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INDUSTRIAL AND ENGINEERING CHEMISTRY
has, because of exposure to light, undergone photochemical change to such a n extent that its spectrum is nearly the same as for the light source alone. The fact that the spectrum for the nonrancid oil with a peroxide value of 116.4 corresponds almost identically with that for the fresh oil with a peroxide value of 3.8 further supports the view that oxidative rancidity is due apparently to photochemical action of light on a compound which probably exists simultaneously with or is produced from the compounds which give rise to the formation of peroxides. SUMMARY
1. The well-known color tests for rancidity and the peroxide test for the decomposition of an oil may not show conclusively that an oil is rancid. These tests are not reliable when applied to oils which have been properly protected from light. 2. Oils which have been protected from light with opaque black paper, or with green paper transmitting light delimited by 4900 to 5800 A,, remain free from rancidity even though they may have a peroxide value equal to or higher than an unprotected oil which has become rancid. 3. Similar results have been obtained when air has been bubbled through the oils a t the rate of 6 liters per hour. 4. Oils protected from light as described have not shown any organoleptic rancidity even after a period of 7 months, although they gave strong positive tests with both the Kreis and the von Fellenberg reagents, and also showed relatively high peroxide values.
5. A portion of a protected sample of oil still free from organoleptic rancidity but having a peroxide value higher than that of an unprotected rancid oil was exposed to diffused daylight. By the end of 52 days it had acquired a rancid odor and taste, while the original protected portion of the same sample remained free from rancidity. 6. I n the case of cottonseed oil and corn oil the results of these experiments support the view that oxidative rancidity may be due principally to photochemical action of light on a compound which probably exists simultaneously in the oil or is produced from compounds which give rise to the formabion of peroxides.
LITERATURE CITED (1) Coe, M.R.,and LeClerc, J. A,, Cereal Chem., 9,59 (1932). (2) Davidsohn, I., Chem.-Ztg., 54, 606 (1930). (3) Fellenberg, T.von, Mitt. Lebensm. Hyg., 15, 198 (1924). (4) Greenbank, G.R., and Holm, G . E., IND.ENO.CHEM.,25, 167 (1933). (5) Heffter, A,, Schweiz. Woch. Chem. u. Pharm., 42, 320 (1904). (6) Kilgore, L. B., Oil & Soap, 10,66 (1933). (7) King, .I.E., Koschen, H. L., and Irwin, W. H., ZMd., 10,105 (1933). (8) Kreis, H., Chem.-Ztg., 26, 1014 (1902). Proc. Rou. SOC.(London), 108B,175 (1931). (9) Lea, C.H., (10) Powick, W.C., J. Agr. Research, 26,323 (1923). (11) Royce, H. D.,IND.ENG.CHEM.,Anal. Ed., 5, 244 (1933). (12) Taffel, A.,and Revis, C., J. SOC.Chem. Ind.,50,87T (1931). J. Oil & Soap, 9,89 (1932). (13) Wheeler, D. H., RECEIVEDSeptember 26, 1933. Preaented before the Division of Agricultural and Food Chemistry a t the 86th Meeting of the American Chemical Society, Chicago, Ill., September 10 to 16, 1933. This paper is Contribution 197 of the Food Research Division, Bureau of Chemistry and Soila.
