\ Digitized by the Internet Archive in 2016 https://archive.org/details/determinationoflOOIove . . . ... J TABLE OF CONTENTS Page I. INTRODUCTION 1 II. REVIEW OF LITERATURE 2 Previous Determination Methods. ....... ............... III. EXPERIMENTAL 5 Calorimetric Method. .... Vapor Pressure Method IV. TABULATED DATA Tabulated Results . 23 V. SUMMARY 24 VI. BIBLIOGRAPHY . 25 ]lj 1 THE DETERMINATION OF THE LATENT HEATS OF VAPORIZATION OF A FEW COMMERCIAL FATTY ACIDS. I. INTRODUCTION. Most of the fatty acids dealt with in this Investigation are used industrially in the manufacture of laundry soaps and washing powders. With the exception of the stearic and oleic acids the stock was obtained from low grade greases and foots. The crude vegetable oils consist principally of a mixture of the glycerides of palmitic, linoleic and oleic acids with varying amounts of the gly- cerides of arachidie and stearic acids. In addition to these gly- cerides there are also present the glycerides of all these acids in various stages of decomposition. Crude cottonseed oil for example is usually refined with caustic soda, whereby the partially and wholly decomposed, glycerides are separated out as a soap technically known as foots. This soap is only partially saponified and contains considerable quantities of neutral oil, together with most of the coloring, nitrogenous and mucilaginous matter that was present in the crude oil. The composi- tion of the foots will vary considerably, depending to a great ex- tent upon the source and upon the amount of neutral oil retained in refining. The foots may be "killed” and acidulated, i.e., the saponifica- tion may be completed by boiling with sufficient alkali and the re- sulting soap treated with mineral acid to liberate the fatty acids. • • r ; .■ . . . 2 Another method may be used in which the foots may be first treated with a mineral acid to free it from alkali, and then saponified by the Twitchell or other process to split off the remaining glyceryl radicals. In either case the resulting product is a mixture of free fatty acids, which must be steam distilled to remove the ob- jectionable coloring matter before they can be utilized in the manu- facture of soap. In the design, development, and calculation of costs of opera- tion of these distillation plants one of the important factors is the latent heat of vaporization of these fatty acids. II. REVIEW OP LITERATURE. A search of the literature gave a great deal of information con- cerning the methods for the determination of the latent heats of vaporization of simple substances that boiled, under atmospheric pres- sure without decomposition. The only article on the substances in question was written by Julius Alsberg 1 when engaged in development work along the lines of fatty acid distillation. He suggested that the heat of vaporization could be calculated from the vapor pressure curves of the fatty acids but preferred to determine a heat balance of a distillation plant which was available. Two distillations were run on entirely different lots of fatty acids and several months allowed to elapse between runs. The distillation plant was operated on fresh fatty acid stock, with no fatty acid or pitch left in the still from previous distillations. Before start- ing the tests distillation was carried on until conditions were con- i . o' • ' r . ' . t ■ 3 stant. A flying start and stop of the tests were used in a manner similar to that employed in making evaporative boiler tests* Thus without interruption or disturbance of the distillation, tests were started and stopped immediately after emptying the condenser drums* The plant consisted of a coal fired still, supplied with superheated steam through a reducing valve and a separately fired superheater* This still was fed continuously so that the volume in the still was constant, the level in the gauge glass being carefully watched. The combined fatty acid vapor and superheated steam passed over from the still to a water cooled tubular type