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INDUSTRIAL AND ENGINEERING CHEMISTRY
and water in the smaller interstices of a loaded filter. But there are limits to the increased pressure head which can possibly be attained through these effects. I n the natural draft experiments, the temperature of the outlet air was found to be about halfway between that of the inlet air and of the water. If the outlet air temperature in a filter of smaller packing or in one containing biological flora were to reach that of the water, the pressure head for a given difference of water and outside air temperature would be doubled. As a maximum condition, the air throughout the height of the tower would be a t the temperature of the water, but even under these extreme conditions the pressure head has only been increased four times. It would take only a minor increase in the resistance of the filter due to the presence of biological flora to offset the higher pressure head gained by the better contact of the air and the filter. In other words, the forces causing a flow will increase but only slightly in comparison to the probable increase in resistance; as a result the actual velocities will always be lower than those observed in a clean filter. The resistance of a filter increases rapidly as the size of the particles is decreased. From the equations of Chilton and Colburn we can deduce that if the flow is viscous, a reduction of stone size from 1.75 to 0.25 inch will increase the resistance to the passage of air (1.75/0.25)2 or forty-nine times ( 2 ) . The highest possible increase in pressure due to temperature, on the other hand, is only fourfold. Although advantages are to be gained in using smaller particle sizes because of the increased surface, it is evident that definite precautions must be taken if adequate air flow is to result in a fine filter. Unless this is done, the gain in area is obtained at the expense of a decrease in air flow which may be the more important factor for the successful operation of a filter. Summary 1. The flow of air a t equilibrium and with continuous water distribution is a straight-line function of the difference between the temperature of the outside air and the temperature of the water.
VOL. 31, NO. 6
a. This relation is not appreciably affected by changes in water dosage rates between the limits of 1 to 20 m. g. a. d. b. The effect of humidification of the air is relatively slight except when the temperature of the air and water is approximately the same. It will tend to cause a slight upward draft under those conditions. 2. The dragging effect of the descending water is negligible. 3. During intermittent distribution pulsations in air, flow will take place as a result of the increased heat transfer during the dosing period. For a given amount of water being dosed on a filter, the data indicate that intermittent dosage will not bring as much air through the filter as continuous dosage. The maximum air flows obtained during the pulsations in intermittent dosage are less than the equilibrium flow set up by continuous distribution. 4. The filter medium, during continuous dosage a t high rates, comes to the temperature of the water and not to that of the air flowing in natural draft.
Literature Cited Baker, T., Chilton, T. H., and Vernon, H. C., Trans. A m . I n s t . Chem. Eng., 31, 296 (1935); Selheimer, C. W., Jr., Chem. & Met. Eng., 41,149 (1934); Baker, E . M., Ibid., 41,243 (1934). Chilton, T. H., and Colburn, A. F., IND. ENQ.CHEM.,23, 913 (1931). Emsweler, J. E.,and Randall, W. C., Univ. Mich., Dept. Eng. Research, Bull. 3 (1926). Furnas, C. E., U. S. Bur. Mines, Bull. 307 (1929). Halvorson. H. 0.. Water Works & Seweraae. 83. 307-13 (1936). Helvorson: Halvorson; H. O.,’Savage, G. M., and Piret, E. L., Sewage’Works __. J., 8,888-903 (1936). Hatfield, W. W . D., Ibid., 3, 175-87 (1931). Levine. Max. and Goresline, H. E., Iowa Ena. - Expt. . Sta.. Bull. 116, (1934). Metcalf, L., and Eddy, H. P., “American Sewerage Practice”, Vol. 111,New York, McGraw-Hill Book Go., 1935. Phelps, E . B., “Principles of Public Health Engineering”, New York, MacMillan Co., 1925. Ponninger, R., Gesundh.-Ing., 61,260-4 (1938). White, A. M., Trans. Am. I n s t . Chem. Engrs., 31, 391 (1935). Whitman and Keats, IND.ENG.CHEM.,14,186 (1922). ~
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Extraction of Saponin from Soap Nut 0
J. L. SARIN AND M. L. BERI Government Industrial Research Laboratory, P. 0. Shahdara Mills, Lahore, India
OAP nut (Figure 1) is the fruit of a handsome tree (Figure 2) found throughout India. Its two species are Sapindus mukorossi Gaerten, and Sapindus laurifolaus Vahl. The former is found throughout northern India and grows in the lower hills up to a n altitude of 4000 feet; the latter is found mostly in western, central, and southern
