Februar). 1935
1NDUSTRIAL AND ENGINEERING CHEMISTRY
equal to the algebraic sum of f T d s and the heat lost by the system, and is in this case equal to 1.88 B. t. u. per pound.
165
tute. Acknowledgment is made to the institute for its assistance. Thanks are due to the Standard Oil Company of California for their cooperation in furnishing the sample of crude oil used and for all the data included in Table I, except the molecular
ACKNOWLEDGMENT This investigation was carried out as a part of the work of Research Project 37 of the American Petroleum Insti-
RECEIVED September 13,
1934.
Pressure -Volume- Temperature Relations for Fractions of an Oil Study of Fractionation:
Physical Properties of Fractions a t Normal and High Pressures
R. B. Dow Harvard 1-niversity, Cambridge, Mass.
The results of fractionation of a light mineral oil from a Midcontinent source are presented. The densities, viscosities, and indices of refraction have been studied for the unfractionated oil, nine cuts, and the bottoms at atmospheric pressure and, in most cases, at two temperatures. -/lbreoz'er, the pressure-volume-temperature relations have been investigated u p to pressures approaching apparent solidification for the eleven samples. Curves for the change of volume with pressure and for the variation of the thermal expansion with pressure are included f o r several samples.
AND
RI. R. FEKSKE The Pennsylvania State College, State College, Pa.
T
HIS investigation is a result of the interest of the Special Research Committee on Lubrication, American Society of Mechanical Engineers, in the physical properties of lubricants at high hydrostatic pressures. The thermodynamic properties of several lubricating oils were examined ( 3 ) at high pressures, and the viscosities of similar oils a t high pressures were studied by other investigators (6-8). Consequently a fair knowledge of these properties exists for mineral and fixed oils under the different conditions of p r e s s u r e and tern p e r a t u r e. In order to study t h e dependence of some of the thermo-
o 883
FIGURE1. RELATIVEVOLUMES AS FUNCTION OF PRESSURE AT 40" C.
orqm
dynamic properties on composition for a hydrocarbon oil, a light mineral oil' from a hfidcontinent source was fractionated, and the fractions or cuts were examined a t normal and high pressures. There appears to be no mention of a similar investigation a t high pressures in the literature. VACUUM FRACTIONATION The vacuum fractionating column of special design is 15 cm. (6 inches) in diameter and 3 meters (10 feet) in height. A noteworthV feature of operation is the low-pressure drop through the column for efficient fractionation, the pressure at the top being 0.2 to 0.3 mm. of mercury and the drop through the column amounting to 3 or 4 mm. These pressures are read on hlcCleod gages attached to the top and bottom of the column. The still, on the other hand, is designed to obtain good circulation in the oil by using t h e r m o s i p h o n effects. It is capable of holding a charge of about 19 liters (5 gallons). The assembly is electrically heated. I
4
8
'2
16
20
Number o f Cuf
14
I 9 8 3 2
BOfhVnS
FIGURE. 2. RELATIVE V O L U I ~ OF S VARIOUSCUTS
1 Thia oil wae obtained from the Atlantic Refining Company, Philadelphia, a n d is known t o t h e t r a d e as Renown Engine oil.
I NDUSTR IAL AND EN GIN EER I N G CH EM ISTR Y
166
Vol. 21, No. 2
TABLE I. VACUUM FRACTIONATION OF RENOWN ENGINEOIL CUT No.
RATEOF TAKE-OFF WEIQHT Grams/min.
Charge 1 2 3 4 5
..
TOTALYo OVER
yo OF CHARQE
Grams
c.
c.
201-264
0.29 0.29 0.23 0.23 0.22
3.2 3.2 3.2 3.2 3.2
143 145 147 147 148
218 218 218 219 219
4.0 3.0 3.0 3.0 3.0
...
...
20bl224
...
...
21+:4 ... ...
30.41 33.14 35.91 38.60 41.14
0.21 0.22 0.23 0.25 0.22
3.2 3.1 3.1 3.0 2.9
148
3.0 3.0 3.0 3.5 4.0
22Ci33
226:7
150 151 152 153
220 221 222 223 223
2.71 2.70 2.73 2.77 2.69
43.85 46.55 49.28 52.05 54.74
0.19 0.19
2.9 2.0 3.2 3.2 3.1
154 156 157 158 159
223 223 224 226 228
6.0 7.0
228-242
439 438 429 443 426
2.74 2.74 2.69 2.76 2.67
57.48 60.22 62.91 65.67 68.34
0.18 0.19 0.20 0.20
3.0 3.0 2.9 2.8 2.8
162 163 164 166 168
229 231 232 234 238
10.0
...
