July 15, 1934
INDUSTRIAL AND ENGINEERING CHEMISTRY
cate blanks with a 0.166 N acid show that a combination of the factors involved results in an average error of 0.3 mg. of carbon.
It is not necessary to have the approximately 0.5 N sodium hydroxide free from carbonate. Neither it nor the strong acid needs to be standardized. The saving in time is considerable and is enhanced if large quantities are prepared a t one time, as is desirable for routine work. A considerable saving of the standard acid is accomplished in the use of the single titration if the proper amount of strong acid is used for establishment of the blank. TABLEI. COMPARISON OF DRYCOMBUSTION AND WET OXIDATION
SUBSTANCE ANALYZED
METHODS
TOTALCARBON wet Oxidation Drycombustion % %
Soluble etarch 36.86 36.89 Potassium acid phthalate 44.04 44.45 Soil 1885 2.01 1.98 Soil 199" 2.04 2.05 Soil 4 1.00 0.99 Soil 7B 0.39 0.40 so11 4 c 0.68 0.58 Samples furnished by E. C. Shorey, Bureau of Chemistry and Soils, Washington.
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ANALYTICAL DATA Although the apparatuswas developed for the determination Of carbon in soils, it has been used to determine itS adaptability to a limited number of other materials. The
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apparatus needs modification for use with Some organic materials, as the reaction with the solution is very vigorous. As presented i t is best adapted to materials of medium to low carbon content* A Of Obtained by the dry combustion and wet oxidation methods is made I* in
LITERATURE CITED (1) Am% J. W., and Gaither, E. W., J. IND.ENQ. CHEM.,6 , 562 (1914). (2) Brown, B. E., Ibid., 19, 629 (1927). (3) Cameron, F. X., and Breazeale, J. F., J . Am. Chem. Soc., 26,29 (1904). (4) Hardy, F., J . Agr. Sci., 19,727 (1929). ( 5 ) Heck, A. F., Soil Sci., 28, 225 (1929). (6) Partridge, E. P., and Sohroeder, W. C., IND.ENQ. CHEM., Anal. Ed., 4, 271 (1932). (7) Robinson, G. W., et al., J . Agr. Sci., 19, 315 (1929). ENO.CHEM.,8, 1126 (1916). (8) Sohollenberger, C. J., 5. IND. (9) Schroeder, W.C., IND.ENG.CHEM.,Anal. Ed., 5, 389 (1933). (IO) Truog, E., J. IND. ENO.CHEM.,7, 1045 (1915). (11) White, 3. W., and Holben, F. J., Ibid., 17, 83 (1928). REcnIvm April 2, 1934. Presented before the Division of Agricultural and Food Chemistry at the 87th Meeting of the American Chemical Society, St. Petersbura. Fla.. March 25 to 30. 1934. Contribution from the laboratory of the Soil Fertility Division, Sandhill Experiment Station, U. S. Department of Agriculture and S. C.Experiment Station codperating. W. M. Quattlebaum, Jr., was associated with the author when the method was developed and credit is due him for much valuable assistance.
Constant-Head Gas Scrubber for Small Pressure Drops ALLENS. SNITH,Cryogenic Laboratory, U. S. Bureau of Mines, Amarillo, Texas
I
N T H E analysis of combustible gases by thermal conductivity, it is often necessary to eliminate one or more constituents by combustion and subsequent removal of the combustion products. I n such a process, particularly if oxygen or air is added for combustion, constant gas flows are essential. To obtain constant rates of flow, the pressure drop through the apparatus must remain unchanged. It is, furthermore, desirable to have as small a gas volume and pressure drop throughout the apparatus as is consistent with satisfactory operation. Of the combustion products, water offers no difficulties in removal. Furnas (I) has described a gas bubbler which is suitable for carbon dioxide removal by caustic solutions but which has the disadvantage of the possibility of a change in liquid head due to d i l u t i o n from absorption of moisture and from the carbon dioxide r e a c t i o n . During the construction of an apparatus for continuous analysis of helium (5), now in use in the Amarillo CM H e l i u m P l a n t of the U. S. FIGURE 1 B u r e a u of Mines, the need arose for a c a r b o n dioxide scrubber to fulfill the requirements outlined above. Such a scrubber has been designed which gives entire satisfaction, and which may find application in similar work. The gas scrubber, constructed on the principle of the
Milligan (2) absorber, is shown in Figure 1. It is made from a 500-cc. round-bottomed flask by sealing a manometer tube m to the neck of the flask about 1 em. below the stopper bottom. The absorbing solution is filled and drained conveniently through tubes f and d, sealed to the side and bottom of the flask. The gas enters through capillary tube c and is scrubbed free from carbon dioxide as it passes upward throughsthe liquid around the spiral which fits snugly in tube t . The spiral is formed from a 2-mm. glass rod wound around the gas inlet tube and fused to it, a t each end and in the middle, to secure the rod in place. The gas, as it breaks into bubbles at the entrance to the spiral, creates a lifting effect which causes fresh solution from the bottom of the flask to rise in tube t and pass around the spiral so that a fresh absorption surface is continually presented to the gas. Increase in pressure head, due to dilution, is eliminated by overflow from manometer tube m, by which a constant level is maintained in the flask. The residual gas leaves the flask through capillary tube e. The scrubbing surface of the spiral is equivalent to a column of solution approximately 20 em. long. Complete removal of carbon dioxide has been accomplished, using 20 per cent sodium hydroxide solution, from 1.5 liters per hour of gas containing 70 per cent carbon dioxide, for 24- to 30-hour periods. The rate of gas flow is limited by the size of the spiral. The dimensions, as given, provide for a maximum flow of about 3 liters per hour.
LITERATURE CITED (1) Furnas, C. C., IND. ENQ.CHEM.,Anal. Ed., 5, 250 (1933). (2) Milligan, L. H., IND. ENQ.CHEM.,16, 889 (1924). (3) Smith, A. S., article in preparation. RECEIVEDJanuary 22, 1934. Published by permission of the Director, U. S. Bureau of Mines. (Not subject to copyright.)
