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INDUSTRIAL A N D ENGINEERING CHEMISTRY
were immediately transferred to a sample bottle free of carbon dioxide and sealed with paraffin until the resistance could be determined. Thus the temperature, pressure, and weight of carbon dioxide absorbed from each volume of air were calculated and the specific resistance determined, as shown in Table I. As examples of the accuracy of this method, two determinations of the carbon dioxide in 3 liters of air showed a difference of 0.05 mg. carbon dioxide and two determinations of the amount in 5 liters of air a difference of 0.11 mg. carbon dioxide. These differences are equivalent to a difference of 0.001 per cent by volume of carbon dioxide in the determinations, an order of accuracy equal to that obtainable with the Sonden air analysis apparatus, hitherto the most accurate devised. Using the cell with a cell constant of 85.204, a difference of 1 ohm in the observed resistance of the barium hydroxide solution, when calculated as specific resistance, was equal to 0.45 mg. carbon dioxide on the middle portion of the curve. Hence a milligram of carbon dioxide when absorbed would change the observed resistance 'of the solution 21.7 ohms. Since the change of resistance with concentration is not linear, an ohm will have a slightly
Vol. 16, No. 2
different equivalent value in milligrams of carbon dioxide on different portions of the curve. From the data so obtained, knowing the original concentration of the solution, the carbon dioxide gram equivalent of each 75-cc. portion, after the desired volume of air had been drawn through, was calculated. This was plotted against the specific resistance of the solution, which was calculated from the observed resistance so that one chart could be used to translate the data obtained when using different cells. Since the curve was to be used in work where the amount of carbon dioxide absorbed by 75 cc. of solution was to be determined, the concentration of the barium hydroxide solution was expressed in gram equivalents of carbon dioxide instead of equivalents of barium hydroxide, thus saving much labor in calculating results. The data were plotted on a scale such that the readings from the chart would be equivalent in accuracy to the resistance measurements. The range of the curve drawn through the points so plotted is limited to a chart of convenient size. A curve allowing for the absorption of 30 mg. of carbon dioxide was found to be the maximum that could be drawn with accuracy.
T h e Simultaneous Production of Pentosan Adhesives and Furfural from Corncobs and O a t Hulls' By Frederick B. LaForge BUREAUOF
CHEMISTRY, WASHINGTON,
D. C.
P
This article describes in detail the process worked out at the to about 2 Per cent without ENTOSAN adhesives Bureau of Chemisfry experimental plant for the production of penserious adverse effecton the are thick solutions of gums obtained by extosan adhesives and furfural from corncobs and oat hulls. The adhesive. With further yields of the two products from both of the raw materials were deheating the adhesive is r a p tracting various materials, termined, a+ well a s the steam consumption, time of ,fhe reaction idly decomposed, with the such as corncobs and oat hulls, with superheated period, and the proper proportion of water to raw material. formation of furfural. With water and concentrating Special reference is made to the use of pentosan adhesives for a reaction period of 2 hours a maximum yield of furthe extract. Previous rebriquetfing anthracite coal. fural is obtained. ports on this subject by the Bureau of Chemistry ADHESIVES FROM CORNCOBS have not described the process in detaiL2 Owing to the simDlicity - - of the method used and the easy availability of SEMICOMMERCIAL PLANT~-FO~ the digestion of the cobs the raw materials, these adhesives can be manufactured at a a cylindrical steel digester, heated by the injection of live comparatively low cost. In the process as originally planned several