimethylaminophenylazo)benzyltrimethylammonium chloride. The dye solution, 0.1% in water, is stable for at least 1week. The dry powder for this dye solution is prepared in three steps. A. m-Nitrobenzyltrimethylammonium Chloride. Bubble trimethylamine through a solution of 200 grams of m-nitrobenzyl chloride in 2 liters of dry acetone for 2 hours. The temperature rises from room temperature to about 40" C. Filter the mixture and wash the product well on the filter mith acetone. Dissolve the damp press cake in 700 ml. of warm absolute ethyl alcohol and add 1500 ml. of dry acetone. Heat to 50" C., then cool to 5 to 10' C. Filter and wash the product on the filter with a little dry acetone. Air dry the product, then dry at 90" C. for about 15 minutes. The dry weight is 146 grams. B. m-lminobenzyltrimethylammoiiium Chloride. Add 0.2 gram of platinum oxide (22) to a solution of 21.7 grams (0.1 mole) of the above nitro compound in 75 ml. of distilled water. Hydrogenate a t 70" C. under 40 to 45 pounds of initial hydrogen pressure until the theoretical amount of hydrogen is taken u p (about 2 hours). Prolonged hydrogenation results in excessive cleavage of the desired product. Filter to remove catalyst and extract the filtrate three times with 100-ml. portions of chloroform to remove side products. Discard the chloroform extracts. Heat the aqueous layer (boiling chips) on a steam bath to remove traces of chloroform. Cool and add 20 ml. of 3 i % hydrochloric acid. Bottle the solution until used in the following coupling reaction. C. m - (p-Dimethylaminophenylazo)benzyltrimethylammonium Chloride. Diazotize the above amine hydrochloride solution with 5LV sodium nitrite at 0' C. About 15 ml. of nitrite is required, indicating 0.075 mole of amine. A4ddthe diazo solution in 1 portion to an ice cold solution of 0.078 mole of *V)-Vdimethylaniline in 10 ml. of 37% hydrochloric acid plus a little water. To the resulting solution add an ice-cold 30% aqueous solution of sodium acetate trihydrate in portions initially raising the pH to 3.0, then in small portions to maintain the p H in the range 2.8 to 3.0 as coupling progresses. A total of about 110 ml. of the sodium acetate solution is required. Allow the coupling to proceed for 7 hours below 5' C., then allow the mixture to stand overnight a t room temperature. Raise the p H to 6.0 with 10Y sodium hydroxide. Extract the mixture with four 200-ml. portions of chloroform; three layers appear upon separation. Discard the lower layer after each separation. Separate the dark center layer, discard the top layer. Heat the center layer on a steam bath to remove a considerable amount of chloroform. Cool the residual viscous oil and add 400 ml. of dry acetone. Agitate and boil down to a volume of 300 ml. on the steam bath. Cool and filter. Wash the orange crystalline product on the filter with cold dry acetone. Air dry the material, then dry at 90" C. for a few minutes to obtain 20.7 grams of dry product. I n order to test the purity of the dry benzyltrimethylammonium chloride derivative, develop a circular chromatogram of a dilute aqueous solution xith Beckman pH 7.0 buffer solution. A single sharp orange band should result. If impurities are present, dissolve the benzyltrimethylammonium chloride derivative in water and adjust the solution to p H 6.0 with 10N sodium hydroxide. Repeat the extraction and isolation steps indicated. Procedure. Into a 125-m1. Squibb separatory funnel neigh a sample to contain approximately 60 y of resin. Add 3 ml. of hydrochloric acid (1 to 1) to adjust pH below 1. Extract this mixture with four 5-ml. portions of chloroform. Shake 2 minutes for each extraction. Transfer the chloroform extracts (20 ml.) quantitatively to a second 125-ml. Squihb separatory funnel. Add 10 ml. of 0.5-V sodium hydroxide and 0.2 ml. of 0.1% dye solution. Thoroughly agitate the funnel contents for approximately 2 minutes. Allow the two liquid phases to separate. Quantitatively transfer the lower chloroform layer to a third 125ml. Squibb separatory funnel. Discard the aqueous sodium
