May, 1928
INDUSTRIAL A S D ENGINEERIJYG CHE-VIXTRY
Fieldner of the Bureau of Mines, Pittsburgh, Pa., through the courtesy of G. B. Watkins. The ultimate analyses of the coals were made a t the Bureau of Mines. The samples include semianthracite, semibituminous, bituminous, and lignite coals. Experimental Work
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the buret to compensate for any dehydration of the gas due to the caustic. A number of gas analyses are made on each run and the average of the results is used to compute the percentage of carbon dioxide. The total carbon is then calculated from the results of the carbon dioxide analysis and the total volume of the gas. The stopcock in the line from the balloon is opened, the bomb is disconnected, and the water in the overflow beaker is returned to the bottle. This flushes the sample out of the apparatus and makes it ready for another run. The leads are left filled with the old sample but, since their volume is only 39 cc., and the percentage of carbon dioxide varies only slightly in the samples of coal, the error introduced ic negligible. The balloon is of good-quality rubber and mill last for a large number of runs. Since the total time for the carbon determination is only 25 to 30 minutes, the amount of difTusion”_f the gaseous product into the mater is so slight that it does not cause serious error.
d 0.3- to 0.6-gram sample of coal is exploded in the bomb calorimeter containing about 15 atmospheres of oxygen. This size sample is found to be more suitable in the apparatus described than the 1-gram sample ordinarily used for coal analysis, as it requires less volume of oxygen for complete combustion. This makes the volume of the gaseous product correspondingly smaller and the balloon expands freely in the bottle without choking the overflow. If 1-gram samples are exploded, a somewhat larger bottle should be used. The initial temperature of the water in the calorimeter is slightly below room temperature and the final temperature is approximately equal to that of the room. The timeResults temperature readings ordinarily taken for coal calorimetry are recorded. As the primary object of the experiment is Table I gives the results of the determinations on benzoic to check the accuracy of the total carbon determination, the acid and Table I1 the data obtained from the coals studied. heating values are not given in the table. ‘However, the A sample computation for total carbon from the experimental bomb is always exploded and allowed to come to thermal data is given. The experiments show that the method deequilibrium in the calorimeter as if a heating value were scribed is accurate and rapid and does not require special actually determined. The bomb is then removed from the or expensive apparatus. calorimeter and connected to the rubber balloon by screm-ing T a b l e I-Total C a r b o n of Benzoic Acid the nipple C into the head of the bomb. The bottle K is THEORETICAL EXPERIMENTAL filled with water a t room temperature. Placing a rubber Per tent Per cent stopper in the bottle fills the overflow pipe L through the 68.6, 69.0, 68.9 Average 68.8 68.8 displacement of water from the neck of the bottle. The beaker M is placed in position. The manometer is read Table 11-Total C a r b o n of C o a l COALN o under atmospheric pressure. The stopcocks in the lines (B. OF &I.) KINDOF COAL B. O F >I. EXPERIMENT~L leading to the manometer and buret are then closed and the Per cent Per cent cock in the line leading to the balloon is opened. The gas A26839 Semianthracite 62 6, 62.5, 62 7, 63 0 Average 6 2 . 7 62 7 is allowed to pass slowly from the bomb by opening the A26566 Semibituminous 83.3, 82.9, 83 1, 8’’ 5 needle valve slightly. The d a t i o n of the balloon causes Average 83.1 83.2 the water to overflow into the beaker, M . When the flow A26840 Bituminous 73.5, 7 3 . 2 , 7 3 . 1 , 73.4 of water slackens, the needle valve is opened further and the Average 73.5 73.3 process is continued until the valve in the bomb is fully open. A26847 Bituminous 76.7, 7 6 . 1 . 7 5 . 9 , 7 5 . 9 Khen the flow of water stops, the system is allowed to come Average 76.1 76.15 to equilibrium. If there are no leaks in the line, the water A27336 Lignite 52.3, 5 2 . 0 , 5 2 . 5 , 5 2 . 1 will stop flowing from the overflow pipe, leaving the pipe Average 52.4 52.2 full of water as it was a t the beginning of the run. The usual time taken by the gas in expanding from the bomb Calculation of Total Carbon from Experimental Data is 7 to 8 minutes. As an example of the use of the experimental data in comWhen the pressure in the system is equalized, the stopputing total carbon, the calculation for the first run listed, cock in the manometer line is opened and the pressure on the manometer is read. This is above atmospheric pressure that of semianthracite coal (Sample A 26839), follows: 0.4770 gram Weight of coal sample as the balloon is always under a slight head of water. The 1651 cc. Volume of overflow water barometer is read and the manometer reading is added 296 cc. Volume of bomb and leads 1947 cc. Total volume of gaseous product to the barometric pressure to determine the absolute presBarometric pressure 737.6 mm. Hg Manometer reading 2 0 . 0 mm. H g sure. The amount of overflow water is weighed and its Absolute pressure 757.6 mm. H g temperature is recorded. To the volume of the overflow Temperature of overflow water 2 5 . 5 C. 3 1 . 4 per cent Average COz content of gaseous product is added the volume of the bomb and leads (296 cc.), which represents the total volume of the gaseous product under 273 12.005 757.6 0.314 1947 X F~ X 22400 X - X - X 100 = 62.6 per cent 298.5 0.477 the conditions of the experiment. The volume of the bomb Factor which occurs in all computations is and leads is determined by weighing the water and the merX 12.005 0.0001925 cury, respectively, required to fill them. 22400
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Gas Analysis The valve in the line leading to the 100-cc. gas buret is opened and gas is allowed to escape into the air through the three-way stopcock in the buret. After this has flushed out the line, a sample is drawn into the buret and measured over mercury. The carbon dioxide content is estimated by bubbling the sample into a caustic pipet. -4few drops of acidified water are always kept on top of the niercury in
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Allegheny Forest Experiment Station Philadelphia has been chosen as headquarters for the Allegheny Forest Experiment Station of the Forest Service, U. S. Department of Agriculture. Headquarters are being established in cooperation with the University of Pennsylvania. Field work will be conducted a t various centers in Pennsylvania, Maryland, New Jersey, and Delaware, in cosperation with a number of organizations and educational institutions, including state agricultural colleges.
