Study of Millin Technique for Determination of Carbon and Hydrogen in Coal R. J. GRACE AND A. W. GAUGER, Mineral Industries Experiment Station, The Pennsylvania State C The Millin technique for determination of carbon and hydrogen in coal has been studied. The procedures have been controlled by -"-I"*:. -6 I. "ll.D .-.."*"i,:compounds and the technique has been
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found rstirfactorv for m a w other substances that are amenable to anialysis by combustion. ~.__ .. HI5 purpose of the
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work described in this peper has been to venfy a new rapid technique first described by Millin (3) for the macrodetermination of carbon and hydrogen in coal. The procedures used have been controlled by the analysis of pure organic compounds, and the technique developed has been found to give satisfactory results for many other substances which are menable to analysis by combustion. Analysis for carbon and hydrogen content of coal requires from 1to 2 hours by thestsndard A.S.T.M. petbad (D-271-44). With the Millin procedure results for bituminous coal and anthracite i r e available in 25 and 45 minutes, respectively. The essential differences between the method described by Millin and that recommended by the A.S.T.M. are in the rate of oxygen flow, 100 ml. per minute in the former and 3 bubbles per second in the latter, and the substitution of silver turnings for a portion of the copper oxide in the combustion tube. The new procedure has been x h p t e d far use with standard equipment and requires only the slight modification, noted above, from standard practice in chwging the combustion tube. APPARATUS
in Figure 1;
Figure 2 illustrates the nositions and lenntbs of Dsekine materids used. PROCEDURE F..m"lma
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Vol. 18, No. 9
INDUSTRIAL AND ENGINEERING CHEMISTRY
564
rheostat on heater 7 is then adjusted to its original temperature setting, and after 5 more minutes, heater 9 is returned to its original position and the flow of oxygen is continued for another 5 minutes. At the end of this time (total of 25 minutes) the absorption tubes are shut off under pressure and then the flow of oxygen is cut off. A blowout tube, not indicated, which automatically controls the maximum pressure in the system makes this last step possible; it also prevents the manometer fluid from being forced into the train in event of misadjustment of the needle valve. At the completion of the above steps the absorption tubes are placed near the balance and the train is ready for the next run. The tubes are allowed to cool to balance temperature, vented to the atmosphere for a few seconds while being wiped with a damp chamois skin, and then weighed, using a similar tube as counterpoise on the balance. A
C
B
Figure P.
D
E
F D
G
D
Table I. Tests on Bureau of Standards Samples Sucrose c, %
H,%
Benzoic acid C % H: %
1
2
3
4
Theoretical
42.08 6.50
42.06 6.49
42.08 6.44
41.98 6.49
42.08 6.48
68.67 4.94
68.75 4.99
... ...
... ...
68.83 4.96
were removed and allowed to cool before weighings were made. In the case of benzoic acid the slightly low results for carbon may be attributed to the rapid rate a t which the substance volatilized; no alteration in time of combustion was tried on this substance. Table I1 gives results of analysis of a bituminous coal sample by the standard A.S.T.M. and Millin procedures. Tables I11 and I V give results by the Millin procedure on anthracites, bituminous coals, carburetting oil, tar, abietic acid, and liquid hydrogenation products. Sucrose is generally used as a control standard in combustion analysis. The data in Table I show that the Millin procedure is satisfactory in the analysis of sucrose. Table I1 shows the results obtained with the two methods on a sample of bituminous coal which was air-dried and ground to pass a 250-micron (So. 60) sieve. All other samples of coal used were prepared in like manner. The specified permissible difference for duplicate analysis,
Fused Quartz Combustion Tube
A . Charging end B . Removable oxidized, copper screen spiral C. Trans arent'section for combustion boat D. Oxidlred copper screen plugs E . Cupric oxide (wire form) F. Silver turnings G . Lead chromate
Table
11.
Comparative Results b y A.S.T.M. and Millin Procedures on a Bituminous Coal 1
2
3
Time, RIin.
c, %
84.00 4.13
83.91 4.10
84.19 4.12
120
C % H: %
84.20 4.13
84.20 4.10
84.30 4.10
25
Method A.S.T.RI.