1591
V O L U M E 27, NO. 10, O C T O B E R 1 9 5 5 hydroxide layer. Add 10 nil. of 0.5X sodium hydroxide to the third funnel, stopper, and thoroughly agitate for approximately 2 minutes. Allow the phases to separate and then carefully transfer the lower chloroform layer to a glass-stoppered 25-ml. volumet,ric flask containing 0.5 gram of anhydrous sodium sulfate. Agitate the volumetric flask for about 15 seconds, dilute to the 25-ml. mark with distilled chloroform, stopper the flask, and thoroughly agitate. Determine the per cent transmittance of the solution in a 5-cm. cell lvith a 435 mp filter against pure chloroform. As the azo dg-e is somewhat sensitive to light, the per cent transmittance must be obtained within 5 minutes after solution preparation. Also, the solution in the colorimeter cell must be exposed no more than 1 minute to the direct light beam in the colorimeter. Read the niicrograms of Resin i31 S-4 corresponding to the per cent transmittance from a standard curve. CALIBRATIOS.Neigh 100 mg. of Resin 731 SA into a 100-ml. glass-stoppered volumet,ric flask, dissolve complet,ely in distilled chloroform, and dilute to the mark with chloroform. One milliliter of this solution contains 1000 y of Resin 731 54. Dilute 10 ml. of this solution t,o 100 ml. with distilled chloroform in it glass-stoppered volumetric flask and agitate well. Tse this diluted standard (100 y of Resin 731 S.4 per ml.) in preparing the standard curve. Emuloying a 1-ml. 1Zohr calibrated pipet, put, 0, 0.20, 0.40, 0.60, 0.80, and 1.00 ml. of the diluted standard into 125-ml. Squibb separatory funnels containing 20 ml. of distilled chloroform. The Reparatory funnels contain, 0, 20, 40, 60, 80, and 100 y of Resin 731 SA, respectively. S o w continue as described in the above procedure beginning with “add 1.0 ml. of 0 . 5 X sodium hydroxide and 0.2 ml. of dye solution.” Construct the standard curve by plotting micrograms of Re&] 731 5 4 against per cent light transmittance on semilogarithmic paper. The standard is illustrated in Figure 5.
containing known quantities of Resin 731 SA yielded results that could be reproduced to i0.5ojO transmittance. Extracting with three 10-ml. portions of 0 . 5 5 sodium hydroxide or with aqueous solutions below p H 9.5 tended to remove about 2% of the resin-dye color compound. DYE SOLUTION.If more than 150 y of Resin 731 SA is suspected in the samples, 0.4 to 0.5 ml. of the dye solution may be employed instead of 0.2 ml. I t is suggested that a standard curve be prepared under similar conditions. SPECTRAL UHARACTERISTICS OF YELLOWCOXPLEX. Figure 6 shows the spectra of the Resin 731 SA-dye compound in chloroform resulting from extracting 60 and 130 y of Resin 731 S-4 from 25-gram samples. The absorption maximum of the yellow compound is a t approximately 430 mp.
Figure 6.
WAVE LENGTH Mp Absorption spectra of Resin 731 SA-dye complex in chloroform A . 2.4 p.p.m. Resin 731 S A oomplexed B. 5.2 p.p.m. Resin 731 S A oomplexed 5 om. cells
Table 111. Colorimetric Determination of Resin 731 SA with rn ( p Dimethylaminopheny1azo)benzyltrimethylammonium Chloride
- -
10
20
Figure 5.
