controlled limits of both the potassium iodide and hydrochloric acid concentrations, attention was focused on a possible error in obtaining the normality of the thiosulfate solution. Kormalities of the thiosulfate solution determined by a scaled-down macro procedure of Kolthoff (3) and Clark ( I ) were compared with those determined by Steyermark’s procedure (6). The values shown in Table I1 were obtained the same day and in the order shown. Data for the Steyermark procedure show a higher value of the normality and also a greater deviation in the results. Although this deviation may explain some erratic results obtained earlier, even more significant is the large difference in normality of the thiosulfate solution found by the two methods. The normalities recorded in Table I1 reveal an average difference of 12 parts per thousand, which is equivalent to
LITERATURE CITED
0.9% arsenic in the case of arsenious oxide. No serious attempt was made to determine the cause of this discrepancy in the normality values, but the moderately high hydrochloric acid concentration employed by Steyermark is favorable to the formation of one of the mixed halogens (4). .Iny iodine thus removed would tend to increase the normality of the thiosulfate. With the normality found by the scaled-down procedure all determinations were repeated and the results are shown in Table I, column IV. These results are well within the acceptable limits (+0.2-0.3%) and the values for an N.B.S. arsenious oxide sample agreed with theory. ACKNOWLEDGMENT
The authors are indebted to Charles Merritt, Jr., for helpful suggestions in the preparation of this manuscript.
(1) Clark, G. L., Kash, L. K., Fischer, R. B., “Quantitative Chemical Analysis,” p. 360, W. B. Saunders Co., Philadelphia and London, 1949. ( 2 ) DiPietro, C., Kramer, R. E., Sassaman, W. A,, ANAL. CHEM.34, 586 (1962). (3) Kolthoff, I. M., Sandell, E. G., “Textbook of Quantitative Inorganic Analysis,” p. 623, Macmillan, New York; 1946.(4) Latimer, W. M., “The Oxidation States of the Elements and Their Potentials in Aqueous Solutions,” p. 61, Prentice-Hall, New York, 1938. ( 5 ) Smith, T . B., “Analytical Processes, A Physico-Chemical Interpretation,” p. 278, Edward Arnold and Co., London, 1940. (6) Steyermark, A., “Quantitative Organic Microanalysis,” p. 367, 2nd ed., Academic Press, New York and London, 1961. CARMINE DIPIETRO A. SASSAMAN WARREK U. S. Army Natick Laboratories Natick, Mass.
Separation of Isomeric Xylidine by Gas Liquid Chromatography EXPERIMENTAL
SIR: The gas chromatography of isomeric xylidine is described only briefly in the literature. Some retention data for anilines were reported by James ( 2 ) ,Jones, Ritchie, and Heine (S), and Fitzgerald ( I ) , but good results for separating the six close-boiling xylidine isomers were not given. K e studied several stationary liquids and found that a sodium dodecylbenzenesulfonate (DBS) gave good resolution of all six isomers.
Apparatus. h Shimazu GC-1A gas chromatograph, equipped with a thermal conductivity detector, was used. Helium and nitrogen were used as carrier gas. The columns were constructed from 6-mm. i.d. stainless steel tubing and were packed by adding coated support while gently tapping the column. Column
Packing
M I NUTES
Figure 1.
Separation of isomeric xylidines
DBS lO%/Celite 5 4 5 4 0 - 6 0 mesh, 2 . 2 5 meters, 1 3 0 ’ C., H e 150 cc./ minute b. DBS 1 Oyo-DG 0.4yo/Celite 5 4 5 60-80 mesh, 2 . 2 5 meters, 1 3 0 ’ C., H e 1 2 0 cc./minute
a.
22 14
ANALYTICAL CHEMISTRY
Preparation.
Column packings were prepared by conventional procedures. Thirty
nrams of 60- to 80-mesh Celite 545 was rreated with concentrated HC1 and 20% N a O H aqueous solution. Diglycerol (DG) (0.12 gram) was dissolved in methanol, slurried with Celite 545, and the solvent was removed by evaporation under vacuum, facilitated by gentle stirring. Then 3 grams of DBS was dissolved in benzene and was impregnated similarly to the solid support. The packing was sieved to the specified range to remove any fines produced.
M I NUTES
Figure 2. Chromatograms of (a)commercial xylidine mixture and ( b ) xylidine fraction in coal tar DBS 1 Oyo-DG 0.4Q/o/Celite 5 4 5 60-80 mesh, 2.25 meters, 1 3 2 ’ C., He 1 2 0 cc./minute
Table I.
