OH
SO, + H20
-+
I S I
=
OH I Weaker arid, reducible
OH 0
+ H+ +
I S- = II
0
0 I1
Stronger acid, oxidizable
As the p H is increased, this reaction shifts to the right. At p H 1, I > 11; a t p H 3. I1 > I : and above p H 7 , there is very litfle, if any, of I present. It is believed that a t pH 1.5 there is more of I present, which is not as readily oxidizable as I1 a t that pH. Thus, interferences resulting from the oxidation of sulfur dioxide by oxidizing substances in the atmosphere are inhibited. There was some deposition of dye on the walls of the contact column due to evaporation. This was not found deleterious and the glassware was easily cleaned by flushing nith 95% ethyl alcohol.
The reagent described has been continuously circulated in the modified Kruger machine for 6 weeks and, with rezeroing of the machine cach time the supply and waste bottles were exchanged, there was no appreciable loss in sensitivity. ACKNOWLEDGMENT
The authors are indebted t o Harold Kruger of Harold Kruger Iiistruments, San Gabriel, Calif., for invaluable assistance in furnishing instrument components and advice in the niodifications of the instrument and for coniparative work in checking sensitivity, specificity, and stability of t h r rcagent described. LITERATURE CITED
(1) Atkins, S., ASAL. CHEJI.22, 947-8 (1950).
(2) Ingole, Robert S., Georgia Institute of Technology, Engineering Experiment Station, Atlanta, Ga., private communication. (3) Kolthoff, I. M.,Miller, G. S., J . A m . Chem. SOC.6 3 , 2818-21 (1941). (4) Kruger, H., Harold Krriger Instruments, San Gabriel, Calif., private .. ....... . ~.. ~ .......
(5) llrKelvey, J. H., Hoelscher, H. E., A S A L . CHEJI. 29, 123 (1957). 16) Moore, G. E.. Cole. -1.F. W., Kate. ( 7 ) 'Paulus, H. J., Floyd, E. P., BJ ers, D. H., i l n i . I n d . Hjjg. .-lssoc. Quart.
15,277-82(1954). (8) Steigniann, .\., .Is.%L. CHETI. 22, 492-3 (1950). ((3) Striemann. -4.. J . Sor. C h ~ n / .I n d . I - -
~
\
-~
(10, Urone, P. F., Boggs, W. E,, SAL. CMEM. 23, 1517-19 (1951). (11) 1Yrs.t. P. IT-.. Gaeke, C;. C., Ihid., 28, 3816-10 ( l W h ) .
RECEIVED for rwien Sovember 2, 1957. Arcepted June 3. 1958. IXvision of Water, Sewage, and Sanitation, Sym~)osiunion Air Pollution, 134th AIeeting, riCS, Chirxgo, Ill., September 1958.
Aromatic Hydrocarbons in the 170" to 180" C. Fraction of Petroleurn BEVERIDGE J. MAIR, SHIRLEY P. DAVIDSON, NED C. KROUSKOP, and FREDERICK D. ROSSlNl Chemical and Petroleum Research laboratory, Carnegie Institute of Technology, Pittsburgh 1 3, Pa.
b Seven hydrocarbons were found to constitute substantially all of the aromatic portion normally boiling between 170" and 180" C. of the representative petroleum which has been under investigation by the American Petroleum Institute Research Project 6. These compounds were individually concentrated by extended use of the fractionating processes of distillation (both regular and azeotropic) and adsorption. Identification of the compounds was made from measurements of the simple physical properiies coupled with infrared spectral examination. The estimated relative amounts of these seven aromatic hydrocarbons are as follows: lI2,3-tri1 -methyl-3methylbenzene, 54.5%; isopropylbenzene, 22.6y0; 1 -methyl44sopropylbenzene, 12.1 %; sec-butylbenzene, 5.0%; 1 -methyl-2-isopropylbenzene, 2.5%; isobutylbenzene, 2.4%; and indan, 0.9%. These seven compounds together constitute 0.35% of the original petroleum.