40 50 60 70 80 90 100 110 RESIN 731 SA, MICROGRAMS PER’eS M L
33
120
130 140
Calibration curve for Resin 731 SA determination
Solvent
Present 2.4
Water Ringer’s solution
Experimental. The m-(p-diniethy1aminophenylazo)benzyltrimethylammonium chloride reagent was specifically synthesized in this laboratory as a cationic-chromogenic reagent for the anion of relatively strong organic acids that may be present in materials such as Resin 731 S,4. Preliminary investigation showed that this dye compound readily formed colored complexes with Resin 731 SA in a halogenated solvent such as chloroform, and the excess dye easily partitioned into aqueous sodium hydroxide while the dye-resin compound remained in the organic solvent. To achieve maximum accuracy and reproducibility, a number of variables were investigated. SOLVESTS.The following solvents proved inferior to chloroform as extracting media: carbon tetrachloride, cyclohexane, benzene, ethyl acetate, ethyl ether, iso-octane, petroleum ether, n-butyl alcohol, and methyl ethyl ketone. The resin-dye compound solubility was unsatisfactory in the first seven solvents, v, hile the excess dye did not partition favorably into aqueous sodium hydroxide from the latter two. HYDROGES IOUCOSCESTRATIOS.The most complete extraction of Resin 731 SA from the sample into chloroform was ohtained when the aqueous sample was adjusted to p H < 1. To achieve complete extraction of the excess dye, the p H of the aqueous u-ash solution should be approximately p H 12 to 12.5. Two 10-ml. portions of 0.5.V sodium hydroxide were found t o remove dye completely. Extractions performed with solutions
Sodium carbonate. pH 10 .4cetic acid, pH 3 Lactic acid, 5 %
Resin 731 SA, P.P.M. Found Present 2.1 20.0 2.1 2.6 2.9 2.4 2.1 2.1 2.2 2.6 2 4
Sucrose solution, 570 -
x SI
I, P
2 6
2.9 2.4 0 31 *0 49 9,570
Found 17.8 17.6 24.2 21.3 19.7 17.8 25.3 17.6 21.2 19 . 7 ._ .
24.2 21.3 20.6 2.79 zt4.35
IATERFERISG MATERIILS. Generally, organic materials such as long chain organic acids of anionic nature that are extractable into chloroform and can combine with the cationic dye to form species not readily extractable into aqueous 0 . 5 s sodium hydroxide tend to give positive errors. Individual experiments were performed by thoroughly agitating 300 i 10 7 of the elastomeric component to be tested for interference with 25 ml. of aqueous sodium carbonate (pH lo), and the solution n a s then analyzed for Resin 731 SA by the above procedure. When 2-anthraquinonesulfonic acid, Lomar PIT, phenothiazine p-tert-butylcatechol, and the sodium salt of dodecylsulfate were considered, the 1ellow color remaining in the rhloroform layer after extracting with alkali was equivalent to -1.1, 9.5, 9.5, 10.0, and 25.8 - , respectively. With a 25-gram sample, the contribution would be f0.2 to +l.Op.p.m. Xancy
1592
ANALYTICAL CHEMISTRY
wood rosin behaves the same as Resin 731 SA. Inorganic salts present in the sample do not interfeie. Results. The accuracy of the method was determined by adding known quantities of Resin 731 SA at two levels to solvents of interest. The results are summarized in Table 111. Discussion. Table I11 shows that Resin 731 SA may be determined with good accuracy a t both the 2- and 20-p.p.m. levels. Statistical variance analysis of the data presented in Table I11 indicated a slight solvent effect when determining resin at lowconcentrations. The 2-minute extractions indicated in the procedure consisted of approximately 150 to 175 cycles and were performed at 26' i. 2" C. Although the estracted resin-dye compound is slightly sensitive to a direct light beam of 430 to 435 mp in a colorimeter, transmittance readings may be easily obtained before noticeable decomposition occurs. The aqueous azo dye solutions were stable for a t least a week. Decomposition is generally indicated by low rosinate recovery together with increasing blanks (low transmittance measurement). These blanks may be adversely affected by impurities in undistilled chloroform. Under proper conditions blanks had a transmittance of 98 to 99%.
Balance the instrument initially with the 5-cm. quartz cells employing an aqueous solution containing 1 ml. (1 to 1) of hydrochloric acid per 25 ml. of solution. Calculate the base line absorbance A , a t 228 and 256 mp for Lomar PW and 2-anthraquinonesulfonic acid, respectively. CALIBRATION.Weigh 100 mg. of Lomar PW into a 100-ml. glass-stoppered volumetric flask, dissolve completely in water, and dilute to the mark wit,h water. Agitate thoroughly. One milliliter of this solution contains 1000 y of Lomar PW. Dilute 10 ml. of this solution to 100 ml. with distilled water in a glassst'oppered volumetric flask, and agit,ate well. Lrse this diluted standard (100 y of Lomar P R per ml,) in preparing a standard solution for spectrophotometric examination. Into a 25-ml. glass-stoppered volumetric flask add 0.60 ml. (60 y ) of the dilut,ed st,andard. Add 1 ml. of hydrochloric acid (1 to 1) and dilute to the mark with distilled water. Stopper the flask and agit'ate the solution well. Esamine the standard solution of Lomar PW as described in the above procedure starting with ultraviolet spectra (200 t,o 400 mp) in a 5-cm. quart,z "Obtain cell . . . . This standardization may be performed a t more than one concentration. Calculate the base line absorbance A and absorbance index at 228 (principal absorption masimum for Lomar PW) and 256 mp. Repeat the procedure and calcu1:itions for 2-anthraquinonesulfonic acid. The principal absorption masimum for it is a t 256 mp.