Relative Retention Time
(2,g-xylidene Stationar) liquid LVt c c Celite 34.3 mesh Column length, meters Column temp , C Carrier gas
Silicone grease 10 80-100 3 75 155
s*
1 00
1 (10
TXPa 10 80-100 2 25 127 ?;,
1 00 1 04
=
1.00)
PEG 4000 10 80-100 2 25 128
Sorbitol 10 60-80 3 75 127 5
s,
1 00 1 19
DBS 10 40-60 2 25
Ii2
130 He
1 00 1 14
1 00 1 13
DBS 15, PEG 4000 0 5 60-80 2 25 130 He 1 00 1 1.5
DBS 10, DGO 4 60-80 2 25 130 He 1.00 1.14 1.22 1.34 1.48 1.63
2,3-Sylidine 3,4-?(ylidine T I P = Tri-2,4-uylenyI-phosphate
Table
II.
Determination of Isomeric Xylidines-
Xylidines, 70 Sample 2,6- 4 2$2,43,sCommercial xylidine mixture 14.0 18.3 44.0 3.0 Xylidine fraction in coal tar 1.7 15.7 26.2 48.4 e Peak area determined directly from the integrated values using the the peaks as a dividing line.
RESULTS A N D DISCUSSION
Results for several liquid I,hases are shown in Table I. The best separation was ohtained using DBS-DG column ]lacking as shown in Figure 1. K h e n the amount of I>G or PEG as tailing reducer was increased, 2,5-xylidine and 2,4-
2,3-
324
13.3
7.3
2.0 6.0 minimum between
xylidine elut'ed simultaneously, but 2,4xylidine was thoroughly separated from 3,5-xylidine. The analytical utility of t,his DBS column is demonst'rated by the data in Figure 2 which show the chromat,ogranis of a commercial xylidine mixture and a
xylidine fraction in coal tar. The semiquantitative analyses of xylidine isomers by the direct area normalization method are shown in Table 11. LITERATURE CITED
(1) Fitzgerald, J. S.,Australian J . ilppl. Sci. 12, 51 (1961). (2) James, A. T., ANAL.CHEM.2 8 , 1565
(1956). (3) Jones, J. H., Iiitchie, C. D., Heine, K. S., J . Assoc. Ofic. Agr. Chemasts 41,749 (1958). W A T A R C FUNAs.4KA
TSUGIO KOJIMA HIROYUKI IGAKI Faculty of Engineering Department of Industrial Chemistry Kyoto University Yoshida, Kyoto, Japan
Quantitative Infrared Microanalysis of High-Boiling Aliphatic Neutral Oil Fractions SIR: In characterizing neutral oils from low-temperature coal tars a quantitative infrared microanalytical procedure had to be developed that could be applied to undiluted samples of aliphatic$ with a variety of both saturate and olcfin types in the CISto C?o range, inclusive. -1 survey of the literature showed that a procedure for this molecular weight range and class misture had not bwn described. Saturates and o1tfm.i have been dealt with separately and the work has been either on relatively low-boiling material or polymers. In othrr work the analyses were cond w t e d in solution and the use of ultramicrocavity cells with a beam condenser for surh an analysis has not been dewri bcd.
pure grade hydrocarbons, in so far as these were available. Apparatus. Spect'ra were recorded on a Perkin-Elmer Model 21 infrared spectrophotometer equipped wit'h sodium chloride optics and a PerkinElmer 6s ultramicrosampling unit mounted in t h e sample beam. With proper alignment, the reflecting optics of the beam condenser will t,ransmit about 40y0 of the energy normally available. The cell masks, with dimensions of 1 X 4 mm., do not further reduce the energy. Sodium chloride liquid ultramicrocavity cells (Type I), Connecticut Instrument Corp.) with nominal pathlengt,hs of 0.05 mm. were used to obtain spect'ra of both pure compounds and neutral oil samples. The liauid cell holder has been described * ( 5 ) . Procedure. The neutral oil dis...~ tillate fractions analyzed in this work were obtained from a low-temperature bituminous coal tar. These had been separated into aromatics and aliphatics bj- countercurrent dist,ribution in a dual solvent system of isooctane and ~
EXPERIMENTAL
Reagents. The pure compounds u w l in the calibration ITere either .A me ri c a n Pet ro le u in I n ?t i t u t e c. t andard xanil)le.: or Phillips Petroleum Co.
~
~~
90 wt. % ethanol in water. T h e aliphatic material was recovered from the upper phase solvent (isooctane) in the automatic fraction collector of a Craig countercurrent distribution (CCD) apparatus. The material was separated from aromatics except for an overlap of a few tubes. However, only a slight separation of saturates and olefins by class mas effected (about two tubes). I t wab necessary t o use ultramicrocavity liquid cells and a beam condenser to obtain infrared spectra because the amount of sample was often as low as 2 me;. after so1 .ent removal. The analysis was performed in a solventfree state because of the low absorptivities of aliphatic compounds and also t o avoid solvent interference at the analytical wavelengths. For the pure compounds used in setting up the analysis, molar absorptivities (e) a t the analytical wavelengths were determined from the relationship e = .1.1f/1000 b d 2 5 (1) where A is absorbance, b is cell thickness in centimeters, d 2 j is the density of VOL. 36, NO. 1 1 , OCTOBER 1964
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