analysis of the hydrocarbons in the aromatic portion of this petroleum normally boiling in the range from 170" t o 180" C. has been completed. M E T H O D OF ANALYSIS
Two lots of aromatic material, 170" to 180' C., w r e available. Lot I came from previous work in which a relatively small sample (about 6 liters) of thr naphtha fraction of this p~troleum was separated by adsorption with silica gel to give two portions: an aromatic and a paraffin-ryclo portion. The aromatic portion \\-as distilled and the niaterial boiling in the rangc from 170" to 180" C. was combined t o constitute Lot I. From these data. tht. aromatic portion from 170" to 180' C. was found to constitute 0.357, of the entire petroleum. Drtails of the foregoing operations have becn given ( I ) ; and Lot I is identical with Lot V of the Ponca petroleum describpd previously. The relative amounts of the individual constituents n-ere detrrmined from infrared measurements on a part of the s PART of the continuing work of entire lot. the American Petroleum Institute Lct I1 was produced by combining Research Project 6 on the composition into one portion all of the aromatic of its representative petroleum (4, material, exccpt for a small sample of
A
1 8 14
ANALYTICAL CHEMISTRY
1.2,3-trimethylbenzene, remaining in t,he desired range from previous work on a large samplc of petroleuni ( 8 ) . Small amount's of nonaromatic constituents were rcniovcd from this material by adsorption n-ith silica gel. Tlic purr aromatic portion was distilled to obtain in one lot all of the aromatic hydrocarbons normally boiling in the rang(' from 170" to 180' C . The data of this distillat,ion arc givc,n in FigurP 1, which shows the location with rpspect t o boiling point aurl refractive index of the compounds found in this material. The first pcrt'ion of the distillatc consisted largely of 1,2,4trimethylbenzene, which boiled below 170" C., and thrx portion near the tail end consisted largely of 1,3-dieth!.lbenzene and I-mcthyl-3-propylbenzene (m-cynirne). both of which boil a b o w 180" C. T h t ~prment analysis does not include thme thwe compounds; 1,2,4triinetIiylb(.iizcne is covered in an analysis of the atljacrnt, loncr boiling portion ( 3 ) . Further processing of this material by distillation '(regular or azeotropic) or by adsorption was designed t o concentrate the individual hydrocarbons for positive identification. The relative amounts of the individual compounds
1
I
'0'1
were estimated from data on boiling points and refractive indices as a function of volume in conjunction with the results of spectroscopic analyses made on selected intermediate and final fractions. The steps in resolving portion A (Figure 1) niay be summarized as follows: Seven distillations (3 regular, 4 azeotropic) were involved. The details of the distillation apparatus and procedure have been given (4, 5 ) . The azeotropic distillations, with cthj-1ene glycol nionohutyl ether as the azcotropic forming substance, caused the separation of substantially pure 1,2,3trimethylbenzene in the tail cnd portions of the distillate. These portions nere oinitted from the charges for subsequent distillations. The data of the two final azeotropic distillations, which gave the best samples of iso- and sec-butj-lhenzcne arid l-methyl-3-isopropylbenzene, are shorn in Figures 2 and 3. Portion E (FigurP 2) was included in the charge used to produce the rcsults shonn in Figurc 3. The spectroscopic analyses of portions A, B, C, and D from both figures are given in Table I. The steps involvd in the resolution of portion B (Figure 1) may be summarized a s follous: Each of the distillation fractions comprising portion B wa5 fractionated by adsorption with silica gel in a column 1.25 meters in length [column 6, page 149, of reference ( d ) ] . The fractions resulting from this operation were combined to give a portion of lower refractive index (nD a t 25" C., 1.489), composed largely of l-methyl4-isopropylbenzene, and a portion of higher refractive index (nn a t 25" C., 1.494 to 1.518), rich in indan and 1,2,3-
I
I
I
9
"I I
d
c
i
\ I
168
I
I
I
400
200
I
I EW
600
,'OLUME
Figure 1 . Regular distillation petroleum
IN
I lmo
I
I 2200
MILLILITERS
of the 170" to 180" C. aromatic fraction of
I= 1.50
W
5
1.49 0:
d I
166
-
X ISaUlYLENZENE
tct+0
e--+
50 VOLUME
IN
I00
I .48
1
X-ISOWTYLBEWENL
I*I
Ibl
IC/
ID/
I
I
MILLILITERS
Figure 2. Final azeotropic distillation which gave concentrate of isobutylbenzene and sec-butylbenzene VOL. 30, NO. 1 1 , NOVEMBER 1958
1815
1.5r
I
I
4 Figure 4. Final adsorption experiment which 1 -1nethyI-4-isogave propylbenzene
$ 1 i' P.
I
I
r
ll
I
+A-X-I-Y~THYL-4-DOWOPYLBENZENE
+A :
I 4e0
VOLUME
IN
4 Figure 5. Final adsorption experiment which gave concenkate of indan
is.
-t 1.49
trinir.thylbenzeiie. Each of these portions n-as again fractionated by adsorption, the former giving the best sample of I-methyl-4-isopropylbenzene (p-cymene) and tlic latter the best saniple of indan (Figures 4 and 5 ) . Table I gives the spectroscopic analyses of the portions designated in tlicse figures. Portion C (Figure 1) vias also fractioiied by adsorption with silica gel. The data of this esperiiiient are given in Figure 6; the highcst concentration of
I. METHYL - 2 . ISOPROPYLBEHZE HE
A
i
. -METHYL-~-lSOPROPILBEHLENE 1
I
0 VOLUME
IO IN
20 MILLILITERS
Table I.
Compound Isobutylbenzene sec-Butylbenzene
2A 28 68 4
l-l\lethyl-3-isopropylbenzene
1,2,3-Trimethylbenzene
IN
MILLILITERS
Figure 6. Final adsorption experiment which gave concentrate of 1 methyl-2-isopropylbenzene
i
I,"I
20
IO
VOLUME
MLLILITERS
1-methyl-2-isopropylbenzene mene) was found in portion A . RESULTS
Table IT summarizes the information regarding the seven aromatic hydrocarbons nornially boiling in the range from 170' t o 180' C. For l-mcthpl-2isopropylbenzene, only the results from Lot I1 u-ere considered in determining the mean, because it appears that Lot I was not c u t a t a sufficicntly high temperature to includc all of this component. It is not surprising that indan, m-hich is present in very small amount,
Infrared Spectrographic Analysis of Selected Portions
2B 20 66 13
2c
20
Percentage in Given Portiona 3A 3B 3C
30
4A
l-~Tethpl-2-isopropylbenzene
1
55 29
4
92 4
(3)
(3)
(2)
8 85