tk
Experimental. ULTRAVIOLET ABSORPTIOS SPECTRUM OF LOPW. Figure 7 , A , shows the ultraviolet spectrum of Lomar P\Y. The curve is characterized by an absorption maximum a t 228 nip. Beer's law was found to apply a t wave lengths 228 and 26G mp for concentrations ranging from 0 to 80 y per 26 ml. solution in 5-cm. cells. The reasons for select.ing these wave lengths for testing for conformity to Beer's law are evident on esamination of curve B, Figure 7 . The absorbance irides was calculnted hy the Bouguer-Beer law ( 3 4 ) .
M.~R
LOMAR P W AND 2-ANTHRAQUINOR~ESULFONIC ACID
Quantitative analytical methods are not readily available in the literature for determining trace quantities of sodium sslt of a condensed mononaphthalenesulfonic acid (Lomar P K ) aiid sodium salt of 2-anthraquinonesulfonic acid (Silver Salt) in relatively complex elastomer extracts. A simultaneous ultraviolet spectrophotometric determination was developed for these coniponents in mixtures containing materials such as p-tert-butylcatechol, phenothiazine, disproportioriated rosin derivatives, and xylene. In principle, the method consists in removing interfering components from an acidified sample with chloroform or ethyl ether estraction. The Lomar PW and 2-anthraquinonesulfonic acid are then extracted into n-butyl alcohol from the aqueous solution, the n-butyl alcohol is evaporated, the residue is dissolved in acidified ethyl alcohol and the components are determined spectrophotometrically. Reagents. Hydrochloric acid (1 t o 1). n-Butyl alcohol, distilled. Lomar PW, sodium salt of a condensed mononapht'halenesulfonic acid. Jacques Wolf & Co., Passaic, K.J. Recrystallized from water. Silver Salt, sodium salt of 2-anthraquinonesulfonic acid, D U Pont. Recrystallized from water. Procedure. Into a 125-m1. separat,ory funnel carefully weigh a sample to contain approximately 50 to 60 y of any single component. Add 3 ml. of hydrochloric acid (1 to 1). Extract this misture with four 5-ml. portions of chloroform. Shake for 2 minutes for each extraction. Transfer the chloroform extracts (20 ml.) to a 50-ml. beaker. The chloroform estract may be discarded or examined. Estract the aqueous solution with four 5-ml. portions of nh u t r l alcohol. Shake for 1 minute for each extraction. Transfer 'the 'n-butyl alcohol extracts to a 50-ml. beaker. Gently evaporat,e the alcohol just to dryness on an asbestos-covered hot plate. Remove the beaker from the hot plate and add 1 ml. of (1 to 1) hydrochloric acid. Gradually swirl the aqueous acid t,o dissolve the residue. Add approximately 5 ml. of water, swirl the solution, and then carefully transfer the solution to a 26-ml. glass-stoppered volumetric flask. Employing three additional 5-ml. portions of water, thoroughly wash the 50-ml. beaker to quantitatively transfer Lomar P W and 2-anthraquinonesulfonic acid to the volumet,ric flask. Finally, adjust the volume with water to the 25-ml. mark, stopper, and thoroughly agitate the flask contents. Obtain the ultraviolet spectra (200 t,o 400 mp) in a 5-cm. quartz cell employing a Cary automatic recording spectrophotometer Kith the following instrument adjust,ment : Scanning speed Silt control Chart range
1.5 mp per second
15
0 t o 2.5
I
log 2 = A = a.bc
(li
I
where la= energy incident on sample I = energy transmitted by sample A = sample absorbance ar = absorbance indes b = centimeters of pat,h length of light. in absorbing medium (5 em.) c = sample Concentration, grams per liter
1 - 8 c228 Mp 1.7 !\ A l . 6'I 1.51-41
/
,
I 1
I
2 5 6 Mp
'
I
CURVE A . 2 . 4 P.P.M. LOMAR PW CURVE B . 2.4 P.P.M. SILVER SALT
----
Figure 7. Absorption spectra of condensed mononaphthalenesulfonic acid (A) and 2-anthraquinonesulfonic acid (B) in ethyl alcohol
1593
V O L U M E 2 7 , NO. 10, O C T O B E R 1 9 5 5 Lomar PW Spectrophotometric Determination
Table I\'.
