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The density and coefficient of expansion of hexamethylethane Bennett, Reginald B. 1945

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T H E D E N S I T Y AND C O E F F I C I E N T O F E X P A N S I O N O F H E M M S T B 3 L E T H M E by fieginald B. Bennett A Thesis submitted i n P a r t i a l Fulfilment of the Requirements for the Degree of Master of Applied Science i n the Department ' of Chemical Engineering The University of B r i t i s h Columbia September, 1945 PREFACE The ultimate purpose of t h i s research was to colle c t data on the density and coefficient of expansion of a "branched straight-chain hydrocarbon, hexamethylethane. During the past several-years similar data has been obtained i n t h i s laboratory on several normal straight-chain hydro-12 25 17 carbons by William Morris, E i j i Yatabe, Halph Patterson, • -7 and John Eeays. Since the normal paraffins (even numbered) have been examined f a i r l y completely between 016 and G34 i t was decided to investigate a branched para f f i n . I t should be pointed out that the density of the compound has not been examined completely between 70°C and 99°C. Care has been taken to describe a l l phases of the work undertaken as completely as possible although the method of measuring the densities was exactly the same as that used i n previous work here. This should serve as an aid to those who f i l l i n the blank region existing i n the density curve. I wish to acknowledge the valuable assistance and helpful suggestions given by Dr. W. F. Seyer of the Depart-ment of Chemistry throughout the course of the work. I am also indebted to H. Soroos of the Ethyl Corporation for the sample of hexamethylethane. R&g. Bo Bennett September, 1945 TABLE Off CONTENTS Introduction . . . . . . . . . . 1 Orystal fforms of Normal Paraffins. . . . . 3 Experimental Procedure . 6 (1) Theory of uilatometer 6 (2) Preparation of Dilatometer 7 (3) Temperature Control 10 (4) Experimental Observations. . . . . . 11 Results (1) Capillary Heights . . 12 (2) Calibration of Capillary Tube . . . 12 (3) Calculation of .Densities . . . . . . 13 (4) Discussion . . . . . . . . . . . . . . 15 Treatment of Results . 17 £^vunmEi2?y « 18 Bibliography . . . . . . . / . . . . . . . , 19 j^.p j) GUCLXIC « « < » « • « • • • • • * • » « « « 21 LIST 03? ILLUSTRATIONS Page Figure 1. The Crystal Forms of Normal Paraffins , 4 Figure 2. F i r s t Apparatus For F i l l i n g Bulb , « . 8 Figure 3. Second Apparatus for F i l l i n g Bulb. . , 9 Figure 4. Thermostat Assembly , 10 A Figure 5„ Density-Temperature Curve. THE DENSITY AND COEFFICIENT OF EXPANSION OF HEXAMSTHYLETHANE. During the past SO years a great deal of research has "been carried out by the petroleum industry, p a r t i c u l a r l y on l i q u i d fuels. Much of t h i s work has been confined to the determination of the physical and chemical properties of the different hydrocarbons which are present. In the case of automotive fuels i t has been found that the presence of certain branched straight-chain hydrocarbons i s essential for the production of high grade gasolines because of their 3 temperature s t a b i l i t y and power. For th i s reason, heza-methylethane (2,2,3,3 tetramethylbutane) i s of prime interest. Data have been obtained for some of the physical properties of hexamethylethane. The heat of combustion at constant pressure was found to be very close to that of iso-octane, being 1301.3 K-cal./mole. The octane number ' 4 t of hezamethylethane i s 103 which makes i t useful for blending purposes. Although i t i s a s o l i d at ordinary o temperatures, hexamethylethane melts at 101.6 C and boils • 4 at 106.6 C. The following vapour pressures of the s o l i d 9 have been determined by E„ Linder: TABLE 1 -10.3°C 1.33 mg Hg - 5.0 2.08 - 0.3 3,55 6.0 5.80 since hexamethylethane i s the simplest compound containing two neo carbon atoms i t i s of particular int e r -est, theoretically, i n the f i e l d of intramolecular rearrange-' 23,24 ments. Investigations have shown that when the quaternary grouping i s symmetrical, as i s the case with t h i s compound, there i s a peculiar effect of r e s t r i c t i n g the l i q u i d range combined with a large increase i n density of the compound. 