INDUSTRIAL AND ENGINEERING CHEMISTRY
76
by rise in temperature. The modification of the bloom of a light motor oil by the addition of olive oil in an amount equal to four times its volume was comparatively slight and quite disproportionate to the amount of mineral oil in the blend. Figures 3 and 4 show the blooms of the two blends in comparison with those of their constituents. Results of Bloom Determinations
A number of 4-ounce sample bottles of oil were inspected for their bloom and classified as they appeared to the eye. The c l a s s i f i c a t i o n s w e r e g r e e n , bluegreen, and blue oils. The fourth class included oils which had been sun debloomed and those commonly considered bloomless. The first three groups are shown in Figures 5, 6, and 7. The few cases i n w h i c h t h e graphs indicate a COLOR somewhat d i f f e r e n t bloom from t h a t Figure 7-Blue Oils which was apparent to the eye is due to the change from an oil-glass to an oil-air interface. I n Figure 8 it is shown that the deblooming of an oil greatly increases its ability to absorb blue light. These oils, in common with fatty oils, give a reflected color similar to their transmitted color. The reflected colors of asphalt and medicinal white oil (dark gray with a blue-green tint) are quite similar. It is
Vol. 19, No. 1
Y
probable that a container more nearly black than the one available a t present would show the white oil to be as dark as the asphalt when viewed by reflected light. I n general, the light distillates are darker by reflected light than are the cylinder oils. As is the case with all colored objects, the reflected color of an oil is indicated by the relative absorption of the different colors of white light. The shape of the curves here presented indicates the bloom of the oil by showing the relative amounts of the five principal colors. The steepness of the curve on each side of the color least absorbed shows the brightness of t h e c o l o r , or i n o t h e r w o r d s , shows how nearly monochrom a t i c t h e color is. For example, a curve with a deep trough in a 5 t h e green shows a 5 b r i g h t green, while the curve for another ,2 oil, which is predominantly green, may be 10 more nearly horizon'' talandif sorepresents a dull g r a y - g r e e n '8 BL 6 I O R COLOR bloom. Furthermore, Figure 8-Debloomed and Bloomless Oils two bloom curves may have the same shape but one may lie higher than the other. If such be the case, the two oils reflect the same color, but the one corresponding to the higher curve is darker because it reflects less light. I n addition to the values of reflection a t various wave lengths, the value of the total reflections may be obtained with the instrument. 21
Diethyl Sulfate in the Examination of Hydrocarbon Oils' By J. N. Taylor BIOCHBMIC DIVISION, BUREAUOF ANIUALINDUSTRY,
ARAFFINS and naphthenes are usually differentiated from aromatic and unsaturated hydrocarbons by sulfonation. The procedure described by Chapin,* in which dimethyl sulfate is employed, is often used in a preliminary examination of such mixtures. As it is poisonous, dimethyl sulfate may be safely used only if carefully handled. Diethyl sulfate, its homolog, is reported to produce no toxic effects, which would appear t o give it an advantage. There is no difference in cost. I n order to determine its efficiency when applied to mixtures of hydrocarbon oils, tests were made and the results were compared with those obtained by the use of dimethyl sulfate and of sulfuric acid.
P
Experimental
Mixtures, in varying proportions by volume, of petroleum oil and benzene were prepared. The petroleum oil was a water-white, high-boiling, refined petroleum distillate, with an initial boiling point of 265" C. and a specific gravity of 0.858 at 25' C. It was immiscible with both dimethyl and diethyl sulfate and was unacted upon by concentrated 1
2
Received September 22, 1926. U.S. Dcpt. A g r . , Bur. Animal Ind., Circ. 167 (1911).
WASHIIGTON,
D.
c.
sulfuric acid. The benzene employed is commonly known as "commercially pure benzol." Its boiling range was within 2" C. and included the true boiling point of benzene. It had a specific gravity of 0.870 a t 25" C., was completely miscible in all proportions with both of the alkyl sulfates, and left no residue upon sulfonation. The alkyl sulfates used were refined, water-white grades, with but a trace of acidity. All of the materials were purchased direct from manufacturers. Original Method
Five cubic centimeters of the mixtures and 8 cc. of the alkyl sulfates were placed in glass-stoppered Egertz tubes. The tubes were vigorously shaken and placed in a constanttemperature water bath and the volumes of the resulting upper layers were measured a t 25" C. Sulfonation was accomplished by the method described in Forest Service, Circular 112. The operation was carried out in Babcock cream bottles. Upon completion the volumes of the oil residues were measured at 25" C., with the results shown in Table I. I n its upper range, the partition curve for diethyl sulfate (Figure 1) is in close agreement with the sulfonation curve.
IlYDUSTRIAL A N D ENGINEERING CHEMISTRY
January, 1927
I n the lower range there is a decided deviation. .As a change in the relative masses of the components of a ternary mixture affects the equilibrium of the system, it was thought that the diethyl sulfate curve could be flattened by increasing the quantity of petroleum. The procedure was therefore slightly modified. Table I-Alkyl
OIL
PRESENT
DIMETHYL
SULFONATIOX
Per cent
when the percentage of residue in the oil is calculated to the percentage amount in the dip from which the hydrocarbon oils may have been extracted. Table 111-Saturated Hydrocarbon Residues (Modified Method) from Oils Extracted from ExDerimeutal Dips ~
FWSIDUE Per cent
SULFATE
RESIDUE Per cent
DIETHYL SULFATE:
zRRoRRESIDUE Per cent
Per cent
Per cent
...
