COKING METHODS AND PRODUCTS
I
M. G. BOOBAR', C. C. WRIGHT2, and C. R. KINNEY Department of Fuel Technology, The Pennsylvania State University, University Park, Pa.
Low-Ash Graphite Prepared from Anthracite Low sulfur content and a supply source independent of another industry make Pennsylvania anthracite a satisfactory raw material for graphite manufacture
T H E principal source of raw material for the carbon and carbon electrode industries in this country is petroleum coke of low ash and sulfur content. Because of the increasing demand for carbon products and the refining of larger proportions of lower quality crudes, the production of high-grade petroleum coke is insufficient to meet demands (74). Pennsylvania anthracite, although containing more ash, is frequently lower in organic sulfur than many petroleum cokes and has the further advantage of being a primary raw material rather than a by-product of another industry. However, little fundamental information is available on the thermal properties of anthracite a t high temperatures. Data are needed on both the volatili-
Present address, Special Defense Projects Department, General Electric Co., Philadelphia, Pa. Deceased.
Component Si02 Ab08
Fez08 Ti02 MgO CaO
Table I.
Analyses of Anthracite Size Analysis
Proximate Analysig
% Moisture Volatile matter Ash Fixed carbon Sulfur
0.8 6.3 10.5 82.4 1.0
zation behavior of the mineral matter and the crystallographic changes that may be induced in the carbon of anthracite by heat treatment. Such information might be of use in developing operating techniques designed to reduce mineral deposits on external boiler surfaces. I t would also aid studies of the effect of crystallographic orientation, porosity, and density of heat-treated
Tyler mesh
%
4-28 28 X 48 48 X 100 100 x 150 150 X 200 - 200 Loss
2.5 29.5 38.3 11.4 7.4 10.6 0.3
anthracite on combustion and gasification rates, as well as possible catalytic effects brought about by chemical changes in the mineral matter. X-ray diffraction methods were used to determine changes in the crystallographic structure of the carbon and certain chemical changes in the mineral matter resulting from heat treatment. Emission spectroscopy was used to
Table II. Spectrographic Analysis of Anthracite Ash" Oxide Basis Elemental Basis yo of ash Av. dev., yo Component 54.9 16.5 Si 32.4 13.7 A1 5.0 f0.6 Fe 1.73 10. 17 Ti 0.69 10.05 Mg 0.42 10.06 CS -
% of ash 25.6 17.1 3.5 1.0 0.4 0.3
95.14
a
Average of six spectrographic plates.
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JANUARY 1958
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Table 111.
X-Ray Identification of Minerals Concentrated in Sink Fraction
Mineral
Chemical Formula
Relative Amount
Kaolin group Quartz Pyrite Hydrous micas Muscavite Biotite Illite Montmarillonoids Magnesite Siderite Gypsum Gibbsite
A1203.2Si02.2H20 Si02 FeSg
Large Large Small
Kz0.3A1203. 6 S i 0 2 . 2 H ~ 0 K 2 0 .6(Mg, Fe)O. (AI, Fe)O3.6SiO~.2H20 2 K ~ 0 . 3 M g .Aln0s.24Si02. 0 12H2O Silica-alumina clays MgCOd FeCOa CaSO4.2H20 A1z03. H z 0
Table IV.
Combined Mineral Analysis
Mineral
Chemical Formula.