(5-Cm. cells) Lomar PW, P.P.N. Present Found Present
Solvent
2.1
Water Ringer's solution Sodium carbonate, pH 10 Acetic acid, p H 3 Lactic acid, 5% Sucrose solution, 5 %
-
x 8r
L P
Table V.
2.2 2.4 2.3 2.4 2 1 2.4 2.4 2.4 2.3 2.4 2.4 2.4 2.3 0.10 10.16 95%
30.0
Found 27.5 29.8 30.4 29.0 26.2 29.6 29.6 29.4 28.5 30.0 30.0 30.3 29.2 1.24 2C1.93
2-Anthraquinonesulfonic Acid Spectrophotometric Determination (5-Cm.oella)
Solvent Water Ringer's solution Sodium carbonate, pH 10 Acetic Acid, pH 3 Lactic acid, 5 5 Sucrose solution, 5%
X 8r
L
P
2-Anthraquinonesulfonic Acid, P.P.M. Present Found Present Found 30.0 30.0 2.4 30.2 2.4 30.3 2.4 30.4 2,4 2.5 30.6 2.2 30.1 33.2 2.4 32.3 2.6 33.5 2.7 33.3 2.7 34.5 2.6 33.0 2.7 31.9 2.6 1.73 0.14 2C2.70 10.23 95%
The absorbance indices of Lomar PK a t 228 and 256 mp were 143.60 and 12.75, respectively. ULTR-4VIOLET d B s O R P T I O N SPECTRUM O F 2-ANTHRAQUISOSESULFONIC - 4 ~ 1 ~Curve . B in Figure 7 shows the absorption spectrum of this compound. The absorbance maximum occurred at 250 mp. Conformity to Beer's law was found a t 228 and 256 nip for concentrations ranging from 0 to 80 y per 25 ml. solution in 5-cni. cells. Higher concentrations were not measured in this long cell. The absorbance index of 2-anthraquinonesulfonic :ic.id a t 228 and 256 mp were 22.08 and 151.08, respectively. SIXULT.YiEOUS ULTR.4VIOLET SPECTROPHOTOMETRIC DETERXIR'.ITION. -4s absorbances of a mixture of Lomar PI\- and 2:inthraquinonesulfonic acid were found to be additive, the folloa-ing equations were used t'o calculate the concentration of both:
+ 110.5 Ca Azas = 64.0 CI + 755.5 Cs
A228
= 718.5 C1
(2) (3)
.where S A = eample absorbanre a t the wave length (A, m p ) indicated C1 = concentration of Lomar PR-, grams per liter C, = concentration of 2-anthraquinonesulfonic. acid, grams per liter T o express results in micrograms per 25 ml., Equations 2 and 3 were modified as follows:
X = 35.25 A228 Y
=
33.53 A m
- 5.16 A m - 2.99 A228
2-anthraquinonesulfonic acid, p.p.m. 7whereS
= sample weight, grams
ACKYOWLEDGMENT
The author wishes to acknowledge the valuable assistance in this work of many persons a t the D u Pont Jackson Laboratory and Rubber Laboratory. Special credit is given to R . J. Barnhart for his wholehearted cooperation and aid with bulk eutractions. Sincere appreciation also is expressed to J. IT. Libby, Jr., A. 31. Neal, G. H. Patterson, A . C. Stevenson, and R. H. Kalsli for very helpful technical advice dui ing the investigation. LITERATURE CITED
(1) Auerbach, RI. E., IND.ENG. CHEX..ASAL. ED., 15, 492-3 (1943); 1 6 , 7 3 9 (1944).