11 The following data i s given by Morgan, Garter, and Duck: TABLE 2 • : M»P « B.P. . ' - ' o n-pentane 130.8 36,3 u 2.2 diethyl propane - 20 9*5 n-nonane - 51 150.5 3.3 diethyl pentane - 41 139.2 n-octane - 57.4 124.7 hexamethylethane (double quaternary grouping) *103 +106 The c r y s t a l l i n e structure of hexamethylethane has ' ' ' 22 . been investigated by several men. 0. West found that the compound was p l a s t i c and isotropic forming dodecahedrons when sublimed. This may be interpreted on the basis of a body-centred packing of roughly spherical mols. Powder photography indicated body-centred crystals containing- two molecules, similar to hexaohlorethane. While determining 15 thermal data on hexamethylethane Parks, Huffman, and Thomas found a t r a n s i t i o n point between two c r y s t a l l i n e forms at -125°C and measured the heat of t r a n s i t i o n (4.20 cals/gm). From cooling curve data obtained by the Ethyl Corporation another t r a n s i t i o n point was found to exist near the melting point. Since the variation i n the c r y s t a l l i n e structure of ^normal paraffin hydrocarbons i s known, i n many cases, to be accompanied by a variation i n the density, i t was decided to investigate the density and tran s i t i o n points of the hexamethylethane by the dilatometer method and determine the coefficient of expansion. CRYSTAL FORMS OF NORMAL PARAFFINS. . .. 20 It has been shown by X-ray studies by S a v i l l e , 14,15 16 Mttller, Piper, and others that many members of the paraffin series, along with other long-chain hydrocarbons, exist i n several enantiotropic forms. I t was also found that at the point of tran s i t i o n from one c r y s t a l l i n e form to another there was only a very s l i g h t change i n the basal area of the crystals but a very large change i n the 001 l a t t i c e spacings, resulting i n a sharp change i n the density. Because of this fact, density changes with temper-ature can be used to determine the tr a n s i t i o n temperature and the relationship between the density change and the cr y s t a l l i n e form. 14,15 I t has been shown by A. Mtiller that the aliphatic hydrocarbons may exist i n at least three c r y s t a l l i n e forms: A. The normal form - the crystals are right rectangu-l a r prisms with the chain axis perpendicular to the lease. In this form the planar spacings are a direct measure of the length of the molecules. is. A lower form of symmetry - the crystals are not rectangular i n cross-section and the chains may be inclined at a constant r e l a t i v e to the "base. 0. A form which has a rectangular cross-section with the • chains t i l t e d r e l a t i v e to the base of the crystals. Figure 1. The hydrocarbons with an even number of 18 or more carbon atoms and odd members of 11 or more carbon atoms exist i n the A form near the melting point. This i s a characteristic property of the even-numbered paraffins up to 044. Even numbered paraffins up to 24 atoms crys-t a l l i z e i n the B modification at normal temperatures. Near the melting temperature the B crystals are converted to the A form but revert to the B form when cooled. Odd numbered chains of 9 or less carbon atoms also exist i n the B form at normal temperatures. The paraffins with 26 or more carbon atoms c r y s t a l l i z e , when pure, i n the 0 modification, and show a higher t r a n s i t i o n temperature. In the case of 16 n-tetratriacontane (34 carbon atoms) Piper i d e n t i f i e d the crystals i n the C form as rhombs of acute angle 73°. Apparently odd number paraffins never take the 0 form, but Muller found single crystals i n the a form with an acute angle of 63°. The paraffin with 26 carbon atoms i s the only hydrocarbon that shows a l l three phases. The members 18, 20, and 22 give a different density curve on heating than they do on cooling. M i l l