the many interferences. It is rapid, however, and frequent calibration is not required. It should be useful for determining fluoride after distillation of silicon tetrafluoride and subsequent hydrolysis. Extension of the principles used in these studies to the ultraviolet spectrophotometric determination of other anions in the concentration range of 1 to 100 p.p.m. should be feasible. A useful technique for further studr should be the measurement of the ultraviolet absorption of organic acids or anions Produced by reaction of metal salt of the acid to be determined.
Studies of other organic acids, particularly other substituted 2,5-dihydroxy-pbenxoquinones, may lead to more sensitive. more specific methods. Salts of bromanilic acid, nitranilic acid, polyporic acid, and atromentin are being studied in these laboratories. ACKNOWLEDGMENT
Assistance of R. W. Fish and Betty Ellen Ries is gratefully acknowledged. LITERATURE CITED
( I ) Barney, J. E., Bertolacini,-$. J., -4NAL. CHEM. 29, 1187 (1901).
Bergmann, J. G., Sanik, J., Ibid., 29, 241 (1957). Bertolacini, R. J., Barney, J. E., Ibid., 29, 281 (1957). Curry, R. P. Mellon, PVI. G., Ibid., 28, 1567 (1956). Lambert, J. L., Ibid., 26, 558 (1954). Lothe, J. J., Ibzd., 28, 949 (1956). Sanchis, J. AI., IND.ENQ.CHEM., A N A L . ED. 6 , 134 (1934). Schnwzenbach, G., Suter, H., Helv. Chim. Acta 24,617 (1941). Taltuitie, S . A., IND.Eso. CHEM., ANAL.ED. 15, 620 (1943). RECEIVED July 26, 1957. Accepted October 24, 1957. Eighth Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, AIarch 1957.
Spectral Absorption of Asphaltic Materials H. E. SCHWEYER Department of Chemical Engineering, University o f Florida, Gainesville, Fla.
b An exploratory study of the absorption of ultraviolet and infrared energy b y several asphaltic materials included consideration of the applicability of the Beer-Lambert law to asphalts dissolved in a mixture of iso-octane and 1 -butanol for ultraviolet absorption, and in carbon tetrachloride and thin films for infrared absorption. Typical spectrograms are illustrated for several asphalts.
F
commercial products are as compleu in chemical nature as those defined by the generic term asphalt or asphaltic bitumen. In the hope that ultraviolet and infrared spectrophotometry might explain differences in asphaltic materials, an exploratory study has been carried out t o establish techniques. The literature on the subject is limited and when this paper was submitted only the publications of Eilers ( 2 ) , and Killiford (12) using x-rays were available to the author. The recent papers of Stewart (10) and Linnig and Stewart ( 7 ) have provided additioiinl information on asphalts separated into fractions by chromatographic techniques. However, the numerous publications on spectral absorption of lubricating oils are pertinent where the oils in asphalts may be considered as higher-boiling hydrocarbons of the same general nature. Pertinent studies on high-boiling petroleum oils are those of Charlet, Lanneau, and Johnson ( I ) , Hastings and associates ( d ) , Hersh, and associates (6)> and Lillard, ,Tones, and Anderson (6). EW
ULTRAVIOLET SPECTROGRAMS
The technique for asphalt requires
the use of solutions. While iso-octane (Phillips Petroleum "spectral grade") is a suitable diluent for most petroleum oils, it is not a good solvent generally for asphaltic materials. A mixture of 15% (volume) of 1-butanol (synthetic, with a boiling range of 1.5" C. including 117.7" C.) and 85% iso-octane is a satisfactory solvent a t asphalt concentrations of 0.02 gram per liter or less and provides suitable transmittance in a Beckman spectrophotometer Model DU, employing the mixed solvent as the blank for a cell thickness of 1 em. Approximately 0.1 gram of asphalt is x%-eighed directly into a tared 50-ml. volumetric flask and the proper amount of premixed stock-solvent solution added to fill the flask. After solution is complete, a 1-ml. aliquot of the concentrated solution is made up to 100 ml. in a volumetric flask with mixed solvent t o give a final concentration of about 0.02 gram per liter (which can be computed exactly from the R-eight of asphalt used). Smaller flasks and a larger number of dilution steps may be used to conserve solvent or sample (10-ml. flasks recommended). As observed bjeye, this technique gave complete solution for the soft residual asphalts studied.
