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The densities and transition points of certain long chain paraffin hydrocarbons Patterson, Ralph Francis 1940-12-31

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THE DENSITIES AND TRANSITION POINTS OF CERTAIN LONG CHAIN PARAFFIN HYDROCARBONS by Ralph Francis Patterson A Thesis submitted i n P a r t i a l F u l f i l m e n t of the Requirements f o r the Degree of MASTER OF APPLIED SCIENCE i n the Department of CHEMICAL ENGINEERING The U n i v e r s i t y of B r i t i s h Columbia A p r i l , 1940. PREFACE The work described i n the f o l l o w i n g pages i s a con t i n u a t i o n of the research begun at t h i s u n i v e r s i t y by W i l l i a m Morris i n 1936 and f u r t h e r pursued by E i j i Yatabe i n 1938-39. As such, t h i s t h e s i s holds no c l a i m to completeness i n i t s e l f and i t should be pointed out that the d e s c r i p t i o n s given by Moriss and Yatabe have not been repeated here except i n such cases where r e p e t i t i o n was considered necessary f o r the sake of c l a r i t y . Care has been taken to describe i n d e t a i l a l l phases of the work undertaken and although t h i s may appear to have been c a r r i e d to an extreme at times i t i s my experience that t h i s w i l l not be considered a f a i l i n g by those engaged i n work of t h i s nature or by those who f o l l o w t h i s procedure i n f i l l i n g i n the blanks s t i l l e x i s t i n g i n the p a r a f f i n hydrocarbon s e r i e s . I wish to acknowledge the valuable assistance and h e l p f u l suggestions given by.Dr. W. F.Seyer i n connection w i t h t h i s research and to express my thanks to Messrs. B e l l , Kemper, L e s l i e , and Morel f o r the synthesis of c e r t a i n of the compounds used. I am a l s o indebted to B. J . Mair of the Bureau of Stan dards, G. W. Stewart of Iowa State U n i v e r s i t y and Dr. Parks of Stanford U n i v e r s i t y f o r the g i f t of hydrocarbon samples. A p r i l 1940 U n i v e r s i t y of B r i t i s h Columbia TABLE OF CONTENTS Preface Page i Introduction 1 The Structure of Normal P a r a f f i n s 1 Preparation and P u r i f i c a t i o n of Hydrocarbons 4 (1) Nonacosane (2) Docosane and triacontane (3) Octacosane Measurement of D e n s i t i e s 8 (1) Theory (2) Temperature Control (3) S e t t i n g up the,dilatometer tubes (4) Experimental Observations (5) C a l i b r a t i o n of the tubes Results 12 (1) C a p i l l a r y heights (2) M e l t i n g points (3) Lower t r a n s i t i o n p o i n t s (4) Upper t r a n s i t i o n p o i n t s THE DENSITIES AND TRANSITION POINTS OF CERTAIN LONG CHAIN PARAFFIN HYDROCARBONS INTRODUCTION The d e n s i t i e s and t r a n s i t i o n p o i n t s of two hydro carbons, tetracosane and dotriacontane, have been p r e v i o u s l y determined i n t h i s laboratory by Yatabe and Morris r e s p e c t i v e l y . These data were not considered s u f f i c i e n t b a s i s f o r g e n e r a l i  zations on the p a r a f f i n hydrocarbon s e r i e s and the aim of the present work has been to amass as much more m a t e r i a l on t h i s subject as p o s s i b l e and then to attempt a c o r r e l a t i o n of a l l r e s u l t s . Octacosane, nonacosane, t r i a c o n t a n e , docosane, tetradecane, pentadecane, and haxadecane have been obtained. The f i r s t three have been i n v e s t i g a t e d and the values obtained are set f o r t h . THE STRUCTURE OF NORMAL PARAFFINS I t has been shown^ that these hydrocarbons may e x i s t i n three forms: A. The normal form - the c r y s t a l s are r i g h t rectangular prisms and the molecular chains are packed i n the c e l l perpendicular to the base. tt 1. A. M u l l e r , Proc. Roy. Soc., London, A138, 516, (1932). B. A form of lower symmetry - the c r y s t a l s are no longer r e c  tangular i n c r o s s - s e c t i o n and the chains may be t i l t e d r e l a t i v e to the base. 0. A form having