Heat Requirements for Fatty Acid Distillation VICTORMILLS AND R. C. DANIELS,The Procter & Gamble Company, Ivorydale, Ohio
W
ITH the old bottom-fired type of fatty acid still commonly used in the oil and fat industry until recently, there was little need for accurate data on heat requirement. With the advent of stills heated with steam or hot water, the need of dependable figures for latent heat of vaporization of fatty acids became more apparent. A number of writers have reported theoretical values for latent heat of pure fatty acids. All of these values are calculated directly or indirectly from vapor pressures by use of the Clausius-Clapeyron equation. The only experimental data of a technical nature seem to be those obtained in 1920 by Alsberg ( 1 ) . Alsberg obtained values of 118 and 130 B. t. u. per pound (65.5 and 72.2 calories per gram) on two different runs of cottonseed fatty acids. A careful perusal of his method, however, leaves considerable question as to the accuracy of the results. There are far too many assumptions and estimates involved. The writers recently had occasion to determine the steam usage in the heating coils of a Gensecke type of fatty acid still. Data were obtained from which a more dependable value for the latent heat of vaporization could be calculated. EQUIPMENT AND MODEOF OPERATION The still illustrated in Figure 1 is a standard make manufactured by the Lurgi Gesellschaft fur Warmetechnik and covered by Gensecke’s patents ( 2 ) . The heating element in the still, a, consists of two copper coils of approximately 270 square feet (25 square meters) mean sur-
face. Steam at about 450 pounds per square inch (32 kg. per sq. cm.) gage pressure is supplied by a motor-driven compressor, b. Vacuum is maintained at 7 to 10 mm. of mercury by use of steam ejectors, e. Approximately 10,000 pounds (4536 kg.) of crude fatty acid are charged to the still at the start of a run, and thereafter for about 20 hours the feed is continuous to maintain an even level. The crude stock going t o the still is preheated by passing through a heat exchanger, d , which also serves as a partial condenser for the fatty acid vapors. Most of the distillate is condensed in the jacketed coolers, e. A small amount of stock is condensed and baffled out in separator f and measured in receiver g. The bulk of the distillate is received in h and pumped out, under vacuum, t o storage.
HEAT MEASUREMENTS Measurement of the heat used for distillation was accomplished by weighing the steam condensate from the heating coils. I n order to avoid loss of water due to flashing highpressure condensate to atmospheric pressure, it was necessary to water-cool the pipe, k , leading from the trap to the weigh tank, m. The still was operated in the normal manner for 5 or 6 hours to establish uniform temperature conditions before measurements were started. Following this period, all temperature and pressure readings as well as measurements of condensed steam and condensed fatty acids were taken every 15 minutes during the 3 to 5 hour test period. This test covered the middle period of the complete 20-hour run. The stock level in the still was kept as constant as possible. Steam pressure variations were not greater than *7 pounds per square inch (0.5 kg. per sq. cm.). The temperature of the
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INDUSTRIAL AND ENGINEERING CHEMISTRY
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stock fed and the temperature in the still did not vary more This seems to indicate that palmitic and stearic acids have a than *So F. (2.8" C.). The distillate receiver was pumped lower latent heat of vaporization than oleic acid. The empty just before the first readings were taken and again recovered-grease fatty acid is a mixture of oleic, stearic, and just as the final reading was taken. The distilled fatty acids palmitic acids, whereas the red oil is predominantly oleic acid. were measured in another tank. It is likely that most of the difference is due to the palmitic A blank run was made to determine the atnount of heat acid in the grease and not to the stearic acid. Theoretical lost due to convection and radiation, The still was filled values of latent heat of vaporization of pure stearic and oleic with crude fatty acids acids calculated from to the n o r m a l level, vapor pressures by and the operating temS k i i r b l o m (4) a r e p e r a t u r e was mainpractically the same, tained with the highwhereas the value for pressure steam. Durpalmitic acid is lower ing this test the vacuum than either. equipment was shut off, and the still held at atcoKcLcsIo~ mospheric p r e s s u r e . In this way the normal The present results hrat losses from t h e on red oil are of the still occurred but no same order, it is true, distillation took place. as those on the sorneA s in the other runs, what s i m i l a r cottonthese conditions were seed f a t t y a c i d s obmaintained for 3 or 4 tained b y A l s b e r g . hours to establish equiThe a u t h o r s believe librium arid then a 4however that Alsberg's hour measurement of value is the result of steam condensate vias compensating e r r o r s . made