15.9 14.7 15.5 13.5 30.3
429 441 449 472 548
2.69 2.76 2.81 2.96 3.41
71.03 73.79 76.60 79.56 82.97
0.19 0.19 0.18 0.17 0.29
2.8 2.8 2.8 2.7 2.7
170 172 174 176 181
242 249 257 264 268
10.5 12.0 13.5 15.0 12.5
...
... ...
2561269
20214
24.0 9.2 6.8
407 423 432 130 965
2.55 2.65 2.70
85.52 88.17 90.87 91.68
0.41 0.17
1.7
184 191
272
10.0
0.50
266:iSO
2+3:2
..
...
... ... ...
..
o:i7 0.28 0.29 0.29
8
9 10
23.9 24.2 26.9 24.6 27.5
431 436 430 418 441
2.70 2.72 2.69 2.62 2.76
16.87 19.59 22.28 24.90 27.66
11 12 13 14 15
23.2 20.8 26.0 22.7 21.3
440 437 443 431 406
2.75 2.73 2.77 2.69 2.54
16 19 20
18.9 17.2 16.9 17.0 17.9
434 431 438 443 430
21 22 23 24 25
20.0 21.9 20.4 24.6 21.2
26
31 32 33 34 Bottom
c.
ESQLERRANQE 50% B. P. REFLUX (040% AT 10 AT 10 MM. RATIO M.M.Hg) Hg
..
2.74 5.99 8.76 11.47 14.17
27 28 29 30
still
...
2:+4 3.25 2.77 2.70 2.70
18 l7
c.
Oil in
...
..
4:s 19.3 19.7 22.7
7
Vapor a t top
..
...
15,980 441 503 443 433 432
6
TEMP~RATURE
PRESSURE Top Bottom M m . of Hg
.. ..
0.81
0.18 0.18 0.18
.. ..
...
6.03
0.18
...
..
The data obtained during the fractionation of the mineral oil are recorded in Table I. The reflux ratio is the ratio of liquid returned to the column as reflux to that taken off as product. These data are probably in error by 20 per cent. The Engler range is the temperature variation required for distillation of 90 per cent of the product a t a certain pressure. It was obtained as a result of a simple distillation of 50 cc. of each fraction a t a pressure of 10 mm. of mercury.
PWSICAL PROPERTIES AT ATMOSPHERIC PRESSURE The densities a t 40" and 75" C., the kinematic viscosities a t 37.8" C. (100" F.) and 98.9" C. (210" F.), and the refractive indices a t 20" C. were studied for the unfractionat,ed oil, nine fractions, and the bottoms. Table I1 is a summary of these measurements. The experimental procedures were according to standard methods. Thus, the densities were determined by the use of specific gravity bottles of 25 cc. capacity that were adjusted in baths of water a t constant temperatures, the viscosities were measured, as previously (Q), with calibrated capillary pipets, and the indices of refraction were obtained with an Abbe refractometer. The errors
...
.. .. ..
... ... ,..
I
.
.
...
233.9
237li50
24214
12.0 11.5 10.5
...
...
10.0
242li56
249:5
8.0
11.0 11.5
.. ..
...
237.0
..
...
...
... ...
...
... ...
... ...
... ... ...
... ... I
.
.
in these measurements may be considered as negligible for present purposes. PRESSURE-VOLUME-TEMPERATURE RELATIONS The thermodynamic properties of the samples at high pressures were studied with the high-pressure apparatus of Bridgman (1). Volumes a t pressures up to those approaching apparent freezing a t 40" and 75' C. were successfully measured by a "sylphon" method that has been extensively used by Bridgman ( 2 ) : Approximately 5 cc. of a sample are enclosed in a small sylphon (flexible metal bellows) to which is attached a suitable slide-wire that is part of an external potentiometer circuit. The assembly of sylphon and holder fits into a pressure chamber to which hydrostatic pressure can be applied. Chan es of volume are obtained from changes of resistance of the sylp%onslide-wire by applying simple conversion and correction formulas to a large-scale plot of slide-wire resistance against pressure. A manganin coil, the resistance of which varies linearly with pressure, serves as an accurate pressure gage, and the temperature of the sylphon is that of a thermostatically controlled bath of water that surrounds the pressure chamber. The total error involved in these measurements is less than 0.5 per cent at any pressure, and it decreases as the pressure increases. T A B L11 ~1. RELA
PRESSURE
ORIQINAL OIL , 750 c. 40' C.
40' C.
CUT 1
CUT 4
CUT 8
40' C.
1.0260
1.0000 0.9968 0.9940 0.Q860 0.9737
40' C.
