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The density and transition points of n-tetracosane Yatabe, Eiji 1939

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i. (1  * THE DENSITY AND TRANSITION POINTS * OF » N-TETRAOOSANE *  A THESIS SUBMITTED FOR THE DEGREE OF MASTER OF APPLIED SCIENCE  by EIJI YATABE DEPARTMENT OF CHEMICAL ENGINEERING THE UNIVERSITY OF BRITISH COLUMBIA APRIL 1939  TABLE OF,CONTENTS I. II.  III.  INTRODUCTION...  1  EXPERIMENTAL PROCEDURE (1) Preparation and P u r i f i c a t i o n of Tetracosane......  3  (2) Determination  3  of the Melting Point  (3j Preparation of the Dilatomeier...  4  (4) Use of the Dllatometer.  5  (5) Calibration of the Dilatometer..  6  RESULTS (1) Calibration of Tubes by the Second Method  ..  (2) Calculation of Densities.  17.  7 8  (3) Density-Temperature Curves.....  13  (4) Melting Point of Tetracosane*.  14  (5) Transition Points of Tetracosane*....  14  TREATMENT OF RESULTS (1) Effeot of Cross-Sectional Area Changes on Density  15  (2) Relation of X-Hay Spacings to Crystal Forms......  15  (3) Density at F i r s t Transition Point as a Function of Number of Carbon Atoms i n Paraffin Molecule.  16  (4) Density Equation and Coefficient o f Cubical Expansion of Liquid Tetracosane (5) Note on Density of Solid Paraffins...  16 17  TABLE OF OOHTMiTS V* VI* VII.  S  U  M  M  A  R  (cont'd) Y  *  X  QONQLUSIOU.• •»•»••••«•»••«•»»*«.»•••»•»»•••»«»•«»«»• BIBLIOGRAPHY* DMSITY-TESPERATURE GRAPHS OF I-TETRAGOSAHE  S X8 19 End  V  THE DENSITY AND TRANSITION POINTS OF N-TETRACOSANE I.  INTRODUCTION It has "been known from X-ray studies and other investigations that  s o l i d paraffins, i n common with other long-chain carbon compounds, exh i b i t sudden transformations i n their c r y s t a l structure as they are passed through certain temperature ranges near t h e i r melting points* According to A. Mullor,* there are three types of p a r a f f i n crystals known so f a r : (A)  The normal form, i n which the chains are packed i n a prismatic c e l l of rectangular cross-section.  The chains are perpendi-  cular to the base of the c e l l . (B)  A form of lower symmetry, i n that the chains may be t i l t e d r e l a t i v e to the base, which i s not rectangular.  (C)  A form which has a rectangular cross-section and chains which are t i l t e d relative to the base.  These forms are i l l u s t r a t e d belows  A.  1. Muller, Proc. Roy. S o c , London., 138 A, 514, (1932).  (2) X-ray measurements show that the length of the chain axis depends much less upon the temperature than the other two axes which are contained i n the plane o f the base*  Miiller, i n measuring the expansion of these axes  i n the A and C forms, found that an abrupt transition took place for tetracosane  (Og^Hgo) and a l l the higher members of the series*  One  ob-  ject of this present work was to determine whether or not this transi t i o n affected the density of the hydrocarbons. S.H.  Piper and his associates have shown that at or near this trans-  i t i o n point studied by Miiller there i s also a change i n the t i l t , whioh may or may not be reversible upon c o o l i n g .  2  molecular  This ohange i s  shown by the large increase i n the 001 spacing when studied by X-rays. This can also be seen when a small sample of a paraffin i s heated i n a melting point apparatus, (Pig. l ) i n which case there i s a d e f i n i t e change i n the opacity and volume of the substance*  Since there i s a den-  s i t y change involved i n t h i s t r a n s i t i o n , the dilatometer method was adopted l a s t year by W.M.  