rectangular c r o s s - s e c t i o n and chains which are t i l t e d r e l a t i v e to the base. As these long chain p a r a f f i n s are heated i t i s found that at about 5° 0 below the melting point a d e f i n i t e change i n s t r u c t u r e takes place as i n d i c a t e d by the sudden change i n the 001 spacing of the c r y s t a l s . A second transformation occurs i n a range a few hundredths of a degree below the melting point and again X-ray a n a l y s i s shows a change i n the 001 spacing. Since these s t r u c t u r a l changes are accompanied by a change i n d e n s i t y i t i s p o s s i b l e to e x p l a i n them as t r a n s i t i o n s from one c r y s t a l form to another. A c o n s i d e r a t i o n of the diagrams of Figure 1 w i l l make t h i s point c l e a r . We w i l l Figure 1 3 suppose that a hydrocarbon e x i s t s i n the C form at ordinary temperatures'; Now when the lower t r a n s i t i o n point i s reached we f i n d that the density decreases at p r a c t i c a l l y constant temperature, which i s e x a c t l y what we would expect i f the c r y s t a l s t r u cture changes from the C to the B form, since i t i s apparent that the volume occupied per molecule has increased, S i m i l a r l y , i f we consider the second t r a n s i t i o n point as a change from the B to the A form then the f u r t h e r decrease i n density experimentally observed i s a l o g i c a l conclusion. That i s to say, the above t h e o r e t i c a l considerations would lead to a density-temperature curve of the type shown i n Figure 2 and t h i s agrees very w e l l w i t h the curve obtained experimentally. 5 I IS Density Figure 2 Attempts have been made to e x p l a i n the reasons f o r these changes. 2 From a c o n s i d e r a t i o n of the heat r e s i s t i n g p r o p e r t i e s and the general i n e r t character of the p a r a f f i n molecule i t seems u n l i k e l y that temperature should produce any change w i t h i n the molecule i t s e l f and the t r a n s i t i o n forces must rather be thought of as intermolecular. C r y s t a l l i n e 2. A. M u l l e r , l o c . c i t . . p.525. 4 e q u i l i b r i u m rua.y be thought of as dependent upon two f a c t o r s , a t t r a c t i v e forces between molecular chains and a t t r a c t i v e forces between end groups. Each of these alone w i l l b ring about an equilibrium, arrangement of the molecules and a com b i n a t i o n of the two may w e l l introduce two p o s i t i o n s of e q u i l i b r i u m f o r the chain depending on the temperature. This explanation i s obviously inadequate since i t p i c t u r e s only two forms of higher p r o b a b i l i t y . I t has, however, the ad vantage of agreeing with the gradual nature of the t r a n s i t i o n as experimentally observed. PREPARATION AMD. .PURIFICATION. OF HYDROCARBONS Nonacosane This hydrocarbon was obtained i n the pure state from a sample supplied by the Bureau of Standards. When received t h i s sample had a melting point of approximately 63.0° C as determined v/ith P i p e r ' s m e l t i n g point apparatus. Since P i p e r and h i s co-workers give 63.4-63.6° as the melt i n g point of the pure compound 7purification was considered necessary. The f o l l o w i n g i s the method used i n the r e c r y s t a l l i z a t i o n of nona cosane but the procedure i s very s i m i l a r f o r a l l the higher- melting point hydrocarbons. A small quantity (about 1 gram) of nonacosane was •weighed out and placed i n a large f l a s k and s u f f i c i e n t g l a c i a l a c e t i c a c i d added to d i s s o l v e the hydrocarbon i n the neighbour- 3. P i p e r et a l , Biochem. Jour., 25, 2085, (1931). 