As solvents for asphaltic materials benzene, carbon tetrachloride, and carbon disulfide were discarded either because their absorption was too high in the spectral ranges of interest or for other reasons. The use of 1-butanol is subject t o some objection from a purity standpoint, but when used in small proportions (15%), the type of impurities likely to be present were not as critical as for the other solvents. The mixed 1-butanol and iso-octane has been found satisfactory for most soft asphalts (up to 130" to 150' F., ring and ball softening points). How-
ever, certain components from harder air-blown asphalts and from soft catalytic-blown asphalts have been found to be incompletely soluble in the mixed solvent. The absorbance for the final dilute solution in comparison with the blank is measured directly on the instrument a t different wave lengths starting a t 400 mp and a t decreasing values by increments of 5 mp until 240 is reached. Then readings are taken a t 2-mp increments until no reading can be made, The absorbance per unit of concentration (grams per liter) and per unit of thickness (centimeters) is the absorptivity as computed from a = log (Io/I)/(cb) = A / ( & ) ,absorptivity
where lais the transmittance of the blank, I is the transmittance of the unknown in solution, and A is the absorbance at a given wave length as read directly on the instrument; if the product cb has a value of 1, then a and A are equal. c is the experimental concentration in grams per liter and b is the cell thickness in centimeters. The validity of this equation for asphaltic materials was checked on an extracted fraction of one asphalt using different concentrations and different cell thicknesses (Table I). The acetonesoluble portion from a butanol extract of a Texas residuum S-160 (see Table 111) by the Trader-Schweyer method (11) was used for these data. Data in Table I indicate that the absorptivity in 1-cm. cells is not affected by concentration within average limits of =t2 units, which the author considers acceptable based on experiments with different spectrophotometers, different operators, and different samples. With identical starting samples, the ultraVOL. 30, NO. 2, FEBRUARY 1958
* 205
Table 1.
Validity of the Beer-Lambert Law for Ultraviolet Measurements (S-157)
B" C D E5 Fa Concn., g./l. 0.02 0.017 0.010 0.004 0.20 Cell thickness, cm. 1.0 1.0 1.0 1.0 0.1 Absorptivity 30.9 28.1 29.7 32.0 At 260 mp C 30.6 At 250 mp C 27.4 28.0 24.7 25.9 31.2 A t 230 mp 52.1 58.5 C 54.7 54.9 50.7 From dilution of same source solution as A. (Cell thickness for F and G obtained by using matched quartz spacers, one also used for blank.) b Same solution as A. Toodark. A 0.04 1.0
violet absorption curves of Figures 1 and 2 were readily reproducible on different machines and with different operators when separate samples were used a t the same concentrations in 1-cm. cells. For asphaltic materials, it is reconimended that the cell thickness be standardized at 1 cm. for comparing data, as the absorptivity appears to be affected by cell width and concentration in 0.1cm. layers. The data are limited, but a comparison of runs G with E and F with B indicates a definite trend. This trend might be caused by technique errors or the inapplicability of the Beer-Lambert law. The former have been minimized by using the same starting solution and careful dilution procedures. It is concluded that the absorptivity may vary with the thickness of the path for asphalt dissolved in the solvent used for these studies. This variation might be caused by scattering effects because of incomplete solubility a t different concentrations, but this is not probable because the sample was selected as being completely soluble in either of the solvents used for making the master solution. A plot of the absorptivity computed for