Julie, 1928
I S D U S T R I A L ASD EAYGISEERISG C H E M I S T R Y
( b ) Differences in the melting points of commercial paraffin waxes are due t o differences in their oil content.
Investigation of the wax mixtures shows that: (a) Paraffin waxes form solid solutions. ( b ) The melting points of r i e solid solutions lie between the melting points of the compor ents. ( c ) Owing t o the existence of solid solutions, paraffin wax does not possess a sharp melting point.
The investigation of oil-wu mixtures leads to the following conclusions: (a) The solubility of paraffin wax in oil increases very markedly a t temperatures appr3ximately 10" C. below the melting point of the wax. (b) The IoMT-melting waxes are more soluble in oil than the high-melting waxes. nlixtures of high- and lcw-melting have solubilities intermediate between the solubilities of the components.
641
( d ) The increase in solubility of the mixtures in oil a t temperatures approximately 1C" C. below their melting points is as marked as in the case of pure waxes. ( e ) The marked increase in solubility explains the loss of wax in the later stages of the sweating process. oilcin f ) wax Paraffin wax apparently retains oil as a solid solution of (g) The wax retains approximately 2 per cent of oil a t room temperature, but the amount retained a t the temperature a t which the final sweating is carried out is too small to be detected. ( k ) The presence of this small amount of oil in solution offers a n explanation for some of the difficulties encountered in the separation of oil from wax.
Acknowledgment -
The authors n-ish to acknowledge the aid of TIT. F.Faragher, who was associated with the lIellon Institute of Industrial Research a t the time of this investigation.
The Viscosity-Gravity Constant of Petroleum Lubricating Oils' J . B. Hill and H. B. C o a t s THE ATLAKTIC REFINING COMPASY, PHILADELPHIA, P A
ITH t h e present From data previously published on the physical ciple was used by Burton3 in properties of the viscous fractions from various types defining the s e r i e s of oils diversity of of crude petroleum, a mathematical relation has been which he obtained from prescrude p e t r o l e u m s worked out between Saybolt viscosity and specific sure-still tar, and for which he and corresponding diversity derived the expression gravity. The relation is a logarithmic one and exof lubricating oils made from presses the specific gravity in terms of the viscosity them, the simple classification o'51cc2+ '06" - 961x betrl-een paraffin-base alld and a constant which is different for each crude and is 2 9 ~ 2- 2 4 4 ~- 53296 = 0 n a p h t h e n e - b a s e oils is no characteristic of it. This "viscosity-gravity constant" is low for the paraffinic crudes and high for the naphThis equation is e x t r e m e l y longer a d e q u a t e . It frecumbersome and no attempt thenic crudes. Its value for any oil is a direct index quently becomes desirable to of the degree of the paraffinic or naphthenic character was made to correlate with it indicate the degree to tvhich a similar equations of oils from particular oil or group of oils which it possesss. other sources. is paraffinic or naphthenic When one oil only is concerned, it has been custoqary to -4 simple graphical inspection of the data on viscosities specify both the gravity and viscosity in order to define it, and gravities of fractions from any one crude indicated that since it has long been recognized that for oils of t.ie same they could be plotted as a straight line on semi-logarithmic viscosity a low specific gravity (high A.P.I. gravity) indicates coordinates, or that the curves conformed to the general a paraffinic oil, while a high specific gravity (low A.P.I. formula gravity) indicates a naphthenic oil. Where it is dekirable G =a blog ( V c) (1) to talk about a group of oils from the same type of crud? but where a, b, and c are constants, G is the specific gravity a t of different viscosities, the matter has not been so simple, 600 F. (15.60 c.1, the Saybolt viscosity at 1000 F, since it would be necessary to specify the particular gra Vity (37.80 c.1. A determination of the tilree for the for each viscosity. optimum plotting of the data for each of the crudes gave I n TOrk on the relation between the boiling points and values as shoTvnin Table I, It TT-illbe noted that the constant physical properties of viscous Oils,' the similarity between is identical for all the given crudes, that b (the slope of the the shapes of the various curves for fractions each series Of straight line) varies slightly, and that a shows a wide \.ariation. which was obtained from one sample of a different Crude, The jnsertion of these values in the gelleral expression gives appeared t o be rather striking. The same type of similarity 5 series of fi>y equations representing, respectively, the visis obtained when the specific gravity data from the above work cosity-gravity relationship betTveen the fractions from each are plotted against the corresponding viscosity data (Figure of five crudes. 1). Since these two properties are among the simplest to \LThile the equations thus obtained may Serve to define determine for viscous oils, an attempt has been made to work the fractions from any one of these givell crudes, they are Out a mathematical relation coordinating the viscosity and undesirable in that it is necessary to specify the values of tTvo gravity for the fractions of varying Tkosities for each crude, constantsin order to effectsuch definition. The calculations and to show the similarity and dissimilarity betn-een the Tvere ther?fore carried further in an attempt to derive an mathematical relations so obtained. The same general prinin Tvhich there appears only one constant which i S Characteristic Of the crude Source. It is h m e 1 Presented under the title "Relation between Viscosity and Gravity of Petroleum Products" before the Division of Petroleum Chemistry a t the diately apparent that the constant b bears, roughly, a straight74th llleeting of the American Chemical Society, Detroit, Mich., September line relationship to 51 and can therefore be expressed for most 5 to 10, 1927.