5 hood of i t s melting p o i n t . I t was found that nonaoosane i s approximately 0.05$ soluble i n g l a c i a l a c e t i c a c i d at 65°. The mixture was warmed and mechanically s t i r r e d u n t i l the compound was completely i n s o l u t i o n . A glass siphon reaching to the bottom of the f l a s k was then s u b s t i t u t e d f o r the s t i r r e r and the s o l u t i o n allowed to cool and c r y s t a l l i z e . Upon standing the c r y s t a l s rose to the surface and the underlying mother l i q u o r was siphoned o f f . Fresh a c i d was added to the remaining c r y s t a l s and the above procedure repeated. A f t e r eight r e - c r y s t a l l i z a t i o n s the c r y s t a l s were separated from the mother l i q u o r by s u c t i o n f i l t r a t i o n and then t r a n s f e r r e d with the f i l t e r paper to a large beaker of d i s t i l l e d water. By heating the water u n t i l the hydrocarbon melted, and then s t i r r i n g the hot mixture, most of the remaining a c e t i c a c i d was removed. The nonaoosane separated out as a s o l i d s u r f a c e - l a y e r upon co o l i n g and was t r a n s f e r r e d to another beaker where i t was di s s o l v e d i n a small quantity of pure ether. The s o l u t i o n was f i l t e r e d to remove any i n s o l u b l e m a t e r i a l and the p u r i f i e d compound was then reclaimed by evaporation of the ether and f i n a l drying i n a vacuum d e s i c c a t o r . The p u r i t y of the product was tested by several melting point determinations, using P i p e r ' s apparatus. Sample tubes f o r use with t h i s apparatus were made by drawing out f a i r l y large bore glass tubing to an outside diameter of about one m i l l i m e t r e . Tubing made i n t h i s manner i s exception a l l y t h i n walled and so i s w e l l s u i t e d to determinations 4, E. Yatabe, M . A . S C . Thesis, U. B. 0. (1959), p.3. 6 i n v o l v i n g heat t r a n s f e r . The nonaeosane used i n density determinations had an average melting point of 63.5° 0. Docosane and Triacontane Docosane and triacontane were prepared by the e l e c t r o l y s i s of l a u r i c and p a l m i t i c acids r e s p e c t i v e l y . The method used was that o u t l i n e d by Petersen^ btiit i n a somewhat modified form. The r e a c t i o n s are according to the general equations: (1) 2RG00- —- 2R + 200 2 + 2 9 (2) 2RC00 ~ — - (R - H) + RC00H -t- COg + 2 0 (3) 2RG00 ~ *• RGOOR -f- 002 + 2 0 I t i s only the f i r s t r e a c t i o n which i s d e s i r e d and the others are repressed by the a d d i t i o n of potassium hydroxide, The o r i g i n a l charge consisted of 20 grams of the organic a c i d j 5 grams of potassium hydroxide, 100 cc. of water and 75 cc-. of e t h y l a l c o h o l . E l e c t r o l y s i s was then begun at a current density of 2.5 amperes per square decimeters and 5 v o l t s . The temperature was maintained at 60° f o r production of docosane and at 70° f o r triacontane* As the r e a c t i o n proceeded more acid was added - about 3 grams every two hours - and the volume of the mixture kept constant by the a d d i t i o n of e t h y l a l c o h o l and water. The hydrocarbon product c o l l e c t e d as an o i l y l a y e r on the surface and was poured o f f and set aside f o r p u r i f i c a t i o n with concentrated s u l f u r i c a c i d g and c r y s t a l l i - .5. Petersen, Z. Eleotrochem., 12, 141, (1906) 6. P i p e r et a l , l o c . c i t . . p.2076. 7 z a t i o n from g l a c i a l a c e t i c a c i d . The y i e l d of crude product •; was about* 80 - 85$'of the weight of the organic a c i d used. The f i n a l melting p o i n t s as determined with the Piper apparatus were and 65.7° f o r the docosane and the triacontane r e s p e c t i v e l y , (of* Pi p e r ' s value - 65.6° to 65.8° f o r triacontane) Ootacosane Ootacosane was obtained from m y r i s t i o a l c o h o l by means of the F i t t i g r e a c t i o n . 25 grams of t h i s s o l i d a l c o h o l .