73 1
V O L U M E 21, NO. 6, J U N E 1 9 4 9 chemically in the South Korks Chemical Laboratory. cal curve data are shown in Table 111.
Analyti-
PRECISION
The general reproducibility of results on a single sample, which is a t present being used as a routine reference, is shown in Table IV. The results shown are for single determinations Ti-ith no corrections for curve shifting, which fortunately appears to be of a very minor character. The figures, taken from routine detrr-
minations, are typical of the checks to be expected and appear t o be of the same order of accuracy as those originally reported by the National Bureau of Standards and the cooperating laboratories on their silica brick 102 sample. Routine samples are generally run either in duplicate or triplicate and the average result is reported. LITERATURE CITED
(1) S t e i n b e r g , R. H., a n d Belic, H. J., ANAL.CHEM.,20,72 (19481 RECEIVED September 29, 1948.
X-RAY DIFFRACTION PATTERNS For the Identification of Surface-Active Agents THO3TiS F. BOYD, J. MALCOLM MAC QUEEN^,
AND
IRVISG STACY2
Philadelphia ,Varal Shipyard, Philadelphia 12, P a .
S
URFACE-active agents have acquired a Fide field of usefulness as detergents, emulsifying agents, dispersants, and wetting agents. Considerable investigation and development of commercial synthetic detergents are conducted a t this laboratory, and a rapid method for the identification of active ingredients was desirable. A4rapid method was also necessary as a basis for specifications requiring certain compositions in lieu of performance tests. The authors have prepared a file of x-ray data for 19 common surface-active agents for use in the synthetic detergent work of the laboratory ( 2 ) . EXPERIMENTAL PROCEDURE
The surface-active agents were separated from commercial products by tn.0 extractions n i t h 95% ethyl alcohol ( 1 ) . X-ray diffraction transmission patterns on film were made using a General Electric X R D unit and a flat cassette. The distance from the film to the sample holder v a s set a t 100 mm. Two-hour exposures were made with unfiltered copper radiation a t 40 kv. and 15 milliamperes. Photographs were taken using both the 0.25-mm. (0.010-inch) and 0.025-inch collimating systems. The distance from the film to the sample !vas calibrated n i t h sodium chloride. EXPERIMENTAL DATA
fi.vn n I s c u s s i o N
Interplanar spacings calculated from photographs are sh0n.n in Table I. The scale of intensities is an arbitrary one on which 10 represents the most dense line and 1 the faintest line. As a supplementary study. measurements of interplanar spacings and intensities Kere also made, using a S o r t h American Philips x-ray spectrometer, Type 12021. It was found that more lines and halos were recorded photographically than on the spectrometer chart and that the spectrometric measurements of 28 were in general less reproducible. However, more reproducible values of 28 were obtained for very high interplanar spacings using the spectrometer. .-it the high interplanar spacings, the width of the incident beam was limited by an extra slit in front of the regular slit and the 28 values n-ere obtained by setting the goniometer manually for the greatest numher of counts. .ACKNOWLEDGMENTS
Acknowledgment is made to Louis Goldberg and Myrtle Oberholtzer who assisted in obtaining data. The authors thank Henry Sloviter, Rubin Bernstein, and Joseph Simkin for their advice during this study. The authors wish to acknowledge the 1 1
Present address, 349 McClain .4ve., Coshocton, Ohio. Present address, 1673 East 13th St., Brooklyn 29, N. Y
Table I. Diffraction Data for Nineteen Crystalline SurfaceActive Agents Sgacing,
A.
1. Sorbitan hlonostearate 61.6 10 15.7 1 4.18 6 Sodium Salt of Sulfonated Ethyl Methyl Oleyl A m d e 51.5 10 25.0 4 16.8 3 5.03 3 4.44 2 3.96 4 3.78 2
2.
3.
4.
Sodium Oleyl Sulfate 50.0 10 36.7 5 24.5 4 16.6 2 4.34 4 4.10 3 Stearyl Amide of Sulfonated Sodium Succinate 48.6 10 22.6 3 14.9 2 4.20 2 Halo 40.7 4
5.
Sodium Salt of Sulfonated Ethyl Oleate 48.4 10 24.5 4 15.7 3 4.08 4
6.
Sodium Lauryl Sulfate 42.7 71.7 13.8 4.34 4.06
7.
Spacing, A.
Intensity
1; 4 1 2
Sodium Lauryl Sulfoacetate 41.4 10 20.8 4 13.7 3 5.17 1 4.59 2 4.14 4
Spacing,
8. Sodium n-Octyl Sulfate 29.6 4.32 4.08 9.
A.
Intensity 15.
1; 4
Dodecyl Benzene Sodium Sulfonate 26.5 10 21.6 1 18.5 1 13.4 2 Halo 4.97 3
10. M o n o b u t y l Phenyl Phenol Sodium hlononiilfnnate 26.2 10 13.0 2 10.4 2 7.02 2 Halo 4.85 I 11. Decyl Benzene Sodium Sulfonate 25.7 10 20.5 1 17.2 1 12.6 2 Halo 4.83 3
12. Sodium Di-3,7dimethyl Octyl Sulfosuccinate 26 2 10 14 4 1 Halos 48.1 4 4.98 1 13. Monobutyl Diphenyl Sodium Monosulfonate 25.0 10 15.5 2 13.0 2 10.4 2 Halo 4.85 1 14. Diootyl Ester of Sodium Sulfosuocinrte 21.7 10 6.17 2 4.32 2 3.27 2 Halo 4.14 3
Intensity
Diamyl Sodium Sulfosuccinate 20 0 10 9.60 1 8 85 1 4.34 1 Halo39.5 1 4.91 2
16. Dihexyl Ester of Sodium Sulfosuccinate 19.7 10 18.4 9 4.96 3 4.70 1 Halo 40.7 3
17. Sodium Tetrahydronaphthalene Sulfonate 19.7 10 15.7 3 5 72 4 5.56 ! 4.87 4 . .53 1 4 31 2 4.11 1 3.84 2 3.68 1 3.48 1 18.