+
+
v
2
Hill and Ferris, IND. ENQ.CHEM.,17, 1260 (1925).
8
U. S. Patent 1,167,884CTanuary 11, 1916).
/
INDUSTRIAL A S D ESGI.1'EERING CHEMISTRY
642
0.85
_-
Vel. 20, No. 6
0. Q!
-
%
I
2
6O.W
0
::
f
c
$
B
g
2- ,
E
B
E
0.85
0.85
Lmo 30 40
80 B2 100
PO0
100 400 800 800 1000
2000 3000
Saybolt viscosity at 100' F. (37.8'C.) .Minus 38 seconds
SAYBOLT vIScC61w AT 1 0 0 n ? . ( ~ 1 . 8 0 ~ .]
practical purposes as a very simple function of a. Specifically, 1.0752 - a b = 10
(2)
The only appreciable deviation from this in the five crudes is in the case of the Gulf Coast 3 oils. T a b l e I-Values of C o n s t a n t s in E q u a t i o n : C = u CRUDE a b Pennsylvania 0.8067 0.02685 Midcontinent 0.8340 0.025 Gulf Coast 1 0.8661 0.020 Gulf Coast 2 0.8832 0.020 Gulf Coast 3 0.8885 0.02685
+ b log (V + c ) C
- 38 ---383838 -38
The general relation between specific gravity and Saybolt viscosity at 100' F. (37.8' C.) may therefore be written G = a +
1.0752 - a log ( V 10
- 38)
100' F. (37.8' C.) viscosity is lost in the case of the Gulf Coast 2 curve for the 210' F. (98.9' C.) viscosity. It will be noted that this curve would actually cross the curve for Gulf Coast oil 1 if extrapolated. This may represent a real change in the chemical composition of this oil in its more viscous fractions. The presumed freak character of this curve has some justification from its source. The crude from which the fractions were obtained was not a single individual crude from one pool, but a mixture of several crudes. It is not unplausible that the highly naphthenic character of one of the constituent crudes manifested itself in the lighter fractions, whereas a heavier and less naphthenic constituent crude predominated in the heavier fractions.
(3)
in which a becomes the only constant characteristic of the oil or of its source. This constant may be known as the "viscosity-gravity constant." Its values, slightly revised from those of Table I to meet better the approximate equation, are shown in Table 11. The series of five curves plotted from these relations appear in Figure 2. The points indicate the actual observed data and show the slight extent of the approximation. While the curves conform to the data very well a t the low viscosities, it is probably inadvisable to use them at viscosities below 45 seconds and quite out of the question at viscosities below 40 seconds. T a b l e 11-Values
of u in E q u a t i o n : C
Pennsylvania Midcontinent Gulf Coast 1 Gulf Coast 2 Gulf Coast 3
= a
-k
10752
-
u
]OB (V - 38)
a 0.8067 0 8367 0 8635 0.8845 0 9025
10
For convenience in calculating the viscosity-gravity constant from data a t hand on an oil, equation (3) may be wristen in the form: a =
10 G
- 1.0752 log (V - 38) 10 7 log ( V - 38)
(4)
An attempt was made to express similarly in a mathematical way the relations between specific gravity and Saybolt viscosity a t 210' F. (98.9' C.) of the more viscous fractions from the various crudes. It was found that the meager data available conformed to the same general relation (1). It will be noted, however, from the actual ~ 1 0 5 sof the observed data (Figure 3 ) that the symmetry o b h i n d from the curves of the
20
Jo 40 BO 80 100 26) 300 SAYSOLT 1ISCOSITi *T 210%- l88.8%.)
0
00
On account of these facts it was thought justifiable to drop this particular crude from consideration and to derive a general expression for the other four. In this case the values for b and c prove to be identical for the four crudes and the expression obtained has the simpler form G = a'
+ 0.022 log (V'
-
35.5)
(5)
where V' is the viscosity a t 210' F. (98.9' C.) and a' the "210' F. (98.9' C.) viscosity-gravity constant" of the oil. The values of this constant are shown in Table 111. The four curves, together with the points showing the observed values, are plotted in Figure 4. It was noted that the 210' F. (98.9' C.) viscosity-gravity constant bears a simple relationship to the 100' F. (37.8' C.) constant as follows:
INDUSTRIAL A X D ENGIiVEERIiVG CHEMI8TRY
June. 1928 a' = 0.24
+ 0.755a
The values of a' calculated from a by this relation are also shown in Table 111.