Morris  3  o f this laboratory who  density and transition points of n-dotriacontane  (dioetyl).  work i s an investigation of the similar properties of employing the same type of apparatus.  gpj.per.vet a l , Biochem. J . , 25, 2083 (1931). Morris, M.A.Sc* Thesis, U.B.Q. (1938).  determined the The  present  n-tetracosane,  (3)  II.  EXPERIMMTAL PROCEDURE  (1) Preparation and P u r i f i c a t i o n of Tetracosane. The n-tetracosane had been previously prepared by H.P. Godard of this laboratory f o r h i s research on the s o l u b i l i t y of tetracosane i n 4 various solvents.  It. had been synthesized from Eastman Kodak Company  l a u r y l alcohol, using Krafft's method, employing the Wurtz-Pittig r e 5  action. It was p u r i f i e d by repeated fractional c r y s t a l l i z a t i o n from g l a c i a l acetic acid, followed by washing with d i s t i l l e d water and drying i n a vacuum desiccator.  The procedure was continued u n t i l a constant melting  point was obtained. The preparation was quite pure,^ so that one of the samples was r e c r y s t a l l i z e d only once.  The other sample was r e c r y s t a l l i z e d fourteen  times. (•2) Determination ,of the Melting Point. The apparatus was the same type as that employed by Piper,  con-  s i s t i n g of a small glass bulb, containing about 100 c.c. of concentrated sulphuric acid, (see Pig. l ) The temperature was raised slowly by a small burner, and was read o f f a calibrated thermometer which was graduated i n tenths of a degree.  The usual stem correction was applied,  using the equation, T where  c  =  Tp T T  0  0  +  0.000156 1 ( T - T ) 0  m  *» corrected temperature, s  observed temperature,  4 _Godard, M.A. Sc. Thesis, U.B.C. (1937). % r a f f t , Ber., 19, 2219 (1886). Piper et a l ( l o c c i t , p. 2081).  n  (4)  L=  length i n degrees of mercury column not at temperat\ire to be measured,  T  m  • temperature of the middle point of the emergent thread.  It was possible with care to repeat melting points within an accuracy of 0.1°0.  By talcing care not to raise the temperature at a rate faster than  0.5° per minute, i t was 50.7° - 50.8°C»  found that the melting point of tetracosane was  Although t h i s melting point was lower than the values  obtained with methods employing more rapid rates of heating, i t was i n accordance with Piper's assertion that h i s method gave results 0.5° ~ 0.7° lower than the others. n-tetracosane vary from 51.0  6  The recorded values of the melting point of 7 n8 9 , 51.1 to 51.5°C.  A second method f o r the determination of the melting point using the dilatometer and thermostat has been discussed elsewhere*  This method  gave the melting point as 50.7°0. (S)  The Preparation of the Dilatometer. The dilatometer tubings used l a s t year by W.M.  again this year.  Morris"^ were employed  These pyrez c a p i l l a r y tubings had been found to be of  uniform cross-section by measuring, at a constant temperature,  the length  of a given amount of raeroury at different points along the tubings.  Know-  ing the mass, and hence the volume of the mercury, i t was possible to c a l culate the cross-sectional area of a tubing.  The cross-sectional areas  of the tubings used f o r this present work were 0.00343 sq. cm. and 0.00521 sq. cm., when calculated by t h i s method.  10  fPiper et a l ( l o c c i t . p. 2081). jHildebrand, J.A.O.S. 51,.2487 (1929). ®Beilstein, Org. Chem., Vol. I (p. 107) 'Krafft, ( l o c c i t . ) . M o r r i s , (loc. c i t . ) .  (1893).  (5)  Uow, a thick-walled bulb of about 2 cm. diameter was blown from a piece of strong pyrex tubing and was weighed accurately.  About 0.7  gm.  of tetracosane was weighed out, melted, f i l t e r e d , and then poured into the bulb by means of a small funnel, whose end was drawn* then attached to a system evacuated to .00005 mm.  The bulb was  and the hydrocarbon was  repeatedly melted and s o l i d i f i e d to remove a l l occluded solvent and gases. This procedure was repeated u n t i l a constant weight was obtained.  The  bulb was now sealed to the 0.00521 sq. cm. dilatometer tubing, the brass zero-point c l i p was attached near the bottom, and the completed d i l a t o meter was weighed.  The dilatometer was now attached to the vacuum system,  evacuated to the same order as before, and mercury was d i s t i l l e d i n . When s u f f i c i e n t mercury had been d i s t i l l e d over the dilatometer was r e moved, and then weighed again, i l l  the weights were recorded to the  nearest 0.1 mg. and corrected for the buoyancy of the a i r . (4)  The Use of the Dilatometer. The dilatometer was now clamped v e r t i c a l l y to a weighted brass rod,  and placed i n the thermostat (Pig. 2) which oonsisted of a c y l i n d r i c a l pyrex glass vessel containing water e l e c t r i c a l l y heated by a c o i l of n i chrome wire controlled by a precision type thermo-regulator. Good a g i tation was obtained with a propellor-type s t i r r e r .  The temperature was  controlled to within 0.02° i n the range S0°-75°0, by means of this arrangement.  Por lower readings, the temperatures were held constant manually  by an adjusted flow of ice water. The height of the mercury l e v e l above the zero point mark at various, temperatures was measured by means of a oathetometer, graduated i n 0.005 cm.  A l l the readings were taken after the temperature had been kept con-  stant for from 3 hours to 75 hours, depending on the temperature.  For  /^/cf.Z  Diagram  of  T^/ier/wos/af  (6)  temperatures very near the *ransitipnipbints, i t was found necessary to keep the temperature constant f o r 24 hours or more, i n order that equilibrium was to be reached* Most of the readings were duplicated* whether they were obtained by heating or cooling the bath. The temperatures were read o f f the calibrated thermometer placed t o t a l l y immersed i n the bath* It was found necessary to add some more mercury f o r the low temperature readings. This was oorrected f o r i n the density calculations.; For  the tubing of 0.00343 sq.* cm. cross-sectional area, about 0.5  gm. of tetracosane was required. To determine the melting point of tetracosane by using the d i l a t o meter and the thermostat, the temperature was raised to 50.4°C» and kept there for 3 hours, then raised 0.1° every 3 hours. It was found that the hydrocarbon melted completely at 50.7°0. a f t e r 2 hours, which agreed very well with the value obtained previously. (5)  Calibration of the Dilatometer. The mercury and hydrocarbon were removed from the dilatometer.  The mercury was removed by applying vacuum, and the hydrocarbon by r e peated washing with hot 95% ethyl alcohol. After making sure that a l l the hydrooarbon was removed, the dried dilatometer was weighed and then a t t ached to the vacuum system. Meroury was d i s t i l l e d into i t , completely f i l l i n g the bulb. After weighing, i t was placed i n the thermostat and the  height of the mercury column was measured at various temperatures.  