70
Clay minerals Quartz Pyrite Rutile Magnesite Calcite
A12 02.2 SiOl. 2 Hz 0 Si02 FeS2 Ti02 MgCOs CaC03
82.0 16.7 7.5 1.7 1.4 0.8 __ 110.1
follow the volatilization of the mineral components. Procedures
Sample History and Analysis. The coal was a sample of dried, flotation anthracite, mined by the Susquehanna Coal Co. in the Northern Field of Pennsylvania. Proximate and size analyses of this sample are given in Table I. Ash determinations were made following ASTM D 271-48. I n certain cases 1.5gram samples were taken to obtain the 5 mg. of ash needed for spectrographic analysis. Mineral Identification. Spectrographic analysis of the ash was made by the procedure developed by Nunn, Lovell, and Wright (73). Accuracies within & l o % of the elemental concentration were obtained. Analysis of the coal ash is given in Table 11. Inorganic components of the coal, the heat-treated samples, and the ash residues were identified by the x-ray diffraction powder technique of Hana-
Table V.
walt (7). The mineral matter of the coal was first concentrated by separating that fraction of a -200-mesh sample having a specific gravity greater than 1.80. About 5 mg. of finely ground sample was mixed with collodion in amyl acetate and spread uniformly on a glass slide. After obtaining and tabulating the x-ray data, a search was made in the ASTM "Index of X-Ray Diffraction Data" (7) for the identification of individual mineral constituents. Heat Treatment. The coal in the range of 950" to 1490' C. was heated in a porcelain tube heated by four Globar units. Temperatures were measured by a Pyro optical pyrometer, No. 6181. which was checked with a calibrated platinum us. platinum-lO% rhodium thermocouple in preliminary experiments with no coal charge. The optical and electrical temperature measurements agree within 5' C. Commercial helium of 99.8% purity flowing through the tube at a superficial linear velocity of 10 feet per minute was used to remove air from the tube. Samples were
Effect of Temperature in Range of 950" to 1490" C. on Anthracite Properties Ash, Fixed Carbon, Si02 % % InteusityC %*
Temp., C."
Vol. Mat.,
950 968 1113 1197 1302 1397 1490
7.10 8.12 9.56 10.13 11.60 14.49 17.31
INDUSTRIAL AND ENGINEERING CHEMISTRY
82.44 81.46 80.07 79.51 78.55 76.09 74.13
10.46 10.42 10.37 10.36 9.85 9.42 8.56
Sample heated 30 minutes at indicated temperature, except at Volatile matter including moisture. c Relative intensity of 3.35-8.peak. d Relative intensity of 2.51-9. peak. a
28
Small Small Small Very small Very small Very small Very small Very small
weighed in preheated, unglazed Leco No. 6 combustion boats made of zirconium silicate. The boat and shield were slowly pushed into the hot zone of the furnace, taking 15 minutes, to avoid decrepitation and loss of sample. The sample was then heated a t the desired temperature for 30 minutes, slowly withdrawn to the cooler part of the furnace, and finally placed in a desiccator to cool. The cooled boat was weighed again, and the percentage of volatile matter plus moisture calculated. The residue was then ashed a t 750" C. in a muffle furnace for about 15 hours, and the percentage of ash was determined. Preparation of Anthracite Pellets. For graphitizing purposes, the anthracite fines were pelletized with water by the method of Day and Wright (4).-4 slurry or moist coal containing about 50% water was allowed to stand about 15 hours to wet the coal completely. I t then was tamped in a die "16 X 3 inches fitted with two opposing pistons and slowly pressed in a Carver press to a maximum of 5000 pounds per square inch. After maintaining this load for 1 minute, the pressure was released slowly and pellet ejected from the die. The pellets disintegrated little, even on prolonged storage. They retained their form even after graphitization at 2900' C. and could be pushed from the graphitizing furnace without appreciable degradation. Graphitizing Furnace. The coal was graphitized in a graphite-tube fucnace originally built by Zelinski (78). The tube employed had a I-inch inner diameter, a 1.5-inch outer diameter, was 45.2 inches long, and was mounted in a Transite box filled with lampblack insulation. Power was supplied by a 10-kv. amp. transformer through watercooled electrodes clamped to the tube. The ends of the graphite tube were closed gas-tight by water-cooled brass caps with rubberized gaskets and suitable taps for gas inlet and outlet. The inlet cap also contained a piece of clear, flat borosilicate glass, 3 / 3 2 inch thick,
950'
++++ ++++ +S+ +++ -
C., which is ASTM 7-minute heat.