(2) Beckman Instruments. Inc.. Fullerton, Calif., "Instructions for the Beckman Flame Spectrophotometer," Bull. 259, p. 15
(4) (5)
where X = micrograms of Lomar PW per 25 ml. Y = micrograms of 2-anthraquinonesulfonic acid per 25 ml. Lomar PW, p.p.m.
S ~ V P LPREPARSTIOS. E Components that absorb in the ultraviolet in the vicinity of 228 and 256 mp would interfere. Some of these interferences such as p-tert-butylcatechol, phenothiazine, Resin 731 SA, xylene, and various aromatics may be removed conveniently by extracting an acidified solution of the aqueous extract with chloroform or ethyl ether. Yeither Lomar PW nor 2-anthraquinonesulfonic acid is soluble in these solvents. Results. The accuracy and precision of the method were evaluated by analyzing two synthetic samples for each solvent, w1iic.h were prepared to contain both Lomar PW and 2-anthraquinonesulfonic acid in the 2- and 30-p.p.m. level. The data are presented in Tables 11' and V. Discussion. Tables I V and V indicate that good recovery may be obtained for synthetic samples in both the 2- and 30p.p.m. levels for both Lomar PW and 2-anthraquinonesulfonic acid. Variance analysis of the data showed that the high results found for the latter with the last three solvents in Table V are due to distinct solvent effects. S o systematic errois are indicated in the Lomar PW procedure. Materials that are not extracted by ethyl ether or chloroform, but are soluble in n-butyl alcohol, are relatively nonvolatile, absorb near 228 and 256 nip, and interfere with the Lomar PW and 2-anthraquinonesulfonic acid determination. When employing ultraviolet spectrophotometry for trace analysi?, it is important to use clean rells. The cells used in thi. work were cleaned thoroughly by rinsing three times with 9570 eth? 1 alcohol and drying the cells with a stream of clean dry air If a Beckman quartz spectrophotometer is used for this work, a cell correction should be considered unless the cells are petfectly matched. For maximum accuracy, it is suggested that the ultraviolet spectra be prepared a t the temperature of instrument calibration. When a sample is to be analyzed whose temperature differs appreciably from the cell block of the spectrophotometer, the mmple should remain in the cell block long enough for temperature equilibrium to be reached before preparing spectra. The chloroform or ethyl ether extract may be discarded or the solvrnt carefully evaporated in a 60" to 70" C. mater bath, the reqidue dissolved in absolute ethyl alcohol, diluted to 25 ml., and the qolution examined in a 5-cm. cell with ultraviolet light in :I Car\. automatic racording spectrophotometer. The spectra obtained may indicate the possible presence of phenothiazine (252 mp), p-tert-butylcatechol (280 mp), and Resin 731 SA (25s mp, 276 nip).
(3)
September, 1951. Boggs, H. AI., and Alben. A. O., ISD.EX.
CHmf..
ANAL.ED.,
8 . 9 7 (1936). I
_
Campbell, J. B., Jackson Laboratory, E. I. du Pont de Semours & Co., private communication. (5) Champa, L. S., and Wallach, A., A N ~ LCHEM.. . 22, 727 (1950) (6) Cholak, J., Hubbard. D. ll., and Burkey, R. E., I s o . ENG CHEM.,ANAL.ED.,1 5 , 7 5 4 (1913). (7) Cohen, H. C., Farben-Ztg., 36, 121 (1930). (8) Cooper, W. C., and hlattern, P. J., A x . 4 ~ .CHEM.,24, 57'5 (4)
(1952). (9)
Cowling, H., and hIiller, E. J . , I m . ESG.CHEM.,ANAL.ED., 1 3 , 1 4 5 (1941).
.