(Cl4H;2gOH) were melted i n a small f l a s k and hydrogen iodide bubbled i n t o the melt. This gas was generated by the a c t i o n of water on a mix&ure of red phosphorus and iodine i n the r a t i o of one to eleven and was passed through water before being l e d i n t o the a l c b h o l . In t h i s r e a c t i o n i t i s important that the a i r above the a l c o h o l be f i r s t d i s p l a c e d as completely as poss i b l e to avoid the formation of o x i d a t i o n products. The r e a c t i o n was considered complete when a l l the m a t e r i a l i n the f l a s k remained l i q u i d upon c o o l i n g to room temperature. A small excess of m e t a l l i c sodium over that c a l  culated was added to 200 cc. of dry ether and the l i q u i d t e t r a d e c y l iodide poured slowly i n . The heat of r e a c t i o n was s u f f i c i e n t to keep the mixture r e f l u x i n g f o r s e v e r a l hours a f t e r which heating was continued with a steam bath f o r about s i x hours. The ether was then evaporated o f f and 95$ e t h y l a l c o h o l added to remove excess sodium. F i n a l l y the a l c o h o l was removed by evaporation and the crude hydrocarbon p u r i f i e d by ten s u l f u r i c a c i d treatments and by repeated c r y s t a l l i z a t i o n s 8 from a c e t i c a c i d . 'The f i n a l melting point abtained was 61.4° which i s i n agreement with P i p e r ' s value of 61.4°-61.5°. MEASUREMENT OF DENSITIES Theory The measurement of d e n s i t i e s by the dilatometer method i s one of the most accurate means of determining t h i s property. The bulb of the dilatometer tube contains an ac c u r a t e l y weighed sample of the hydrocarbon and the remainder of the tube i s f i l l e d with f r e s h l y d i s t i l l e d mercury I. The whole tube i s immersed i n a constant temperature bath. Changes i n volume of the compound are r e f l e c t e d i n changes of height i n the mercury column i n the c a p i l l a r y tube. The volume of the mercury and of the apparatus being known i t i s p o s s i b l e to c a l c u l a t e the density of the hydrocarbon. Su i t a b l e corrections must be made, of course, f o r the expansion of the mercury and f o r the change i n volume of the apparatus w i t h the expansion of the g l a s s . A completely worked example i s given with the c a l c u l a t i o n s . Temperature C o n t r o l The temperatures at which d e n s i t y measurements were ' made were held w i t h i n ± 0.02° C of the recorded values by immersing the dilatometer tubes i n a bath regulated by a p r e c i s i o n type thermoregulator. The bath i t s e l f consisted of a pyrex g l a s s c y l i n d e r 45 em. high and 25 cm. i n diameter, f i l l e d T H E R M O S T A T A S S E M B L Y F I G U R E 3 with water. The bath assembly i s shown i n the accompanying diagram. (Figure 3) C i r c u l a t i o n was obtained with a motor driven s t i r r e r A. Large temperature changes were f a c i l i t a t e d by the use of a f l a t heater B but t h i s was cut out of the c i r c u i t e n t i r e l y when e q u i l i b r i u m was being maintained pre paratory to making a d e n s i t y measurement. At these points the temperature was kept constant by the thermoregulator tube C i n conjunction with the r e l a y D and the nichrome heating c o i l E. The e l e c t r i c a l connections are shown d i a - grammatically i n Figure 3 but i n the a c t u a l experimental work the degree of heating was adjusted w i t h a v a r i a b l e r e s i s t a n c e c o i l and several e l e c t r i c lamps. Below room temperature i t was necessary to c i r c u l a t e the water through an e x t e r n a l copper c o i l cooled i n i c e . For t h i s purpose a 110 v o l t c e n t r i f u g a l pump having a continuous r a t i n g of two and a h a l f g a l l o n s per minute was used. S e t t i n g up the Dilatometer Tubes Glass bulbs about 2 cm. i n diameter were blown from t h i c k walled pyrex tubing and a c c u r a t e l y weighed. The p u r i f i e d hydrocarbon sample was melted and approximately 0.7 grams introduced i n t o one of these bulbs through a very small funnel having a slender stem reaching down into the bulb. This