Sic Intensityd .-
-
+++ ++++
COKING METHODS AND PRODUCTS Table VI,
Ash Percentage of Heat-Treated Anthracite as Function of Temperature, Heating Rate, and Soak Time Ash. ?' ?,
c.
1500 1800 2 100 2250 2400 2700 2900
8.8
13.8
20.0
1
2
4
10.34 10.25 7.53
9.85 9.90 6.19
0.88 0.26 0.05
1.26 0.33
10.71 8.93 7.25 4.68 2.54 0.22
10.27 7.90 3.30 0.43 0.25 0.04
9.84 6.98 2.27 0.38 0.23 0.01
10.34 6.23 0.51 0.25 0.15 0.01
...
...
Furnace heating rates and soak temperatures were regulated by a GycoPhen electronic temperature controller. T h e heating cycle was obtained by a Flexo-Action motor mounted on the controller case which, by suitable pulleys, gears, and cams, turned the control index knob a t known constant rates. A platinum us. platinum-10% rhodium thermocouple, protected by a McDanel high temperature porcelain tube, was inserted through the brass exit cap of the furnace tube into the cooler portion. I t furnished the variable electrical impulse to the controller for maintaining the furnace temperature. This arrangement was also adjusted by hand so that temperatures of the samples, as measured by the optical pyrometer, could be maintained within f 3 0 ' C. for periods of a t least 4 hours. Graphitization Procedure. The graphitization procedure involved raising the temperature to 800' or 900' C. in about 20 minutes using manual controls. The automatic controls were then set in operation. At the maximum temperature desired the furnace was switched off, if no soak period was wanted; or the controller was switched to maintain a constant temperature level for any desired soak period. X-Ray Analysis. Crystallite parameters of the carbons produced by heat treatment were calculated from x-ray diffraction data obtained on powdered samples using a technique later used and described by Walker, McKinstry, and
for sighting on the sample with the optical pyrometer. The pyrometer was equipped with a special filter and was calibrated up to temperatures of 3000' C. Observed pyrometer temperatures were also corrected for the absorption of light by the borosilicate glass window, assuming 90% transmittance (72). This correction amounted to 8' a t 1000' C., 24' a t 2000' C., and 50' a t 3000' C. Exploratory runs showed that two pellets of combined length of about 3 inches could be graphitized a t one time with no detectable difference in their properties. T o obtain better temperature readings, the pellets were preceded in the furnace by a graphite disk of approximately the size of the furnace tube and drilled with several '/le-inch holes to permit the sweep gas to pass. With this arrangement essentially black body conditions were achieved. The system used for controlling the furnace temperature and heating rates was of original design and is believed to be unique. Inasmuch as a convenient, commercial-type radiation pyrometer was not available, a platinum us. platinum-I 0% rhodium thermocouple was inserted in the cooler portion of the furnace as the sensing element. Calibration of this system showed a logarithmic relationship between the temperature of the sample and the temperature measured by the thermocouple, making it possible to design and cut cams for the heating cycle motor which would control the heating rate of the furnace.
Table VII.
Temp. of Carb., O C . 950 1500 1800 2100 2250 2400 2700 Q
Soak Time (Heating Rate 20.0' C./Min., Hr.)
Heating Rate, O C./Min.
Temp.,
Si, % Soak Time, Hr. 0 2.7 2.7 2.2 2.9 2.1 1.1
...
4
3.1 3.1
0.6
... ...
...
Discussion
Mineral Matter. The ash of the anthracite used is typical of Pennsylvania anthracite (9, 73) and is composed mainly of silica and alumina with smaller amounts of iron, titanium, magnesium, and calcium oxides (Table 11). Identification of the corresponding minerals in the original coal was made on the basis of their characteristic d-spacings calculated from x-ray diffraction peaks and confirmed by microscopic analysis using refractive indices. These studies indicated the presence of kaolin clays, quartz, pyrite, hydrous micas, and several other minerals in relatively small amounts (Table 111). Combining the spectrographic and x-ray diffraction
Spectrographic Analysis of Elements in Anthracite Cokes"
AI., % Soak Time, Hr.
