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The density and transition points of n-tetracosane 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. INTRODUCTION... 1 II. EXPERIMENTAL PROCEDURE (1) Preparation and Purification of Tetracosane...... 3 (2) Determination of the Melting Point 3 (3j Preparation of the Dilatomeier... 4 (4) Use of the Dllatometer. 5 (5) Calibration of the Dilatometer.. 6 III. RESULTS (1) Calibration of Tubes by the Second Method .. 7 (2) Calculation of Densities. 8 (3) Density-Temperature Curves..... 13 (4) Melting Point of Tetracosane*. 14 (5) Transition Points of Tetracosane*.... 14 17. 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 Firs t Transition Point as a Function of Number of Carbon Atoms in Paraffin Molecule. 16 (4) Density Equation and Coefficient of Cubical Expansion of Liquid Tetracosane 16 (5) Note on Density of Solid Paraffins... 17 TABLE OF OOHTMiTS (cont'd) V* S U M M A R Y * X S VI* QONQLUSIOU.• •»•»••••«•»••«•»»*«.»•••»•»»•••»«»•«»«»• X8 VII. BIBLIOGRAPHY* 19 DMSITY-TESPERATURE GRAPHS OF I-TETRAGOSAHE End V THE DENSITY AND TRANSITION POINTS OF N-TETRACOSANE I. INTRODUCTION It has "been known from X-ray studies and other investigations that solid paraffins, in common with other long-chain carbon compounds, ex- hibit sudden transformations i n their crystal structure as they are passed through certain temperature ranges near their melting points* According to A. Mullor,* there are three types of paraffin crystals known so far: (A) The normal form, in which the chains are packed in 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, in that the chains may be t i l t e d re- lative to the base, which is 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 illustrated belows A. 1. Muller, Proc. Roy. Soc, 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 in the plane o f the base* Miiller, in measuring the expansion of these axes in 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 trans- ition affected the density of the hydrocarbons. S.H. Piper and his associates have shown that at or near this trans- ition point studied by Miiller there is also a change in the molecular t i l t , whioh may or may not be reversible upon cooling. 2 This ohange is shown by the large increase in the 001 spacing when studied by X-rays. This can also be seen when a small sample of a paraffin is heated in a melting point apparatus, (Pig. l) in which case there is a definite change in the opacity and volume of the substance* Since there is a den- sity change involved i n this transition, the dilatometer method was adopted last year by W.M. Morris 3 of this laboratory who determined the density and transition points of n-dotriacontane (dioetyl). The present work is an investigation of the similar properties of n-tetracosane, 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). (3) II. EXPERIMMTAL PROCEDURE (1) Preparation and Purification of Tetracosane. The n-tetracosane had been previously prepared by H.P. Godard of this laboratory for his research on the solubility of tetracosane in 4 various solvents. It. had been synthesized from Eastman Kodak Company lauryl alcohol, using Krafft's method,5 employing the Wurtz-Pittig re- action. It was purified by repeated fractional crystallization from glacial acetic acid, followed by washing with d i s t i l l e d water and drying in a vacuum desiccator. The procedure was continued until a constant melting point was obtained. The preparation was quite pure,^ so that one of the samples was re- crystallized only once. The other sample was recrystallized fourteen times. (•2) Determination ,of the Melting Point. The apparatus was the same type as that employed by Piper, con- sisting 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 off a calibrated thermometer which was grad- uated in tenths of a degree. The usual stem correction was applied, using the equation, T c = Tp + 0.000156 1 (T 0-T m) where T 0 *» corrected temperature, T 0 s observed temperature, 4 _Godard, M.A. Sc. Thesis, U.B.C. (1937). % r a f f t , Ber., 19, 2219 (1886). Piper et al ( l o c c i t , p. 2081). n (4) L = length in degrees of mercury column not at temp- erat\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 found that the melting point of tetracosane was 50.7° - 50.8°C» Although this melting point was lower than the values obtained with methods employing more rapid rates of heating, i t was in accordance with Piper's assertion that his method gave results 0.5° ~ 0.7° lower than the others. 