e r recorded this phenomenon from measurements of the length of the carbon chain. I t was shown by Keays that the density-temperature characteristics of 20 and 22 were the same as 24, 26 etc., with decreasing temperatures and similar to the lower even-number members of the series with decreasing temperatures. An investigation of the l i q u i d state of several hydrocarbons by Keays showed that the density-temperature li n e s were straight and almost p a r a l l e l . Since the l i n e s are straight and have,:the same slope i t has been concluded that the molecules are i n a l i q u i d c r y s t a l l i n e state, ii'rom observations made by Mailer i t i s believed that hexagonal packing occurs i n t h i s temperature region. The c r y s t a l l i n e structure of the normal paraffins has also been investigated by 0. G. Gray by microscopic methods. He has shown that there are four c r y s t a l l i n e forms. 1. The hexagonal system 2. The orthorhombic system 3. The monoclinic or t r i c l i n i c system with the molecules t i l t e d at an angle of 73° to the base of the c r y s t a l . 4. The monoclinic or t r i c l i n i c system with two unequal side spacings but with the molecules t i l t e d at an angle of 61°30' to the base of the c r y s t a l . The ranges of the four modifications are as follows: 1. Odd paraffins from 0 11 upwards; even from 0 18 upwards. • >, . 2. Odd from C 11, even from 0 18 upwards. 3. Odd from 0 5 to 0 9 inclusive, even from 0 6 to C 22 inclusive. 4. Even only from 0 24 to C 26 inclusive. This modification has been obtained only by c r y s t a l l i z a t i o n from solvents. I t has not been obtained by c r y s t a l l i z a t i o n of melts or by tr a n s i t i o n from one of the other modifications. I t must be remembered that the c r y s t a l l i n e forms given have been determined for the normal paraffins only. I t s t i l l remains to be found whether or not the branched paraffins w i l l also c r y s t a l l i z e i n the same forms, since hexamethylethane i s isotropic i t i s doubtful that the same c r y s t a l l i n e forms are present. B3CPERIMMTAL PROCEDURE, (1) Theory of the Dilatometer. The dilatometer method i s one of the most accurate means of determining the density of organic com-pounds. An accurately weighed sample of the substance i s placed i n a dilatometer and then mercury i s d i s t i l l e d i n under a vacuum u n t i l the bulb i s f i l l e d . Density changes i n the compound at different temperatures are indicated by changes i n the height of the mercury column i n the c a p i l l a r y tube of the dilatometer. Since the volume and'weight of the mercury i s known along with the weight of the substance and the volume of the dilatometer, i t i s possible to c a l -culate the density of the substance* Corrections must be made for the coefficient of expansion of the mercury and the dilatometer and for buoyancy of the a i r . (2) Preparation of Dilatometer. The c a p i l l a r y tube for the dilatometer was selected from a piece of small bore c a p i l l a r y tubing of uniform diameter. The diameter of the tube was determined by measuring the length of a weighed amount of mercury at centimeter intervals, A glass bulb approximately 2 cm. i n diameter was then blown from heavy pyrex tubing. Before weighing the bulb was cleaned with dechrornate cleaning solution and dried by washing with absolute alcohol and heating to 50°u. The hydrocarbon was then placed in,.the bulb and the weight determined. The c a p i l l a r y tubing was then sealed on and mercury d i s t i l l e d into the bulb under a pressure of Ix 10~4mm. The dilatometer was then weighed and placed i n bath. Some d i f f i c u l t y was encountered i n placing the hexamethylethane i n the bulb. The high vapour pressure and the narrow l i q u i d range of the compound made i t d i f f i -c ult to handle. Two methods were used. A diagram, of the apparatus f i r s t used i n f i l l i n g the bulb Is shown i n U'igure 8. The dilatometer bulb i s shown with three ground glass connections, one for the