Dibutyl Sodium Sulfosuccinate 16.4 10 9.19 4 7.79 2 6.55 1 5.39 1 5.08 4 4.66 1 3.97 4 3.47 4 3.28 2 3.14 1 3.05 1
19. Sodium m-Xitrobenzene Sulfonate 20.3 4 15.5 10 8.25 1 5.84 1 5.07 3 4.18 4 4.01 3 3.38 2 3.27 4
ANALYTICAL CHEMISTRY
732 sponsorship of the Bureau of Ships, Navy Department, which initiated this investigation. Thanks are expressed to James McCambridge and Leonard Zoole, under whose supervision this work was conducted, for their continued interest. The views expressed by the authors are their own and are not to be construed as representing the official views of the Navy Department.
LITERATURE CITED
(1) Bureau of Ships, Navy Department, ~ p e c i f i c a t i o n51-S-47(IXTT) (Oct. 1, 1947). (2) Hanawalt, J. D., Rinn, H. W., and Frevel, L. K., ISD. ENG. CHEY.,ANAL.ED.,10, 467-513 (1938).
RECEIVED September 15, 1948.
Spectrophotometric Determination of Hydrogen Sulfide Methylene Blue Method JAJlES K . FOGO' AND MILTON POPOWSKY Southern California Gas Company, Los Angeles, Calif. Hydrogen sulfide is absorbed from gases and precipitated as zinc sulfide. The precipitate is then redissolved and allowed to react with p-aminodimethylaniline in the presence of ferric chloride. The optical density of the resulting methylene blue solution is measured at 670-millimicron wave length and the corresponding quantity of sulfide is read from a previously prepared calibration curve. The method is sensitive to about 3 micrograms and the range up to about 500 micrograms. The procedure is convenient for occasional as well as frequent use.
T
HE determination of hydrogen sulfide in gases has usually
been accomplished by iodometric methods (2,6). These give accurate results on appropriate samples but are often too insensitive for samples containing very little hydrogen sulfide. A much more sensitive method is that of Field and Oldach ( S ) , in which the sulfide is converted to bismuth sulfide which is determined photometrically while in suspension. This method, although very sensitive (1.4 micrograms), is not well suited for the occasional user, because very rigid control of technique is said to be necessary and all solutions must be protected against oxygen. The method described herein is a refinement of the methylene blue method (1, 5, 7 ) . The technique has been improved by use of optimum conditions for the principal reaction and by applying modern spectrophotometry to the measurement of concentration. The manipulation is simple and the results are not affected by minor variations. The method has been in successful use in the form given for several pears. The hydrogen sulfide is absorbed from a stream of gas in a suspension formed by adding sodium hydroxide to a solution of zinc acetate. The stripped gas is then suitably metered. The suspension then containing the absorbed sulfide as zinc sulfide is treated with an acid solution of p-aminodimethylaniline, followed by the addition of a small amount of ferric chloride solution. Bfter time has been allowed for the formation of the methylene blue, the solution is diluted in a volumetric flask and an aliquot is transferred to the spectrophotometer for measurement. The correspondin quantity of sulfide is then determined from a previously preparef calibration curve, plotted from similar measurements on methylene blue solutions prepared in the same manncr with known amounts of sodium sulfide or hydrogen sulfide. The method is sensitive to about 3.5 micrograms of sulfide when used as given. Greater sensitivity could be obtained fairly easily by appropriate reductions in the volumes of solutions used. The upper limit of the method as given is about 500 micrograms. The 1 Present addreas, Chemistry Department, University of Southern California, Los Angeles, Calif.
precision at such high concentration is somewhat poorer than a t about 100 to 200 micrograms, where it is *3%. APPARATUS
The list of apparatus includes the items necessary for taking two samples simultaneously and thereafter treating them consecutively. Two 250-ml. coarse sintered-glass type gas washing bottles. (Those made by Corning Glass Works are suggested.) Two test meters, either wet or dry type. One pipet, 25-ml. Two pipets, 5-ml. One graduated cylinder, 250-ml. One glass tubing cross, 8-mm. Three tubing clamps, screw type. Ten meters of 7-mm. Tygon tubing. Three volumetric flasks, 250-ml. One spectrophotometer or filter photometer. REAGENTS
KO especial care need be taken in the preparation of the reagents. Deviations up to 5y0 in the concentrations given are allowable. If the diamine used produces a dark colored solution, a fresh supply should be obtained. Zinc acetate, c.P.,1% solution in distilled Kater. Sodium hydroxide, c.P., 12y0solution in distilled water. Ferric chloride, c.P.,0.023 molar solution in 1.2 molar hydrochloric acid. p-Aminodimethylaniline sulfate, Eastman white label, 0.5 gram in 500 ml. of 5.5 molar hydrochloric acid. SAMPLING
A dual sampling procedure in which two samples are obtained simultaneously is recommended. The absorption should be done if possible directly a t the source. Gas samples brought into the laboratory in metal or rubber vessels usually give low results due to the reaction of hydrogen sulfide with the metal or its oxide or to its solubility in rubber. The pressure a t the source must be a t