Fe, % Soak Time, Hr.
4
0
2.4 0.9 0.3 0.01
0.4 0.3 0.4 0.4 0.1 0.01
0
1.8 1.6 1.8 0.9 0.3 0.1 0.01
Pustinger (77). d-Spacings and L, values were calculated from the (002) reflection and L , values from the (10) peak. No attempt was made to refine the L , values using the method of Houska and Warren (8). No difficulty was encountered by interference of mineral components. Silica gives a strong reflection of a 3.35 A. spacing which would be expected to interfere with the measurements of the (002) peak of carbons, because of a similar spacing, but silica is completely converted to silicon carbide a t temperatures below 1500' C. and therefore does not interfere if the graphitizing temperatures are above 1500' C. The data obtained are presented in graph form (Figures 1 to 5).
... ...
...
Ti, % Soak Time, Hr.
4
0
0.4 0.1
0.1 0.1 0.09 0.07
... ... ... ...
0.09
0.05 0.01
Mg,% Soak Time, Hr.
0
4
0.1 0.06 0.03 0.02 0.01
...
0.04 0.04 0.02 .
I
.
... ...
9 . .
4
0
0.02
... ... ... ... I
.
Cat % Soak Time. Hr.
.
0.03 0.03 0.03 0.04 0.02 0.02 e . .
4 0.04 0.03
... ...
... ...
Heating rate to temperature, 20' C. /rnin.
VOL. 50, NO. 1
JANUARY 1958
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I
I
I
1
FLAKY FRACTIONS 1.-
I HOUR S!,M
2O0/min.-2 20°/min.-4
I
I
"
"
$1
.If\Yd,"-1 4 --A&' '/ /
~
NO SOAK
fi'88OAnin.-
I
lsoo
I
I
I
2100
2400
2700
moo
TEMPERATURE, 'C.
Figure 1.
Effect of heat treatment on crystallite height
remaining oxygen, hydrogen, and other elements combined with the carbon of the 950" C. coke. Additional losses were probably due to the conversion of silica to carbon monoxide and silicon carbide, which is not oxidized back to silica during ashing and which has a lower molecular weight. The change
analyses gave the approximate percentages of minerals (Table IV). When the coal was heated from 950" to 1490' C. increasing amounts of volatile matter were formed and there was a noticeable loss in ash (Table V). .4 large part of the volatile matter was probably due to the expulsion of the
I '
I
1
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I
I
300k
ml 2
/ /
FLAKY FRACTIONS
1
\
x
,/
/'
LI x,
1500
1800
2100
x
I
I
2400
2700
I
3OC
TEMPERATURE, T.
Figure 2.