sample tube was then connected to a vacuum system and evacuated to about 1 x lO""^ mm. At t h i s pressure the compound was repeatedly melted and allowed to r e c r y s t a l - l i z e i n order to f r e e i t of occluded gases and any remaining traces of a c e t i c a c i d or water. This procedure was continued u n t i l the bulb and i t s contents a t t a i n e d constant weight, (In some eases t h i s may involve keeping the hydrocarbon l i q u i d f o r a period up to s i x hours at low pressure since the l a s t traces of i m p u r i t i e s are evolved as a slow stream of very minute bubbles.) The bulb was given a f i n a l accurate weighing and then sealed on to the dilatometer tube to which was attached a s m a l l , brass zero c l i p . The completed tube was weighed and then connected to a vacuum mercury s t i l l as shown i n Figure 4. The whole system was evacuated to a pressure of approximately 5 x 10"^ mm. and mercury was d i s t i l l e d slowly i n t o the tube u n t i l enough to f i l l the bulb and c a p i l l a r y had been added. I t was found most convenient to d i s t i l an excess of mercury into the tubes and to adjust the volume to the required point by heating the dilatometer to about 10° G. above the highest temperature to be i n v e s t i g a t e d and then pouring o f f the excess mercury. For the purpose of t h i s s e t t i n g a small g l y c e r i n bath i s recommended* The completed tube and contained mercury were weighed and then fastened i n p o s i t i o n i n the bath. A l l the weighings mentioned i n the foregoing were to the nearest 0.1 mg. and were corrected f o r the buoyant e f f e c t of a i r . Experimental observations The only experimental measurements required are the temperatures and the corresponding c a p i l l a r y heights. The former were obtained from an ordinary'mercury thermometer graduated i n tenths. This had been p r e v i o u s l y c a l i b r a t e d against a platinum r e s i s t a n c e thermometer at various tempera tures and found to have an accuracy of ±0.05° C over the range used i n t h i s work. C a p i l l a r y heights were measured with a Gaeintner cathetometer graduated i n 0.005 cm. In making these l a t t e r readings the mercury columns were i l l u m i n a t e d from behind the bath with e l e c t r i c lamps. In order that the hydrocarbon reach i t s f i n a l state at any one temperature i t was necessary to maintain the thermostat at that temperature f o r at l e a s t three hours before the cathetometer readings were made. In the neighbour hood of the mel t i n g and t r a n s i t i o n points a much longer time may be required - i n some cases about 48 hours. I t was found, i n general, that the f i n e r the temperature was c o n t r o l l e d , the quicker a steady sta t e was reached. C a l i b r a t i o n of the Tubes When a complete set of measurements had been made, the dilatometers were taken from the bath and the mercury and hydrocarbons removed. This was accomplished by applying vacuum and then repeatedly washing w i t h hot 95$ e t h y l a l c o h o l to d i s s o l v e out the hydrocarbon. The tubes were then d r i e d , evacuated, ansa f i l l e d with mercury as before* They were then weighed and again fastened i n place i n the thermostat. A s e r i e s of measurements of c a p i l l a r y heights .was made and from the known mass of the mercury i t becomes po s s i b l e to c a l c u l a t e the volume of the dil a t o m e t e r s , i n c l u d i n g the bulb and c a p i l  l a r y , f o r any desired height above the zero c l i p s . I f the tubes are of uniform bore the c r o s s - s e o t i o n a l area may be determined 5 and used i n l a t e r c a l c u l a t i o n s . RESULTS From the d i s c u s s i o n already given of the d i l a t o  meter method i t w i l l be obvious that i f the c a p i l l a r i e s are of uniform bore the general shape of the density-temperature curves can be obtained immediately by p l o t