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Equilibrium studies on pure compounds : normal propyl alcohol Croil, Thomas Arnold 1959

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EQUILIBRIUM STUDIES ON PURE COMPOUNDS: NORMAL PROPYL ALCOHOL  by  THOMAS ARNOLD CROIL Diploma i n Chemical Engineering, Royal M i l i t a r y College, 1956 B.A.Sc, University of B r i t i s h Columbia, 1957.  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENT FOR THE DEGREE OF MASTER OF APPLIED SCIENCE i n the Department of CHEMICAL ENGINEERING We accept t h i s thesis as conforming to the required standard  THE UNIVERSITY OF BRITISH COLUMBIA APRIL 1959.  ABSTRACT Three grades of normal propyl alcohol have been purified by several methods.  The degree of purity has been established by  refractometric, ebulliometric, and viscometric measurements, the best product being 99.65 volume % pure as measured by gas chromatographic analysis. A vapor-liquid equilibrium apparatus has been modified and reconstructed i n preparation for vapor pressure measurements of npropanol up to the c r i t i c a l point. Several semi-empirical equations have been f i t t e d to Young's vapor pressure data for n-propanol with a view to t h e i r u t i l i z a t i o n i n presenting data on an homologous series or on a generalized basis. In a l l cases the per cent difference between calculated and experimental values was less than 2.0$ with a maximum average difference of 0.9$.  In p r e s e n t i n g  this thesis i n partial fulfilment of  the r e q u i r e m e n t s f o r an advanced degree a t t h e U n i v e r s i t y o f B r i t i s h Columbia, I agree t h a t t h e L i b r a r y s h a l l make i t freely  a v a i l a b l e f o r r e f e r e n c e and s t u d y .  agree t h a t p e r m i s s i o n f o r e x t e n s i v e  I further  copying of t h i s  thesis  f o r s c h o l a r l y purposes may be g r a n t e d by t h e Head o f my Department o r by h i s r e p r e s e n t a t i v e s .  I t i s understood  that copying or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t be a l l o w e d w i t h o u t my w r i t t e n permission..  Department o f  Chemical Engineering  The U n i v e r s i t y o f B r i t i s h Columbia, Vancouver Canada. Date  F e b r u a r y  '  1 9 5 9  -  i TABLE OF CONTENTS Abstract L i s t of Tables  i i  L i s t of Figures  i i  Nomenclature  i i  INTRODUCTION  1.  LITERATURE REVIEW 1.  Purification  2.  2. 3.  Apparatus Presentation of Vapor Pressure Data  4> 6.  PURIFICATION 1. Materials 2. Apparatus  8. 10.  3. Procedure 4. Purity Determinations a) Methods b) Results 5. Discussion a) Apparatus and Methods  12.  b) P u r i f i c a t i o n  14. 17. 24. 26.  VAPOR PRESSURE APPARATUS  30.  VAPOR PRESSURE CORRELATIONS 1. Methods 2. Discussion  33. 36.  LITERATURE CITED  38.  ii LIST OF TABLES 1. 2. 3 a,b. 4. 5.  Physical Properties of Normal Propanol I n i t i a l Investigations Physical Data of Normal Propyl Alcohol from the Literature Constants f o r Vapor Pressure Correlations  34  Correlation Deviations  35  LIST OF FIGURES I  Following  Chromatograms of Normal Propanol from a Flexol 20  P l a s t i c i z e r Column II III IV  Page 19 20 22  Effect of Suspected Impurities on Chromatogram Peaks  27  Schematic Representation of the Vapor Pressure Apparatus  30  Correlation Deviations  35  NOMENCLATURE  1.  a, b, c,o4, j j  2.  A, B, C, D  constants from the Biot Formula. =  T  constants f o r the Riedel, Frost and Antoine Equations =• temperature, °R. (unless otherwise noted)  Tg  =  reduced temperature (T/T^)  P  =  vapor pressure, p.s.i.a. (unless otherwise noted)  P^  reduced pressure  JJ =  v i s c o s i t y , centipoise.  (P/PQ)  ACKNOWLEDGEMENT The author wishes to express his appreciation f o r the financial assistance of the Dr. F. J . Nicholson Scholarship Fund and the National Research Council during the course of t h i s research.  1. INTRODUCTION Chemical engineering design requires an adequate knowledge of the physical properties of materials. While accurate experimental data i s desirable, i t s measurement i s often d i f f i c u l t and time consuming. For this reason chemical engineering l i t e r a t u r e has recently emphasised methods of correlating and predicting such data, especially i n the f i e l d of thermodynamic properties ( l ) . Because the thermodynamic properties of the normal alcohols, and their solutions, have been the subject of considerable interest i n these laboratories (2,3), t h i s investigation of the vapor pressure of normal propanol was undertaken. Although Speers (4) has examined the thermodynamic network for n-propanol, his calculations were based primarily on the long Standing data of Young (5). While these data are considered most reliable by a l l c r i t i c a l compilers, no measurements above the normal boiling point have been made since that time ' ( f i f t y years ago). In view of the increasing importance of highly accurate c r i t i c a l point measurements, i t was considered worthwhile to re-explore the vapor-liquid relationship of pure normal propanol up to the c r i t i c a l point. This consideration was partly influenced by the a v a i l a b i l i t y of a high pressure apparatus designed for multi-component vapor-liquid equilibrium, but equally suitable for such a one component system. The selection of normal propyl alcohol as the single component was also influenced by the fact that benzene-n-propanol had been selected as the f i r s t binary system to be studied i n these laboratories (through a range of pressure). This made the purification, and hence, the physical properties of propanol of considerable interest. The need for such a study became even more apparent i n l i g h t of the meagre data available i n the l i t e r a t u r e on purification techniques. Moreover i t was essential to ascertain to what extent impurities would affect the vapor pressure of normal propanol before confronting the more complex problem of their effect on a binary system. This consideration i s particularly important near the c r i t i c a l point (5,6). Vapor-liquid equilibrium data for one-component systems (vapor pressure data) have t r a d i t i o n a l l y been correlated by theoretical, semi-empirical and  2.  empirical equations i n order to enhance t h e i r usefulness. While data on individual compounds i s often considered separately, there i s a growing tendency to consider families of compounds (7) and of course to determine a completely generalized approach ( l , 8, 9). Re-evaluation of vapor pressure data on n-propanol can therefore be usefully considered i n a l l of these categories. This thesis, then, presents information on obtaining and measuring the purity of highly purified n-propanol, on the apparatus for making vapor pressure measurements up to the c r i t i c a l point, and on correlations for existing data on n-propanol that can be used for evaluation of new data that may be obtained. LITERATURE REVIEW 1.  P u r i f i c a t i o n of Normal Propanol According to Timmermans (10 ) and Speers (4) the only worker who has measured the vapor pressure of propanol above one atmosphere i s Young (5). His f i r s t concern was with the purity of the l i q u i d to be investigated. "The physical properties of a substance, especially at or near i t s c r i t i c a l point, may be seriously affected by the presence of even a very small quantity of impurity; i t i s therefore of the utmost importance that the purification of the substances investigated should be carried out with the greatest possible care," (5) Almost a l l the purification methods for n-propanol involve some form of fractional d i s t i l l a t i o n of a commercial grade. There i s , however, one method, as described by Timmermans and Delcourt ( l l ) , which i s an exception. They stated that there are traces of isomers and homologues which cannot be removed by simple f r a c t i o n a l d i s t i l l a t i o n alone. In t h i s case the p u r i f i c a t i o n was made by fractional c r y s t a l l i z a t i o n of a solid propyl ester, l i k e the acid phthalate. The ester was either reduced or hydrolysed back to the alcohol and the usual d i s t i l l a t i o n carried out. However the purity of a Kahlbaum sample (as determined by density and the c r i t i c a l temperature of solution i n petroleum (12)) was found to be the same before and after transformation into the phthalate. Young's n-propyl alcohol (13, 14) was procured from Kahlbaum.  It  3. was p u r i f i e d by f r a c t i o n a l d i s t i l l a t i o n and then d i s t i l l e d with benzene through a very e f f i c i e n t s t i l l head to remove the l a s t traces of water. The specific gravity of t h i s specimen at 0°/4° was 0.