hexamethylethane, one for applying a vacuum, and the l a s t for the d i s t i l l e d mercury. The bulb was evacuated and heat applied to the bulb containing the hexamethylethane. Dry ice was packed around the dilatometer bulb to condense the sublimed hexamethylethane*v Although most of the compound condensed i n the bulb some also c r y s t a l l i z e d i n the ca p i l l a r y tubing and i n the mercury reservoir. I t was found possible to remove a l l of the hydrocarbon from the wall of the c a p i l l a r y tubing by heating but some always r e c r y s t a l l i z e d back on the tubing when cooled. To prevent the formation of crystals on the c a p i l l a r y walls i t was decided to melt the hexamethylethane under pressure and pour i t into the bulb. A diagram of the apparatus i s shown i n i'igure 3. The dilatometer bulb was sealed i n a tube with a small funnel and the bulb of hexamethylethane. The tube was then evacuated and hydrogen gas admitted u n t i l the pressure was 25 l b s . per sq_, i n . As the apparatus was heated the hexamethylethane melted and flowed freely through the funnel into the dilatometer bulb. The bulb was removed from the tube, weighed accurately, and the c a p i l l a r y tube sealed on. The mercury was d i s t i l l e d into the bulb under a pressure of figure 3. O 10. -4 - -1 x 10 "mm. Calibration of the dilatometer was l e f t u n t i l the end of the investigation when the mercury was removed and weighed, and the dilatometer cleaned of a l l the hydro-carbon. Mercury was d i s t i l l e d i n under a pressure of 1 x 10 mm. and the l e v e l of the mercury noted at different temperatures. In t h i s way i t was possible to determine the volume of the dilatometer and check the bore of the ca p i l l a r y . A l l weights were.corrected for buoyancy. In previous dilatometer work done i n this labora-tory much smaller samples of hydrocarbon were used (1 gnu in place of 5.9 gms.). I t was believed that t h i s would give the dilatometer. increased s e n s i t i v i t y . This made i t necessary, however, to remove mercury several times during the course of the work. The weight of mercury varied from 86.0971 grams for lower temperatures to 70.0516 grams for the melting region. (3) Temperature Control. . ' A constant temperature bath was used to obtain constant temperatures. The bath was a pyrex glass cylinder 25 cm. i n diameter and 46 cm. high and was f i t t e d with a-s t i r r e r , variable heating c o i l controlled by a precision-thermo-regulator, and a stand for the dilatometer. The bath assembly i s shown i n Figure 4. For temperatures below 70°C water was used i n the bath but was replaced by Stanolax o i l at higher temperatures because of large temperature losses. At f i r s t temperature control was maintained by Resistance Thermometer Dilatometer S t i r r e r Hexamethylethane Mercury To Relay Heater The rmo-r e gulat o r Figure4. Thermostat Assembly. 11. means of the thermo-regulator hut i t was found that the temperature varied as much as 0.1°0. In the actual experimental work the degree of heating was adjusted by insulating the "bath and immersing a 100 watt lamp i n the o i l * The temperatures at which density measurements were made are within *0.0S°0 of the recorded values. (4) - Experimental Observations. The only experimental measurements required for the density determinations were the temperatures and corresponding;capillary heights. A l l temperature measure-ments were obtained from a platinum resistance thermometer (#169134). The thermometer had been calibrated by the U. S. Bureau of Standards. The c a p i l l a r y heights were •' measured with a eathetometer graduated i n 0.001 mm. I t was not possible, however, to check readings any closer than £0,004 mm. The mercury column was illuminated from behind the bath to f a c i l i t a t e reading the c a p i l l a r y heights. I t was found that the time required for the hydrocarbon to reach i t s f i n a l state at any one temperature varied from 15 minutes to 48 hours depending on the region being examined. Equilibrium was