unit concentration and unit thickness versus wave lengths permits quantitative comparisons of the absorption of different materials (Figures 1 and 2). The first figure shows the results for four residual asphalts and the second illustrates the curves for the saturate (paraffinic) and cyclic fractions obtained from three typical asphalts by the Traxler-Schweyer method (11) for separating asphalt into its components. It also has been determined that essentially identical results can be obtained for dilute samples that, after standing 72 hours, indicate no aging effect. The absorption curves for asphaltic materials are all similar, showing high absorption in the 220- to 240-mp region indicative of conjugated acyclic dienes based on Woodward's work (IS). Absorption a t about 260 mp indicates mono- and polycyclic aromatics and/or conjugated acyclic trienes. Broad absorption bands above 270 mp may be caused by polycyclic aromatics and also are attributed to possible scattering effects which preclude any accurate observations with 206
ANALYTICAL CHEMISTRY
the technique employed unless definite peaks are found. The presence of nonhydrocarbon groups may also lower the sensitivity in this region. The absorption curves for most straight asphalts are of similar nature, as shown in Figure 1, and the asphalts
cb 0.04 0.1
35.8 44.8 75.4
cannot be characterized by ultraviolet analyses alone. However, components separated from asphalt, when studied by ultraviolet techniques, may provide interesting and valuable information, based on the differences from asphalt to asphalt for the saturate and cyclic
40
K
I M T L R Y L D I A T L R E B I D U U M , TAR 2 RLBIDUUY, TAR 1
0 AROMATIC 0
> t> -
1o
n E
a0
I-
FLORIDA
RLBIDUUY
,
101- 0
3
m
a
IO
0
0
210
200
aoo
X , WAVE LENGTH, MILLIMICRONS Figure 1 .
50
Ultraviolet spectrograms for four residua
+5 0-NAPHTHENIC RESIDUUM. TAR I X-INTERMEDIATE RESIDUUM, TAR 2 A-AROMATIC RESIDUUM, TAR 3 CELL WIDTH-ONE
>-
CY.
4
> a
t-
E 0
cn m a d
A , WAVE LENGTH, MILLIMICRONS Figure 2.
Ultraviolet spectrograms for components of three residua
fractions as indicated in Figure 2. Certain other data of this type have been presented by Schweyer, Chelton, and Brenner (9), and Schmeyer ( 8 ) . Vacuum-reduced asphalts and their source residuum show about the same absorption characteristics, but air-blown products show a trend of reduced absorption compared to the charge stock. This trend is usually not great but seems to be a definite characteristic indicated by ultraviolet analysis. This appears to be a reasonable result of the airblowing process, because polymerization at the points of unsaturation might be expected to reduce the quantities of absorbing materials (double bonds and unsaturates) that were present in the original charge stock. Cross linkages with a higher degree of naphthenicity might also be expected from polymerization a t those points in the molecule where dehydrogenation has occurred. INFRARED SPECTROGRAMS
A Perkin-Elmer Model 21 spectrophotometer with sodium chloride was used for the infrared studies reported here. Preliminary results were obtained on asphalt residua dissolved in methylcyclohexane, but as this is not a complete solvent for harder asphalts, the solvent was changed to carbon tetrachloride (c.P. grade, Fisher Scientific Co.). Methyl cyclohexane and isooctane absorb in the region where asphalts absorb and thus require special considerations (probably very high concentrations) to obtain sensitivit~y.
Table II.
Cell thickness, cm. Concn., ,g./l. Absorptivity A t 3.41 microns A t 3.49 microns A t 6.85 microns A t 7.28 microns Spectrogram No. Cell thickness, cm. Concn., g.11. Absorptivity At 5.85 microns At 6.20 microns A t 9.7 microne A t 10.3 microns At 11.5 microns A t 12.3 microns A t 13.45 microns A t 13.9 microns Spectrogram No. a
Yo sensitivity.