&L923 and the boiling point 97.20°C. at one atmosphere. This requirement of high purity propanol f o r physical property measurements stimulated further experimentation with purification techniques i n more recent years. de Brouckers and Prigogine (15) purified technical grade propanol by refluxing over lime for five hours and then d i s t i l l i n g through a one meter column. Kretschmer (16) found that a commercial grade of n-propanol contained 1.5$ a l l y l alcohol as i t s main impurity.  He carefully purified the alcohol  by treating one l i t r e with 15 ml. of bromine.  The alcohol was f r a c t i o n a l l y  d i s t i l l e d with a small amount of potassium carbonate through a 75-plate column.  The middle fraction of 600 ml. was dried with 1 gram of magnesium  ribbon, freshly cleaned with steel wool, i n a storage flask attached to a vacuum system.  Before the flask was sealed, 1 gram of 2,4-dinitrophenyl  hydrazine was added to react with any propionaldehyde formed by the bromine treatment that had not been removed by d i s t i l l a t i o n . Both Keyes and Winninghoff (17) and Kraus and Bishop (18) dried propyl alcohol with metallic sodium and f r a c t i o n a l l y d i s t i l l e d . Goldschmidt and Thomas (19) dried 1-propanol with aluminum amalgam and, to remove basic impurities, d i s t i l l e d over s u l f a n i l i c or t a r t a r i c acid. Berner (20) boiled n-propanol with lime for s i x hours and after d i s t i l l i n g warmed the middle fraction with calcium hydride i n a stream of hydrogen. Other workers who purified propanol include Lund and Bjerrum (21) and Brunei, Crenshaw and Tobin (22). The main criterion for purity i s considered to be the constancy of vapour pressure (5, 6) when the l i q u i d i s evaporated, or the vapor condensed, since impurities usually divide themselves unequally between l i q u i d and vapor. Wullner and Grotrian (23) found appreciable differences i n pressure i n the i n t e r v a l between the condensation of the f i r s t drop of l i q u i d from the vapours of several organic liquids and the disappearance of the last bubble  4. of vapor, and these were shown by Tammann (24) to be due t o impurities. Tammann found that 0,0001 part of benzene i n water was enough to cause an inconsistency i n pressure during evaporation or l i q u i f a c t i o n , the vapor pressure depending on the volume of the vapor phase. Constancy of vapor pressure i s , therefore, an extremely sensitive test of purity, far exceeding b o i l i n g point i n delicacy (6). A test of purity i s to evaporate the l i q u i d by pumping off vapour u n t i l only one twentieth the volume of l i q u i d remains, when the vapor pressure should be unchanged (25). Another test i s the constancy of temperature during freezing (26). Young (5) embraced these principles of purity and added others. Amongst these he required close agreement between physical constants of two different specimens of the same l i q u i d . . While Weissberger (27) makes no mention of any specific c r i t e r i a , Timmermans (10) states the c r i t e r i a of purity to be the density to the f i f t h place (28) and the c r i t i c a l temperature of solution i n petroleum (12). 2.  Apparatus  The high pressure apparatus available was designed by Whittle (29) after apparatus described by Sage and Lacey (30). I n general i t can be classed as a s t a t i c or bomb equipment. The work by Young, longstanding and s t i l l highly regarded for i t s accuracy, was carried out by a s t a t i c method also, and hence should be considered i n more d e t a i l f o r comparison to the method and apparatus intended here. Young*s apparatus consisted b a s i c a l l y of a long wrought iron tube having one end f i t t e d with a screw plunger and the other end sealed. This tube, firmly secured i n the horizontal position, had three shorter tubes running i n a v e r t i c a l direction from i t . Three thickwalled glass tubes, graduated i n millimeters and carefully calibrated, had one end pressure f i t t e d into the iron tubes and the other end sealed. The f i r s t two served as a i r manometers f o r different pressure ranges, and the t h i r d was the experimental tube containing the l i q u i d under investigation. The iron apparatus was f i l l e d with mercury and pressures applied by means of the plunger. The temperature around the experimental tube was controlled by passing vapors from various boiling liquids through a jacket around the tube.  5. When the vapor i n the jacketing tube was at the required temperature, readings of vapor pressure were taken with the l i q u i d and vapor i n the experimental tube occupying a series of different volumes. Young corrected his calculated pressure, l ) for the difference i n l e v e l of the mercury i n the experimental tube and the manometer, 2) for the pressure of the column of unvaporized l i q u i d , 3) for the expansion of the heated column of mercury, 4) i f necessary, for c a p i l l i a r i t y , 5) for the deviation of a i r i n the manometer from Boyles Law. He made no correction for the vapor pressure of mercury because he was of the opinion that evaporation through a long column of l i q u i d was an exceedingly slow process. The assumptions made by Young i n t h i s statement have been seriously studied i n the past few years. Jepson and Rowlinson (31) have shown that a correction for the v o l a t i l i t y of mercury should be applied to observed pressures of compressed gases where the confining f l u i d i s mercury. The usual correction, when applied, was simply the substraction of the normal vapor pressure of mercury corrected for the hydrostatic pressure (the Poynting effect (32)). They showed that this i s not an adequate treatment of the problem, as the mixture of mercury atoms and compressed gas cannot behave as an ideal mixture. An estimation of the intermolecular forces between mercury atoms and the added gas leads to values of the v i r i a l coefficients from which a revised correction can be computed, assuming that the system i s at equilibrium. This revised correction can be considerably larger than the usual correction and i s often of opposite sign. While i t i s true that i n most vapor pressure measurements l i q u i d i s present over the mercury surface, i t s density rapidly decreases as the c r i t i c a l point i s approached. Young's theory may be quite v a l i d for long columns of l i q u i d over mercury but i t seems that the height and density of the l i q u i d would be quite important. Jepson and Rowlinson's correction would be particularly applicable near the c r i t i c a l point, i n Young's type of measurement. Kay (33) and l a t e r Bahlke and Kay (34) improved Young's apparatus and also carefully considered the corrections required. A similar method has also been employed previously i n these laboratories for measurement of n-butanol (35). The bomb apparatus of Whittle, described below, requires similar  6.  corrections to those above.  The correction having regard to mercury  requires special notice since the mercury surface i s many times larger than i n the case of Young's apparatus. 3.  Presentation of Vapor Pressure Data Numerous equations, both empirical and theoretical, have been given  relating vapor pressures, P,with absolute temperature, T (6, 36, 37, 38). Young used the Blot Formula (39) t o correlate his data on n-propanol. log P  =  a + b o ^ + eft*  where a = 4.479470  (1)  log<X,= 0.001641423  log b = T. 3915059  log  log c - 0.5509601  t  = T. 99657025 = T°C - 20.  The constants were calculated from pressures at 20, 80, 140, 200 and 260°C. (13). The agreement between calculated and experimental data was good, but the nature of the equation made i t d i f f i c u l t to use. Other investigators (40) also found the formula inaccurate and i t has subsequently f a l l e n into dis-use. Reid and Sherwood (38) have recently recommended the Eiedel correlation (41) for most accurate work. log P = A -J3_ + C I n T + DT^ R R  R  (2)  T  (Actually t h i s i s the relation that Riedel used as a basis f o r his single constant reduced vapor pressure equation).  I t has i t s disadvantage,;  however, i n that the c r i t i c a l temperature and pressure must be known.  In  many cases the accuracy of these constants cannot be too heavily r e l i e d upon. Thomson (36), i n his well known review of 1946, recommends the use of two Antoine equations,  7.  log P = A -  B  (3)  T - C where P T C A,B  = = = =  vapor pressure, p.s.i.a. temperature, °R. constant, °R. constants.  one up to T = 0.8 or 0.85 and the other from T = 0.8 to T = 1.0, R  for most accurate results.  