6 The recorded values of the melting point of 7 n8 9 n-tetracosane vary from 51.0 , 51.1 to 51.5°C. A second method for 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 last year by W.M. Morris"^ were employed again this year. These pyrez capillary 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 for this present work were 0.00343 sq. cm. and 0.00521 sq. cm., when calculated by this method. fPiper et al ( l o c c i t . p. 2081). jHildebrand, J.A.O.S. 51,.2487 (1929). ®Beilstein, Org. Chem., Vol. I (p. 107) (1893). 'Krafft, ( l o c c i t . ) . 1 0Morris, (loc. c i t . ) . (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, filtered, and then poured into the bulb by means of a small funnel, whose end was drawn* The bulb was then attached to a system evacuated to .00005 mm. and the hydrocarbon was repeatedly melted and solidified to remove a l l occluded solvent and gases. This procedure was repeated until 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 dilato- 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 sufficient mercury had been d i s t i l l e d over the dilatometer was re- 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 vertically to a weighted brass rod, and placed i n the thermostat (Pig. 2) which oonsisted of a cylindrical pyrex glass vessel containing water electrically heated by a c o i l of n i - chrome wire controlled by a precision type thermo-regulator. Good agi- tation was obtained with a propellor-type s t i r r e r . The temperature was controlled to within 0.02° in the range S0°-75°0, by means of this arrange- ment. Por lower readings, the temperatures were held constant manually by an adjusted flow of ice water. The height of the mercury level above the zero point mark at various, temperatures was measured by means of a oathetometer, graduated in 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 for 24 hours or more, in order that equi- librium was to be reached* Most of the readings were duplicated* whether they were obtained by heating or cooling the bath. The temperatures were read off the calibrated thermometer placed totally immersed in the bath* It was found necessary to add some more mercury for the low temp- erature readings. This was oorrected for in 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 dilato- 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. after 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 re- 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 att- 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 in 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 capillary 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 recrystallized once from Godard's preparation, (loo. oit.) while Sample 2 refers to that which had been recry stallized 14 times. (r) Calibration of Tubes by the Second Method. Sample calculations for the two tubings are given: Sample 1. Mass of Mercury - Volume at 50°0. Volume at 30°C. Difference in Volume Correction for Expansion of Glass • (20)(3.49727)(0.0000096) a Net expansion of Mercury Difference in Levels « 7.820 - 5.530 - 2.290 cm. Area - 0.01194/2.290 s 0.005214 sq.cm. Volume of Bulb to Zero-Point at 30°G. , hA • 3.49727-5.530(0.005214) « 3*46844 C C 47.2891 gm. 3.50988 c c . 3.49727 c c 0.01261 c c . 0.00067 c c . 0.01194 c c . ?So • ^ Sample 2. Mass of Mercury Volume at 50°C. Volume at 30°C. Difference in Volume - Correction for Expansion of Glass • (20)(4.68179)(0.0000096) * 63.3057 gm. 4.69873 c c . 4.68179 c c . 0.01695 c c 0.00090 c c (8) Net Expansion of Mercury - 0.01605 c.c Difference in levels = 11.275 - 6.585 = 4.690 cm. Area = 0.01605/4.690 = 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 in 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 capillary tubings computed by the above method are seen to agree very well with the values obtained by the f i r s t method, viz., 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 ex- ample has been given. The following symbols were used: A - oross-sectional area of the tube. temperature at which reading was taken, volume of bulb at the zero mark, the subscript indicating the temperature, 30°C, at which the volume was determined, height of mercury column above zero mark, volume at height h at 30°G. . volume at height h at t°G. V^ 0( 1 a(t - 30) ) where a - 9.6 x 10"6 c . c / °C#* the coMf&eient of cubical expansion of pyrex glass* t - v: 30 h - ^ 0 1 ' (9) W - mass of mercury in the bulb. V̂ . - volume of mercury i n the bulb at t°0. - W X (Specific Volume of Mercury at t°0.) w - mass of tetracosane in the bulb. v^ - volume of tetraoosane in the bulb at t°0. - A. - 7 t - density of tetracosane at t°C. Example t - 50.90° C. A - 0.005214 sq.cm. h - 32.665 cm. M «= (0.005214) (32.665) * 0.17032 c c . V°,A - 3.46844 c c 30 v30 « 3.46844 + 0.17032 » 3.63876 o.c V11 = 3.63876( 1 + (9.6 X 10~6) (50.90 - 30.00) ) 50.90 » 3.63949 c c . W•.