1.0260
.... ....
1.0000 0.9965 0.9932 0.9844 0.9717
0.9633 0.9543 0.9462 0.9393
0.9807 0.9706 .... 0.9535
0.9616 0.9527 0.9450 0.9373 0.9305
0.9790 0.9689
0.9263
0.9388 0.9267 0.9164 0.9073 0.8989
(0.924)a
0.9372 0.9258 0.9150 0.9049
40' C.
1.0249
1,0000 0.9970 0.9941 0.9956 0.9736
1,0079 0.9931
CUT 12 750 c.
750 c.
750 c.
750 c.
Kg./sq. cm.
1 50 100 250 500
1,0000 0.9967 0.9936 0.9847 0.9723
.... ....
1.0037 0.9907
1.0000 0.9959 0.9918 0.9825 0.9691
750 1000 1250 1500 1750
0.9615 0.9522 0.9437 0.9359
0.9791 0.9687 0.9589 0.9504
0.9569 0.9461 0.9365 0.9275 0.9191
....
1.0177
....
2000 0.9219 0.9352 (0.917)n 2500 0.9226 3000 0.9115 3500 0.9018 4000 0.8931 0 Values in parenthesis are extrapolated.
.... ....
1.0070 0.9916 0.9769 0.9644
....
0.9439
....
0.9269 0.9119 0,8983 0.8860
....
....
....
....
....
1.0035 0.9905
....
0.9509
....
1.0261
.... ....
1.0050 0.9935
0.9636 0.9548 0.9470 0.9398
0.9818 0 9718
....
0.9545
(0.926)'
0.9405 0.9283 0.9174' (0.906)
....
....
INDUSTRIAL AND ENGINEERING
February, 1935
TABLE11. PHYSICAL CONSTANTS OF SAMPLES KINEMATIC
REFRACTIVE
INDEX
DEN0ITY 40'C. 75'C. Gradcc. 0.884 0.869
37.8' C. Stoke 0.3141
98.9' C. Stoke 0.0470
1 2 3
0.883
0.861
0.1068
0.0251
1.5000 1.5008 1.5008
4 5 6 7
0.885
0.862
0.1531
0.0308
1.5005 1.5000 1.5000 1.4995
8 9 10
0.884
0.861
0.1905
0.0351
1.4990 1.4990 1.4984 1.4985
12 13 14 15
0.883
0.860
0.2334
0.0396
1.4980 1.4980 1.4980 1.4980
16 17 18 19
0.883
0.860
0,2818
0.0443
1.4978 1.4975 1.4974 1.4975
20 21 22 23
0.882
0.860
0.3342
0.0488
1.4972 1.4977 1.4974 1.4978
24 25 26 27
0.884
0.860
0.4068
0.0549
1.4980 1.4980 1.4984 1.4990
28 29 30 31
0.886
0.864
0,5623
0.0650
1.4992 1.4994 1.5010 1.5010
32 33
0,890
0.869
0.8057
0.0793
1.5010 1.5010
0.895
0.873
1,262
0.1045
1.5350
SAMPLE
Original oil cut
VISCO0ITY
20' C . 1.4992
11
Bottoms
The pressure-volume-temperature relations for the twelve samples of oil and cuts are complete in Table 111:. The volumes are expressed relative to the volume a t atmospheric pressure and 40" C. The table was constructed, however, by first measuring the volume decrements by division to values corresponding to the weight of liquid which by calculation would occupy one cc. a t 40" C. a t atmospheric pressure, and then finding the actual volumes by subtracting these volume decrements from 1.0000. The curves of volume against pressure a t 40" C. are drawn in Figure l'for several of the samples. As would be expected the relative volume cut 1 varies most with pressure and the relative volume of the bottoms varies least. Excluding these two samples, there are no significant differences for the remaining ones, the pressure-volume curves being similar, Recalling that the compressibility is the slope a t a certain point on an isotherm, Figure 1 shows that the compressibilities of the unfractionated oil and cut 16 are nearly equal, and that similar pressure-volume curves are obtained for the other TIVE
CHEMISTRY
167
cuts. However, the relative volumes of the cuts a t a given pressure and temperature vary significantly as Figure 2 shows. Here isobars are plotted for 40" and 75" C. Certain interesting points are indicated by Figure 2. First, cuts 1 and 20 differ most from the other cuts, particularly a t higher pressures. With the exception of these two, all the other cuts are less compressible than the original oil. The reasons for the behavior of these two cuts are not obvious. The molecular weights, when calculated by a method previously described (4), show that cut 1 has the lowest molecular weight and that the molecular weights increase steadily with the number of cuts. It is interesting to note, then, that cut 1 has the lowest molecular weight, while cut 20 has the lowest refractive index and also has very nearly the viscosity of the original oil. T h e thermal expansion, o n t h e other hand, varies more with pressure. The average t h e r mal expansion between 40" and 75" C. a t atmospheric a n d higher pressures has been computed for the same samples (Figure 1) and the results are shown graphically in Figure 3. It is evident on examination of the c u r v e s that the p r e s s u r e variation of the exPressure k g / q . cm. pansion is complex FIGURE 3. AVERAGE THERMAL Exfor the cuts. But PANSION (40" TO 75' C.) AGAINST t h e v a r i a t i o n is PRESSURE somewhat different for ordinary oils. For unfractionated oils, the pressure curve of the expansion through the same temperature interval varies in such a way that 6%/6p6t is a maximum a t approximately 300 kg. per sq. cm. (3). It is noteworthy that neither the cuts nor the bottoms exhibit this effect.