R  R  The disadvantage here, of course, i s the  necessity for two equations when only one i s desired. Among the more recent equations i s that proposed by Frost and Kalkwarf (42), log P = A + B + C l o g T + DP T "T?  (4)  i n which they t r y to explain the reverse curvature of the plot of l o g P versus 1 on the basis of the non-ideal behavior of the vapor together T with the change i n heat of vaporization with temperature. This equation has been successfully used by Thodos (43) to consider the vapor pressures of a series of the normal paraffin hydrocarbons.  I t s usefulness here indicates the strong p o s s i b i l i t y of i t  playing a similar role for the n-alcohols.  The Antoine equation has  also been most successfully used f o r families of compounds, notably by Dreisbach (7). From the large number of equations available, these three have therefore been selected to be used with the vapor pressure of n-propanol. Young's data are employed, and any l a t e r re-evaluation or re-determination could always be compared to these i n the same fashion.  The equations  selected (Riedel, Antoine, and Frost) a l l have a semi-empirical basis, offer r e l a t i v e simplicity i n calculation, and provide the p o s s i b i l i t y of interesting comparisons with other members of the normal alcohol series.  8. PURIFICATION 1.  Materials I  Fisher Certified Grade n-Propanol  This material was supplied with the following stated specifications: Acidity  0.002$  (CH^ COOH)  Boiling Range  96 - 97.5°C  Non-Volatile Matter  0.000$  Substances precipitated by 1^0  None  This n-propanol i s one of the co-products produced from carbon monoxide and hydrogen i n the high pressure catalytic synthesis of methanol (44). The chief method of separations of these co-products and f i n a l p u r i f i c a t i o n of the n-propyl alcohol i s careful fractionation. The higher alcohol mixture produced by this synthesis has been found to contain the following primary alcohols (45)  :  n-propanol  (b.p. 97.19°C.)  isobutanol  (b.p. 108.39°C.)  2 met hyl-l-but anol  (b.p. 128°C.)  2 methyl-l-pentanol  (b.p. 148°C.)  2,4 dimethyl-l-pentanol 4 methyl-l-hexanol iso-propanol  (b.p, 82.3°C.)  3 methyl 2-butanol  (b.p. 114°C)  2,4 dimethyl 3-pentanol  (b.p. 140°C.)  2,4 dimethyl 1-hexanol 4 or 5 methyl-l-heptanol 3 pentanol  (b.p. 115.6°C.)  2 pentanol  (b.p. 119»28°C.)  9.  II  Canadian Chemical Company Technical Grade Normal Propyl Alcohol  This material i s stated to have the following specifications: Specific gravity at 20/20°C max  0.8074  D i s t i l l a t i o n range °C max  2  Colour APHA max  5  Acidity as Acetic % by wt. max.  .003  A l k a l i n i t y as N E ^ by wt. max.  0.2  Water content % by wt. max.  0.2  Non-volatile materials gms/l00 ml  0.001  Mass spectrometer analysis of the product stream gives (46):  2-Butanol  High  Low  Avg.  4.4#  2.8£  3.5#  2-Propanol  traces traces  n-Propanol  97.1  95,5  0.1  0.0  Methoxy-Methylal  96 0.05  for August 18-25, 1958. This propanol i s produced as a by-product of propane oxidation. III  Eastman n-Propyl Acetate  The highest grade Eastman n-propyl acetate obtainable commercially was used. b o i l i n g point: IV  The only manufacturer's specification i s the  97 - 102°C.  Auxiliary Materials  The following materials were used as available commercially: Reagent Grade Bromine, Reagent Grade Anhydrous Potassium Carbonate, Magnesium ribbon (freshly cleaned with steel wool), Cylinder nitrogen (purified grade). Reagent Grade Sodium Hydroxide.  10 2.  Apparatus a.  D i s t i l l a t i o n Apparatus  A l l d i s t i l l a t i o n s were done on a Todd Precise Fractionation Assembly, employing a 25 mm. I.D. column packed with single turn case hardened Pyrex brand glass helices 4 mm. i n diameter.  The length of the  column gave a fractionation efficiency of up to 60 theoretical plates. The apparatus was equipped with jackets and a dual heating unit designed to enable the fractionation column t o be operated under adiabatic conditions up to 360°C. An automatic s t i l l head timer controlled the reflux r a t i o from 2: 1 to 50: 1  i n five integral steps by means of a solenoid operated  valve made of teflon and containing a soft i r o n core. b. Refractometer A l l refractive index readings were made on a P u l f r i c h refractometer using the l i g h t prism with a sodium lamp to provide D - l i n e readings. constant temperature apparatus maintained the prism at 20°C - 0.1°C. refractometer , was  A The  read t o the nearest 0,5 minutes.  The normally immersed thermometer w e l l was equipped with a rubber gasket which sealed the top of the c y l i n d r i c a l sample container when the w e l l was lowered into i t . c.  Gas Chromatograph  A Beckmann GC-2 gas chromatograph was used consisting of the following elements:  a chromatographic column, a carrier gas flow control,  a heated sample i n l e t system, a thermal conductivity c e l l , an electronically controlled heater system, and an electronically regulated voltage supply. The columns were f l a t s p i r a l s of £ inch copper or stainless s t e e l tubing interchangeable with ones of different packing and different length. Cylinder helium was used as the carrier gas.  The conductivity c e l l was an  e l e c t r i c a l l y balanced filament type giving a reproducibility of - 0.1$ of f u l l scale deflection (47).  The instrument had a temperature range from  40° to 220°C, maintained by an internal full-proportional heater,  11. electronically controlled.  Zero s t a b i l i t y was 2% per hour or better,  under normal operating conditions (47). The l i q u i d samples were injected into the chromatograph from a Beckmann 22400 l i q u i d sampler.  A syringe type instrument, i t was  for introduction of precisely measured small quantities of l i q u i d s cc to .05 cc). 0.1$  to 0.5# d.  designed (.005  Uniform results were obtained with reproducibility of  (47). Ebulliometer  B o i l i n g points were determined by the comparative method as described by Swietoslawski (48). Two d i f f e r e n t i a l ebulliometers constructed according to the standard specifications of Barr and Anhorn (49) were used. Ebulliometer A (50) contained the primary standard, and B (51) the sample to be studied. Both pieces of apparatus consisted b a s i c a l l y of a b o i l e r with a thermometer w e l l and drop counter, a condensation temperature element with a thermometer w e l l and drop counter, and a condenser. In addition, B had a r e c t i f y i n g element between the two thermometer wells and was equipped with a s i l i c a gel drying tube above the condenser. Both A and B were w e l l insulated with asbestos. The thermometer wells were b u i l t up with cork and insulation so that the thermometer was immersed to the same l e v e l as i t was during calibration. These wells were f i l l e d with mercury and covered with a light o i l so that the l i q u i d l e v e l would r i s e to the top of the well when the thermometer was immersed. The boiler sections were wrapped with nichrome heating wire and the heat input controlled with a variable auto transformer. In the case of A, the b o i l e r tube was packed with pyrex glass wool to give undisturbed b o i l i n g during operation with the primary standard. The Beckmann thermometer used i n the ebulliometers had 100 divisions per degree. I t was calibrated i n a constant temperature o i l bath against a Leeds and Northrup platinum resistance thermometer with a 1955 NBS c e r t i f i c a t e (52). D i s t i l l e d water having a specific conductivity greater than 800,000 ohms ^ cms ^ was used as the primary standard.  12. e. Viscometer A routine Cannon-Fenske viscometer of the type recommended by the ASTM (54) for testing petroleum products, and as described by Cannon and Fenske (53), was used. 3.  