and from t h e s e For example, he asmeasurements the sumed a specific heat of \:.I-..;i ' heat loss w a s c a l c u 0.46 as compared with lated. t h e 0.60 t o 0.66 r e FIGURE 1. GENSECKE TYPEOF FATTYACIDSTILL ported by Lederer, which was used here. This is a serious error, as almost one-fourth of the heat involved is sensible heat and not CALCULATION OF RESULTS latent heat of vaporization. In addition, Alsberg estiThe total heat supplied to the still during each test period mated his heat loss which is probably much too low, was calculated from the observed steam pressure, steam whereas the authors measured their loss. They found temperature, and weight of condensate by use of Keenan's nearly 25 per cent of the total heat supplied was lost by steam tables. No question of steam quality was involved, radiation and convection from the still pot. Further, exas in all cases the steam was superheated because of com- perience with the type of still used by Alsberg leads the pression from a much lower pressure. There is a possibility witers to believe that much of the water he measured was not of some error in measuring the amount of condensate. If the condensed steam but condenser leakage. Finally the figure trap on the condensate end of the heating coil should allow obtained here for latent heat of mixed fatty acids from some steam to pass, along with the condensate, the present set-up would have measured it as condensate and caused high results. No evidence of this was found. The radiation and TABLEI. DATAFOR CALCULATING LATENTHEAT OF FATTY ACIDS convection test showed a total heat loss from the still of 129,800 B. t. u. (32,550 calories) per hour under operating Date 6/17/32 6/28/32 6/24/32 6/18/32 Heat Red oil Recovered Recovered conditions, This would, of course, vary with weather condi- Stock distilled loss areaae grease tion in the still house, but all runs to which this loss is applied Length of run hr. 4 4 3 d condenbed, lb. 625 2,785 2,087 3,804 were made during a 12-day period in June, during which Steam Steam pressure, lb./sq. in. abs. 440 435 485 455 time the temperature was fairly uniform. Steam 54 1 511 540 541 .. . - temn ~ ~ - -. ~ , F. ~. By deducting the heat loss from the total heat supply in the Total heat of steam, B. t. U. /lb. 1,288 1,247 1,261 1,264 test runs, the total heat per pound of fatty acid can be deter- Heat of liquid, B.t . u./lb. 435 434 446 439 831 813 815 825 mined by direct ratio. Part of this heat is used in raising the Heat available, B. t. u./lb. Total available heat, B. t. u. 519,400 2,247,900 1,700,900 3,138,300 feed from 353' F. (178" C.) to the still temperature of 432" Heat loss, B.t. u. ~519,400~ 519,400 389,400 849,000 taken up by agitato 442" F. (222" to 228" C.). I n calculating this quantity Heat tion steam. B . t. u. 6,800 5,800 8,700 the recent specific heat data of Lederer (3) were used, and it Heat supplied to fatty 1,721,700 1,305,700 2,480,600 acid, B.t . u. was assumed that the amount of stock fed was just equal to Total distillate, lb. 7,635 13,500 10,390 355 Feed temp.. F. 352 353 the amount distilled. This may not be strictly true, owing Still temp., F. 448 432 442 434 to a small change in gravity of the stock in the still, but the Mean specific heat: From 19l0 F. to feed error is small. After deducting the heat loss, the preheat temp. ..... 0.60 0.80 0.82 From 191' F. to still required for raising the feed to distillation temperature, and temp. 0.64 0.65 0.60 the heat absorbed by the agitation steam from the total heat Heat required for preheat, B. t. u. .. . 589,000 487.000 808,000 supply, the latent heat of vaporization was found. This was Heat available for vaporization, B.t . u. . 1,132,700 818,700 1,674,800 108 B. t. u. per pound (60 calories per gram) for recovered- Latent heat of vaporization, B.t. u./lb. ,.... 109.0 107.2 124.0 grease fatty acids and 124 B. t. u. per pound (69.7 calories per gram) for red oil under actual distillation conditions. a 129,800B. t. u. per hour. ~~
O
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recovered grease is considerably lower than any others reported, in spite of the fact that any possible errors in these measurements were in the direction of high results. The latent heat of vaporization will, of course, vary with temperature. However, the temperature range over which it is practical to distill fatty acids and obtain good aualitv is rather limited, and it is felt that these results Will cover most technical needs. -
Vol. 26, No. 3
LITERATURE CITED (1) Alsberg, Julius, IND. E m . CHEM., 12, 490-3 (1920). (2) Gensecke, Wilhelm, U. S. Patent 1,713,431 (May 14, 1929): G e r m a n Patent 545,764 ( M a r c h 5 , 1932). (3) Lederer, E. L., Seifensieder-Ztg., 57, 329-31 (1930). (4) SkRrblom, K. E., Arch. W8meWirt.t 10, 174-6 (1929)-
1
September 28, 1933. Presented before the meeting of the American Oil Chemists’ Society, Chicago, Ill., October 12 t o 13, 1933. RECEIVED
Economics of Corrective Treatment for Cold Water Corrosion Application in Public Water Supplies EDWARD S. HOPKINS, JAMES W. ARMSTRONG, Bureau of Water Supply, Baltimore, Md.,
AND
JOHNR. BAYLIS,
Bureau of Engineering, Chicago, Ill.