by-products, steam, was employed. The average charge consisted of about one of which is furfural, are obtained. The main object of 200 pounds of cobs and 850 pounds of water a t room temperaor 950 pounds when hot water was used. At the end the first experiments, however, was to obtain the maximum ture, of the heating period the pressure was relieved by blowing yield of adhesive material. Later developments having off through a condenser, after which the contents of the brought out the importance of furfural as a commercial article, it seemed desirable to attempt to increase the yield digester weye discharged by means of a valve into a drain box. The solid residue was then further freed from the of this product. absorbed by means of a hydraulic press. As a rule The former method, worked out by the Bureau of Chem- the press liquor cake was moistened with water and the pressing istry for the preparation of corncob adhesive, consists in heating corncobs with water in a pressure digester and con- operation was repeated. The discharge and wash liquors were evaporated to the proper consistency in an open steamcentrating the resulting solutions of gums to about 28" BB. jacketed kettle. (about 65 per cent solids). With a temperature of about Most of the furfural formed in this process was found in the 180" C. and a heating period of about 28 minutes, the yield condensed blow-off vapors, the furfural content of the disof adhesive is 40 to 45 per cent and the yield of furfural is tillates varying from 0.75 to 1-00 per cent. A large part of 1 to 1.5 per cent, based on the air-dry weight of the cobs. the total quantity produced, however, was found in the It was found that by prolonging the heating period for 7 discharge liquor in about 0.1 per cent concentration. This to 15 minutes the same yield of adhesive could be obtained fraction was determined by analysis, but was not generally and a t the same time the yield of furfural could be increased isolated. In commercial practice, the portion contained in 1 Received September 26, 1923. the discharge liquor would be recovered as a weak solution
2 THIS JOWRNAL, 10,025 (1918); U. S. Patent 1,285,247 (November 19, lgl8); Chem. Age (N.Y.),a8.332 (1920).
THISJOWRNAL, 15, 828 (1923).
INDUSTRIAL A N D ENGINEERING CHEMISTRY
February, 1924
and used in a subsequent charge. The quantity of furfural contained in the liquor remaining in the press cake was practically negligible. Data from several typical runs are given in the table. I n some cases the adhesive was evaporated to concentrations greater or less than 28" Be. Calculated to this figure, however, the yields varied from 41 to 44 per cent of the weight of the air-dry cobs. The quantity of steam consumed for any particular run may be calculated by subtracting the quantity of charge water from the quantity of discharge liquor plus the quantity of distillate obtained. C STB:AMCoivSuMPTIoN-The quantity of steam required for"Runs 1 to 4 was approximately 500 pounds. For Run 5, where hot water was used, the requirement was about 400 pounds. For the concentration of the discharge liquor to the proper consistency it would be necessary to evaporate about 1000 pounds of water. If the liquor were fed to a single-effect evaporator a t about 70" F., approximately 1,120,000 B. t. u. would be required. Since the average heat requirement for the digestion process is around 500,000 B. t. u., the total requirement would be about 1,700,000 B. t. u. for a charge of 200 pounds of cobs. This is assuming that there is no saving of heat in the process. TABLEI-ADHESIVE-FURFURALRUNS USINGCORNCOBS AND OAT HULLS DisCharge Heating charge DistilMaterial Water Period Liquor late Lbs. Run Lbs. Lbs. Min. Lbs.
1 2 3
4 5 6
7 a
200 200 196 203 200
Corncobs 1171 200 1200 175 1172 196 1155 195 1090 270 Oat Hulls 43 1093 230 52 1179 247 charge water 90' C.
Yield of 2 8 O Be. Fururalb Lbs. Percent Percent
44 43 45 42 41
1.50 1.16 1.35 1.81 2.04
200 930a 122 61 202 l O O O a 112 55 Temperature of Calculated from analysis by Ghloroglucinol method.