Infrared Absorption on S-152
Film 0.00187 1000
Solution in Carbon Tetrachloride 0.0527 0.0205 0.0106 5.01 9.94 5.01 9.94 5.01 9.94
1.00 0.636 0.336 0.172 3467
1.99 1.06 0.43
Film 0,010
Solution in Iso-octane 0,0527
0.021 0.036 0.036 0.037* 0.034 0.036 0.044* 0.063 4200
*
Where the supply of sample is limited, these required concentrations would be a limitation. Carbon disulfide as a solvent appears to give interference effects at 4.35, 4.65, and 11.7 microns which are regions where it, alone, also shows absorption. Carbon tetrachloride is an excellent solvent for all asphalts, but it is not an ideal solvent for spectroscopic work because it appears to give some interference effects and becomes opaque a t about 12 microns. It is known to affect the properties of the asphalt in solution over a period of time, but these effects were
0.2
0
z a
m LT
0 0.4
m m
a
0.6
Figure 3. solutions
I
:Y-
2 22 1.08
0.48 0.24 3464
2.58 1.19 0.56 0.29 3480
2 33 1.16 0.48 0.25 3465
2.40 1.17 0.58 0.30 3481
9.07' . . ,
... ...
4437
Shoulder only.
W
I .5
3463
1000
0
I .o
0.20
2.22 1.06 0.42 0.18 3479
CEL,
'
Infrared spectrograms for two residua in carbon tetrachloride
not investigated. However, it was considered the most suitable solvent available for the purpose up to a wave length of 8 microns. For wave lengths greater than 8 microns, studies were made with iso-octane as a solvent a t concentrations of 10 grams per liter without success because of lack of sensitivity. For the long wave lengths, thin films of 0.1 mm. were used. However, they cannot be used a t short wave lengths because of the high absorption, although some data for thin films a t wave lengths below 8 microns are reported herein (8). For the quantitative data the experiments were run a t a concentration of 10 grams of sample per liter of carbon tetrachloride solution using 0.5-mm. cells. The absorptivities were computed by the above equation. Its validity was checked by: the use of a thin film obtained by squeezing a sample between sodium chloride plates with no spacer using calipers to measure the over-all thickness before and after placing the sample, the use of cells of varying thickness, and the use of two concentrations, with the results as given in Table 11. The material r a s a saturate fraction (S-152) from 5-158 (Table 111) obtained by a large scale component analysis by the Traxler-Schweyer method (11). The results for the solutions may be considered comparable on a relative basis, but it is doubtful if they may be compared with the thin-film data. The wave lengths shown in Table I1 are those where absorption occurs to an extent sufficient to be considered as significant. The wave lengths a t which significant absorption was indicated without sharp peaks may vary from significant wave lengths for pure comVOL. 30, NO. 2, FEBRUARY 1958
207
pounds as reported in the literature. These variations are attributed to the complex chemical composition of asphalts with overlapping and envelope effects being expected. I n Figure 3 the dotted line is displaced slightly to the left for purposes of illustration. The absorption a t 3.41 and 3.49 microns indicates paraffin side chains on cyclic nuclei based on the work of Charlet (1) and Hastings and associates (4). The latter indicate that absorption a t 6.5 to 7.0 microns is caused by both CH2 and CH3 but only the latter in the 7.1- to 7.5-micron range. Absorption for carbon tetrachloride solutions a t 6.5 microns in Figure 3 is obscured by the carbon tetrachloride absorption. Some absorption a t 5.20, 5.85, and 6.20 microns was also indicated for thin films ( 8 ) , but these are not illustrated. This region is attributed to polycyclic rings and possibly to groupings containing nitrogen and oxygen. Stewart (10) suggests a C=O grouping for the 5.85-micron region. However, the data in these regions for carbon tetrachloride solutions are not informative. At the film thickness of 0.00187 cm. shown in Table 11, the S-152 sample showed no appreciable absorbance a t
Table 111.