30
Effect of heat treatment on crystallite diameter
INDUSTRIAL AND ENGINEERING CHEMISTRY
to silicon carbide was observed by means of the relative x-ray diffraction intensities of the substances involved (Table \'). The calculated loss of weight based on the conversion of the silica to silicon carbide is 2.0270 compared with the observed loss of 1.90% (10.46% - 8.56%). Further volatile matter would be evolved by the reduction of ferrous sulfide resulting from the primary reduction of pyrite a t temperatures below 950' C. (15). The total amount of carbon involved in these reductions and the formation of metal carbides is insufficient to account for all of the volatile matter loss in this temperature range. For this reason, it seems possible that reduction of alumina begins below 1500 " C., although 1800" C. is usually cited as the temperature at which reduction occurs (70). A second important devolatiiization of the mineral matter of the coke occurred above 1800' C., depending on the rate of heating and the soak time (Table VI). At a heating rate of 8.8' C. per minute, the ash was reduced from 10.25% to less than 1% a t 2400" C., but at 20" C. per minute a temperature of 2700' C. was required. However, when a 4-hour soak was added to the 20" C. per minute heating rate, only 2100' C. was needed to lower the ash to 0.51%. T o reduce the ash to the order of0.01%, a temperature of2700" C. and a soak time of a t least 2 hours were required. Inspection of x-ray spectrometer tracings of anthracite cokes heated above 1500" C. showed well-defined peaks at 2.51 A., characteristic of silicon carbide. The 1.54- and 1.31-A. peaks of the compound were also easily observed in the ashes from these samples. Experimentation indicated that silicon carbide could be detected in cokes in concentrations approaching 1.5%, and on this basis, silicon carbide is reduced to indetectable amounts a t 2700' C. with no soak and a t 2100" C. with 4hour soak. The elimination of individual mineral components of the cokes with temperature of heating was also followed by spectrographic analysis of the ash. The percentages of elements thus obtained multiplied by the fraction of the coke that was ash gave the percentages of elements in the coke (Table L'II). Examination of these values shows that magnesium was the first to disappear and was effectively removed at 1800' C. with a 4-hour soak. Iron and calcium were next, and a t 2100' C. they were essentially eliminated during the 4-hour soak. Silicon, aluminum, and titanium were more refractory. Silicon, as silicon carbide, required a temperature of 2700" C. for rapid removal, but with a 4-hour soak it was eliminated a t 2250' C.
COKING METHODS AND PRODUCTS Aluminum was more resistant than silicon, and even a t 2700' C. traces could be detected. With the 4-hour soak, aluminum was completely removed a t 2400' C. Titanium required 2700" C. and a 4-hour soak for its effective removal. Graphitization. Graphitization of the carbon of the coal was followed by means of x-ray diffraction studies. Average crystallite heights, L,, determined by this means, rapidly increased with the temperature of treatment, as shown in Figure 1 in which the data are plotted o n semilogarithmic coordinates. The effect of heating rate on crystallite height, however, is small. A much larger effect was obtained by adding a soak time of from 1 to 4 hours to the heating rate of 20' C. per minute. Thus the 4hour soak time approximately doubled the crystallite heights a t temperatures above 2100' C. As no abrupt changes in the direction of these curves occurs, some mechanism other than the socalled carbide mechanism (3) must be effective in graphitizing this anthracite sample. During the powdering of the graphitized samples prepared a t 2250' to 2700' C. for x-ray examination, small amounts of flaky, graphitelike material appeared, which were separated from the bulk of the products. The flaky material in each case exhibited large Lo values, as shown in the upper part of Figure 1. Possibly this material resulted from the decomposition of silicon carbide or from a component that was more easily graphitized than the bulk of the coal. No attempt was made to identify the source of this product, but the difference in properties was striking. Crystallite diameters, La, were also affected by variable heating rates and soak times, but the effect was small, as seen in Figure 2. The shape of the curves seems to suggest that the average crystallite diameter grows a t a fairly constant exponential rate from 1500' to about 2700' C. The high point at 2900' C., however, indicates that possibly the curve has a tendency to turn upward a t this temperature. The effect of the 4-hour soak time was to increase average crystallite diameters about 10A. Schaeffer, Smith, and Polley (76) have shown that carbon black crystallites cease to grow after about 10 minutes of heating a t the maximum temperature. The fact that anthracite crystallites continue to grow attests to a fundamental difference which is probably that growth in the anthracite carbon is not limited by particle size as in carbon blacks. Crystallite diameters of the flaky material separated from the high-temperature samples are markedly larger
3.45
I
I
&,
t ,\
I
I
I
3.4401\
R;;tii 8.8 OWmin.
,HEATlE
3.430
,H y 7 ;:s ;z + ;\
I
,
3 360
3.350 1800
1500
2100
2400
2700
3000
TEMPERATURE, 'C.