S
India and Ceylon (6). The trees are called locally by the vernacular name, Ritha. Soap nut has been employed as a detergent from very ancient times and in certain cases, especially in washing woolen fabrics and silk, and in cleaning jewelry, it is given preference over soap and other cleansing agents. Some work has been done in the past to extract saponin from the nut, but the methods cannot be employed on a commercial scale. Asahina and Shimidzu (1) tried to
prepare saponin from the alcoholic extract of soap nut pericarp by adding lead subacetate, removing the excess lead by hydrogen sulfide, acidifying a t 40’ C. with hydrochloric acid, and storing for several days; it is stated that saponin was then precipitated as white crystals. It was purified by being dissolved in alcohol and filtered through animal charcoal. As stated by the authors, saponin precipitated very slowly and with difficulty by this method. Besides, the method of purification is wasteful since animal charcoal retains much of the saponin. The authors did not state the percentage yield obtained. Basu ( 2 ) tried the different methods that are used for preparing saponin from important saponin-yielding plants but was unsuccessful in suggesting a practical method for extracting it from soap nut (3). I n the present investigation
JUNE. 1939
INDUSTRIAL AND ENGINEERING CHEMISTRY
A method has been worked ont for the extraction of saponin from soap nut, a raw material which is found abundantly in India.. This method is efficient and is practicable commercially. The yield of saponin was 17.21 per cent of the weight of the nut. This is the highest so far obtained from any saponin-yielding plant.
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It has no definite melting point hut starts to fuse at 95' C . Its specificrotation [el? in ethyl alcoholis -15.5. Withconcentrated sulfuric acid it is reddish yellow in color which changes to violet on standing. With sulfuric acid and acetic anhydride i t gives a deep red coloration. It is acidic in nature. When subjected to various methods of separation i t was found that no of the saponins from each other (4, neutral saponin could he separated. Elementary analysis showed the following results: carbon, 56.90 per cent; hydrogen, 8.26; oxygen 34.84. When hydrolyzed with 3 per cent sulfuric acid or, better still, with an alcoholic solution of hydrochloric acid, saponin gave crys-
an attempt has been made to develop an efficient method for the industrial extraction of saponin from soap nut. Extraction The soap nut selected was from the Sapindm mzkkorossi species. The nut consisted of 56.2 per cent pericarp and 43.8 per cent seed. Saponin is found in the pericarp. No attempt was made to determine the exact composition of the pericarp. Besides saponin, it is known to contain gnms, resins, etc. The following practical method for the extraction of saponin from map nut was worked out:
drawn off. Three extractions with this solvent-were sufficient to remove all the available saponin. The fractions of ethyl acetate extract were collected and subjected to distillation: ethvl acetate that Dassed over BS distillate was collected and ihe residue left WDS removed. The residue is a pale yelloiv, viscous, semiplastic substance. It dried under a desiccator to a hard mass at room temperature. When owdered, this mass gave saponin that WBS almost creamy in c&r. For purification a concentrated aqueous solution was treated with a saturated WBS
FIGWE 1. SOAPNUTS solution of barium hydroxide. The precipitated barium salt of saponin w s washed with barium hydroxide in which it is insoluble, suswnded in dilute ethyl alcohol. and decomposed by carbon
taliized sapogenin. The melting point of this sapogenin was 31&319' C. The other derivatives prepared were triacetyl and benzoyl. The mefting point of the crnde triacetyl derivative was 125-140" C., brit it could not be crystallized from any solvent. The benzoyl derivative was crystallized from water. The melting point of the crude product was 105-107c C. and that of the crystallized product was 113-114" C. The soap-mit saponin prepared could be utilized for the same purposes as saponin from other sources-e. g., as an emulsifying agent for vegetable and essential oils, as a foam stabilizer, and in the manufacture of soapless shampoos. Literature Cited (1) h a h i n a and Shimiduu, J . pharm. a i m . , [7] 14,188 (19lG). (2) Bee". K.. Indian Soap J . , 3, 9, 217 (1937).
(3) Kofler. Ludwig, "Die Sapmine", Berlin. Julius Springer. 1927. (4) Rosenthaier. L.. and Ghosh. S., "Chemical Investigstlon of Plants'', London, Bell & Sons, 1930. ( 5 ) Thorpe,"Dietionary of Applied Chemistry", London, Longmans. Green & Go., 1922 and 1934. (6) Watt, G., "Commeroiai Prod"& of India", P. 979, London. John Murrey, 1908.