Sample No.
wave lengths longer than 7.5 microns, except for a weak absorbance at 13.9 microns, and only weak indications a t regions other than listed. This same sample was run a t a thickness of 0.01 cm. to determine if the absorbance at higher wave lengths would be of value. Fred and Putsher (3) used such thicknesses and absorption in the 10.3micron region as a criterion for composition and attributed absorption in this region to internal olefins, but Stewart (10) suggests the possibility of cycloparaffins. Lillard, Jones, and Anderson (6) also commented on absorption in this region and indicated absorption a t 6.25 microns is attributable to aromatics as did Stewart (10). In carbon tetrachloride solutions only a shoulder appears a t 6.25 microns, with a weak dip occurring for thin films and a stronger absorption being found for thicker films a t 5.85 and 6.20 to 6.25 microns. This is not illustrated. There is a possibility that the relative absorbance a t 6.20 microns may be a useful criterion, since refined mineral oils show relatively no absorption in this region whereas furfural extract (S-174) did (see Table 111). Furthermore, one pressure-still residue (S-175) showed definite absorption a t 6.20 microns.
Spectral Absorption of Certain Asphaltic Materials"
S-174 5-159 S-160 S-175 InterNaphthene mediate Aromatic Resid. Resid. Furfural Press Still Resid. TAR-2 TAR-3 Extract Residue T.4R-1 5-158
Material Saybolt Furol viscosity, sec./210° F. 93
Ultraviolet absorption, 0.02 g./l., 1.0 cm. A t 230 mp 30.0 At 250 mp 19.7 At 260 mp 21.2 Infrared absorption, 10 g./l. CCL, 0.0527 cm. A t 3.41 microns A t 3.49 microns At 6.85 microns At 7.28 microns Spectrogram Yo.
2.02 1.04 0.44 0.21 3482
S-142 Mineral Oil
88
92 Absorptivity
546
185
...
34.5 38.6 24.8 20.8 24.9 23.4 Absorptivity
61.8 28.0 31.9
b b
0 0 0
1.68 1.66 0.82 0.84 0.40 0.41 0.20 0.22 3483 3484 Absorptivity
1.49 0.77 0.40 0.20 3506
1.20 0.58 0.34 0.16 3507
b
1.52 1.20 0.50 0.24 5466
Thin film, 1000 g./l., 0.1 mm./film 0.004 0.048 0.028 0.014 0.055 A t 5.85 microns 0.023 0.074 0.110 0.005 0.048 0.060 A t 6.20 microns 0.055 0.020c 0.064 0.059 At 9.7 microns 0.044 0.040 0.052 0.030 0 ,044c 0.037 A t 10.3 microns 0 ,037c 0.022c 0.048 0 ,013c 0.110 0.065 0.044 0.051 A t 11.5 microns 0.049 0 OlOC 0.143 0.097 0.058 0.070 A t 12.3 microns 0.054 0.018 0.143 0.082 At 13.45 microns 0.056 0.059 0.057 0.032 0 ,044c 0 .077c 0.052 0.046 A t 13.9 microns 0,068 4203 4467 4204 Spectrogram No. 4202 4451 4201 a Com onents of several of these samples by ext.raction are shown in Figure 2 and Table Infrared analysis made in carbon tetrachloride up to 8.0 microns and in thin films over entire range (illustrated above 8.0 microns only). * Insoluble. c Shoulder only.