-,«• 36.6789 gm. ?50.90 9 3 6* 6 789 (0.07423506) •> 2.72287 c c o n  a 3.63949 - 2.72287 s 0.91662 c c 50.90 w - 0.7137 gm. D50.90 " ° » 7 1 3 7 / 0.91662 - 0.7786 gm. / c c The results for the two samples for the complete temperature range are as follows; TABLE II Sample 1. iV̂ Q - 3.46844 c c (10) A - 0.005214 sq. cm. W - 0.7137 gm. W - 36.6789 gm. t ft hA V30 Y* 1 t 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) 15.435 15.875 18.255 32.615 32.645 32.665 32.925 33.625 33.865 34.805 35.990 37.155 38.350 5.220 5.930 6.630 7.215 7.865 8.545 9.315 10.135 10.905 11.220 12.055 22.050 M 0.08048 0.08277 0.09518 0.17005 0.17021 0.17032 0.17167 0.17532 0.17657 0.18147 0.18765 0.19373 0.19996 v30 3.54892 3.55121 3.56362 3.63849 3.63865 3.63876 3.64011 3.64376 3.64501 3.64991 3.65609 3.66217 3.66840 3.54961 3.55191 3.56433 3.63921 3.63937 3.63949 3.64088 3.64464 3.64592 3.65096 3.65732 3.66357 3.66998 2.72257 2.72267 2.72272 2.72277 2.72282 2.72287 2.72341 2.72487 2.72537 2.72733 2.72978 2.73225 2.73470 With AdditionalnJaercury 2t 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 - 37.2142 gm. 0.02722 3.49566 3.49482 2.73974 0.75508 0.9452 0.03092 3.49936 3.49869 2.74223 0.75646 0.9435 0.03457 3.503Q1 3.50251 2.74472 0.75779 0.9418 0.03762 3.50606 3.50572 2.74721 0.75851 0.9409 0.04101 3.50945 3.50928 2.74969 0.75959 0.9396 0.04455 3.51299 3.5129? 2.75218 0.76081 ' 0.9388 0.04857 3.51701 3.51718 2.75467 0.76251 0.9360 0.05284 3.52128 3.52162 2.75717 0.76445 0.9336 0.05686 3.52530 3.52577 2.75917 0.76660 0.9310 0.05850 3.52694 3.52745 2.75966 0,76779 0.9296 0.06285 3.53129 3.53183 2.76015 0.77168 0.9249 0.11497 3.58341 3.58403 .2.76115 0.82288 0.8673 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 (12) Sample 2. V*L - 4.65926 o.o. A - 0.003422 sq. cm. w - 0.4561 gm. W - 56.3663 gm. t 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) t h h i 4 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 Merc ury W - 56.9624 gi a. 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. . for 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 in Beilstein, viz., 0.7786 gm./c.c. The low values found for Sample 2 are probably due to an error in 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 in the literature by •u.o- r (Hmilstein, (loc. cit.) (14) 0.2° to 0.8U, but i s ingeneral agreement with Piper's results. (5) The transition points of tetracosane, as indicated by definite breaks in the density curves, have been found to occur at 47.9°C. and 50.6+°G.. At these temperatures definite changes take place in the crys- talline structure. The-opaque form stable at room temperature is converted completely int6>idjhertasaneluaent form at the lower transition point, while at the higher transition point, the translucent form is converted into a second opaque form, which is stable only within a few hundredths of a de- gree. Immediately above this second transition temperature, the hydrocar- bon 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 in 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 recrystallizations w i l l 13 purify a hydrocarboni confirming the results obtained by Morris with his work on dotriacontane* 1 2Piper et a l , (loc. c i t . p.208l)« l sMorris, (loo..cit.). (15) IV. TREATMENT OF RESULTS. (1) From the density-temperature curves, i t may be seen that no sudden change takes place at 40° - 41°C, at which temperature Muller* 4 ob- served a definite expansion in the cross-sectional area of the unit mol- ecular crystal of tetracosane. From this fact, i t may be inferred that changes in 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 Savile 1^ to be 32*5 % and 30.4 2., respectively, for tetracosane. The ra- tio of the B to the A spacing i s then 0.935. How, i f the density (<0;8676) at the f i r s t transition point, 