All results for bituminous coals reported on in this paper were obtained by this procedure. I n the paper by Millin (3) a time of 20 minutes is given for the analysis of coals; this lower rate may be due to the longer length of combustion tubing which was employed, thereby allowing the use of 35 em. of copper oxide and 10 cm. of silver turnings in the center furnace, whereas the authors were limited, because of the standard design of the apparatus, to 23 cm. of copper oxide and 10 cm. of silver turnings. KO indication was given that any of the samples analyzed were anthracites. In the case of anthracites more time was found necessary for complete combustion of the samples; hence the regular procedure was changed to allow heater 7 to be placed over tlie charge immediately and to remain there 10 to 15 minutes longer than usual. The procedure was used for various other materials which, because of their greater volatility, required slight changes in technique. The increase in time required was used to volatilize the material slowly without allowing it to catch fire; the rate of oxygen flow was decreased slightly in some cases, although this was more of a conservative measure than a necessity. I n the preliminary teits to establish a minimum time for combustion, two Ascarite absorption tubes were placed in series on the train; the second in the series would show a gain if the first did not completely absorb all carbon dioxide formed during combustion. Through this procedure it was found that Fisher-type tubes, which have about one fourth the capacity for Ascarite as the Nesbitt tubes finally adopted, were too small to absorb the carbon dioxide quantitatively. To test for complete conversion of the carbon to carbon dioxide a bubbler tube containing a solution of palladous chloride (4) was attached to the end of the train. RESULTS AND DISCUSSION
Table I shows typical results obtained using Bureau of Standards samples of sucrose and benzoic acid. I n each case the ignition period was completed in 25 minutes and the sample tubes
H, % Millin
Table
111.
Sample Designation
Typical Results on Coals by Millin Procedure
Time of Combustion
Run 1
Anthracite
F G
40 40 40 40 40
H
I J
Table
IV.
.
Carburetting oil K
L hZ
Tar N 0 AGetio acid (recrystallized)
n
R T U S
Run 1
Hydrogen Run Differ2 ence
%
%
%
%
%
%
79.14 75.27 82.65 72.38 79.15
0.05 0.00 0.25 0.28 0.06
4.62 5.18 4.32 4.89 5.06
4.66 5.21 4.30 4.87 5.01
0.04 0.03 0.02 0.02 0.05
81.65 79.08 80.87 84.36 85.14
81.60 79.09 81.04 84.32 85.12
0.05 0.01 0.17 0.04 0.02
2.01 2.39 2.47 2.15 2.09
2.06 2.43 2.44 2.12 2.10
0.05 0.04 0.03 0.03 0.01
Typical Results on Organic Materials b y the Millin Procedure
Sample Designation
Li;uid
Difference
79.19 75.27 82.91 72.66 79.21
Min. Bituminous coal A 25 B 25 C 25 D 25 E 25
Carbon Run 2
hydrogenation products
(Time of combustion, 75 minutes) Carbon Difference Hydrogen Difference Run or Run Run or 1 2 Theoretical 1 2 Theoretical
Run
%
%
%
%
%
%
84.92 85.49 85.44
84.70 85.57 85.24
0.22 0.08 0.20
13.82 13.89 13.71
13.80 13.86 13.76
0.02 0.03 0.05
92.58 92.63 92.50
92.40 92.71 92.49
0.18 0.08 0.01
6.39 6.51 6.39
6.37 6.51 6.42
0.02 0.00 0.03
79.35
79.30
79.40
9.87
9.90
10.00
87.68 88.13 88.68 88.92
87.73 88.19 88.67 88.93
0.05 0.06 0.01 0.01
12.14 11 78 10.95 10.91
12.12 11.73 10.99 .10.91
0.02 0.05 0.04 0.00
. ANALYTICAL EDITION
September, 1946
Table
V.
Win.
Max.
%
%
Statistical Analysis lor Carbon and Hydrogen Zn
m
a
Zn’
mr
8’
B’
y’
-
Carbon, A.S.T.M. permissible difference 0.3% Anthracites 6 5 . 7 4 . 91.73 208 100 0.181 207 100 0.172 0.4 Bituminous coals 34.10 91.10 124 50 0.420 118 48 0.317 0.4