18
208
ANALYTICAL CHEMISTRY
A t these thicker path lengths the absorption at the lower wave lengths and a t 6.85 and 7.28 microns is too great to be useful, so this region of the spectrum must be considered separately. All spectra studied show absorption a t the 9.7-micron region which is noted also by Stewart (10)and may be oxygen, nitrogen, or sulfur linkage indications. The absorption a t 11.5 microns is attributed t o cyclic compounds, and in the higher range of 12.5 to 14.3 is considered to be caused by CH2 groups in paraffins and paraffin side chains; it is suggested here that these may be attached to cyclic compounds. Actually this region will require more study and the work of Linnig and Stewart (7) is of value for this purpose. Aromaticity might be indicated by high relative absorption a t 6.20, 11.5, and 12.3 microns and low relative absorption in the 13.9-micron region. In addition, relatively high absorption in the ultraviolet region (230-nip region) together with low absorption (relatively) in the 3.41- and 3.49-micron ranges might also be associated with aromaticity. (Most of these comnients on composition are based on studies by others on pure compounds and not complex mixtures such as asphalt and deductions refer to relative rather than absolute effects of composition.) The data in Table I1 indicate that the absorptivity tends to increase with dilution a t most wave lengths. This tendency is definite in going from the film to solutions. There are additional indications that the value of a also increases as the path length decreases for the solutions, but this trend apparently is not as significant as the effect of dilution. Standardized procedures were adopted using concentrations of 10 grams per liter of solution with a 0.5-mm. cell for carbon tetrachloride solutions up to S microns and the use of thin films a t 0.1 mm. for measurements above 8 microns as illustrated in Figure 4. After adoption of the standard procedures, a number of asphaltic residues from Texas crude oils, a furfural extract, a pressure-still residue, and certain fractions from asphalts were run (Tables I11 and IV). In Table I11 the ultraviolet absorption is given for reference on a variety of asphaltic materials with increasing values of n as the aromaticity increases except for the intermediate residue (S-159). Infrared data indicate a decrease in absorptivity coefficient as the aromaticity increases at those wave lengths generally attributed to CH2 and CH, groups. The term aromaticity is used in a relative sense to indicate those materials considered to be relatively aromatic such as pressure-still residues, furfural extract, and other solventfractionated residues such as the cyclics
Table IV.
Infrared Absorption on Certain Asphalts and Their Components
Naphthenic Residue, TAR-1 Asphalt Saturates Cyclics Sample hTo.SAbsorptivity A t 3.41 microns A t 3.49 microns A t 6.85 microns At 7.28 microns Spectrum KO. Absorptivity A t 5.85 microns A t 6.20 microns At 9.7 microns At 10.3 microns A t 11.5 microns At 12.3 microns At 13.45 microns At 13.9 microns Spectrum no. Shoulder only.
158
152
2.02 1.04 0.44 0.21 3482
2.01 1.06 0.43 0.20 3463
0.023 0.055 0.044 0.0375 0.049 0.054 0.056 0.068 4202
0.021 0.036 0.036
Intermediate Residue, TAR-2 Asphalt Saturates Cyclics
153 159 154 155 160 10-g. sample per liter of CCL solution, 0.0527-cm. cell 1.38 1.68 1.88 1.45 1.6G 0.70 0.82 0.99 0.75 0.84 0.38 0.40 0.43 0.39 0.41 0.21 0.20 0.20 0.19 0.22 3503 3483 3502 3508 3484 0,084 0.105 0.078 0.053" 0.092 0.134
0.028'
0.034 0.036 0.042" 0.063 4200
0.113
0.064O 4456
l
-
a
-_
-A
1.5
NAPHTHENIC RESID
TAR I
A R O M A T I C RESID.
TAR 3
I
I
12
W A V E LENGTH, Figure 4.
0. 7 0. 1
0.09 0.070 0.096 0.150 0.116 0.058 4455
Johnson, F. B., ANAL.CHEX.26, 861 (1954). ( 2 ) Eilers, h-.,J . Phys. Chem. 53, 1195 (1949). (3) Fred, &I.,Putsher, R., ASAL. CIIEM. 21, 900 (1949). (1)Hastings, S. H., A'atson, A. T., ii-illiams, R. B., Anderson, J. A., Jr., Zbid., 24, 612 (1952). 151 Hersh. R. E.. Fenske. M. R.. Matson. H. J., Koch, E. F:, Booser, E. R.; Braun, IV. G., Ibid., 20,434 (1948). (6) Lillard, J. G., Jones, W. C., Jr., Anderson, J. A., Jr., I n d . Eng. Chem. 44, 2623 (1952). ( 7 ) Linnig, F. J., Stewart, J. E., J .