Knowing the mass of the mercury, the volume of the mercury was easily determined as was the cross-sectional area of the c a p i l l a r y tubing, which value agreed excellently with that obtained by the f i r s t method.  (7) III.  RESULTS In the following tables and discussions, Sample 3. refers to the  tetracosane which had been r e c r y s t a l l i z e d once from Godard's preparation, (loo. o i t . ) while Sample 2 refers to that which had been recry s t a l l i z e d 14 times. (r) Calibration of Tubes by the Second Method. Sample calculations for the two tubings are given: Sample 1. Mass of Mercury  -  47.2891 gm.  Volume at 50°0.  3.50988 c c .  Volume at 30°C.  3.49727 c c  Difference i n Volume  0.01261 c c .  Correction f o r Expansion of Glass •  (20)(3.49727)(0.0000096) a  Net expansion of Mercury Difference i n Levels « Area  -  0.00067 c c . 0.01194 c c .  7.820 - 5.530 - 2.290 cm.  0.01194/2.290  s  0.005214 sq.cm.  Volume of Bulb to Zero-Point at 30°G. , ?So •  ^  hA  •  3.49727-5.530(0.005214)  «  3*46844  CC  Sample 2. Mass of Mercury  63.3057 gm.  Volume at 50°C.  4.69873 c c .  Volume at 30°C.  4.68179 c c .  Difference i n Volume  -  0.01695 c c  Correction f o r Expansion of Glass •  (20)(4.68179)(0.0000096) *  0.00090 c c  (8)  Net Expansion of Mercury Difference i n l e v e l s = Area  =  -  0.01605 c . c  11.275 - 6.585  0.01605/4.690  =  =  4.690 cm.  0.003422 sq. cm.  Volume of Bulb to Zero-Point at 30°C. , V^  v£  -  0  -  hA  •  4.68179  - I 6.585(0.003422)  =  4.65926 o.C.  The values are tabulated i n Table I below: TABLE I. Sample  Temperature  Area of Capillary  Volume at Zero Pt.  1  30° G.  0.005214 sq.cm.  3.46844 c.c.  2  30° 0.  0.003422 sq.cm.  4.65926 CO.  . The areas of the c a p i l l a r y tubings computed by the above method are seen to agree very well with the values obtained by the f i r s t method, v i z . , 0.00521 sq.cm* and 0.00343 sq* cm* . (2). Calculation of Densities. Since a l l the calculations follow the same pattern, only one example has been given. The following symbols were used: A  -  oross-sectional area of the tube.  t  -  temperature at which reading was  v:30  taken,  volume of bulb at the zero mark, the subscript indicating the temperature, 3 0 ° C , at which the volume was  h ^0 1'  -  determined,  height of mercury column above zero mark, volume at height h at 30°G. . volume at height h at t°G. V^ ( 1 0  a(t - 30) )  the coMf&eient  where a  -  9.6 x 10"  6  c . c / °C#*  of cubical expansion of pyrex glass*  (9)  W  -  V^. -  w  mass of mercury i n the bulb. volume of mercury i n the bulb at t°0.  -  W X (Specific Volume of Mercury at t°0.)  -  mass of tetracosane i n the bulb.  v^ -  volume of tetraoosane i n the bulb at t°0.  - A. -  7  t  density o f tetracosane at t°C.  Example t  -  50.90° C.  A  -  0.005214 sq.cm.  h  -  32.665 cm.  «=  (0.005214) (32.665)  V°, 30  -  3.46844 c c  30  «  3.46844 +  =  3.63876( 1 +  »  3.63949 c c .  M A  v  V  11  50.90  0.17032  *  0.17032 c c .  »  3.63876 o . c  (9.6 X 10~ ) (50.90 - 30.00) ) 6  W•.-,«• 36.6789 gm. ?  50.90 50.90  9  3 6  D  50.90  •> 2.72287 c c  6 7  3.63949 - 2.72287  a  o n  w  * 8 9 (0.07423506)  -  0.7137 gm.  "  °»  7 1 3 7  / 0.91662  s  0.91662 c c  -  0.7786 gm. / c c  The results f o r the two samples f o r the complete temperature range are as follows; TABLE II Sample 1. iV^Q  -  3.46844 c c  (10)  t  A  -  0.005214 sq. cm.  W  -  0.7137 gm.  