Modified Method
I n the Egertz tube was first placed 5 cc. of the petroleum oil previously described, which, of course, contained no aromatic or unsaturated hydrocarbons. Then 5 cc. of the mixture under examination were added, followed by 16 cc. of diethyl sulfate. After agitation the t u b e s were placed in the bath and the volumes of the upper layers noted. All measurements were made at 25" C. The percentage residue was calPercentage determination of petroleum oil i n1 culated by subtractmixtures Figure 1-Partition Curves of Dimethyl ing 5 front the read( , , . . . . o j a n d Diethyl (-. - . - x ) Sul- ing and multiplying f a t e s as Compared with Sulfonation t h e r e s u l t b y 20. (-.j T a b l e I1 gives the results obtained by this method. Figure 2 shows them graphically. The diethyl sulfate curve does not follow the sulfonation curve as closely as it was hoped that it would. The error due to mutual solubility is augmented by those introduced as a result of the modification in technic. The additional reading made necessary when the 5-cc. portion of petroleum oil is placed in the tube a t the outset constitutes an opportunity for error, and if all three readings are made by interpolation the likelihood of additional errors presents itself, especially when the quantity of residue is small. Again, upon calculation of percentage results, the cumulative error is multiplied by 20. However, the final error is reduced Table 11-Diethyl PETROLEUM OIL PRESEBT Per cent 10.0 20.0 30.0 40.0 50.0 20.0 (0.0 80.0 90.0 100.0
Sulfate Residues (Modified Method) Compared with Sulfonation Residues SULFONATION DIETHYL SCLFATE RESIDUE Per cent 10.0 20.0 30.0 40.0 50.0 60.0 70.0 79 6 90 0 100 0
___- --
RESIDUE Per cent 11.2 22.0 33.6 44.2 54.4 63.4 73.4 S3.0 90.6 100.0
ERROR
Per cent 12.0 10.0 11.7 10.5 8.8 5.7 4.9 3.8 0.7 0.0
~~
~
SULFONATION DIETHYL SULFATE RESIDUE RESIDCE FROM
EXTRACTED ESTRACTED ERROR
FROM
OILS Per cent
OILS Per cent
Per cent
0.0 5.4
8.0 31.0 44.0
High teinperature 8.0 Low temperature 29.4 Containing petroleum oil 4 4 . 4
0.0
-60.0 -23.3 -9.5 -3.4 0.7 0.3 1.6 0.6 0.0
~~~~~~
TYPEOF DIP
Sulfate Residues f r o m Benzene-Petroleum Mixtures Compared with Sulfonation Residues
PETROLEUM
77
-- 0 . 9
Application of Method t o Commercial Products
Hydrocarbons having properties similar to those of the saturated hydrocarbons found in certain petroleums also occur in the creosote derived from tars produced during the carbonization of coal3 a t low temperatures (500' to 600" C.). A dip was prepared containing a creosote of this character obtained through the courtesy of a corporation engaged in the complete gasification of coal and in the recovery of the by-product low-temperature tar. The oily components of this dip were extracted and tested with diethyl sulfate by the modified method. Table I11 shows the results. comDared with those of similar tests on oils extracted from a high,w temperature dip y and from a dip cont a i n i n g petroleum .$ oils. :. The neutral oils B obtained from a @ n u m b e r of animal d i p s a n d s p r a y s 2~ which had been sub- 3 do mitted t o the labora$ L( tory for a n a l y s i s 8 were also examined 2 Io b y t h e modified P 10 30 LO M 96 m e t h o d . The re- Percentage determination of petroleum oil in mixtures s u l t s a r e given in Figure 2-Diethyl Sulfate Curve, Modified Method (-, - x) Compared with SulTable IV.
-
$
70
Io
10
fonation
Table IV-Saturated
40
50
70
101
(-.I
Hydrocarbon Residues from Oils Extracted f r o m Commercial Samples
Diethvl sulfate test (modified method) compared with sulfonation BROM
DOMESTIC NUMBER 16,189 16,694 21,273 18,104 21,031 20,306 21,289 21,232 19,212 -21~494 , ~ .
SULFONATION D I E T H Y L SULFATE RESIDUE Per cent
~~~~~
68.0 48.3 72.0 14.0 74.0 64.0 65.4 8.0 66.0 77.0
67.0 45.0 72.0 14.0 75.0 65.0 67.0 8.2 68.0 80.0
ERROR
Per cent
-1.5 -0.6 0.0 0.0 1.3
1.5 2.4 2.5 3.0 3.9
Conclusions
Diethyl sulfate is useful in differentiating paraffins and naphthenes from aromatic and unsaturated hydrocarbons. The method of employing it is not as simple as the procedure which calls for dimethyl sulfate. Diethyl sulfate, however, is thought to be safer than dimethyl sulfate. The procedure employing diethyl sulfate affords results comparable with those obtained through sulfonation. The method is applicable to commercial hydrocarbon oil mixtures and to articles from which such oils can be extracted. 8
hlorgan and Soule, THISJ O U R N A L , 15, 367 (1923).