condenser. Here the fatty acids were condensed and collected in a drum at the bottom of the condenser The distilled fatty acids were allowed to stand until laboratory tests showed that all the moisture had settled out. The steam passed over to a barometric condenser, and the fixed gases were taken care of by a vacuum pump. The barometric condenser discharged into a separatory catch basin, where the small quantity of entrained fatty acid was recovered by skimming. The cooling water w as carefully weighed, allowance being made for surface evaporation from the top of the open condenser and scale tanks. This allowance was based on actual loss in evaporation of an open vessel immersed in the top of the condenser. The quantity of steam was determined by a specially calibrated Gebhardt steam flow meter located between the reducing valve and the superheater. From the tabulated data Alsberg struck a heat balance. In this 4 balance it was assumed that the steam as measured was dry and satu- rated. An error of perhaps one -half of one per cent enters here. It was further assumed that there was practically no condensation in the vapor pipe connecting the still with the condenser. Total heat above 32°F in the fatty = acid distilled. + + + Heat Balance (Heat taken up by) (condensing water) (Heat lost by ra-) (diation from con) (denser shell ) (Total heat above) ( 32°F of steam ) (leaving conden- ) + ( ser ) (Heat to raise ) (stock ig dnum ) (from 32 F to ) + (drum temperature) (Heat lost by evapo-) + (ration of conden- ) (sing water ) Total heat above 32° B' of steam entering condenser o (Heat above 32 F in ) (water carried over ) (with stock into ) (settling tank ) (Heat to raise stock) (from cajch basin ) (from 32 F to con- ) (denser temperature ) Alsberg then gives the following values for cottonseed oil fatty acids . 130.5 B.t .u./ lb at 24.51 inch vacuum 118.0 B.t.u./ lt) at 25.14 inch vacuum Alsberg accounts for the discrepancy by the difference in the stock used for the two determinations, and by the fact that the tests were made at different pressures and temperatures. Alsberg admits a discrepancy of 9 per cent whereas the actual discrepancy is nearer 11 per cent as calculated from his figures. The actual pressures within the apparatus in each case were 4.45 \ ; • ; • f ' ; ■ . i • • ■ ■ • i 5 inches and 4.59 inches of mercury. This difference is too small to account for an 11 per cent difference in results. III. EXPERIMENTAL. It was decided to make calorimetric de terminations on several commercial samples and later to attempt to check these values from the vapor pressure curves of the fatty acids by means of the Clausius-Clapeyron equation. One of the most serious causes of error in all calorimetric work is the more or less uncertain correction for cooling# This was obviated by the use of a modified form of a Parr Adiabatic Calorimeter. The still used in conjunction with the adiabatic calorimeter was similar to a modified form of Kahlenberg's apparatus that was used by T. W. Richards and J. H. Mathews 2 in their redeterraination of the heat of vaporization of water. (Figure I) The boiling liquid was surrounded by a vacuum jacket whose walls were about one centimeter from the walls of the boiling compartment save at the bottom where the space was five millimeters across. In addition to a hood covering the upper end of the vapor delivery tube, the tube was also provided with another trap to catch and re- tain any liquid that might in any way gain access thereto. This distance between it and the condenser might be reduced to a minimum, yet it was surrounded by the boiling liquid in order to prevent con- densation v/ithin it. The heating coil was placed so low as to make 6 sure that the liquid surrounding the trap was at the boiling point. The interior of the vacuum jacket was brightly silvered to a height of 4 or 5 centimeters, the silvering being on both walls, so that the heat passing from the boiling liquid to the calorimeter water by radiation had to pass