W  -  36.6789 gm.  ft  hA  Y* t  1  V  30  30.00  1.340  0.00699  3.47543  3.47543  2.71259  0QV76284  0.9356  35.00  2.050  0.01069  3.47913  3.47930  2.71505  0.76425  0.9339  40.00  2.590' 0.01350  3.48194  3.48227  2.71751  0.76476  0.9332  42.00  3.155  0.01645  3.48489  3.48529  2.71874  0.76655  0.9311  45.00  3.560  0.01856  3.48700  3.48750  2.71996  0.76754  0.9299  46.00  4.220  0.02200  3.49044  3.49098  2.72045  0.77053  0.9262  46.60  5.175  0.02698  3.49542  3.49598  2.72075  0.77523  0.9206  46.60  5.530  0.02883  3.49727  3.49783  2.72084  0.77699  0.9185  46.90  5.885  0.03068  3.49912  3.49969  2.72089  0.77880  0.9164  47.00  6.380  0.033327  3.50171  3.50228  2.T2094  0.78134  0.9134  47.10  7.855  0.04096  3.50940  3.50998  2.72099  0.78899  0.9046  47.20  8.495  0.04429  3.51273  3.51331  2.72104  6.79227  0.9008  47.40  9.910  0.05167  3.52011  3.52070  2.72114  0.79956  0.8926  47.50 10.510  0.05480  3.52324  3.52383  2.72119  0.80264  0.8892  47.60 10.630  0.05542  3.52386  3.52445  2.72124  0.80321  0.8886  47.70 13.350  0.06961  3.53805  3.53865  2.72129  0.81736  0.8732  47.80 13.900  0.07247  3.54091  3.54152  2.72134  0.82018  0.8702  47.90 14.385  0.07500  3.54344  3.544055  2.72139  0.82266  0.8676  48.00 14.440  0.07529  3.54373  3.54434  2.72143  0.82291  0.8673  48.30 :L4.550  0.07586  3.54430  3.54492  2.72158  0.82334  0.8668  49.00 L4.780  0.077065  3.54550  3.54615  2.72194  0.82421  0.8659  49.30 L4.885  0.07761  3.54605  3.54671  2.72209  0.82462  0.8655  50.00 u5.130  0.07983  3.54827  3.54895  2.72242  0.82653  0.8635  (11)  M  v  15.435  0.08048  3.54892  3.54961  2.72257  15.875  0.08277  3.55121  3.55191  2.72267  18.255  0.09518  3.56362  3.56433  2.72272  32.615  0.17005  3.63849  3.63921  2.72277  32.645  0.17021  3.63865  3.63937  2.72282  32.665  0.17032  3.63876  3.63949  2.72287  32.925  0.17167  3.64011  3.64088  2.72341  33.625  0.17532  3.64376  3.64464  2.72487  33.865  0.17657  3.64501  3.64592  2.72537  34.805  0.18147  3.64991  3.65096  2.72733  35.990  0.18765  3.65609  3.65732  2.72978  37.155  0.19373  3.66217  3.66357  2.73225  38.350  0.19996  3.66840  3.66998  2.73470  30  2t  With AdditionalnJaercury  -  0.82704 0.82924 0.84161 0.91644 0.91655 0.91662 0.91747 0.91977 0.92055 0.92363 0.92754 0.93132 0.93528  0.8630 0.8607 0.8480 0.7788 0.7787 0.7786 0.7779 0.7760 0.7753 0.7727 0.7694 0.7663 0.7631  37.2142 gm.  5.220  0.02722  3.49566  3.49482  2.73974  0.75508  0.9452  5.930  0.03092  3.49936  3.49869  2.74223  0.75646  0.9435  6.630  0.03457  3.503Q1  3.50251  2.74472  0.75779  0.9418  7.215  0.03762  3.50606  3.50572  2.74721  0.75851  0.9409  7.865  0.04101  3.50945  3.50928  2.74969  0.75959  0.9396  8.545  0.04455  3.51299  3.5129?  2.75218  0.76081  ' 0.9388  9.315  0.04857  3.51701  3.51718  2.75467  0.76251  0.9360  10.135  0.05284  3.52128  3.52162  2.75717  0.76445  0.9336  10.905  0.05686  3.52530  3.52577  2.75917  0.76660  0.9310  11.220  0.05850  3.52694  3.52745  2.75966  0,76779  0.9296  12.055  0.06285  3.53129  3.53183  2.76015  0.77168  0.9249  22.050  0.11497  3.58341  3.58403  .2.76115  0.82288  0.8673  (12)  Sample 2.  t  V*L  -  4.65926 o.o.  A  -  0.003422 sq. cm.  w  -  0.4561 gm.  