Procedure 1  Fisher C e r t i f i e d Grade Normal Propyl Alcohol  The n-propanol was charged t o the s t i l l pot i n one l i t r e l o t s with several grams of anhydrous potassium carbonate and a few boiling chips. The apparatus was then purged f o r several minutes with purified grade cylinder nitrogen to remove any a i r atmosphere. The system was closed and the vent on the d i s t i l l a t e collecting vessel connected t o a glass tube which dipped into a flask of propanol. The system was then opened at the vent stopcock allowing N^ i n excess of atmospheric pressure, to bubble out through the propanol. The heater under the s t i l l pot was turned on and the charge brought to b o i l i n g . When refluxing was observed from the packing at the bottom of the column the heater was cut back and the two column heaters switched on. When d i s t i l l a t e began condensing i n the top condenser the temperature i n the upper part of the column was adjusted to the column top temperature. Similarly the lower part was adjusted to the s t i l l pot temperature. The column packing was inspected for signs of l o c a l heating and then the apparatus was l e f t to come to equilibrium. When t h i s point was reached, the reflux timer was set at 50* 1 and d i s t i l l a t e was collected. The f i r s t 500 mis. were drawn o f f and then a centre cut of 150 mis. was collected over freshly cleaned magnesium ribbon i n a nitrogen purged flask. The flask was then sealed with a ground glass stopper and stored. Additional runs were made, under exactly the same conditions, with 15 ml. of bromine per l i t r e of propanol i n the s t i l l pot, part of the p u r i f i c a t i o n procedure described by Kretschmer (16). I I Canadian Chemical Company Technical Grade Normal Propyl Alcohol 2 l i t r e s of n-propanol were d i s t i l l e d by similar procedure at  13. 5 0 : 1.reflux ratio. The f i r s t 5 0 mis. were discarded and last 1 0 0 mis. l e f t i n the b o i l e r . This d i s t i l l a t i o n procedure was repeated twice more and the f i n a l cut stored over Mg ribbon i n a nitrogen atmosphere. I l l Hydrolysis of Normal Propyl Acetate to Normal Propyl Alcohol The production of high purity n-propyl alcohol by hydrolysis of the acetate, as i n the following reactions, was suggested (46): NaOH CH C 0 0 C H 2 CH CH^ + H 0 3  2  CH COOH + NaOH 3  2  =  CH^ CH CH OH + CE^ COOH  =  CH COONa + H 0  2  3  2  2  1 5 0 0 grams of Eastman white-label n-propyl acetate was fractionated on the Todd s t i l l at 1 5 : 1 r e f l u x r a t i o , and a heart cut of the 1 0 1 . 6 ° C . fraction taken. About 1 l i t r e of the r e c t i f i e d propyl acetate was placed i n a 2 - l i t r e flask with 2 0 0 ml. of water and 5 0 grams of sodium hydroxide p e l l e t s , and the flask was closed with a rubber stopper. The contents were given vigorous and prolonged shaking by hand, with frequent addition of more sodium.1 hydroxide i n 1 0 to 2 0 gm. portions, u n t i l a sudden generation of heat indicated the commencement of hydrolysis. The stopper was then loosened and agitation was reduced to a gentle swirling, l e t t i n g the flask cool undisturbed whenever i t became uncomfortably hot to the hand. At this stage the ester odour had been replaced by the alcohol odour. Periods of gentle swirling and cooling were alternated u n t i l further agitation produced no further heat. The mixture was transferred to a 2 - l i t r e s t i l l flask, 2 0 0 mis. of water added, and the n-propanol-water azeotrope was removed by fractionation, collecting the 8 7 » 7 ° C . cut at 1 0 : 1 reflux r a t i o . The azeotropic cut was treated with an excess of anhydrous potassium carbonate to salt out the alcohol as an upper layer. The upper layer was removed i n a separator funnel and dried by shaking with successive portions of anhydrous potassium carbonate. The f i n a l s e t t l i n g period was extended overnight.  The dried alcohol was then f i l t e r e d into a 1 - l i t r e flask,  14.  and l a s t traces of water removed by fractionating at 15: 1 reflux r a t i o , collecting a heart cut, when the temperature had steadied near 97° (uncorrected s t i l l head temperature), as pure n-propanol. 4.  Purity Determinations a. Methods 1.  Refractive Index  The refractometer was prepared for use by ensuring that the sample container was clean and dry and that the zero reading was correct. The sample to be analysed was sealed i n a serum bottle with a rubber serum bottle stopper, previouslj'- boiled i n propanol. The sealed bottle was placed on a tray i n the refractometer constant temperature bath and l e f t for about twenty minutes. At the end of this period the bottle was removed from the bath and about 5 mis. of sample withdrawn into a hypodermic syringe. After the a i r was ejected from the syringe, the sample was run into the refractometer sample container and the thermometer w e l l , (with rubber gasket) lowered into place as quickly as possible. The angle of refraction was read immediately and then at successive time intervals u n t i l the reading was constant within 0.5 minutes. This reading was recorded and then the procedure was repeated with new samples from the serum bottle u n t i l the readings were consistent within 0.5 minutes. 2.  Chromatographic Analysis  Preliminary investigations were required for determining the optimum values for the variables connected with the chromatograph operation.  In the case of flow rate, current and column length, the  manufacturer's specified values were used (47).  However sample s i z e ,  column temperature and column composition were determined by a series of investigations. The procedure involved finding a combination of these three variables which would give the best resolution, and hence, the clearest qualitative and quantitative indications of the sample composition.  15.  Five recommended columns (46, 47, 54a) of £ inch copper tubing, each s i x feet long, were packed with 30 - 40 mesh brick dust.  The dust  was made by grinding up C - 22 S i l - o - c e l brick, removing the 30 - 40 mesh cut, washing out the fines with water, and then drying i n an oven. The brick for each column was treated with a different partitioning l i q u i d i n the following way.  S i x to eight mis. of partitioning l i q u i d  were made up to 40 mis. i n a 100 ml. graduate with a dissolving solvent. Complete mixing was ensured by inserting a teflon piston into the graduate and pulling i t back and forth.  The piston was l e f t at the  bottom of the graduate and 50 mis. of brickdust pored slowly into the l i q u i d mixture so that each particle f e l l independently through the f l u i d . After l e t t i n g the particles settle for a few minutes, the coated brick dust was removed by extracting the piston.  The dust was spread out on a  tray to be a i r dried and subsequently packed into the copper tubing. The five partitioning l i q u i d s used were: 1. Tricresol phosphate (reagent grade) 2. Flexol p l a s t i c i z e r - 8N8 (Carbide and Carbon Chemical Company) 3. Vacuum pump o i l (Hyvac-Central S c i e n t i f i c Company) 4. Glycerine (reagent grade) 5. Polyethylene glycol di-2-ethylhexoate (Carbide and Carbon Chemical Company) The optimum sample size and column temperature were determined with the best column of those l i s t e d above, following the procedure as outlined below. The warm up period for the chromatograph was normally two hours. In this period the column was purged with helium at the operating pressure and was brought up to the operating temperature. In order to check for zero d r i f t and hence an indication of insufficient warm up period, the attentuator was set at i t s lowest value and the zero adjusted to the 50 m i l l i v o l t position on the chart.  If  there was no perceptible shift i n the zero position over a period of ten minutes, the apparatus was considered ready for use. The sample to be injected into the column was drawn into and  16. rejected from the sampling syringe u n t i l i t was obtained i n an a i r free state. At the appropriate moment the chromatogram chart drive was switched on and the sample injected as quickly as possible into the column. During the run the lowest attenuation was maintained to allow for maximum detection of the components. When no more peaks appeared after running at 0 m i l l i v o l t s for several minutes, the chart drive was switched o f f . However, i n order to detect any possible additional components, the instruments were l e f t running, with the recorder pen on the chart, for ten to twenty minutes after the chart drive had been stopped. Identification of the unknown sample was traced again by a series of investigations. Suspected components were obtained i n a f a i r l y pure state and run separately on the chromatograph. When peaks appeared at the same position on the two chromatograms, i t was generally accepted as positive i d e n t i f i c a t i o n . However, i n cases where more than one suspected component coincided at the same position, known volumes of the suspected components were added to the unknown sample and the effect on the peak i n question observed. The peak height measurement technique was employed to obtain a quantitative analysis of the chromatograms. Only one calibration run (at 100$) was traced for each component, assuming a linear relationship between peak height and composition. The volume per cent of the components was determined as follows: Volume %  =  component peak height component calibration peak height  x  iOO  In cases where the purest form of the component i n question showed impurity peaks, the calibration peak height was substituted for what was considered a more accurately determined value (see Discussion, b) Results).  