through two brightly silvered surfaces and a vacuum space. The conduction of heat to the calorimeter through the glass itself cannot be prevented, but was made small by having the glass as light as was consistent with the strength demanded. The apparatus that was tried for the distillation of the fatty acids was practically a duplication of Richards apparatus with the following two exceptions. A jacket filled with cottonseed oil was placed between the Dewar jacket and the boiling compartment. The heating element was placed in this oil bath because it was thought that local heating of the fatty acids in immediate contact with the wire would cause considerable decomposition. The objection to this apparatus was that in spite of all pre- cautions bumping was so violent that some liquid was unquestionably carried over. The acids worked with were mixtures of constituents o whose boiling points varied over 30 C. The lighter fractions would distill early. The heavier fractions that were spattered on the hot walls of the oil bath vaporized and later condensed in the de- livery tube. This made a calorimetric determination out of the question for the length of time available. The Clausius-Clapeyron relation may be written in various forms the more common being 6a A B C c' D. E E G. LEGE ED S/ bye reef surface Si /(erect sucfuce Vapor trap Vapor trap Det/yerp tube E/ectr/ca/Zp ZeatecZ o/Z pacZet Water }/ne DeZ/rerp tube to cor? (Leaser tin t/re apparatus mac/e of" Eprep Er/ass. T 1 P J dP dT P (v" - v* ) T dp J P dT absolute temperature at boiling point, latent heat of vaporization per unit weight, absolute pressure. Joules mechanical equivalent of heat, specific volume of vapor, specific volume of liquid. the temperature rate of change of pressure or the slope of the vapor pressure curve. For all practical purposes v' is so small as compared to v" that it may be neglected without a serious error. In this form it is necessary to determine the specific volume of the vapor at the pressure in question. At this time W. K. Lewis and H. G. Weber 3 published a method of estimating the vapor pressure of a liquid at any temperature, one point on whose vapor pressure curve is known, and a method of getting heats of vaporization from vapor pressure data by a consideration of the Clausius equation. At reduced pressures vapors may be considered to obey the gas laws and the Clausius equation applied to vaporization of a liquid may be written: (1) dP PdT L R RT 2 in which molal heat of vaporization the gas constant 8 The vapor pressure curves of all liquids possess great curva- ture; consequently where only a few points on a curve are known it is very difficult to interpolate either mathematically or graphically with accuracy. On the other hand the vapor pressure curves of all liquids are more or less parallel and it is a fact that if instead of plotting the vapor pressure of a liquid at a given temperature one will plot against the temperature, the temperature at which some liquid of reference, e.g., water, exerts the same pressure, one will obtain a curve which is very flat, often sufficiently so to be con- sidered a straight line over a wide range of temperature. This fact was first developed by J. Johnston". The Clapeyron relation as applied to the liquid of reference is: ( 2 ) dPw = Lw PwdTw RTws The method of plotting Tv/ against T, given above is equivalent to placing P = Pw, when also dP = dPw. Dividing equation (1) by equation (2) we obtain (3) dTw = _L (Tw) 2 dT Lw (T ) The left hand hand side of equation (3) is the slope of the Tw - T plot mentioned above. Since the curve is substantially a straight line the slope may be written A Tw, i.e. finite temper a- AT ture differences may be employed in calculation. 