W  -  56.3663 gm.  h  hA  30  <  35.00  0.345  0.00118  4.66044  4.66066  4.17235  0.48831  0.9340  40.00  1.275  0.00436  4.66362  4.66409  4.17613  0.48796  0.9347  42.00  2.190  0.00749  4.66675  4.66729  4.17802  0.48927  0.9322  45.00  2.940  0.01006  4.66932  4.66999  4.17990  0.49009  0.9306  46.00  4.720  0.01615  4.67541  4.67613  4.18063  0.49550  0.9205  46.60  5.370  0.01838  4.67764  4.67839  4.18111  0.49728  0.9172  46.60  5.805  0.01986  4.67912  4.67988  4.18127  0.49861  0.9147  47.10  6.040  0.02067  4.67993  4.68070  4.18149  0.49921  0.9136  47.20  8.705  0.02979  4.68905  4.68982  4.18157  0.50825  0.8974  47.50  9.350  0.03200  4.69126  4.69205  4.18180  0.51025  0.8939  47.60  9.485  0.03246  4.69172  4.69251  4.18188  0.51063  0.8932  47.60  13.120  0.04490  4.70416  4.70497  4.18203  0.52294  0.8722  48.00  14.200  0.04859  4.70785  4.70867  4.18217  0.52650  0.6663  48.30  14.350  0.04911  4.70837  4.70920  4.18240  0.52680  0.8658  49.00  14.665  0.05018  4.70944  4.71030  4.18292  0.52738  0.8648  50.00  15.165  0.05189  4.71215  4.71306  4.18367  0.52939  0.8616  50.50  15.825  0.05415  4.71341  4.71434  4.18406  0.53028  0.8601  50.60  18.280  0.06255  4.72181  4.72275  4.18414  0.53861  0.8466  50.70  32.385  0.11082  4.77008  4.77103  4*18421  0.58682  0.777S  52.00  32.830  0.11234  4.77160  4.77261  4.18519  0.68742  0.7764  55.00  33.890  0.1159?  4.77523  4.77638  4.18745  0.58893  0.7744  (is)  h  t  4  hi  v  t  D  t  6Q.00  35.630  0*12193  4.78119  4.78257  4.19122  0.59135  0.7713  65.00  37.385  0.12793  4.78719  4.78880  4.19500  0.59380  0.7681  70.00  39.110  0.13383  4.79309  4.79493  4.19878  0.59615  0.7651  75.00  40.835  0.13974  4.79900  4.80107  4.20256  0.59851  0.7621  •  •  m .th Additi onal Mercury  a. W - 56.9624 gi  5.00  5.750  0.01968  4.67894  4.67782  4.19363  0.48419  0.9420  10.00  6.960  0.02383  4.68309  4.68219  4.19744  0.48475  0.9409  15.00  8.190  0.02803  4.68729  4.68662  4.203.25  0.48537  0.9397  20.00  9.205  0.03150  4.69076  4.69031  4.20506  0.48525  0.9399  25.00  10.460  0.03579  4.69505  4.69482  4.20887  0.48595  0.9386  30.00  11.735  0.04016 ,4.69942 4.69942  4.21268  0.48674  0.9370  35.00  13.030  0,04459  4.70585  4.70408  4.21649  0*48759  0.9354  40.00  14.385  0.04923  4.7Q849  4.70894  4.22031  0.48863  0.9334  44.00  15.560  0.05325  4.71251  4.71314  4.22336., 0.48976  0.9312  45.00  15.925  0.05450  4.71376  4.71444  4.22412  0.49032  0.9302  46.00  16.560  0.05667  4.71593  4.71667  4.22488  0.49179  0.9274  48.00  27.150  0,09291  4.75217  4.75299  4.22641  0.52658  0.8662  (3) The density-temperature curves have been plotted for the range 0° to 80°C. . f o r the two samples. (Plate I at the end.) The density at 51.1°0», 0.7785 gm./c.c, obtained with Sample 1, has been found to correspond very 11 well with the value found i n B e i l s t e i n ,  v i z . , 0.7786 gm./c.c. The low  values found f o r Sample 2 are probably due to an error i n the calibration of the dilatometer. (4) The melting point of tetracosane has been found to be 50.7°0. using two methods. The value i s lower than those found i n the l i t e r a t u r e by •u.o-  r  (Hmilstein,  (loc. c i t . )  (14)  0.2° to 0.8 , U  but i s ingeneral agreement with Piper's results.  (5) The t r a n s i t i o n points of tetracosane, as indicated by definite breaks i n the density curves, have been found to occur at 47.9°C. and 50.6+°G.. At these temperatures d e f i n i t e changes take place i n the cryst a l l i n e structure. The-opaque form stable at room temperature i s converted completely  int6>idjhertasaneluaent form at the lower transition point, while  at the higher t r a n s i t i o n point, the translucent form i s converted into a second opaque form, which i s stable only within a few hundredths of a degree. Immediately above t h i s second transition temperature, the hydrocarbon melts* A l l the reactions were found to be reversible at the transition points* or more correctly, transition regions* It was  