reached, i n a few minutes with temperatures up to 80°0 and i n the melting region. In thi s case readings were taken every half hour. Above 80°0 i t was found that several hours elapsed before a state of equilibrium was reached. At the tr a n s i t i o n and setting points i t was found that 48 hours was required. In general, equilibrium was reached more rapidly when the temperature 12. intervals were kept f a i r l y large. Small intervals of 0.1°c sometimes required two or three hours before equilibrium was reached. RESULTS. (1) Capillary Heights. Erom the discussion of the dilatometer method already given i t i s readily seen that i f the c a p i l l a r y i s of uniform diameter the general shape of the density-temperature curves can be obtained simply by pl o t t i n g the c a p i l l a r y heights against the resistance of the platinum resistance thermometer. In the case, the sample of hydro-carbon was so large that mercury had to be removed every 20° or so with the result that the curve was not continuous. I t was possible, however, to determine any discrepancy i n the densities i n the region being examined, wherever possible c a p i l l a r y readings were checked with Increasing and decreasing temperatures. (.2) Calibration of Capillary Tube. The bore of the c a p i l l a r y tube was determined by measuring the length of a known weight of mercury at centimeter intervals along the length of the tube. These results were l a t e r checked at different temperatures when the bulb was f i l l e d with mercury. These results checked very closely. The average area determined by the f i r s t method was 0.0039315 sq. cm. One calculation of the area determined by the second method i s given. 13. Mass of mercury Volume at 84.80°o Volume at 43.94°C = 149.236S gms. = 11.146631 ccs. 11.063626 ccs. Difference i n volume = 0.083005 ccs. Correction for expansion of glass s (40i86)(11.065626)(0.0000096) - 0.004340 ccs. Net expansion of mercury 0.078665 ccs. Difference i n mercury levels = 19.853 cms. Area of cross-section = ° * 0 7 8 6 6 5 s 0.003962 sq_. cm. (3) Calculation of Densities. The following symbols are used: t s temperature at which readings were taken - °0.. h s height of mercury above zero reference mark. A = cross-sectional area of the c a p i l l a r y tube. o ' _ ~V20 = Volume of the bulb to the zero point at 20°u. V2011 = Total volume to height h at 20°o. s V20° * hA. Yth = Total volume to height h at t°u, = V20 h * V20 h(t-20)a, where a » 0,0000096 cc/cc/°C, the coefficient of expansion of pyrex glass, W = t o t a l mass of mercury i n dilatometer with hydrocarbon. Vt = Volume of mercury i n dilatometer at t°C (see appendix). w - mass of hydrocarbon' i n bulb. art = volume of hydrocarbon i n bulb at t°C, v t h - Vt density of hydrocarbon at.t°C. w /Vt Example of Calculations: A l l density calculations were made i n the same manner. t = 91.50°C h = 30.509 cms. A = 0.00393 sci, cm. hA - 0.12026 ccs. V20° = 11.05358 ccs. V20*1 - Y20°thA r 11.05358 *• 0.12026 r 11,17384 ccs. V t h = 11.17384 t- 11.17384 (91.50-20.00) (0.0000096) s 11.18151 ccs, W =82.6576 gms. Vt = (82.6576)(0.0747816) = 6.18127 ccs. OJ-t = Vt h-Vt = 11.18151 - 6.18127 « 5.00024 ccs. w =; 3.8851 gms. V" w 3.8851 • .'• . , 'D* = = * nnno, ~ °*7770 glUs/cC. /Vt 5.00024 , o 6 ! ^ TABLE i Temp. „j ."-^  Density Temp. Density 20.69 ^ - ^ r • 6.8240' 36.12 0.8151 21.18 0.8257 56.43 0.8149 22.12 - 0.8231 37.31 0.8144 24.36 0.8221 38.96 0.8132 25^06^ 0.8217 39.55 0.8131 25.21 0.8214 41.73 0.8117 25.67 0.8210 43.53 0.8107 26.73 0.8207 43.59 r 0.8106 26.96 0.8206 43.90 ^'0.8103 27.75 0.8199 45.24 %P 0.8097 27.98 h 30.28 3 t ? ^ 0.8198 48.30 AV 0.8075 0.81937" 51.78 • 0.8055 31.57 i 0.8178 52.07 0.8051 51.75 0.8174 56.93 0.8021 33.151 0.8168 58.11 0.8010 53.92 0.8164 58.61 0.8008 Temp. Density Temp. Density 61.86 0.7989 100.00 0.7645 63.66 g^ .