Figure 3.
Effect of heat treatment on d- spacing the scatter of the individual points was too large to be satisfactorily plotted. This suggests that there may be minor factors affecting graphitization which are not included among those studied. I n general* the straight-line nature of the relationship between d-spacing and graphitizing temperature seems to show that anthracite carbon graphitizes in a normal manner. The proportion of disoriented layers of carbons graphitized under varying conditions is of importance, and Franklin ( 5 ) has devised a n equation for relating the proportion, p , to the observed dspacing compared with that of what she
than the bulk samples (upper part of Figure 2). These values, while erratic, are more than double those of the bulk samples. This fact no doubt accounts for a part of the difference in behavior on grinding. The effect of heat treatment on the interlayer d-spacing of the carbons is shown in Figure 3. The two curves show the results obtained under the extremes of the conditions used-Le., a t heating rates of 8.8' C. per minute with no soak and a t 20' C. per minute with 4-hour soak a t the six temperatures. Intermediate conditions gave values lying between these curves; however, 1.0 [
I
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I
I
15Oo~C.
n 7
I 1
I
0
18ocp
c.
0
Q
t 0
i I
2
3
SOAK TIME,
Figure 4.
4
hours
Effect of soak time and temperature on p factor VOL. 50, NO. 1
JANUARY 1958
31
cite is a satisfactory raw material for graphite manufacture. Graphitizing temperatures normally used in the industry can effectively remove the mineral matter and graphitize the carbon. The former, however, would probably be reduced by some other method before graphitization in a n industrial process. Although the elirnination of larger amounts of mineral matter than those found in petroleum cokes would complicate operations, the low sulfur content, which is further greatly reduced during graphitization and the advantage of a source of supply independent of another industry, should tend to offset this disadvantage somewhat.
.‘
loot
I,
/‘
y
/’ /
8
/
,,’ ‘ NON-GRAPHITIZING CARBON ---GRAPHITIZING CARBON
I/
-P I
0
ANTHRACITE X
ORLGINIU. COAL
e 15000~. 0
A V
1800*C. 21OO’C.
B
2i?50°C. 24oooc.
V
27000C.
Acknowledgment
I
I
I
I
I
20
40
60
00
101
NUMBER QF LAYERS PER CRYSTALLITE, L,/d
Figure 5. Relationship between layer diameter and number of layers per parallel group for graphitizing carbons, nongraphitizing carbons, and anthracite
considers to be completely disoriented carbon ((‘nongraphitic graphitizing” carbon) and of completely oriented graphite. d
3.440
- 0.086 (1 - p’)
Increasing graphitizing temperatures from 1500’ to 2900’ C., with no soak period, decreased p from about 0.9 to below 0.3 for the bulk samples (Figure 4). The flaky product had an even lower p value, which approached 0.2 a t the higher temperatures. The effect of heating rate was negligible and can be ignored. However, soak time has a pronounced effect. This is also shown in Figure 4, in which a marked drop in p occurs at 2250’ C. and above. At 2700” C. the maximum decrease is observed at I-hour soak, and if the trend continues, even less time should be required for maximum graphitization at higher temperatures than 2700’ C. Graphitizing and nongraphitizing carbons may be distinguished according to Franklin (6) by comparing crystallite diameters with the number of parallel layers per crystallite. I n Figure 5 , the behavior of heat-treated anthracite is compared with Franklin’s curves for graphitizing and nongraphitizing carbons. Below about 2100’ C., the anthracite sample behaves like Franklin’s nongraphitizing carbons, but a t higher temperature more rapid graphitization sets in, and the number of parallel layers per crystallite, L,/d, rapidly increases, as is characteristic of graphitizing carbons. Franklin also observed this anomaly with anthracite and explained it on the basis that anthracite crystallites heated below 2000’ C . are nearly parallel in respective orientation (presumably because of the manner