found, however, that  the metamorphosis from the translucent into the opaque form required many days, and perhaps weeks, before the transformation was complete* The change from the opaque into the translucent form did not require more than a few hours, before equilibrium was established* At the second transition point, equilibrium was reached i n a few hours whether approached from below or above i t * It was not possible to obtain a reading right at this point# because of the limitations of the thermostat* (6)  Prom the density-temperature curves, i t can be seen that the curve  for Sample 2 has a steeper slope at the f i r s t transition point than that for Sample 1* This shows that repeated fractional r e c r y s t a l l i z a t i o n s w i l l 13 purify a hydrocarboni work on  confirming the results obtained by Morris  dotriacontane* 1 2 ls  P i p e r et a l , (loc. c i t . p.208l)« Morris, (loo..cit.).  with his  (15)  IV.  TREATMENT OF RESULTS.  (1) From the density-temperature curves, i t may be seen that no sudden change takes place at 40° -  4 1 ° C , at which temperature M u l l e r * ob4  served a d e f i n i t e expansion i n the cross-sectional area of the unit molecular crystal of tetracosane. From t h i s fact, i t may be inferred that changes i n cross-section of the crystal have l i t t l e or no effect on i t s density. (2) The A and B forms of the 001 spacings have been found by Muller and S a v i l e ^ to be 32*5 % and 30.4 2., respectively, f o r tetracosane. The 1  t i o of the B to the A spacing i s then 0.935. How,  ra-  i f the density (<0;8676)  at the f i r s t transition point, 47.9°G.» i s divided by the estimated dens i t y (0.927) at the same temperature found by extrapolating the low temperature part of the curve, the ratio i s found to be 0.955 again* It may therefor be inferred that,the B form corresponds to the opaque form of t e t racosane which i s stable at.low temperatures, and the A form corresponds to the translucent form* One may also say that the change i n density at the t r a n s i t i o n point i s due wholly to the change i n molecular t i l t * I f one appliesthe same calculations to the density curves of d o t r i a 16 oontane obtained by Morris, the r a t i o of the densities i s found to be 0.8770 / 0.934 , i . e . 0.939. This shows that the opaque form of t^his hydrocarbon i s of the B type as i n the case of tetracosane. One wonders why Piper and h i s associates could not obtain B spacing measurements f o r dotriacontane•* I f i t i s assumed that the A form i s the translucent and v e r t i c a l type of c r y s t a l , then the ratio B:A corresponds to the sine of the angle of ^Muller, ( l o c cit.) M u l l e r and Savile, P r o c Roy. S o c Lond., 127A, 417 (1930) 17 J^Morris, (loc* c i t . ) Piper et a l , (loc. c i t . ) 1 5  o&eoo  O-079O O&70O O077O ^$0-<&760  I 4 X ^  •s  0-&73O  0-072O  ^0.07/0  ^0^700  0.06ZO 0.0660 Z3  2  <  2  ^  2G  <5V  27  2  3  f7~°  9  /><zy<?  7<sJ  -32  (16)  molecular t i l t , which angle when calculated f o r the case of tetracosane comes to 69.5°« (3) Since the A spacing i s a l i n e a r function of the number of carbon atoms 18 i n the hydrocarbon molecule,  i t i s perhaps safe to i n f e r that the density  at the f i r s t transition point i s also a similar function. Using the values obtained with tetracosane and dotriacontane, a graph has been plotted f o r 0g  g  to G  g s  paraffins. (Pig. 3.) The predicted densities are tabulated be-  low: TABLE III Ho* of 0 atoms  (4)  Density at F i r s t Trans. Pt.  23  0.8664 gm./c.c.  25  0.8688  26  0.8700  27  0.8711  28  0.8723  29  0.8734  30  0.8746  31  0.8758  33  0.8782  Prom the density-temperature curve f o r Sample 1, the following den-  s i t y equation was established f o r the l i q u i d lines D  t  .