- 0.7974 100.10 Of7641' 65.12 " 0.7964 100.14 0.7620' 65.76' 0.7962 100.25 0.7614 68.01 «t)'^ 71.53,' f K 0.7943 100.28 0.7608 0.7920 100.35 0.7600 72.62 v 0.7915 100.40 0.7584 72.89 - 0.7914 100.44 0.7572 73,05 0.7913 100.50 0.7548 74.51 0.7898 100.56 0.7518 74.82 f> 0.7897 100.60 cf 100.5^ / C\ 100.7l~-|/ M.P -,s 78.75 1* ' 0.7869 0.6567 -79.87 >0'' " 0.7861, 0.6568 84.52:-' 0.7826 100.84 0.6566 85.55 \ 0.7,820 101.18 0.6563 85.9'7 0.7812 101.92 0.6557 87.72 ^ 0.7797 TO 2.26 0.6553 89.23 . - ,^ 92.07 T 0.7786 102.58 0.6551 0.7764 102.64 0.6550 99.48, 0.7682 102.80 0.6549 99.92" 0.7657 103.42 0.6543 99.981 0.7649 Descending Temperatures Only. Temp, Density Tempi Density 99.63 0.7336 93.16 0.7389 99.17 0.7340 90,87 0.7404 98.76 0.7342 89.77 0.7411 98.32' 0.7345 89,02 0.7417 98.11 0.7346 87,56 0.7424 97.97 0.7351 y 86.50 0.7433 97.01 0.7359 "85.38 0.7442 96.02 0.7362 84.12 0.7457 95.81 0.7369 83.50 0.7469 94.97 0.7370 82.60 0.7473 94.65 0.7377 (4) Discussion. The density-temperature curve for hexamethylethane i s given i n Figure 5. In the temperature range "between 20° and 92°C the densities were checked with both increasing and decreasing temperatures at least twice. Every 20° or so i t was found necessary to remove some mercury from the bulb so that measurements could be made at higher temperatures. This was done i n each case without melting,the hydrocarbon. Khen mercury was removed from the bulb to measure the density between 92° and the melting point the hydrocarbon was melted. I t can be seen from the density-temperature that the hexamethylethane s o l i d i f i e d i n a different phase. Hence there i s a region where hexamethylethane has two densities at one temperature, representing two c r y s t a l l i n e phases. I t was not realized during the measurements that two phases existed and as a result there i s a blank space i n the density curve. I t was noted, however, that i t was impossible to obtain consistent readings i n this region. I t was l a t e r found that the mercury tended to s t i c k i n the ca p i l l a r y tube when the temperature was lowered. Only one set of measurements has been obtained for t h i s phase between 82°C and 99°C. The existence of a similar hysteresis i n the density-temperature curve has been determined by Keays for the normal paraffin hydrocarbons 018, 020, and 022. Some d i f f i c u l t y was encountered i n obtaining good readings between 99.5°0 and 100.5°0. U n t i l the presence of the dense phase had been detected the hydro-carbon was usually s o l i d i f i e d at 98°0. To determine the density of the hexamethylethane just below the melting point the temperature was f i r s t set at 100.4 0 and then dropped to 100.l°u after 48 hours. In th i s region the temperature had to be controlled within 0.1°G or less before accurate readings could be made. The dense region could be deter-mined with both increasing and decreasing temperatures 3.80 D.78 0.76 0.74 0.72 0.7O 0.68 0.66 1 l - \? ] 1 y. T< j Ellin k t _C hVi FO R-- r — \ TJ 3 A i R P li • I T • — | t i li 3 J n t 1 X ] {•') r i J • 40 50 60 70 80 90 100 110 Temperature C. 3 • • f.. 17. I showing that supercooling was not present. On one occasion ) the dense region was supercooled to 98.0°0. Apparently i the dense region between 99.9°0 and 100.6°G i s not stable, i Density measurements i n the l i q u i d range were obtained readily. Readings were reproduced several times. The melting point of the hexamethylethane was found to be 100.60°0. Treatment of Results. 1. The density-temperature curve for hexamethylethane has been plotted from the results obtained and i s given In Figure 4. The melting point of the sample was found to be 100.6°0 and a tr a n s i t i o n point was found to exist between 65°0 and 80°C. The less dense phase i s apparently unstable between 99.9°G and 100.6°G. Density determinations have not been made between 92° and 90°C for the more dense phase between 60°C and 82°C for the less dense phase. The melting 4 point,is d e f i n i t e l y lower than that given by Doss (101.6°C). 