17.  3.  Boiling Point  Ebulliometer A (50) was f i l l e d with d i s t i l l e d water and the heat input set so that there was rapid b o i l i n g .  The b o i l i n g rate was  adjusted to give 5 - 10 drops/minute at the two drop counters.  The  temperature was measured i n both thermowells to get an additional check on the purity of the primary standard. Ebulliometer B (51) was f i l l e d with a sample of the n-propanol being studied and brought to a steady b o i l giving about 100 drops/minute at both drop counters.  The temperature at each thermowell was measured  to ascertain the purity (55). A b o i l i n g point determination was begun by obtaining a steadytemperature (within ,002°C.) i n the lower thermowell of A.  The  thermometer was then quickly transferred to the lower thermowell of B. This procedure was repeated u n t i l the temperatures were constant within .002°C. i n both thermowells. The temperature obtained i n A was used i n conjunction with the pressure-temperature relationships and the interpolation formulae f o r water, as recommended by the International Union of Chemistry, to obtain the  atmospheric pressure. Assuming a value of  dT/dB for n-propanol at 760 mm...  as 0.038 C/  mm. (10), the actual b o i l i n g point of the sample i n B at 760 mm. calculated.  was  The pressure range over which this correction had to be  applied was a maximum of 10 mm. 4.  Viscosity  The procedure for measuring the viscosity of n-propanol was described by de Verteuil (56) and his results are presented below. b. Results For  the various starting materials, several "grades" of n-propanol  were prepared, and determination of b o i l i n g point, refractive index, and v i s c o s i t y , made as detailed above.  The results are tabulated i n Table 1  along with estimates of purity and water content. In addition, the results obtained from the i n i t i a l investigations  18. into suitable methods of p u r i f i c a t i o n of the available "grades" of n-propanol are presented i n Table 2. Two chromatograms, t y p i c a l of those used to calculate the percent impurities of Table 1, are i l l u s t r a t e d i n Figure I . For comparison purposes, the physical properties of n-propanol from the l i t e r a t u r e are tabulated i n Tables 3a and 3b.  19.  TABLE 1. Physical Properties of Normal Propanol  II bp. °C. at 760 mm.  a ' b  20 °D  3  96.1-98.1 70.X 97.16  3  • J L —  97.17*  1.38546 1.33539  a b  3.5 1.2  3.5 0.7  0.35  1  a b  0.1 0  0.1 0  0.1 0  (cp.)  b  1  % Water (by volume)  2  1.385 1.38524  I  a b  % impurity ' (by volume)  X  96.0-97.5  III  3  15 C 2.486  25°C  1.946  30°C 1 . 7 1 8  (See Page 21 f o r explanatory notes)  1.38524  20.  TABLE 2. I n i t i a l Investigations n^  1,2 (j'j^voiTume)  1.38546  3.5  25:1  1.38543  1.7  25:1 50:1  1.38543 1.38539  1.2  -  3.5  D i s t i l l a t i o n Conditions Notes  Reflux Ratio  before distillation bromine added  before distillation JJ  III  1st distn.  50:1  -  1.2  2nd distn.  50:1  -  0.7  3rd distn.  50:1  -  0.5  1st distn.  50:1  -  0.12  (See Page 21 f o r explanatory notes).  5  5  Following page 20  TIME 2. Purified  Technical  Grade  n-Propanol  Figure I CHROMATOGRAMS OF NORMAL PROPANOL FROM A FIEXOL PLASTICIZER COLUMN.  21  Notes f o r Tables 1 and 2. I  Fisher Certified Normal Propyl Alcohol  II  Canadian Chemical Company Technical Grade Normal Propyl Alcohol  III  Normal Propyl Alcohol produced by hydrolysis of Normal Propyl Acetate  1.  a  - before p u r i f i c a t i o n  b  - after purification These volume percentages were calculated from the chromatograms  obtained under the following conditions: Flow rate:  150 cc/min.  Sample size:  0.005 cc.  Current:  150 ma.  Temperature:  70°C.  Column Partitioning Liquid: Flexol Plasticizer-8N8 Column Length: 2.  6 feet.  The percentages here were calculated using 3«5 volume per cent  sec-butanol impurity i n n-propanol I l a as the standard.  This i s i n  accordance with the mass spectrometer analysis from Canadian Chemical Company (see Materials). 3.  Manufacturer's  4»  This reading was obtained using a Cenco U.S. Weather Bureau  specifications.  type standard mercurial barometer for the atmospheric determination.  pressure  The procedure for determining the b o i l i n g point was  exactly as described above except that the barometer was substituted for ebulliometer A.  Pressure readings were made to the nearest 0.1 mtn.  21a.  and the brass scale correction applied at room temperature. Reduction of the barometer to latitude 45° was neglected. Since the manufacturer considers t h i s barometer "of the highest type of excellence", i t was assumed accurate to 0.1 mm.  Even an  error of 0.1 mm., which corresponds to less than 0.005°C, would not affect the b o i l i n g point any more than the errors involved i n the comparative method.  For this reason the accuracy of the two  methods i s considered comparable. 5.  This value was obtained using a 5 mm. I.D. column on the Todd  Fractionation Assembly, rather than the 25 mm. I.D. column which was used f o r the f i n a l products, as described on p.19.  22. TABLE 3a. Physical Data for Normal Propyl Alcohol from the Literature. AUTHOR  DATE  b.p.°C. (760 mm)  Young and Fortey Dorochewsky  1903 1909 1911 1913  97.19 97.20 97.26 97.1  1921 1923 1923 1933  97.19 97.15 97.19  1934 1936  97.15 97.209  1937 1945 1948  97.15 98.0  1949 1950 1951  97.19 97.2 97.2  Dorochew3ky  Mundel Brunei, Crenshaw and Tobin Brunei Grimm and Patrick Trew and Watkins Timmermanns and Delcourt Wojciechowski ZepalovaMikhailova Addison Vogel Carley and Bertelsen Mumford and P h i l l i p Howey McKenna, Tartar and Lingafelter Wetzel, M i l l e r and Day Purnell and Bowden Croil I II  m  REFRACTIVE INDEX  (57) (58) (59) (60) 1.3833 1.3833 1.38343  1.3856 1.38556  (66) (67) (68)  1.3862 1.3858  1.3838  (69) (70) (71)  1.3837  (72)  1.3841 1.3840  (73) (74)  97.2 97.16  (61) (28) (62) (63) (64) (65)  1953 1953 1954 1958  REF.  1.38539 1.38524 1.38524  This Research  23. TABLE 3b. Physical Data for Normal Propyl Alcohol from the Literature.  AUTHOR  Gartenmeister  DATE  1890  TEMP.  DENSITY  REF.  °C.  g./ml.  cp.  10 20 30  .8125 .8052 .7973 .7890 .7802  2.934 2.273 1.791 1.416 1.148 2.555 1.990 1.971 1,962  (76) (77) (78) (79)  1.928 1.915 1.962  (80) (81) (82)  2.522  (64)  1.722 2.004 2.29 2.015  (83) (70)  40  Thorpe and Rodger Thole Baker Dunstan & Thole English and Turner Herz Whitman Timmermanns and Delcourt  1894 1910 1912 1913  50 15.06 25 25 25  1914 1918 1930  25 25 25  .7999  1934  Jones Mumford & P h i l l i p  1948 1950  15 25 30  de Verteuil and C r o i l n-propanol I I  20 25  .80749 .79957 .79567 .8015 .8053 .8016  1958  15 25 30  .8075^ .7998* .7957  *  VISCOSITY  25  .8010  .7957  Assumed Values.  (75)  1.924(calc)  2.486 This 1.946 research 1.718  24. 5.  Discussion a.  Apparatus and Methods 1.  Refractive Index  While the refractometer could only be read t o the nearest 0 . 5 minutes, successive readings were s u f f i c i e n t l y reproducible t o give an average deviation from the mean of a group of readings of less than 0 . 2 5 minutes. This corresponds to a maximum error of about 4 i n the f i f t h decimal place of the refractive index value. The rubber gasket, sealing the sample container when the thermowell was lowered into i t , reduced the exposure of the sample t o room a i r to a very small period of time. Thus any moisture pickup by the materials used was insufficient t o cause detectable changes i n refractive index. Similar precautions were taken with the l i q u i d before analysis by storing i t i n a serum bottle and retracting samples, as required, with a hypodermic needle. 2.  Chromatographic Analysis  The gas chromatographic analysis provided a most useful means of detecting impurities present. The selection of the best column and operating conditions was d i f f i c u l t , however. Of the s i x columns tested ( s i l i c o n , t r i c r e s o l phosphate, f l e x o l p l a s t i c i z e r , vacuum pump o i l , glycerine and polyethylene glycol 2 - d i e t h y l hexoate) the f l e x o l p l a s t i c i z e r column alone gave clear d i s t i n c t peaks for water, n-propanol and an unknown impurity. I n the other columns the impurity was either hidden by the propanol peak or the peak was so f l a t i t was d i f f i c u l t t o analyze. As a result this column was selected and used for a l l the tests made t o provide information on the purity of n-propanol. According to the manufacturer's instructions ( 8 4 ) for determining volume % a calibration curve should be obtained of composition versus peak height. The errors involved i n taking this relationship to be linear are not l i k e l y t o be significant here since the primary interest i s y  not i n absolute quantitative values but rather i n r e l a t i v e ones.  