32
INDUSTRIAL AND ENGINEERING CHEMISTRY
of deposition of the original coal molecules-that is, parallel to the bedding plane) but are strongly cross-linked within the crystallites which effectively prevents crystallite growth below 2000 C. O n heating above 2000” C., Franklin believes the cross links begin to break, leading a t once to rapid crystallite growth. This explanation for the behavior of anthracite on graphitizing is satisfactory, but the terminology is not, as a carbon must be classified either as graphitizing or nongraphitizing. In view of the fact that anthracite graphitizes rapidly above 2100’ C., it seems that it should be classified as a graphitizing carbon regardless of its behavior below this temperature. The work of Maire (77) also indicated that coke from a high-rank coal (89.4Yo carbon) was graphitizable, while cokes from lower rank coals were not. He found a correlation between graphitizability of carbons and their conversion to graphitic acid by Brodie’s reagent. This seems to indicate a relationship between the two properties based on a similarity of constitution. Austin and Heddon (2) have heat-treated a variety of cokes, other than coal cokes, and state that Franklin’s classification of carbons into graphitizing and nongraphitizing classes is not borne out by their work. HOWever, most of their carbons were nongraphitizing in so far as d-spacings were concerned, and this should be taken into consideration. Conclusions
On the basis of the results described it is concluded that Pennsylvania anthra-
The generous financial support of the anthracite industry is gratefully acknowledged. The authors are indebted to H. T. Darby, H. L. Lovell, R. C. Nunn, H. T. Grendon, and H. A . McKinstry for their advice and assistance in performing a great many of the analyses. literature Cited
(1) Am. Soc. Testing Materials, Philadelphia, Pa., “Alphabetical and Group Numerical Index of X-Ray Diffraction Data,” Spec. Tech. Pub. 48-B (1950). ( 2 ) Austin, A. E., Heddon, W. A,, IND. ENG.CHEM.46, 1520 (1954). ( 3 ) Brusset, H., Bull. SOC. chim. (France) 16, D49 (1949). (4) Day, R. J., Wright, C. C., Pennsylvania State University, Tech. Pub. 139 (1948). (5) Franklin, R. E., Acta Cryst. 4, 253 (1951). (6) Franklin, R. E., Proc. Roy. Soc. (London) A209. 196 (1951). ( 7 ) Hanawalt, j, D.,‘ othgrs, IND.ENG. CHEM.,ANAL.ED.10,457 (1938). (8) Houska, C. R., Warren, B. E., J . Appl. Phys. 25, 1503 (1954). 19) . . Jones, J. D., Buller, E. L., IND.ENG. C&M., ANAL.ED. 8, 25’(1936) (10) Kirk, R.E., Othmer, D. F., “Encyclopedia of Chemical Technology,” vol. I, p. 603, Interscience Encyclopedia, New York, 1949. (11) Maire, J., Compt. rend. 232, 61 (19511; (12) Morev, G. W., “Properties of Glass, Reinhold, New York, 1938. (13) Nunn, R. C., Lovell, H. L., Wright, C. C.. “Trans. 11th Anthracite Conferknce,,) Lehigh University, Confer; 1953,” p. 51. (14) Petroleum PTOC.9, ?351 (1952). (15) Powell, A. R., J. 1IND.END.CHEM.12, 1069 (1920); 13, 33 (1921). (16) Schaeffer, W. D., Smith, W. R., Polley, M. H., Ibid., 45, 1721 I1 Or;?) (1953). P. L., Jr., McKinstry, H. A, .. (17) TWalker, Pustinger, J. V., Ibid., 46, 1651 PU (1954). (18) 1Zelinski, J. J., thesis, Pennsylvania State University, University, 1950. lY5b ~
RECEIVED for review August 27, 1956 ACCEPTED December 7, 1956 Division of Gas and Fuel Chemistry, 131st Meeting, ACS, Miami, Fla., April 1957.