0.73 1.00
865 805
865 865 950a
28 28 32 35 43
Yield of Adhesive of
88 86 88 85 82
UssS OF THE ADHESIVE-It was expected that the corncob product would find its principal application as a substitute for silicate of soda in pasting fiber container board, and several mill runs were made to test its adaptability in this line. Facilities were not available for systematic experimentaution, however, and it was impossible to continue this line of investigation. Up to the time when the work was discontinued, it seemed probable that the application of cmncob adhesive in fiber container manufacture could be successfully worked out. Another promising field for this material seemed to be in its use as a substitute for cheaper grades of glue and dextrin in lines where appearance and strength were not of first importance. Thus it would probably be suitable as an adheshe for certain types of paper bags, cartons, etc. Corncob adhesive has also been used with some success as a wallsizing material. Still another use which suggests itself is that of a foundry core-binder. The most promising field for this adhesive, however, has been opened up recently in its application as a binder in the manufacture of anthracite coal briquets. I n the now rapidly expanding briquet industry, the culm and other fines resulting from the grading and screening of the more easily marketable sizes of anthracite coal are compressed with automatic machinery into briquets. I n this process various binders are used, pitch being the one most widely employed. After the briquets are molded they are usually subjected to heat treatment to remove the volatile constituents. The requirements for an ideal briquet are as follows: They must be waterproof and practically odorless and dustless; they must not contain large quantities of ash and sulfur; and they must not soften under heat. The binder must be cheap and
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available in large quantities. For briquets for domestic use none of the binders now employed are entirely satisfactory.4 Experiments made by a commercial concern in cooperation with the bureau indicate that a binder consisting largely of corncob adhesive will meet all the desired conditions if it can be produced cheaply enough to enable it to compete with those now in use. BY-PRODUCTS AND THEIRUSES-If adhesive alone were manufactured by the process worked out in this bureau, its cost would probably be somewhat too high to permit its use in this industry. It seems probable, however, that with a market for the by-product, furfural, produced in the manufacturing process, the cost of adhesive could be reduced to the point where its employment in this field could be considered. The cellulosic residue resulting from the digestion of cobs under the conditions described is usually delivered by the press with a moisture content of about 60 per cent, and about 125 pounds, calculated as dry material, are produced from 200 pounds of cobs. In the dry state it has a B. t. u. value of about 9000. Thus in commercial practice the residue, if used for fuel for the process, will furnish a very substantial part of the heat requirement. Several other uses for this material have been worked out. For instance, a satisfactory substitute for wood flour and a short fiber pulp can be prepared from it by extracting with weak caustic soda ~ o l u t i o n . ~Promising results have also been obtained by using the untreated residue for the manufacture of wood substitutes and of wall board.6 A small quantity of acetic acid is obtained in the digestion process, but it is doubtful whether it would pay to recover it. ADHESIVEFROM OAT HULLS Although the quantity of oat hulls produced in the United States is very much less than the quantity of corncobs, this material is an important source of adhesive and furfural. Large quantities of hulls are produced a t oatmeal factories, where their disposal is often a problem. The process employed for the treatment of oat hulls is practically identical with that used for corncobs. The yield of adhesive from oat hulls is greater than that obtained from corncobs. (Runs 6 and 7 of the table.) On the other hand, the yield of furfural is much smaller. The yield of adhesive given in the table is the quantity actually obtained on evaporatioh of the total extract recovered. In general, the pentosans from oat hulls seem to be more resistant to the action of superheated water than those resulting from the treatment of corncobs under the same conditions. The steam consumption is the same for the treatment of oat hulls as for corncobs. PROPERTIES AND USES O F OAT HULLADHESIVE-The concentrated extract obtained from the digestion of oat hulls resembles very closely the product obtained under the same conditions from corncobs. Oat hull adhesive, however, is somewhat lighter in color and is less hygroscopic than the product from corncobs. It should h d the same application as corncob adhesive and should offer some advantages over that material for fiber container pasting and similar uses. Oat hull adhesive seems to be the equivalent of corncob adhesive in coal briquet manufacture. 4 Briquetting Circular No. 1, Vulcan Iron Works, Wilkes-Barre, Pa., 1922, p. 2. 8 C h e n Age ( N . Y.), 28, 334 (1920). 8 Gruber and Bashioum, U. S. Patent 1,427,378 (August 29, 1922).
Robert A. Millikan, chairman of the executive board of the California Institute of Technology, who recently received the Nobel Prize in physics, has been awarded the Hughes Medal by the Royal Society of London in recognition of his work on the determination of physical constants.
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