Failure  25.  to exactly identify the main impurity makes the former impossible. Other sources of error i n t h i s type of analysis are outlined by the manufacturer (84) but, i n general, have not been considered relevant to these measurements. 3.  B o i l i n g Point  D i f f i c u l t y was encountered i n controlling the drop rate from ebulliometer A (50),  containing the primary standard.  The rate at the  top of the apparatus always exceeded that at the bottom which i s exactly the reverse of what was expected.  I t appeared that an error  i n construction permitted refluxing l i q u i d from the top to return to the b o i l e r section without passing through the bottom drop counter. Nevertheless this seemed to have no particular detrimental effect on the equilibration. The measurement of the temperature i n both thermowells of ebulliometer A gave the same value to within 0.001°G. indicating that the primary standard was of an acceptable purity. case of ebulliometer B (51), of each other.  S i m i l a r l y i n the  the two temperatures were within .005°C.  According to Swietoslawski (55) this places both  liquids i n the f i r s t degree of purity class. Only one thermometer was used to eliminate the errors involved i n using two or more, where the p o s s i b i l i t y of scale corrections i s presented.  On the other hand, i t was almost impossible to measure  the temperature i n two ebulliometers with one thermometer, while the room pressure remained constant. Nevertheless, corrections applied, as described previously, provided b o i l i n g points at 760 mm. a maximum error of .005°C.  pressure which are considered to have  This error takes into account possible  errors i n calibration, lack of precise equilibrium conditions, and limitations i n reading the thermometer and applying normal corrections to i t . 4. Viscosity The apparatus and procedure f o r making the v i s c o s i t y measurements  26.  tabulated above have been c r i t i c a l l y discussed by de Verteuil (56). b.  Purification  The purification of n-propanol presents a number of problems. The work described herein has c l a r i f i e d these problems, and proceeded towards t h e i r solution. A significant problem i s the vagueness of the l i t e r a t u r e already available, with i t s omissions, discrepancies and conflicting statements. A second important problem i s the fact that the impurities and normal propanol are so close b o i l i n g that not only i s i t very d i f f i c u l t to separate them, but also to detect them by the measurement of physical properties. The purification procedure adopted f o r n-propanol I was essentially that of Kretchmer (16), although details of the bromine treatment were lacking. Successive t r i a l s at brominating some npropanol I , to assist i n removing any a l l y l alcohol, showed l i t t l e improvement over the o r i g i n a l sample when measured by means of a gas chromatographic analysis. This i n i t i a t e d doubts about l ) the bromination method, 2) differences i n the commercial grades of propanol used, 3) Kretchmer's conviction that the impurity was a l l y l alcohol. Further d i s t i l l a t i o n s at higher reflux ratios began to confirm the doubts about 2) or 3). The impurity peak decreased with d i s t i l l a t i o n at higher reflux ratios even without any bromination. The use of a nitrogen purge was found to be incidental since the product obtained from d i s t i l l a t i o n i n an a i r atmosphere was i d e n t i c a l , within the l i m i t s of detecting differences i n successive gas chromatograms, to that i n a nitrogen atmosphere. The n-propanol I I , for which a mass spectrometer analysis was available, showed as i t s main impurity sec-butanol. The successive d i s t i l l a t i o n s at high reflux ratios gave a rate of decrease of the impurity peak on a chromatogram corresponding f a i r l y w e l l to that of n-propanol I . In addition the two impurity peaks appeared i n the same positions on the chromatograms. A sample of the n-propanol I I I , as produced from n-propyl acetate,  27.  also gave a small impurity peak i n the same position.  This n-  propanol I I I would have been more easily and e f f i c i e n t l y prepared i f potassium hydroxide had been used rather than sodium hydroxide, because of the much greater s o l u b i l i t y of the l a t t e r .  No difference i n  purity obtainable would be expected however. On the basis that either a l l y l alcohol or see-butanol was the main impurity indicated as being present, chromatograms were run on f a i r l y pure (  90 - 95$) samples of each.  These were used as  standards for determining percentage impurity as described above.  In  addition a l l y l alcohol-propanol and sec-butanol-propanol mixtures were prepared and chromatograms obtained.  In each case small  concentrations of the suspected impurity (beginning at 1.0$ by volume) were introduced i n order to detect i t s effect on the impurity peak without completely masking i t . The essential aspects relating to the possible impurity i d e n t i f i c a t i o n as obtained from these chromatograms i s i l l u s t r a t e d schematically by Figure I I . Increasing proportions of a l l y l alcohol i n the n-propanol caused distance "a" to decrease as peak A increased, i . e . s h i f t i n g the impurity peak to the r i g h t .  Conversely, addition of sec-butanol to the  n-propanol caused the impurity peak to shift to the l e f t . This behavior make i t impossible to attribute the impurity effect to either a l l y l alcohol (b.p. 97.08°C. (27)) or sec-butanol (b.p; 99.53°C. (27)), and could not, i n i t s e l f , eliminate the p o s s i b i l i t y of another compound being present.  The decrease i n concentration of the impurity  with continued d i s t i l l a t i o n (see Results) would apparently be easier to achieve with sec-butanol having a b o i l i n g point difference of more than 2°C.  However there i s an azeotrope between a l l y l alcohol and n-  propanol b o i l i n g at 96.73°C (85) which should separate from propanol quite readily.  At the same time, the f a i l u r e of the bromination  procedure to remove the impurity seems to indicate that a l l y l alcohol i s not a major impurity. None of the columns tested could cause separation of these peaks (A, B, C, F i g . I I ) .  I t was therefore concluded that the impurity was  Following page 27  Figure I I EFFECT OF SUSPECTED IMPURITIES ON CHRGMATOGRAM PEAKS  28. l i k e l y a single compound, and probably sec-butanol, although i t s amount could be determined as a percentage of either a l l y l alcohol or sec-butanol. The> percentage impurity, as determined from either of the two chromatograms run as standards, was 5.5 volume per cent.  In each  case the standard had unknown impurities whose percentage could not be determined exactly, thus making 5*5% an uncertain value.  The mass  spectrometer analysis of n-propanol I I , with i t s average value of 3»5% sec-butanol, was therefore taken as representing the impurity peak i n n-propanol I and I I .  A l l purified sample impurity concentrations were  determined on this basis (84). From the chromatographic analysis, Table 1 shows n-propanol I I I to be the purest of the three different samples, with a value of better than 99.65 volume %. The b o i l i n g point was determined f o r n-propanol I I and I I I . (97.16°C and 97.17°C. respectively).  Although there i s 0.01°C  difference i n the reported values, they are essentially the same within the accuracy obtained.  Moreover any error introduced by using two  different methods of obtaining the atmospheric pressure i s considered negligible. Considering the difference i n impurity percentages for n-propanol I I and I I I , the b o i l i n g point should probably not be taken as a primary c r i t e r i o n of purity i n t h i s case.  