+
-
0.02210g (V' 35.5) Table 111-Values of u' i n E q u a t i o n : C = u' CRCDE DETERMIXED COMPUTED FROM a 0.8491 Pennsylvania 0 8492 0.8717 Midcontinent 0.8720 0.8919 0.8916 Gulf Coast 1 0.9078 .... Gulf Coast 2 0.9214 Gulf Coast 3 0 9354
643
has a definite value, readily calculable, for any oil. The higher the value the more naphthenic the oil, and the lower the value the more paraffinic. Oils of different viscosities but of the same viscosity-gravity constant are of similar chemical compositions and are probably from similar sources. Furthermore, the higher the viscosity-gravity constant the higher the rate of viscosity change with temperature. Table V-Values
of u for Oils Blended from C u t s of S a m e Crude
FRACTION Cut A Cut B Blend Cut C Cut D Blend Cut A Cut B Blend cut c Cut D Blend -
~'ISCOSITIES
GRAVITY 100' F. 210' F . GULF COAST1 . a = 0.8635 45-50y0 0.9025 102 120 75-807, 0.9338 504 50B 0.9222 526 50-5570 0,9080 154 82 70-75% 0,9283 50C 50D 0.9189 442 GULFCOAST3 : a = 0.0025 81 50-6070 297 85-90% 620 50A 50B 121 6045% 106 80-85%, 5i3 50C 50D
a'
a
0,8644
+
0.8914
-
0,8916
+ +
0,9354
0.8658 0.8655 0.8638 0,9050
0.9364
0.9122
0.9081 0.9140
In connection nith the latter thought the authors have been tempted to combine equations (3) and ( 5 ) , eliminating the gravity and expressing the viscosity a t 210" F. (98.9" C.) in terms of the viscosity a t 100" F. (37.8" C.) and the viscosity-gravity constant. The resultant expression has the form log (V' - 35 5 ) = (4.88 - 4 . 5 6 ~ log ) (I.'- 38)
+ 1l.la - 10.9
Viscosity-Boiling Point Relationship
The 50 per cent boiling point on the distillation test under 10 mm. pressure plotted against the logarithm of the Saybolt viscosity a t 100" F. (37.8" C.) for the five crudes shows a regularity similar to that of the two sets of data already considered. These boiling-point data are also given in the previous paper.2 In order to tie these data in with the other relationships, the same type of equation was applied. The general equation Tg=d+-
138 -
0.6812
log (Ti
- 36)
was found to be where T B is the 50 per cent boiling point in degrees Centigrade under 10 mm. absolute pressure, d is the characteristic constant, and V is the Saybolt viscosity a t 100" F. 137.8" (3.). The d values for the different crudes are given in Table IV. The accuracy with which these equations fit the data can be seen by Figure 5, where the straight lines represent the equation and the plotted points are the original data. Table I\'-S'alues CRUDE
Gulf Coast 3
d
138 - d + 0.6812 log ( V - 36)
DETERMIXED 74.6 83.2 91.5 100.4 105.1
CALCULATED FOR a 74.6 83.2 91.7 99.0
of d i n E q u a t i o n :
TB =
105.6
It is thus seen that the boiling point-viscosity data yield a characteristic constant, d, which serves to designate the degree of paraffinicness as do a and a'. This constant d is closely related to the viscosity-gra\eo
,LO
140
Saybolt viscosity at 10OOF. (37.8' C.) Minus 36 seconds
It will be noted that the entire conception of viscositygravity constant involves the assumption that the same general chemical composition-4. e., the same degree of paraffinicness or naphthenicness-is characteristic of the successive fractions from any one individual crude. Until more is known of the chemical composition of viscous petroleum distillates, this assumption is convenient and does not seem to be altogether unwarranted.
INDUSTRIAL AND ENGINEERING CHEMISTRY
644
It will be further noted that the data applied to these calculations are on fractions which are distillates and of fairly narrow boiling range. To determine the application to wider boiling oils a few blends have been prepared of light and healy fractions from the same crude and the constants calculated. These values are shown in Table V. Apparently the relations
Vol. 20, Xo. 6
continue to hold for blended oils from components of widely different viscosities. The viscosity-gravity constant is certainly not above criticism. It has been found, however, to be a useful index in the authors' laboratory and is communicated in the hope that it may prove similarly useful to others
Fusion of Coal, Coke, and Motor Fuel by Sodium Peroxide' George E. Mabee ROCHESTER GAS A L D ELECTRIC CORPORATION, ROCHESTER, N. Y.