2. From the density-temperature curve the density equation was established f o r the l i q u i d region Dt = 0.6568 - 0.00089(fc -100.6) where Dt i s the density at any temperature t°G. The extrapolated l i q u i d density at 20°t; i s 0.7288 gms/cc.. This agrees f a i r l y well with the result 1 0.7219 gms/cc. obtained by &„ Galingaert from solutions of hexamethylethane i n n-octane. The coefficient 0.00089 agrees f a i r l y well with average value 0.00085 obtained by Galingaert for several branches hydrocarbons. The density coefficient i s larger than the value 0.00064 given by Yatabe for n-tetracosane. 3. The density for hexamethylethane at 20°u i s 0.8230. This compares f a i r l y well with the value 0.83 22 given by West. . 4. The coefficient of expansion of the l i q u i d was calculated to be 0.0013513 cc/^c/^Cj The specific volume equation for the l i q u i d hexamethylethane i s then: Vt = 1.5226 (1 + 0.0013513-100.6)) where Vt xfi the specific volume at any temperature t°U. The molecular volume of the l i q u i d hexamethyl-ethane at 20°U was calculated to be 156.42 ccs. This f i t s 2 f a i r l y well i n the curve given by Oalingaert. SUffiMAEY. , The density of hexamethylethane has been deter-mined between 20°G and 103°C. There i s a region between 92°C and 99°C for the dense phase and between 60° and 82°o for the less dense phase where the densities have not been determined. The existence of a hysteresis i n the density curve has been established but the tra n s i t i o n temperature between the two phases has not been determined. The temperature at which the less dense phase reverts to the more dense phase has been determined (99.9°u). 19. B I B L I O G R A P H Y 1. Galingaert, Beatty, Kuder, Thomson. Ind. Eng. Chem. 35, 105, 1941. 2. Galingaert and Hladly. J . Am, Chem. Soc. 58, 155, 1956. 5. Day and Pease. 'J. Am. Chem. Soe. 56, 1211, 1954. 4. Doss, Physical Constants of P r i n c i p a l Hydrocarbons, 1942. 5. Everhart, Hare, Mack. J". Am. Chem. Soc. 55, 4894, 1955. 6. Francis. Ind, Eng. Chem., 55, 554, 1941. 7. Keays, Master's Thesis, University of B r i t i s h "Columbia, 1942. 8. Kurtz and Lipkin. Ind. Eng. Chem., 33, 779, 1941. 9. Linder, J . Phys. Chem. 35, 531, 1931. 10. Lambert and Lecompte, Ann. Phys. 10, 503, 1938. 11. Morgan, Garter. Duck. J . Chem. Soc. 127, 1257, 1925. 12. Morris., Master's Thesis, University of B r i t i s h Columbia, 1938. 13. Mttller, Proc. Roy. Soc. (Lond.) A124, 517, 1929. 14. MOller, Proc. Roy. Soc. (Lond.) 514, 1932. 15. Parks, Huffman. Thomas. J . Am, Chem. Soe. 52, 1032, 1930. 16. Piper, Chibnall. Hopkins. Po l l a r d , Smith. Biochem. J'. 25, 2073, 1931. 1 7 • Patterson, blaster's Thesis, University of B r i t i s h ~~ Columbia, 1940, 18. Parks and Todd, Ind. mga Chem. 21, 1235, 1929. 19. Ritzer and Scott, J". Am, chem. soc. 65, 2419, 1941. 20. S a v i l l e , Chem. Soc. 127, 591, 1925. 21. Thacker, Eolkins. M i l l e r . Ind. Eng. Chem. 35, 584, 1941. 22. West, Z(. K r i s t , 88, 195, 1934. 23. tvhitmore, Marker and Plambeck. J". Am. Chem. Soc. 63, 1626, 1941. jb GK...CL..& v i 4 J J 8r £l - $ f(l f ' 20. 24. Whitmore. J. Am. Chem. Soc. 54, 3274, 1932. 2 5• Yatabe, Master's Thesis, University of B r i t i s h ~ 'Columbia, 1939. A P P E N D I X Specific Volume of Mercury from 0°0 to 105°0„ The following values for the specific volume for mercury were used: Temp* Spec.Vol, Temp. Spec.Vol. 20.0 0.0738235 63.0 4246 21.0 8367 64.0 4381 22.0 8501 , 65.0 4516 25.0 8635 66.0 4650 24.0 8765 67.0 4785 25.0 8902 68.0 0.0744650 26.0 9036 69.0 4785 27.0 9170 70.0 4919 28.0 9304 71.0 5053 29.0 9437 72.0 5188 30.0 9571 73.0 5522 51.0 9705 74.0 5457 32.0 9839 75.0 5587 53.0 9973 76.0 5733 34.0 0.0740107 77.0 5868 35.0 0241 78.0 5996 36.0 0374 79.0 6130 57.0 0508 80.0 6264 38,0 0642 81.0 6399 39.0 0776 82.0 6535 40.0 0891 83.0 6670 41.0 1024 84.0 6804 42.0 1158 85.0 6939 43.0 1223 86.0 7074 44.0 0.0741426 87.0 7209 45.0 1560 88.0 7344 46.0 1695 89.0 7479 47.0 1829 90.0 7614 48,0 1963 91.0 7749 49.0 2097 92.0 7884 50.0 2231 93.0 8019 51.0 2365 94.0 8154 52.0 2500 95.0 8288 53.0 2634 96.0 0.0748423 54.0 2768 97.0 558 55.0 2903 98.0. 693 56.0 3037 99.0 828 57,0 3171 100.0 963 58.0 3505 101.0 0.0749008 59.0 3440 102.0 143 60.0 3843 103,0 278 61.0 3978 104.0 413 62.0 4112 105.0 548 

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