t i n g c a p i l l a r y heights against temperature. As the p o s s i b i l i t y of serious impurity always e x i s t s , the value of such curves should not be under-estimated since they w i l l show up any large d i s  crepancies and i n d i c a t e whether or not i t w i l l be of value to perform the c a l i b r a t i o n s and enter i n t o the c a l c u l a t i o n of the d e n s i t i e s . In Table I the temperatures and corresponding c a p i l l a r y heights f o r ootacosane, nonaoosane, and triacontane are given. I n Figure 5 immediately following,these are p l o t t e d , together with the temperature-density curves obtained f o r tetracosane and dotriacontane.„ 7. E. Yatabe, l o c . o i t . , and W. M o r r i s , M .A.So. Thesis, U. B. G. (1938), 13 TABLE I Temp. Ootacosane Nonacosane Triacon Height - om . Height - om. Height 35.0 12.070 23.895 8.200 40-. 0 13.095 24.980 9.180 45.0 14.240 26.090 10.295 48.0 14.930 26.810 10.940 51.0 1 5 . 6 7 5 2 7 - 5 9 0 1 1 . 6 3 0 52.0 1 5 . 8 9 5 27 . 8 9 5 I I • 8 4 o 53.0 16. i oo 2 8 2 3 0 1 2 . o 5 5 54.0 Zo.I6o 2 8 . 5 o o 1 2 . 2 7 5 5 5 . 0 20.595 28.800 12.355 55.5 20.800 28.845 12.460 56.0 20.995 28.860 12.575 56.5 21.165 28.990 12.790 57.0 21.360 30.030 12.810 57.5 21.535 32.025 12.945 58.0 21.705 32.025 13.070 58.5 21.935 32.565 13.175 59.0 22.120 32.565 13.565 59.5 22.340 32.625 14.265 60.0 22.675 32.710 20.160 60.5 23.310 32.905 20.465 61.0 27.82-28*92 33.100 20.695 61.2 36.595 33.100 20.765 61.4 36.645 33.165 20.850 62.0 36.820 33.475 21.090 62.5 36.955 33.600 21.290 63.0 37.095 35.78-35.93 21.475 63,2 37.155 36.345 21.550 64.0 37.370 36.530 21.870 64.5 37.510 36.650 22.115 65.0 37.645 36.760 22.695 65.2 37.705 36.805 24.035 65.4 37.760 36.845 38.885 65.5 37.790 36.900 38.920 65.6 37.825 36.925 38.955 65 . 7 37.845 36,950 38.980 65.8 37.875 36.980 39.005 66.0 37.940 37.045 39.080 68.0 38.480 37.480 39.580 70.00 39.040 37.965 40.115 75.0 40.410 39.130 41.480 Se n s i t i v e L i q u i d E t h y l ether Carbon d i s u l f i d e Acetone Chloroform Methyl a l c o h o l Carbon t e t r a c h l o r i d e E t h y l a l c o h o l 14 An examination of Table I and of the curves i n Figure 5 shows the f o l l o w i n g r e s u l t s : - (2) The melting points are i n a l l cases somewhat lower than those determined with the.Piper apparatus. This i s to be ex pected , however, as the rate of heating i s here very much smaller. For the same reason the dilatometer method would be expected to y i e l d low melting p o i n t s i n a l l cases and t h i s appears to be t r u e . For octocosane Hildebrand and Wachters give an average value of 62° f o r the m e l t i n g point and t h e i r curve shows a minimum recorded value of 60°. The value ob tained i n t h i s work i s 61.2°. For nonaoosane the average i s 64° with a minimum of ;62.5° i n comparison with 63.3° deter mined with the dilatometer. Triacontane shows an average of 66.0°, minimum 65.6°, and dilatometer 65°. I t i s not f e l t that the low values obtained herein are a r e s u l t of i m p u r i t i e s , as the bydrocarbons were i n a l l cases r e c r y s t a l l i z e d to constant melting point from g l a c i a l a c e t i c a c i d and treated with a l l p o s s i b l e care i n charging the dilatometers. In view of the f a c t that the three hydrocarbons were each prepared by a d i f f e  rent method and that the scheme f o r p u r i f i c a t i o n was somewhat d i f f e r e n t i n the three cases, i t again seems more l i k e l y that these consistent low values are a r e s u l t of the method of measuring. (3) The f i r s t t r a n s i t i o n p o i n t s on heating were obtained f o r the three compounds. In each case the t r a n s i t i o n was accom panied by an abrupt change i n volume, confirming the explana t i o n of t h i s transformation as a change from the G to the A 8. Hildebrand and Wachter, J . Am. Ghem. Soc.,51, 2487 (1929). form of c r y s t a l s t r u c t u r e . g I t must be noted, however, that i t would serve equally w e l l i f the t r a n s i t i o n were from B to A form. This matter i s discussed l a t e r where d e n s i t i e s can 10 be\ used to i n d i c a t e the a c t u a l nature of the change. The t r a n s i t i o n temperatures determined are 5 3 . 