ANALYTICAL CHEMISTRY
1594 (10) Cupples, H. L., Ibid., 14, 53 (1942). (11) Davies, 0. L., “Statistical Methods in Research and Production,’’ pp. 76, 79, Oliver and Boyd, London, 1947. (12) Deichman, W., and Scott, E. W., ASAL. CHEM.,11, 423 (1939). (13) Eddy, C. Fv.,and DaEds, F., Food Research, 2,305 (1937). (14) Emerson, E., J . Org. Chem., 8, 417, 433 (1943). (15) Ettinger, M.B., ASAL. CHEM.,23, 1783 (1951). IND.ENCI. CHEM.,ANAL.ED.,6,412 (1934). (16) Evans, T. W., (17) Feicht, F. L., Schrenk, H. H., and Brown, C. E., U. S. Dept. Interior Bureau of Mines, Rept. Invest. 3639 (1942). (18) Fischer, H., and Leopoldi, G., 2. and. Chem., 107, 241 (1937). (19) Foerster, P., Ann. chim. anal., 14, 14 (1909). (20) Gardiner, K. W.,and Rogers, L. B., - ~ N A L .CHEM.,25, 1393 (1953). (21) ~,~Gibbs. H. D.. J . B i d . Chem.. 72. 649-64 (1927). (22) Gilman, H., ‘and Blatt, A. H., ’“Organic Syntheses,” 2nd ed. p. 463, Wiley, New York, 1941. (23) Gottlieb, S.,and Marsh, P. B., IND.EKG.CHEM.,.%K.AL. ED., 18, 16-19 (1946). (24) Hibbard. P. L., Ibid., 9, 127 (1937) : 10, 616 (1938) (25) Hicks, E. F., I n d . Eng. Chem., 3,86 (1911). S., J . Assoc. Ofic.Agr. Chemists, (26) Holland, E. B., and Ritchie, UT. 22,333 (1939). (27) Jones, J. H., Ibid., 28, 398 (1945). (28) Karush, F., and Sonenberg, hl., ANAL.CHEM.,22, 175-7 (1950). (29) Kaye, F., India-Ruhher J . , 66, 43542 (1922). (30) Ihtd., 67,233-8 (1924). (31) Kniaseff, Vasily, AXAL.CHEM.,20,329-30 (1948). (32) Lott, W. L., IND.ENG.CHEM.,ASAL. ED.,10,335 (1938). (33) hlantell, C. L., and others, “The Technology of Katural Resins,” p. 441, Wiley, New York, 1942. (34) illellon, M. G., “ilnalytical Absorption Spectroscopy,” p. 93, Wiley, New York, 1950. (35) Mellor, J. W., “Comprehensive Treatise on Inorganic and Theoretical Chemistry,” Vol. 111, pp. 158, 160, 161, 178, Lonnmans. Green. Kew York. 1938. (36) llenrei, R. G., and Jackson, 11. L., - 4 s ~CHEM., ~. 23, 1861 (1951); 24,732 (1952). (37) Nimer, E. L., Harnm, R . E., and Lee, G. I., Ibid., 22, 790 (1950). (38) O’Conner, R. T., IKD.ENG.CHEM.,ANAL.ED.,13, 597 (1941). (39) Oliner, A. W., and O’Keil, F. W., Paper Trade J . , 125, 55-62 (1947). (40) Overholser, L. G., and Yoe, J. H., IND.EXG.CHEM.,Ss.4~. ED.,14,646 (1942). ~I
(41) Owens, A. F., U. S.Patent 2,474,801 (June 28. 1949). (42) Payfer, R., and Narshall, C. V., J . Assoc. Ofic.Agr. Chemists, 28, 429 ( I 945). (43) Prudhomme, R. O., Bull. soc. pathol. ezotique, 31, 929 (1938). (44) Prudhomrne, R. O., J . pharin. chim., 1, 8 (1940). ISD. EKG.CHEM.,As.4~. (45) Reed, J. F., and Cummings, R. K., ED.,12,489 (1940). (46) Reiniteer, F., Z . anal. Chem., 69, 114-21 (1926). (47) Reenek, S..J . Am. Pharm. dssoc., Sci. Ed., 42, 289 (1953). (48) Rodden, C. J., “Analytical Chemistry of the Rlanhattan Project,” 1st ed., pp. 392-5, McGraw-Hill, Sew York, 1950. (49) Rogers, L. H., and Gall, 0. E., ISD.EXG.CHEM.,AXAL.ED.,9, 42 (1937). (50) Sandell, E. B., “Colorimetric Determination of Traces of hletals,” 2nd ed., pp. 620-3, Interscience, New York, 1950. (51) Ibid., pp. 623-8. (52) Sandermann, W., A s a ~ CHEM., . 21, 587-9 (1949). (53) Schatr, F. I-.,Specfrochim. Acta, 6, 198-210 (1954). (54) Schniteer, R. J., and others, Can. Public Health J . , 17, 24 (1942). (55) Schrapper, I., and hdler, I.. ASIL. CHEM.,21, 939 (1949). (56) Smith, L. E., ISD.ESG.CHEM., .ki.