However when compared with  Weissberger's value, 97.15°C. (27), these b o i l i n g points both give further indication of the presence of higher b o i l i n g impurity. The refractive indices decreased with decreasing per cent  either of these two compounds. I f plots of refractive index versus per cent composition of secbutanol ( i n n-propanol) and a l l y l alcohol ( i n n-propanol) are considered l i n e a r , then the fact that n-propanol I I (before purification) l i e s  29. closer to the former plot indicates that sec-butanol i s more l i k e l y the impurity. While water present as impurity lowers the refractive index, of n-propanol, removal was clearly shown by the chromatograms. The best value obtained here i s 1.38524 as compared to 1.38556 selected by Weissberger (27) and based on a determination by Vogel (68), using a simple fractional d i s t i l l a t i o n for p u r i f i c a t i o n . From the experience of t h i s investigation one d i s t i l l a t i o n i s not s u f f i c i e n t , and Vogel's result should be regarded dubiously. The viscosity values were calculated by de V e r t e u i l (56) assuming the density values as shown i n Table 3b. The densities were carefully selected and agree well with several other investigators. There are large differences among reported viscosity values, however, and while the results reported here are self-consistent and considered to be accurate to 0.5%, they cannot be used as a means of purity comparison and are given only for completeness.  30. VAPOR PRESSURE APPARATUS The apparatus designed by Whittle ( 2 9 ) for vapor-liquid equilibrium measurements can of course be employed for 1-component vapor pressure measurements, as mentioned above, and i n so doing be simplified by eliminating the phase sampling section. Basically the apparatus consists of a glass p u r i f i c a t i o n t r a i n connected to an equilibrium bomb ( i n a constant temperature bath) and a mercury storage bomb. The two bombs, of stainless s t e e l , are identical and are connected i n a v e r t i c a l position by a movable rod used for measuring levels i n the equilibrium bomb. They are also connected by high pressure tubing so that mercury can be transferred from one bomb to the other, thus enabling the rod to be moved without changing the mercury l e v e l i n the equilibrium bomb. The temperature and pressure of the sample are varied by means of the constant temperature bath, and nitrogen pressure on the mercury i n the mercury storage bomb, respectively. A schematic representation of the bomb assembly, revised from that of Whittle ( 2 9 ) , i s shown i n Figure I I I . The revisions that have been required may be l i s t e d as follows: 1.  The synthetic rubber 0 - r i n g between the bottom bomb face and the pressure closure assembly was replaced with a teflon 0-ring.  2.  The l e v e l indicator, an N.R.C. design as described by Whittle (29), was replaced by a Pemberthy r e f l e x type l e v e l gauge (Model No. V - 9 0 5 ) , pressure tested from 0 to 3 0 0 0 p s i . at  100°F. 3.  The previously s i l v e r soldered joint between the measuring head and the connecting rod was welded to eliminate the p o s s i b i l i t y of mercury attack on the solder.  4.  For the purposes of vapor pressure measurements the position of the l i q u i d vapor interface i s not essential. reason the hot wire anemometer was not i n s t a l l e d .  For t h i s  31  5.  Instead of using a resistance bridge for measuring the mercury l e v e l , an ordinary relay c i r c u i t with an indicating l i g h t was found to be satisfactory.  The c i r c u i t was  opened or closed by raising or lowering the measuring head out of or into the mercury. to within 1.0 mm.  The l e v e l could be ascertained  This error was p a r t i a l l y eliminated by  consistently measuring from above the mercury surface. Pressure tests were i n i t i a l l y made on the entire system, excluding the glass p u r i f i c a t i o n t r a i n and the l e v e l gauge, using nitrogen from a regular storage cylinder up to 1000 p . s . i . and soap solution as a leak detector.  Subsequently the system was f i l l e d with  S.A.E. 10 o i l and the pressure raised to 4500 p . s . i . at room temperature then reduced to 2000 p . s . i .  This pressure was held for  three days with no evident sign of leakage. In order to transfer a sample into the equilibrium bomb, the p u r i f i c a t i o n t r a i n and equilibrium bomb had to be vacuum t i g h t . A _3  vacuum of better than 10 ^ mm. of merctiry was obtained using a mercury diffusion pump i n conjunction with a Cenco Megavac vacuum pump. rate of leakage caused a pressure change of approximately 0.001  The mm./  minute. To f a c i l i t a t e cleaning of the system, technical grades of benzene, toluene, and n-propanol were circulated through the apparatus* cold.  Once the exit solvents became clean, some n-propanol was pumped  into the bomb (leaving sufficient room for expansion) and the bomb temperature raised t o about 250°C.  As the exit solvent from t h i s  treatment contained d i r t particles and a considerable amount of discoloration, further batches of n-propanol were introduced.  As the  number increased, the solvent became cleaner and apparently clearer. However, on standing, the discoloration appeared, similar to the f i r s t batch.  This was attributed to the a i r i n contact with the n-propanol  causing an aldol condensation reaction which formed a coloured polymer (54a).  It was then noted, after the above heating and cooling process,  32.  that the equilibrium bomb was no longer vacuum or pressure t i g h t , due to the apparent f a i l u r e of the teflon V-rings i n the packing gland above gland nut A (Figure I I I ) . Increasing the pressure on the rings, by means of the gland nut and inserted s p l i t steel washers, had no apparent effect on the leak. The f a i l u r e was ascribed to teflon's lack of geometric s t a b i l i t y with respect t o the heating and cooling cycle, possibly with some extrusion at the high temperatures. However, the manufacturer's specifications (86) state that t e f l o n i s f l e x i b l e to 260°C. Above 335°C. i t loses strength and around UOCpC. i t decomposes slowly. Further examination of the packing w i l l have t o be made i n order to ascertain whether a major change i n design i s required. Other aspects of the apparatus design appear satisfactory for such measurements as that of the vapor pressure of n-propanol which has a c r i t i c a l temperature of 263°C. and a c r i t i c a l pressure of about 735 p . s . i .  33.  VAPOR PRESSURE CORRELATIONS 1. Methods Vapor-pressure-temperature  correlations have been made using  the data of Young and the selected equations discussed i n the Literature Review. In addition to Riedel's reduced vapor pressure equation, log  P = A - B_ + C In T R  T  R  + DT  R  (2)  R  i t was considered of interest to check his equation using actual temperatures and pressures; i . e . log P - A - B + C In T + DT T  6  (5)  The two Antoine equations, of the form log P - A - B_. T-C  (3)  were evaluated on the basis of the selection of the constant C. Thomson's graphical method f o r estimating C (36) was used, taking T  Q  = 97.17°C and P = 760 mm. as the point assumed free from error. Q  A plot of log P versus log P - log P  q  i s linear i f the Antoine  T -T o equation holds. When t h i s present data was plotted two straight lines were drawn through the points. The slopes for these two l i n e s , -(To - C), and hence the values of C, -230°C. (below the b.p.) and -176°C. (above the boiling point), were used i n the equations. On conversion to engineering units they became 77.5 and 175°R. respectively. The t h i r d equation, proposed by Frost and Kalkwarf,  34.  log P = A - B + C log T + DP T T2  (4)  was applied directly to the data. In each case the best f i t f o r the data was obtained by the method of least squares. The regression coefficients were calculated on the U.B.C. electronic d i g i t a l computer, Alwac I I I E, programmed with Routine S-3 (87) f o r correlation and regression. In a l l cases, at least s i x significant figures were carried through the computation, reducing the possible error to less than 0.05$. The constants determined for these equations are tabulated i n Table 4. TABLE 4. Constants f o r Vapor Pressure Correlations. Name  Equation  A  S  P  .  Riedel  5  6.5592  Riedel  2  32.694 6323.4 -3.3916  Antoine below b.p.  3  6.7282 3276.4  77.5  Antoine above b.p.  3  5.6444 2200.0  175  Frost  32.233  6.5984 -3.4819  6288.6  -7.6641V  2 .0348 3.0x1020  18.31  The per cent deviation of the values of P calculated from these equations i s compared i n Table 5 and Figure IV with those obtained by Young using the Biot Formula. t log P = a + bpr  t + qj9  (1)  35 TABLE 5 COBRELATION DEVIATIONS  T°R.  P exp. p.s.i.a.  % Deviation of C a l c from p  Biot  491.688 509,688 527.688 545.688 563.688 581.688 599.688 617.688 635.688 653.688 671.688 689.688 707.688 725.688 743.688 761.688 779.688 797.688 815.688 832.688 851.688 869.688 887.688 905.688 923.688 941.688 959.688 966.348  .066519 .140386 .280385 .533701 .970717 1.68619 2.84254 4.62154 7.27071 11.0994 16.2915 23.3204 32.5442 44.3397 59.4419 78.3535 101.790 129.461 162.102 202.381 247.533 301.174 361.196 428.392 506.513 595.290 698.124 737.126  +1.45 +1.79 +1.93 +1.92 +1.83 +2.06 +1.34 +0.60 -0.18 -1.02 -0.78 -0.65 -0.35 +0.12 +0.20 +0.12 -0.20 +0.04 +0.42 -0.20 +0.06 -0.23 -0.06 +0.34 +0.26 +0.07 -0.54 -0.45  -0.69 -0.39 +0.94 +1.30 +1.37 +1.60 +0.73 -0.13 -1.21 -2.00 -1.81 -1.63 -1.24 -0.66 -0.38 -0.23 -0.32 +0.19 +0.83 +0.40 +0.80 +0.59 +0.76 +1.06 +0.73 +0.17 -0.97 -1.32  Average Deviation 0.69  0.87  P  exp. Riedel (2) Riedel (5) Antoine  Frost  -1.10 -1.03 +0.79 +1.24 +1.14 +1.26 +1.09 +0.09 -0.99 -2.06 -1.80 -^1.70 -1.30 -0.75 -0.51 -0.64 -0.49 -0.22 +0.58 +0.15 +0.55 +0.36 +0.78 +1.04 +0.63 +0.12 -0.90 -1.13  +1.10 -0.01 +0.60 +0.25 +0.49 +0.67 +0.03 -0.43 -0.69 -0.79 +0.50 +0.51 +0.46 +0.58 +0.40 +0.10 -0.35 -0.18 +0.18 =0.40 -0.08 -0.30 -0.06 +0.40 +0.30 +0.04 -0.73 -0.46  -1.97 -0.24 +0.89 +1.35 +1.39 +1.60 +0.30 -0.17 -1.10 -2.00 -1.80 -1.60 -1.20 -0.60 -0.32 -0.04 -0.14 +0.35 +1.00 +0.60 +1.40 +0.45 +0.93 +1.16 +0.78 +0.13 -1.10 -1.56  0.87  0.40  0.93  Following page 35  J 510  i  600 Figure IV  1  i  690  |  780  CORRELATION DEVIATIONS  I  870  U — I  960°R.  36. 2. Discussion In general, a l l the plots of Figure 17 show the same tendencies. Positive peaks occur at 581.7, 815»7, 851.7, 905.7 °R. and negative ones at 653.7, 833.7, 869.7 °R. i n nearly a l l cases. The large negative peak near the b o i l i n g point i s of particular interest. This occurs for Frost, Riedel, and Biot equations but i s eliminated by the use of two Antoine equations. Of the four equations compared, the Antoine correlation appears to give the best f i t . However, as was mentioned previously, the disadvantage of using two equations must be taken into consideration. Although Thomson (36) recommends T = 0.8 as the R  intersection point of the equations, T = 0.45 was used here for the R  best results.  The extension of the equations beyond the intersection  point results i n increased deviations, as i s shown by the dashed lines i n Figure IV.  This tends to support the choice of T = 0.45 as the R  intersection point. The next best f i t for the data i s given by the Biot formula. Although the deviations are quite large i n the low temperature regions they become considerably less significant above the boiling point. Blot's formula does have the advantage of covering the f u l l range of data, but i t i s questionable whether i t i s any better i n the low temperature region than the extension of the high temperature range Antoine equation. However this consideration becomes insignificant when the evaluation of the Biot constants i s taken into account. The solution of t h i s five constant equation, following Prony's Method of Interpolation by Expotentials (88), requires much computation and almost excludes the p o s s i b i l i t y of using the method of least squares. The f i t of the two Riedel equations appear to be almost identical indicating that the c r i t i c a l data have been carefully measured. Both equations f i t this data well enough to consider applying them to other members of the n-alcohol series. However  37. there i s a greater p o s s i b i l i t y of chain length relationships between the constants of a reduced form of the equation used for a homologous series. On the other hand, the equation using actual temperatures and pressures i s not dependent on the c r i t i c a l data for i t s correlation. This would be an advantage where c r i t i c a l constants have not been accurately determined or where available data i s fragmentary. The deviations of the Frost equation are very similar to those of the Riedel equations. These are, of course, identical except f o r the l a s t term and the graphs indicate that this difference i s not very significant. I t would appear that the Frost equation does not account for the reverse s " shaped curve i n the plot of log P versus VT. as Thodos (43) found i t did for the normal hydrocarbons. 11  In the f i n a l analysis, the Antoine equations are the simplest to use. Although they f i t the data very w e l l , there i s the d i s advantage of two equations. The Biot equation should not be considered because of the d i f f i c u l t y involved i n calculating the constants. There i s l i t t l e to choose between the Frost and two Riedel equations. Possibly the reduced form of the Riedel equation i s most useful because of i t s a p p l i c a b i l i t y to the theorem of corresponding states.  38. LITERATURE CITED 1.  Lydersen, A. L., Greenkorn, R. A, and Hougen, 0. A., University of Wisconsin, Eng. Experimental Station Report No. 4 (1955).  2.  Shemilt, L. W., The Thermodynamic Properties of the Normal Alcohols, Joint Conference on Thermodynamic and Transport Properties of Fluids, The Institute, London (1957).  3.  Esplen, R. W., M.A.Sc, Thesis i n Chemical Engineering, University of B r i t i s h Columbia 1950.  4. Speers, E. A., M.A.Sc. Thesis i n Chemical Engineering, University of B r i t i s h Columbia 1958. 5. Young, S., S c i . Proc. Roy., Dublin Soc. 12, 374, (1910). 6. Partington, J . R., An Advanced Treatise on Physical Chemistry Vol. I , para. 3 VII B, Longmans, Green, London, 1951. 7. Dreisbach, A. M., Pressure-Volume-Temperature Relationships of Organic Compounds, Handbook Publishing, Ohio, 1952. 8. Riedel, L., Chem. Eng. Techn., 24, 353 (1952). 9. P i t z e r , K. S., J . Am. Chem. Soc., 77, 3427 (1955). 10. Timmermans, M. J . , Physics-Chemical Constants of Pure Organic Compounds. Elsevier. N. Y., 1950. 11.  Timmermanns, M. J . , and Delcourt, M. Y., Journal de Chimie Physique, 31, 101 (1934).  12.  Crismer, L., B u l l . Soc. Chim. Belg., 18, 18 (1904) and 20, 382 (1906).  13. Ramsey,W., and Young, S., Trans. Roy. S o c , 180, 137 (1889).  39.  14.  Fortey,  and Young, S., Trans. Chem. S o c , 81, 717 (1902).  15.  de Brouckers and Prigogine, B u l l . S o c Chlm. Belg., 47, 399 (1938).  16.  Kretchmer, C. B., J . Phys. and Colloid Chem., 55, 1351 (1951).  17.  Keyes, F. G., and Winninghoff, W. J . , J . Am. Chem. S o c , 38, 1178 (1916). Kraus, C. A., and Bishop, J . E., J . Am. Chem. S o c , 43, 1568 (1921).  18. 19.  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Private correspondence with Canadian Chemical Company Limited.  47.  Beckmann Instruments Inc. catalogues: 545-C, 561-A.  48.  Swietoslawski, W., Ebulliometric Measurements Reinhold, New York (1945).  49.  Barr, W. E., and Anhorn, V. J . , S c i e n t i f i c and Industrial Glass Blowing Laboratory Techniques. Pittsburgh, Instruments Publishing, 1949.  50.  I b i d , p.310, F i g . 179.  51.  Ibid, p.311, F i g . 180.  52.  Whittle, D., M.A.Sc. Thesis i n Chemical Engineering, University of B r i t i s h Columbia, 1958.  53.  Cannon, M. R. and Fenske, M. R., Ind. Eng. Chem. (Anal. Ed.) 10, 297 (1938).  54.  A.S.T.M. Standards on Petroleum Products and Lubricants, p.192, 1954.  54a. Consultation with the Department of Chemistry, University of B r i t i s h Columbia, 1958. 55.  Swietoslawski, W., op. c i t . , p.79.  56.  de V e r t e u i l , G. F., M.A.Sc. Thesis i n Chemical Engineering, 1958.  57.  Young, S., and Fortey, E. C , J . Chem. Soc. (London) 83, 45 (1903).  58.  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Thesis i n Chemical Engineering, University of B r i t i s h Columbia, 1951.  72. McKenna, F. E., Tartar, H. V., and Lingafelter, E. C i , J . Am. Chem. S o c , 75, 604 (1953). 73«  Wetzel, F. H., M i l l e r , J . C. and Day, A. R., J . Am. Chem. S o c , 75, 1150 (1953).  43. 74.  Purnell, J . H. and Bowden, S. T., J . Chem. S o c , 539 (1954).  75.  Gartenmeister, R., Z. physik Chem., 6, 524 (1890).  76.  Thorpe, T. E. and Rodger, J . W., P h i l . Trans., 185A, 464 (1894).  77.  Thole, F. B., Z. physik Chem., 74, 686 (1910), J . Chem. S o c , 105, 2011 (1914).  78. Baker, F., J . Chem. S o c , 1409 (1912). 79.  Dunstan, A. E., and Thole, F. B., J . Chem. S o c , 12? (1913).  80.  English, S., and Turner, V. E. S., J . Chem. S o c 105, 1658 (1914).  81. Hertz, W., Z. Anorg. Chem., 47, 104 (1918). 82. Whitman, J . L. and Hurt, D. M., J . Am. Chem. S o c , 52, 4762 (1930). 83.  Jones, W. J . , S. T. Bowden, W. W. Yarnold and W. H. Jones, J . Phys. and Colloid Chem., 52, 753 (1948).  84.  Beckmann Instruments Inc. Catalogue No. GC-86-M1, Peak Height and Peak Area Measurement Techniques. 1958.  85. Azeotropic Data. Advances i n Chemistry Series No. 6, American Chemical Society 1951. 86. Anchor Packing Company Limited, Montreal, Catalogue No. 2. 87.  Computing Centre, University of B r i t i s h Columbia, 1959.  88. Whittaker, E. T., and Robinson, G., The Calculus of Observations. Blackie, London, 1932, p.369.  


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