8 ° , 57.1°, and 60.0°,for Gg^gg, G 3 9 H 6 0 i " a n d G30 H62 r e s p e c t i v e l y . I t w i l l be noticed that the slopes are very steep at these t r a n s i t i o n p o i n t s . This again seems to confirm the assumption of p u r i t y made above. (4) The second t r a n s i t i o n - i . e . , from the translucent to the opaque form - was observed i n the samples very near t h e i r melting p o i n t s . The exact temperatures were not determined as i t was found impossible to maintain the thermostat any closer than i 0*02° over a long period of time due to the e f f e c t of changing barometric pressure on the thermoregulator and the adjustments which t h i s n e c e s s i t a t e s . In t h i s case the t r a n s i t i o n does not seem t o be accompanied by any appreciable change i n volume. (5) In Figure 6 melting points and lower t r a n s i t i o n p o i n t s are p l o t t e d against the number of carbon atoms. In both cases the values obtained by Morris and by Yatabe have been in c l u d e d . I t w i l l be seen that the melting points f a l l very nearly along a smooth curve. The values f o r melting p o i n t s of other hydro carbons taken from t h i s curve are i n good agreement with those found i n the l i t e r a t u r e 9. P i p e r et a l , l o o . c i t . , p.2080. 10. E. Yatabe, l o o . o i t . , p.15. 11. Hildebrand and Wachter,, H o c . o i t P i p e r et a l . , l o o . c i t . , p.2080; K r a f f t , Ber., 19, 2219, (1886). FIGURE 6 fVo or C r t K s o ^ ATOMS 16 The p l o t o f lower t r a n s i t i o n p o i n t s (heating) does not agree w i t h Piper's r e s u l t | g o n the same'question. He considers i t necessary to use two. l i n e s , one f o r the even- numbered carbon atoms and a second, lower l i n e f o r the odd- numbered atoms. I t w i l l be seen from Figure 6 that i n t h i s work, due to a large d i f f e r e n c e between the value f o r the lower t r a n s i t i o n p o i n t of ootacosane as determined by the P i p e r apparatus and by the dilatometer method, a s i n g l e l i n e s u f f i c e s to place a l l these p o i n t s . Assuming Piper's value f o r ootacosane to be i n e r r o r , but at the same time using h i s other r e s u l t s , we f i n d that w i t h i n the l i m i t of experimental er r o r the t r a n s i t i o n p o i n t s l i e along a s i n g l e s t r a i g h t l i n e from Ggy to C^. Below Cg^ there seems to be a d e v i a t i o n from t h i s r u l e which would bear i n v e s t i g a t i o n by the methods out l i n e d here. 12. P i p e r et a l , l o c . o i t . , p.2082. BIBLIOGRAPHY 1. Backmann and C l a r k , Journal of the American Chemical S o c i e t y , 49, 2089 (1927). 2. Garner et a l , Journal of the Chemical S o c i e t y , 1533,(1931). 3. Gascard, Annales Chemie ( 9 ) , 15, 332, (1921). 4. Hildebrand and Wachter, Journal of the American Chemical Society, 51, 2487, (1929). 5. K r a f f t , Beriohte, 19, 2219 (1886). 6. M o r r i s , W. M., "Density and T r a n s i t i o n P o i n t s of D o t r i a - contane", Master's Thesis, U. B.C., April,1938. 7. M u l l e r , A . , Proceedings of the Royal S o c i e t y , London, A138, 514, (1932). tt 81 M u l l e r and S a v i l e , Proceedings of the Royal S o c i e t y , London, A120, 437, (1928). ft 9. M u l l e r and S a v i l e , Proceedings of the Royal Society, London, A127, 417, (1930). 10. Peterson, Z e i t . f u r Electrochemie, 12, 141, (1906). 11. P i p e r et a l , The Biochemical J o u r n a l , 25, 2072, (1931). 12. Yatabe, E., "The Density and T r a n s i t i o n P o i n t s of N.- Tetracosane", Master's T h e s i s , U.B.C., April,1939, 

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