9 Water was used as the reference substance because steam tables were available. Two boiling points at two different pressures were obtained and the values substituted, in the above equation. The apparatus used to determine the vapor pressure of the fatty acids was set up as illustrated in Figure 2. A charge of the sample was placed in the still A and the cottonseed oil bath heated by means of a Bunsen burner. The pressure regulator F was partially filled with mercury, the entire apparatus closed and the vacuum pump started. The weight of mercury in the tube F kept the valves G closed until the difference in pressure between that of the atmos- phere and that within the apparatus was sufficient to lift the valve. Adjustments of pressure were made by varying the amount of mercury in the regulator. The fatty acid were raised to the boiling point and refluxed until the thermometer read.ings were fairly constant. A series of ten readings of temperature and pressure were then re- corded at one minute intervals. The average of these was assumed to be the boiling point of the sample. The pressure regulator was suf- ficiently sensitive to maintain the pressure within one millimeter providing all joints were tight. ' • ' • * ' • « - . . . • * - • • • « 10 O/ayrammat/c sketch of apparatus s/sec/ /n tAe determination of the vapor / ressare of fatty acids. A ~ Pyrex. ct/st/i/iny ftask, 3~ ftermo meter y rad a a ted to read to tenths of a deyree , C. ~ Pef/u X condenser . Dr Merco/ry manometer E. ~~ Three t/ter f/ask l/sed to ass/st /n yoressane reya/at/on. p— AAerco/ny f '//ed pressare reyutator. Dr Erroanct ytass poppet va/ve. 11 Sample Calculations Since only temperature differences are required it is not neces- sary to make temperature corrections for stem exposures. a Tw _ L x (Tw) 3 AT Lw rT T Baker’s Purified Stearic Acid T P Tw 267.7 248,3 19.4 83 47 . 9 38 33.2 14.7 ATw = 14.7 AT' 19.4 0.758 = slope of Tw - T curve Tw) 3 (47.9 + 273. I) 3 - 1 (267.7 + 273 .lT 2.84 Lw 1 77.6 x lw x 18 where 1 = heat of vaporization of water per gram 0.758 x 569.7 x 18 x 2.84 284.4 = 139.6 B.t.u. per 5 = 77,6 calories per gram pound • TABLE I 12 Baker’s Stearic Acid 1st Determination 2nd Determination v © © £ xj Jh *a O CCS Cl O cJ £ a £ i •H © a. .a i T-I © cd &0 •H ■d a! bO •H! »d > *H iH £ © cd r-‘ & © cd -P rH p 1m +3 r- 3 £ *rH i — \ © cd rH p p -P rH P P ft p •H B bQ ft P •H b 5b O j © © p © •H }>s © © B © P ft o B © P Ph O ■P © © B a -p © © B a Cd P P O © 09 cd P P o © 09 P h0 B P •P © P bO B P -P © © © w © © © © 09 © © ftd w a B & Ph d 09 a a p © © w a _ © © bO © p p ft -p © © p p ft ■P © EH iH PH O co d Eh *H pH o co d 241.9 30 64 242.0 28 48 242.1 242.4 242.4 242.5 242.5 242.8 243.1 65 242.5 48 242.5 242.3 242 . 9 243.0 242.6 242.5 242.4 242.8 242.5 68 242.3 48 kv .242 • 5 30 66 Av. 242.4 28 48 266.1 80 63 271.5 95 65 266.3 272.5 96 266.6 272.0 95 266.5 272.6 96 266.8 271.6 95 266.9 81 271.8 95 266.8 81 65 272.1 95 65 266.5 80 272.3 95 266.6 271.8 95 266.3 272.1 95 Av.266.5 80 64 Av. 272.0 95 65 Sample of Commercial Stearic Acid obtained from Armour 1 s Soap and Glue Works of Chicago, Illinois • \ < I vS \ TABLE III 14 Commercial Oleic Acid 1st Determination 2nd Determination w ra Ph Ph 0 0 0 Ph t d +3 Ph »d ■P c a 0 £ O cti 0 £ ft ph g •H 0 ft Ph s •H 0 ai bQ •H •d d bQ ♦H •d > .H rH 0 CCS > *H • — i 0 d +3 r-i Pi £ rH £ Ph CM £ •H £ bQ Cm £ •H 3 bO O © g +3 *H O 0 g 43 »H o d -P O aJ 43 0 £ P-1 £ 0 £ Ph £ Ph w •H !>s 0 0 Ph CO •fH 0 0 p 0 Ph ft o £ 0 Ph ft o -p 0 0 £ £ -P 0 0 £ B 0) Ph P-i o 0 w aS Ph Ph O 0 w Ph bQ £ £ -p 0 Ph bO P Ph -p 0 0 0 GO 0 0 © 0 OQ 0 _ 0 ft^ w g g pH ftt) W £ B Ph £ 0 0 bQ £ _ 0 0 bO 0 £ £ ft i — i 0 cd > ft ft 0 cd ft i-) G G JO ft G G ft p ft p b0 fti P ft p qO o 0 & ft ft O 0 G ft ft o cd ft O cd ft 0 P G P 0 G G P G co •H i>5 0 0 G “ ft E-s 0 0 P 0 G ft O P 0 G a o ft 0 0 P s ft 0 0 p a ! G o 0 K Cd G G o © CO G HQ P G -P 0 G b3 P G ft 0 0 0 CO 0 0 0 0 co 0 0 ftrd ra S S G ftdi W S a g S 0 0 tiO rj & 0 © oO 0 P G ft ft 0 0 P G ft ft © EH ft ft o CO rp E-t ft ft o co 'd 252.8 57 60 248.8 48 41 252.7 249.0 252.8 249.1 253.0 248.9 253.1 249.0 39 252.8 249.2 252.7 248.9 252.7 249.0 252.6 65 248.8 42 Av. 252.8 57 63 Av. 249.0 48 41 268.6 106 60 268.7 107 34 268.6 268.9 268.7 269.0 268.7 60 269.0 37 268.8 269.1 268.7 269.0 268.7 61 269.1 37 268.7 268.9 268.8 268.8 268.7 61 269.0 35 Av. 268.7 106 61 Av. 269.0 107 36 Sample of U. S. P. Oleic Acid obtained from Baker Chemical Company TABLE V 16 Double Distilled Garbage Grease Fatty Acids . 