ACKNOWLEDGMENT The help of Forrest P. Dexter, Jr., in making a preliminary determination of the Saybolt viscosities is appreciated. Acknowledgment is also due the Special Research Committee on Lubrication, American Society of Mechanical Engineers,
VOLUMES
40' C. 1.0000 0.9967 0.9936 0.9849 0.9730 0.9626 0.9538 0.9460 0.9388 0.9258
CUT 16
750
c.
1.0261
.... ....
1.0050 0.9921 0.9811 0.9710
,...
0.9548
....
0.9412 0.9288 0.9172 0.9083 0.9002
CUT24
CUT 20 40' C. 75' C.
40'C.
1.0000 0.9967 0.9936 0.9851 0.9728
1.0000 0.9969 0.9941 0.9553 0.9736
1.0249
.... ....
1.0060 0.9926
0.9624 0.9536 0.9460 0.9387
0.9524
,...
.,..
(0.925)O
0.9807 0.9699
....
0.9371 0.9231 o.9100a (0.898)
0.9634
0.9543 0.9470 0.9402
....
0.9273
CUT 28 75O C.
75O C.
40'C.
1.0272
1.0000 0.9972 0,9944 0.9864 0.9747
....
....
0.9858 0.9736
1.0248
....
1.'0060 0.9931
0.9634 0.9548 0.9470 0.9531
0.9647 0.9560 0.9476 0.9407 0.9346
0.9818 0.9714
0,9390 0.9272 0.9171 0.9077 0.8991
(0.927)'
0.9405 0.9287 0.9183 0.9092
....
.... 0.9548
....
40'C.
COT 32 75O C.
1.0000 0.9969 0.9940 0.9857 0.9740
1.0236
.... .... 1.0052
0.9925
0.9643 0.9557 0.9478 0.9409
0.9810 0.9708
(0.927)'"
0.9409 0.9292 0.9185 0.9087
....
.... 0.9546
....
BOTTOM0 4OOC. 75O C. 1.0000 0.9968 0,9943 0,9866 0.9757 0.9663 0.9577 0.9498 0.9430 0.9366 (0.929)"
1.0248
....
....
1.0069 0.9927 0,9818 0,9727
.... ....
0,9571 0.9437 0.9316 0.9214 0.9115
I N D U S T R I A L A N D E IC’ G I N E E R I N G C H E hl: I S T R Y
168
for financing part of this investigation. Finally, an expression of thanks is due P.W.Bridgman and T. Lyman of HarVard for use Of the Of the Research Laboratory Of Physics. LITERATURE CITED &idgman, p. JV,, physics High Pressure,,, Chapt,, ?, 3, New York, Macmillan Co., 1931. ( 2 ) Bridgman, P. W., Proc. Am. A c e d . A r t s Sci., 66, 185 (1931). (3) Dow, R . B., J . W a s h . A c a d . Sci., 24, 516 (1934).
Vol. 27, No. 2
(4) Fenske, &I. R., McCluer, W.B., and Cannon, M. R., IWD.ESG. CHEX, 26, 976 (1934). ( 5 ) Hersey, hl, D,, J . wash. Acad, sei,, 6 , 525 (1916.. (6) Hersey, Lf. D,, and Shore, H., -JIech, E n g , , 50,221 (1928). (7) Hsde, J. H., Proc. Roy. S o t . (London), -197,240 (1920). (8) Kleinschmidt, R. V., Trans. Am. Sot. Mech. E I L ~ P Applied S., Mechanics, 50, 4 (1928). (9) Willihnganz, E. A . , McCluer, JV. H., Fenske, XI. R., and McGrew, R. V., ISD.ESG.C H m r . , A h a l .Ed., 6, 231 (1934). RECEIVEDSovember 3, 1934.