%L. ED.,10, 60 (1938). (57) Snell, F. D., Snell. C. T., “Colorimetric Methods of hnalysis,” Vol. 11, pp. 369-71, Van Sostrand, New York, 1936. (58) Stout, P. R., Levy, J., and Williams, L. C., Collection Czechoslou. Chem. Communs., 10, 129 (1938). (59) Swann, 11. H., i i l v . 4 ~ .CHEM.,23, 885 (1951). (60) Theis, R. C., and others, J . B i d . Chem., 61, 67-71 (1924). (61) United States Dispensatory, Osol, A , , and Farrer, G. L., editors, 24th ed., p. 289, Lippincott, Kew York, 1947. (62) Vallee, B. L., .%NAL. CHmi., 26, 914 (1954). (63) Yon Richter, Victor, “Organic Chemistry,” Vol. 3, p. 266, Blackstone’s, Philadelphia, Pa., 1923. (64) Walsh, R. H., Abernathy, H. H., Pockman, W.W., Galloway, J. R., and Hartsfield, E. P., T a p p i , 33, 232-237 (1950). (65) Wheeler, G. W., Borders, A. ll., Swanson, J. W., and Sears, G . R., Ibid., 34, 297-301 (1950). (66) Wolff, H., and Toeldte, IT., Farben-Ztg., 31, 2503-5 (1926). (67) Yost, D. bl.,and Aiken, W. H., T a p p i , 34, 30-9 (1951). (68) Ibid., pp. 40-8. RECEIVED for review September 27, 1951. Accepted July 5 , 1966. Contribution No. 172 from Jackson Laboratory. Division of Rubber Chemistry, 126th hleeting ACS, New York, September 19.51.
Precipitation of Metals with Potassium Ferrocyanide in Presence of Complexing Agents KUANG LU CHENGI D e p a r t m e n t o f Chemistry, University o f Connecticut, Storrs, Conn.
The reactions of metals with potassium ferrocyanide in the presence of complexing agents have been studied. By utilizing (ethylenedinitri1o)tetraacetic acid, thiosulfate, and fluoride to sequester interfering ions, a qualitative test for zinc and manganese in the presence of other metals has been developed. The test is capable of detecting 1 y of manganese at a limiting concentration of 1 to 1,000,000 and 50 y of zinc at a limiting concentration of 1 to 20,000. A quantitative volumetric determination of manganese with ferrocyanide has also been developed. No prior separations are necessary. OTASSIUM ferrocyanide is used extensively for titration of p z i n c . Because more than two dozen metals form precipitates or colored complexes vrith ferrocyanide, its use as an analytical reagent is rather limited. It was found that ferrocyanide was a very selective precipitant for manganese and zinc if (ethylenedinitri1o)tetraacetic acid (ethylenediaminetetraacetic acid, 1
Present address, R‘estinghouse Electric Corp., East Pittsburgh. Pa.
EDTA) and other complexing agents \yere used. I n the presence of (ethylenedinitri1o)tetraacetic acid, ferrocyanide formed a. specific deep blue color with ferric iron and a specific bluish tur-bid solution with ferrous iron. I n the presence of (ethylene-. dinitri1o)tetraacetic acid, copper(I1) was reduced by ferro-cyanide, which formed a brownish red soluble complex with copper(1). REAGENTS AND INSTRUMENTS
Potassium ferrocyanide solution, 0.05M, stored in a brown bottle. (Ethylenedinitri1o)tetraacetic acid sol,ltion, 5y0. Five grams of the disodi7im snlt of (ethylenedinitri1o)tetraacetic acid were. dissolved in 100 nil. of w-at,er. Nitrilotriacetic acid, 5%. Five grams of nitrilotriacetic acid were dissolved in 100 ml. of water. Thiosulfate solution, 5%. Five grams of sodium thiosulfatepentahydrate were dissolved in 100 ml. of water. Fluoride solution, 5%. Five grams of potassium fluoride were, dissolved in 100 nil. of water. This solution should be stored in a waxed bottle. Potassium ferricyanide solution, 1%, freshly prepared. Indicator solution, 1%. One gram of diphenylamine was dis--