47.9°G.» is divided by the estimated den- sity (0.927) at the same temperature found by extrapolating the low temp- erature 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 tet- racosane which is stable at.low temperatures, and the A form corresponds to the translucent form* One may also say that the change in density at the transition point i s due wholly to the change in molecular t i l t * If one appliesthe same calculations to the density curves of dotria- 16 oontane obtained by Morris, the ratio 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 hy- drocarbon is of the B type as in the case of tetracosane. One wonders why Piper and his associates could not obtain B spacing measurements for do- triacontane•* If i t i s assumed that the A form is the translucent and vertical type of crystal, then the ratio B:A corresponds to the sine of the angle of ^Muller, ( l o c cit.) 1 5Muller and Savile, Proc Roy. Soc Lond., 127A, 417 (1930) J^Morris, (loc* cit.) 17 Piper et a l , (loc. cit.) o&eoo O-079O O&70O O077O ^$0-<&760 I 4 X ^ 0-&73O •s 0-072O ^0.07/0 ^0^700 0.06ZO 0.0660 Z3 2< 2 ^ 2G 27  2 9 <5V -32 3 f7~° /><zy<? 7<sJ (16) molecular t i l t , which angle when calculated for the case of tetracosane comes to 69.5°« (3) Since the A spacing i s a linear function of the number of carbon atoms 18 in the hydrocarbon molecule, i t is perhaps safe to infer 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 for 0g g to G g s paraffins. (Pig. 3.) The predicted densities are tabulated be- low: TABLE III Ho* of 0 atoms Density at First 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 (4) Prom the density-temperature curve for Sample 1, the following den- sity equation was established for the liquid lines D t .« 0.7788 - 0.00064 (t• - 50.7) where D̂  i s the density at temperature t° G* 19 Applying this equation to three densities found in Beilstein, the val- ues corresponded very well. They are tabulated below: 1 8 P i p e r et a l , (loc* c i t . p.2080) 1 9 B e i l s t e i n , (loc. cit.) (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 of the liq u i d hydrocarbon was determined. Its value was found to be 0.0008411 c.o./o.c./ °G. The specific volume equation for the liquid tetracosane i s then: V t • 1.2840 ( 1+ 0.0008411 (t-50.7) ) where t is any temperature above 50.7°C. The liquid line was found to be exactly parallel to that for dotria- oontanes showing that a l l liquid paraffins have the same coefficient of cubioal expansion. (5) For the solid part of the curve, i t was seen to require a complicated form of equation. Due to lack of time, its derivation was not carried out. The curve was, however, seen to be quite parallel to that of dotriaoontane. A further observation indicated that both hydrocarbons in the opaque solid form have practically the same density. (18) V. SUMMARY* (1) The density-temperature curves for two samples of n-tetracosane nave been determined and plotted for the range 0° to 80°0. (2) Two transition points have been determined. (3) An equation has been developed for the density above the melting point. (4) The coefficient of oubioal expansion of the liquid hydrocarbon has been determined. (5) An attempt has been made to correlate the results obtained with tetracosane to those of dotriacontane in order to generalise some properties. (6) The density has been found to be independent of changes in cross- • sectional area of the crystals, but is affected greatly by the mole- cular t i l t . VI. CONCLUSION. The author wishes to take this opportunity to express his apprecia- tion to Dr. W . P . Seyer for his kind interest in this work. Without his valuable suggestions and assistance this work would not have been possible- 119) 711. BIBLIOGRAPHY. (1) Beilstein: Handbuch der organisohen Chemie, 7ol. I, p. 107 (1895) (2) Godard, H.P., ''Solubility of Tetracosane in Propane, Butane and Pen- tane/' Thesis submitted for M.A.Sc. Degree, U.B.C., April, 1957. (5) Krafft, Berichte, 19, 2219 (1886). (4) Morris, W.M., "Density and Transition Points of Dotriacontane (Dice- t y l ) , " Thesis submitted for M.A.Sc. Degree, U.B.O., April, 1938. (5) Muller, A., Proceedings of the Royal Society, London, 130 A, 514 (1932). (6) Miller, 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 2 5 30 3 5 40 T E M P E R A T U R E 4 5 5 0 degrees C 5 5 60 65 7 0 EUGENE DIE TZ6EX C 73 60

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