Nature and Constitution of Shellac X.
Compatibility of French Varnish with Nitrocellulose Solutions’
WILLIAMHOWLETTGARDNER AND BERNARD GROSS,The Polytechnic Institute of Brooklyn, Brooklyn, N. Y.
N
ITROCELLULOSE SOThe compatibility of French varnish with ties, will o f t e n b r i n g t o light nitrocellulose solutions and diluents increases many f a c t s i n relation to the lutions have been w i d e l y used as dopes, manufacture which would otherwith the age of the shellac mrnish. Since these primers, and impregnating mawise remain obscure, changes are manifest long before any chemical terials; but when the cellulose COMPATIBILITY ester is the only solid constituent, change can be detected, they appear to be colloidal the resulting compositions lack Compatibility may be defined in character. The rate of change is determined by the alcohol in which the shellac has heen cut. as complete m i s c i b i l i t y i n a p e r m a n e n t flexibility, gloss, hardness, durability, and resistpolynary system (4) or part of A simple method for judging compatibility of ance to s u n l i g h t . Since all such a system. T h e t e r n a r y these properties can be supplied French rarnishes is Presented, as well as data for s y s t e m water-ethyl alcoholby the addition of shellac, the compatibility with nitrocellulose in a number of ether is a simple example which fairly volatile solvent mixtures such as might be shows both compatibility and use of special French varnishes used for dope and impregnating solutions. incompatibility. W a t e r a n d in combination with nitrocellulose offers many c o m m e r c i a l ether are completely miscible possibilities. For instance, comwith alcohol, b i t i a t e r a n d positions have been prepared which not only impart tautness ether exhibit only a limited solubility in each other. Hence to a fabric such as is required by airplane dopes but a t the there are only definite ranges of composition where all three same time show sufficient adhesion to be used as a primer for liquids are mutually miscible. If a miscible solution containmetal ( 2 ) . The degree of tautness obtained is controlled in ing several liquids is allowed t o evaporate, it may become the formulation of the composition. Pigments, dyes, and fire- immiscible as a result of the more rapid evaporation of one or proofing agents can also be incorporated where desired. more of the constituents. Many manufacturers, however, have encountered considerIn a similar manner a liquid may be an excellent solvent able difficulty in attempting t o incorporate French varnish in for both a resin and for nitrocellulose, but it does not necessuch types of compositions, especially when they cut their sarily follow that both can be held in the same solution. own shellac in preference to buying special varnish for the Hofmann has shown (4)that in many cases of “resin blush” purpose. In several cases these difficulties arise from the the heterogeneity is a result of immiscibility of solutions of use of freshly cut resin, and it appears that the age of the two substances in the same solvent. The absorption of varnish may be an important factor in determining its com- moisture from the air by solvents may cause the same type of patibility with nitrocellulose solutions. phenomenon to take place. Although the advantages of making a systematic survey of When heterogeneity occurs in the solution, it is usually compatibility were pointed out by Hofmann and Reid (5) referred to as “incompatibility;” if it takes place in the quasi several years ago, their method has not yet received the usage dry or dry film, it is called “blushing.” Since it is difficult if it deserves. Many chemists feel that the time spent in ob- not impossible to determine a t what point a film can no longer taining such complete data is unnecessary, whereas experience be considered a solution, the authors prefer to classify as comin a number of instances has illustrated the contrary to be patible mixtures only those compositions which show comtrue, There is too great a tendency for investigators in this plete homogeneity throughout the entire range of evaporafield to start with some established formula as a base and to tion, and not to make any marked distinction between inproceed by substituting one ingredient for another without compatibility and blushing except where it may be of interest giving consideration t o the exact effect of the substitution ex- to physical chemists. cept in a very general manner. PENTAMEROUS SYSTEMS Frequently time and money would be saved if a systematic survey were made. The information obtained, especially Preliminary experiments showed that, in five-component when used in conjunction with similar studies of other propersystems containing shellac, nitrocellulose, two solvents, and a 1 Other articles in this series appeared in IND.ENG.CHEM.as fOlloW6: diluent, changes in the ratio of shellac to nitrocellulose and in 21, 226 (1929); 23, 1402 (1931); 2 5 , 550, 696 (1933); and in IND.ENG the ratio of total solids t o total liquids had little if any apC H ~ MAnal. ., Ed., 1 , 205 (1929); 4, 48 (1932); 5 , 267 (1933); 6, 259, 400 preciable effect upon the values for compatibility. Hence it (1934).