T
HERE are now in service
If- mains are cleaned and the A re‘sum; is given of the principles underlying many m i l l i o n d o l l a r s water not corrected, corrosion water-pipe corrective treatment. Studies have worth of iron pipe, and activity is increased because of been made to show the economic relation of this it does not seem probable that the exposure of fresh iron surtreatment to the cost of steam generation and indusfaces, and i t will be only a few a metal less corrosive than iron trial water softening by the use of lime, caustic years before they again require will be used to any extent for cleaning, The many buildings large water pipes in the near soda, and soda ash. Comparison of these costs connected to water supplies are future. Consequently, if there with the tax rate has been made to indicate their equipped with expensive piping is to be a substantial reduction economic distribution between industrial acsystems of wrought iron, steel, in corrosion, it must be brought tivity and the municipality. The question of and galvanized iron, which are about by treatment of the water soap consumption and pipe renewal by consummore readily attacked by corroand not to the use of other masive water than cast iron. While terials or m o r e d u r a b l e pipe ers is discussed. Utilizing the data obtained i t is not possible to determine coverings. The mains are inat Baltimore, a n estimation of the cost and beneaccurately the cost of corrosion stalled, and, except in p l a c e s fits in a selected group of cities is given. The in such systems, it is very great where they are too small or have value of this protection to the pipe system is where no provision is made for corroded to the extent that they demonstrated. prevention. will no longer withstand the presAn e n g i n e e r i n g project is sure, it would not be economy often decided exclusively on the to redace them bv another materiai, regardless “of how cheap- the other metal might be. basis of cost. The one estimated to be the cheapest is conComplete elimination of corrosion is not to be brought about sidered the best. Such decisions omit the source of important by water treatment, but the value of the reduction where the factors such as a reasonable assurance of security, a satisfied water is fairly corrosive greatly exceeds the cost of treatment. public, freedom from complaints, and reduced maintenance It is probably safe to say that no neutral water would be costs. Should the “soft water” cities omit corrective treatsatisfactory to all users in any city, and, if i t should be treated ment, the familiar “red water trouble” would cause innumerto remove the constituent that is objectionable to some users, able complaints from householders regarding the staining of i t would become objectionable to others. I n considering clothes, bathroom fixtures, etc. I n addition to the direct the desirability of corrective treatment for water, the ques- replacement cost of pipe due to corrosion, a host of indirect tion should be determined on the basis of the most good to costs would accrue, occasioned by damage to plaster, furniture, and other goods. the majority of consumers. While it is not possible to place a material value upon an The formation and continued maintenance of a thin film of calcium carbonate on the inside of pipe as a protective intangible asset, freedom from complaints and ill feeling is coating for prevention of corrosion results in a number of worth much to any community or company and in itself benefits. Any attempt to evaluate the savings to a dis- justifies a large monetary outlay. Corrective treatment in the Baltimore supply was inaugutribution system resulting from the use of corrective treatment would be futile without exact cost data extending over rated in 1922 (2) and utilized a pH value of about 8.3, proa long period of time, because of the many factors not charge- ducing a slight “egg shell” precipitate of calcium carbonate able to corrosion. It would however be a serious matter to in the system as a protective coating on the interior pipe permit the corrosion and pitting of the many miles of mains surface. This hydrogen-ion concentration has been gradually in our cities, which, for Baltimore and vicinity, are valued reduced because of changing buffer characteristics of the water and regulation by the von Heyer “marble test” (4) a t over $30,000,000. The corrosion of mains causes the formation of incrustations to a pH value of 7.9. This alkalinity has maintained the and tubercles that greatly increase friction losses and reduce coating in good condition, It has been demonstrated (6) their carrying capacity. I n the case of small mains, they may that water, when initially treated with lime to the calcium become almost useless unless they are occasionally cleaned. carbonate equilibrium point, will hold its pH value after