1
14
MICRONS
ditional work on separations by chromatography or other methods may prove fruitful when the range of compositions is reduced by closer fractionation. These preliminary experimental results may be of value to the asphalt technologist contemplating work in this field.
Table V. Relative Absorbance of Certain Asphaltic Materials at a Given Wave Length
Type of Material Naphthenic .4romatic V1tra.violet absorption at 230, 250,260 mh Low High Infrared absorption at 3.41, 3.49 mierons High 6.20, 11.5, 12.3, 13.45 microns Low 13.9 micronso High Correlation not rigorous. 0
0.021 0 038 0.035 0.034 0.030 0.035 0.034 0.043 4454
(1) Charlet, E. hi., Lanneau, K. P.,
Infrared spectrograms for two residua in thin films
in a component analysis (11). Naphthenicity is considered here as a measure of the propensity of the residues to forin the more gel-like products usually associated with the saturated or paraffinic type oils. Table V based on the data in Tables I11 and IV is a summary. The result's regarding relative absorbance are for t,hose wave lengths considered significant at this time. The results do not appear to show that asphalts or tlicir components in gross fractions can be characterized specifically by their spectral absorption. This is in accord with a concept advanced that compensating absorption effects in such complex mixtures as asphalt' may preclude the use of such techniques for other than gross absorption bands. However, all processed asphalts show lower absorption than their source residua. This is also true of weathered asphalts compared with the original roofing aspha,lt, but the differences for materials from different sources do not appear significant. Ad-
1.32 0.72 0.40 0.21 3510
LITERATURE CITED
I
IO
1.81
0.95 0.44 0.23 3509
LJ
I
T H I N FILMS
I 8
I
157
The cooperation of A. H. Gropp and R. D. Walker is acknowledged, and the author is also grateful to G. R. Kulkarni, H. H. Brenner, and L. Monley for their assistance in the experimental work, much of which has not been reported here.
0.4
---
0,055 0.060 0.052 0.048 0.051 0.070 0.057 0.046 4201
156
ACKNOWLEDGMENT
z a m 0.6
.
Thin films (0.01-em. thickness) 0.014 0.016 0.038 0.048 0.030 0.059 0.040 0.033 0.061 0.022" 0.025" 0.034O 0.044 0.030 0.057 0.058 0.037 0.085 0.059 0.043 0.086 0.052 0.060 0.048" 4451 4453 4452
o.21 i I I m m
Aromatic Residue, TAR-3 Asphalt Saturates Cyclics
Reseurch h a t l .
.
Low
High
Low
Bur.
Standards
59, 27 (1957). (8) Schweyer, H. E., "Asphalt Composition and Properties," Fla. Eng. and Expt. Station, Bull. 89 (1957). (9) Schweyer, H. E., Chelton, H., Brenner, H. H., Proc. Assoc. Asphalt Paving Technologists 24, 1 (1955). (10) Stewart, J. E., J . Research Il'atl. Bur. Standards 58, 265 (1957). (11) Traxler, R. S., Schweyer, H. E., Oil Gas J . 52, S o . 17, p. 133; 19, p. 158; 21, p. 143; 23, p. 167; 24, p. 157; 25, p. 151; 26, p. 133 (1953). 112) Williford. C. L.. Texas Em. Exnt. Station, Texas A&M -Coll&e, Bull. 73 (1943). 1131 Woodward. R. B.. J. Am. Chem. ' SOC.64, '72 (194%). I
RECEIVEDfor review February 13, 1956. ACCEPTED September 18, 1957. VOL. 30,
NO. 2,
FEBRUARY 1958
209