1st Determination 2nd Determination CO CO P p 0 © © 0 p •£> p P p O crf © p O crf © p Ph P g •H 0 Ph P a ♦H © Crf W •H •0 crf tafl ti r-i 0 Crf *H r—i 0 crf P rH P P P rH P P «H P •H p t»D U P •H p bQ O 0 a P *H O 0 a p »H O Crf P O Crf P 5 0 0 p CO «H >5 0 0 P CD P Ph O p 0 p Ph O P 0 © P s p 0 0 p S Crf P P ° 0 M crf p P O 0 CO P bO P P P 0 P bO P P P 0 0 © W 0 0 © 0 C0 0 0 Pi*© co S E P P. 1 © co a s h a 0 © QO S ^ 0 0 bO © c P Ch P © 0 P p

*H rH © erf JO 1 2 G G ft G •H p bO O © a P p 0 erf P © G ^ G G G © •H ^5 © © 3 © G ft 0 P © © 3 a erf G G O © w G SO 3 G p © © © © © ^ © ftt^ © a fa G a © © bO © G G ft P © EH iH ft 0 CO np 249.0 50 65 248.6 248.5 248.9 249.0 248.7 249.0 248.8 248.7 248.8 60 •. 248.8 50 63 266‘.4 98 74 266.2 97 266.1 266.2 265.8 266.0 77 266.3 266.5 266.4 266.1 75 . 266.2 97 ~76~ Brown Grease Fatty Acids obtained from Armour’s Soap and Glue Works of Chicago, Illinois ) 1 ~f ) * TABLE VII 18 Double Distilled Coconut Oil Fatty Acids 1st Determination 2nd Determination Temperature of vapor in degrees centigrade Pressure in millimeters of mercury Stem temperature in degrees centigrade Temperature of vapor in degrees centigrade Pressxire in millimeters of mercury Stem temperature in degrees centigrade 212.0 64 63 208.5 62 45 212.7 66 209.0 215.1 67 208.9 213.2 67 64 209.3 43 213.0 209.1 213.4 209.0 213.3 66 209.5 40 213.0 209.3 213.0 209.0 213.0 66 208.5 40 Av. 213.0 67 65 Av. 209.0 62 42 223.6 110 64 225.0 111 74 223.8 110 224.8 111 224.0 110 224.3 110 224.1 61 224.0 73 224.0 224.5 224.2 224.4 224.3 61 224.6 72 224.0 224.3 223.9 224.4 224.0 61 224.7 73 Av. 224.0 110 62 Av. 224.5 110 73 Sample of Double Distilled Coconut Oil Fatty Acids obtained from Armour* i 3 Soap and Glue works of Chicago, Illinois. J ' . ■ TABLE VIII 19 Double Distilled Neats Foot Oil Fatty Acids 1st Determination 2nd Determination © 03 Sh © Sh •£ ft O erf © 2 ft Sh a ft © erf to ♦h 'd t> «H i — i © erf ft ft g a ft £ •H 2 to o © a ft ft o erf ft © £ Sh £ Sh 03 ft >s © © £ © G 2. o ft © © 2 a erf Sh Sh O ft ft ft £ O © O 5 © 3 CO © CO g © Sh ft ft O £ ft © •G © erf a G qO ft ft erf ft Sh £ © © ft O a © CO ft © © £ h © to ft © m *d 242.5 38 49 242.7 38 243.1 39 243.1 39 51 243.1 39 242.7 38 243.2 39 50 242.8 39 243.5 41 243.5 41 51 . 243.0 39 50 262.8 87 59 263.0 88 263.3 89 263.0 88 262.8 87 60 263.2 88 263.2 88 263.0 263.0 263 • 0 61 . 263.0 88 60 Sample of Double Distilled Neats Foot Oil Fatty Acids obtained from Armour’s Soap and Glue Works of Chicago, Illinois TABLE IX 20 Twitchellized Soya Bean Oil Fatty Acids 1st Determination 2nd Determination Temperature of vapor in degrees centigrade Pressure in millimeters of mercury Stem temperature in degrees centigrade Temperature of vapor in degrees centigrade Pressure in millimeters of mercury Stem temperature in degrees centigrade 248.8 35 62 252.2 43 50 249.0 35 252.3 249.4 36 252.4 250.3 37 64 252.7 250.8 37 253.0 249.5 36 252.6 249.5 36 65 252.4 249.2 36 252.3 249.2 36 252.8 249.0 35 63 252.5 55 Av. 249.5 36 64 Av. 252.5 53 270.0 82 75 271.0 88 51 270.2 271.2 88 269.8 271.0 88 269.9 271.8 89 270.0 271.5 89 270.4 271.5 89 270.2 75 272.0 89 269.8 272.2 90 270.0 271.7 90 270.0 271.5 89 60 Av. 270.0 82 75 Av. 271.5 89 59 Sample of Twitchellized Soya Bean Oil Patty Acids obtained from Armour 's Soap and Glue Works of Chicago, Illinois TABLE X 21 Double Distilled Corn Oil Fatty Acids 1st Determination 2nd Determination Temperature of vapor in degrees centigrade 03 ^ o Stem temperature in degrees centigrade Temperature of vapor in degrees centigrade to u p •H r—l •H 3 £ •r-! >s *H rH cd > ft iH 0 cd ft i — i P P P rH P P ft £ •H 2 bO ft Si •H 3 bO O s CD CD P CO ft >5 0 00 P 0 P ft o P CD p ft o ft 0 CD £ a P CD 00 2 a 05 P P O 00 CO P P P o 0 co P bQ d p P 0 P bO 3 p p 0 0