«  0.7788  -  0.00064 (t• - 50.7)  where D^ i s the density at temperature t° G* 19 Applying t h i s equation to three densities found i n B e i l s t e i n , ues corresponded very w e l l . They are tabulated below: 1 8  1 9  P i p e r et a l , (loc* c i t . p.2080) B e i l s t e i n , (loc. c i t . )  the v a l -  (17)  TABLE IV Density * Temperature  Be11stein  Calculated  51.1° C.  0.7786  0.7785  76.0°  0.7628  0.7626  98.9°  0.7481  0.7480  From the same curve the coefficient of cubical expansion o f the l i q u i d hydrocarbon was determined. c.o./o.c./ °G.  Its value was found to be 0.0008411  The s p e c i f i c volume equation f o r the l i q u i d tetracosane i s  then: V  t  •  1.2840 ( 1 + 0.0008411 (t-50.7) )  where t i s any temperature above 50.7°C. The l i q u i d l i n e was found to be exactly p a r a l l e l to that for dotriaoontane  s  showing that a l l l i q u i d paraffins have the same coefficient of  cubioal expansion. (5) For the s o l i d part of the curve, i t was seen to require a complicated form of equation.  Due to lack of time, i t s derivation was not carried out.  The curve was, however, seen to be quite p a r a l l e l to that of dotriaoontane. A further observation indicated that both hydrocarbons i n the opaque s o l i d form have p r a c t i c a l l y the same density.  (18)  V.  SUMMARY* (1) The density-temperature curves for two samples of n-tetracosane nave  been determined and plotted f o r the range 0° to 80°0. (2) Two transition points have been determined. (3) An equation has been developed f o r the density above the melting point. (4) The c o e f f i c i e n t of oubioal expansion of the l i q u i d hydrocarbon has been determined. (5) An attempt has been made to correlate the results obtained with tetracosane to those of dotriacontane i n order to generalise some properties. (6) The density has been found to be independent of changes i n cross• sectional area of the crystals, but i s affected greatly by the molecular t i l t . VI.  CONCLUSION. The author wishes to take this opportunity to express h i s apprecia-  tion to Dr. W . P . Seyer f o r h i s kind interest i n this work.  Without his  valuable suggestions and assistance this work would not have been possible-  119)  711.  BIBLIOGRAPHY.  (1) B e i l s t e i n :  Handbuch der organisohen Chemie, 7 o l . I, p. 107 (1895)  (2) Godard, H.P., tane/'  ''Solubility of Tetracosane i n Propane, Butane and Pen-  Thesis submitted for M.A.Sc. Degree, U.B.C., A p r i l ,  (5) K r a f f t , Berichte, 19, 2219 (4) Morris, W.M., tyl),"  1957.  (1886).  "Density and Transition Points of Dotriacontane (Dice-  Thesis submitted f o r M.A.Sc. Degree, U.B.O., A p r i l ,  1938.  (5) Muller, A., Proceedings of the Royal Society, London, 130 A, 514 (1932). (6) M i l l e r , A and Savile, Proceedings of the Royal Society, London, 127 A, 417  (1930).  (7) Piper, S.II., Ghibnall, A.G., Hopkins, S.J., Pollard, A., Smith, J.A.B., and Williams, E.F., Biochemioal Journal, 25, 2072-2094, (1931). (8) Hildebrand and Wachter, Journal of the American Ghemioal Society, 2487 (1929).  0  10  15  1^1 LLJMETERS  EUGENE  DIETZ.b'EN  C  25  30  35  40  TEMPERATURE  45  50  degrees C  55  60  65  73  70 EUGENE  DIE TZ6EX  C  60  

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