A
RECENT valuable article on the fusion qf coal and coke by Fieldner and Selvig,2 of the Bureau of Mines, tabulates results which afford a comparison of three methods for determining sulfur in fuel. Since the sodium peroxide method is thought worthy of a place among the A. S. T. M. Standards, it seemed timely to the writer to call attention to the manner of conducting the fusion, before the method is finally written up. I n the article mentioned the method as it is now used is set forth, and the results are said to be sufficiently close to those obtained by the Eschka method to justify its use as an alternate standard. The purpose of this article is t o show another way by which coal and coke may be fused with equal facility and more completely in the case of coke. It probably has been noticed that coke does not fuse completely by the present method, although the amount of unburned material has not been found to exceed 2 per cent. The combustion seems to be arrested by loss of heat, especially with slow-burning material like coke. Several years ago the writer, using the Parr peroxide calorimeter while working on bituminous coal, found from 0.4 to 0.6 per cent of unburned material. The cartridge used in the calorimeter is essentially the same as that used for sulfur determinations, but is immersed in water, which increases the rate of radiation and thus makes it difficult to complete the combustion. This criticism does not apply to bomb calorimeters, in which the fuel is burned in a cup and is not in contact with the walls of the bomb. Regardless of the means used to ignite the charge, the cartridge should not be immersed in water during combustion. The 15 grams of sodium peroxide used can supply all the oxygen needed for the combustion of 0.5 gram of coal or coke, and the addition of chlorate, because of its ability to furnish more oxygen, constitutes a daring attempt to outrun the effect of radiation, which nevertheless succeeds with those fuels having sufficient volatile matter. The use of benzoic acid with anthracite and coke is simply a means of supplying the volatile matter that they lack. Following this conclusion, it was decided to use means to prevent radiation losses through which it was hoped to dispense with the use of potassium chlorate and benzoic acid. This was done by placing the cartridges in a muffle furnace a t about 800" C. The screw couplings and washers were, of course, left off, and in order to have sufficient clearance in the muffle the milled knob was removed from cartridge cover. This produced a complete fusion with a wide variety of fuels, as will be shown later, and demonstrated that potassium chlorate and benzoic acid are not necessary. The cartridge became evenly heated all over before the 1 9
Received September 9, 1927. IXD.ENG.CHEM.,1 9 , 7 2 9 (1927).
charge ignited, instead of having one hot spot as formerly, which favors a better combustion. The cartridges were given 2 minutes in the furnace, although less might have been sufficient. The ignition was found to occur in from 20 t o 30 seconds. The muffle can be protected from any possible spattering of peroxide by placing one thickness of asbestos paper on its floor and allowing it to extend a little way up on the sides. The accompanying table gives a partial list of the fuels tested. They are samples received from the Bureau of Mines, on which the writer had previously made tests, the results of which were incorporated in the article cited.2 They represent widely separated sections of our country and are as widely separated in their nature. These tests have been carried through to completion-i. e., sulfur content-to show that concordant results are possible. SAMPLE A B C
D
E F
G H I
JK
.I
hl h-
0 P
SOURCE
A P P R3XIMATE ~ A X A L Y S ~ SDRY , BASIS Volatile Ash ---Sulfur-matter
Pennsylvania Washington Illinois Appalachian field West Virginia Kansas Appalachian field Appalachian field Unknown Interior Province Illinois Mississippi lignite Illinois Interior Province Anthracite Metallurgical coke
%
%
%
%
24 45 32 37 25 35 22 26 45 39 43 27 39 37
11.0 7.8 14.8 12.6 11.2 8.8 5.9 14.5 13.2 8.4 12.1 44.0 10.6 16.0 16.9 16.3
2.58 0.56 1.11 3.87 1.31 4.36 1.99 4.46 6.84 3.26 8.23 17.42 5.54 10.47 0.87 0.59
2.65 0.53 1.19 3.68 1.42 4.28 1.90 4.52 6.84 3.26 8.35 17.57 5.34 10.42 0.88 0.62
% 3.73 2.01
8.24 17.56 5.38 0.61
The proposed method requires no more time than the one now in use and is somewhat simpler since there is less weighing and couplings are not needed. Aside from this the possible danger from chlorate, as pointed out in the Bureau of Mines article, is eliminated. The difference in sulfur results, however, may not be apparent because of the small amount of sulfur in coke. Fusion of Gasoline, Motor Benzene, or Highly Volatile Mixtures Difficult to Handle in Calorimetric Bomb (For purpose of determining sulfur)
A 50-ml. nickel crucible is set on a standard in a 600-ml. beaker, about 3 mm. off the bottom of the beaker and surrounded by water to half its height. The charge consists of 15 to 18 grams of sodium peroxide and 1 ml. of the fuel to be tested, which are mixed in the crucible and a thin layer of peroxide spread over it. The crucible cover is replaced by a copper canopy of the same diameter as the beaker and similar to a watch glass with the convex side up,
