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The specific heat of cis decahydronaphthalene by the isothermal method Cavers, Stuart Donald 1946

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THE SPECIFIC HEAT OF CIS DECAHYDRONAPHTHALENE BY THE ISOTHERMAL METHOD STUART DONALD CAVERS, B.A.Sc. A thesis submitted i n part ia l fulfilment of the requirements for the degree of MASTER OF APPLIED SCIENCE i n the Department of CHEMICAL ENGINEERING THE UNIVERSITY OF BRITISH COLUMBIA Sept ember, 1946. &*c*f&J™ A ^ Y ^ M C freff^Z-*-*-AC KNOWLEDOEMENTS I wish to acknowledge the help of Mr. H. J . Howie with whose assistance the whole of the research was carried out. Thanks are also due for the many help-f u l suggestions of Dr. W. F. Seyer who directed the work. Table of Contents Page Summary of Prev ious Work 1 Object of the Research 3 Methods of S p e c i f i c Heat De te rmina t ion 3 Comparison o f A d i a b a t i c and I so thermal Methods 3 The I so thermal Method 5 Apparatus 10 Apparatus of Previous I n v e s t i g a t o r s 10 M o d i f i c a t i o n s to the Apparatus d u r i n g Th i s Research 11 Thermopile 14 G l y c e r i n e Ba th S t i r r i n g 21 C a l i b r a t i o n o f the Apparatus 21 Heat o f S t i r r i n g and Evapora t ion 21 Water Equ iva len t of the Ca lo r ime te r 25 Exper imenta l Procedure 29 P r e p a r a t i o n for a Run 29 Procedure d u r i n g the Runs 29 Readings and C a l c u l a t i o n s 33 R e s u l t s 40 Runs 1-18 ( 1 . 5 ° C . Temperature R i s e ) 40 Runs 19-36 ( 0 . 1 5 ° C . Temperature R i s e ) 40 D i s c u s s i o n o f the R e s u l t s 51 C a l c u l a t i o n o f the I n t e r n a l Pressure of C i s Deoahydro-naphthalene 54 Suggest ions f o r Future Work 55 B i b l i o g r a p h y 58 L i s t o f I l l u s t r a t i o n s F igu re Page 1 The Anomaly i n the C i s Decahydronaphthalene S p e c i f i c Heat Curve at 50°C. 2 2 T y p i c a l Hea t ing and C o o l i n g Curve f o r the I so thermal Method 6 3 Views of the Assembled Apparatus 12 4 Views o f the E x t e r i o r of the Ca lo r ime te r 13 5 Apparatus f o r C a l i b r a t i n g a Thermopile 15 6 Graph Showing the V a r i a t i o n i n E . M . F . per Degree D i f f e r e n c e i n Thermopile Leg Temperatures w i t h the Magnitude o f That D i f f e r e n c e 17 7 The Copper C o n s t a n t i n Thermopile w i t h Glass Removed from One Leg 19 8 Graph f o r De te rmin ing the Heat of S t i r r i n g 21 9 Thermopile C i r c u i t Runs 1-18 31 10 Thermopile and B a t t e r y C i r c u i t s Runs 19-36 32 11 Hea t ing and C o o l i n g Curve Run 30 37 12 S p e c i f i c Heat of C i s Decahydronaphthalene Runs 1-18 (Graph) 42 13 S p e c i f i c Heat of C i s Decahydronaphthalene Runs 23-26 (Graph) 46 14 S p e c i f i c Heat o f C i s Decahydronaphthalene Runs 27-29 (Graph) 47 15 S p e c i f i c Heat of C i s Decahydronaphthalene Runs 30-32 (Graph) 48 S p e c i f i c Heat of C i s Decahydronaphthalene Runs 33-36 (Graph) S p e c i f i c Heat of C i s Decahydronaphthalene Runs 1-36 (Graph) THE SPECIFIC HEAT OF CIS DECAHYDRONAPHTHALENE BY THE ISOTHERMAL METHOD": SUMMARY OF PREVIOUS WORK Research work on the p h y s i c a l p r o p e r t i e s of decahydro-naphthalene has been under way f o r some years now i n the Chemical Eng inee r ing Labora tory of the U n i v e r s i t y o f B r i t i s h Columbia , under the d i r e c t i o n of D r . W. F . Seyer." The reasons f o r t h i s study are very adequately set f o r t h i n the t h e s i s of J . D . L e s l i e . 1 As a r e s u l t of the measurements that have been made i t appears that the c i s isomer undergoes some sor t of t r a n s -i t i o n i n the l i q u i d s ta te at. approximate ly 50° C. Miss M. 2 Robinson summarized some of the ev idence . She went on to p lo t c o o l i n g and h e a t i n g curves f o r c i s decahydronaphthalene, and showed that there are abrupt changes i n the s lope of these curves between 50.3 and 50.4 C . She a l s o found wh8t appeared to be evidence o f an anomaly i n the s p e c i f i c heat versus o 4 temperature curve i n the r e g i o n between 50 and 50.5 C . Shee obta ined t h i s anomaly when she used the i s o t h e r m a l method 1 L e s l i e , J . D.5 M . A . S c . T h e s i s , pp. 1 - 8 . 2 Robinson , M . A . t h e s i s , , pp. 1 - 3 . 3 I b i d . , pp. 27-363. 4 I b i d . , pp. 37-44. (2) 0. O 1 X o tC o v 0. 50 50.5 Tern pfcra+ure deg C P i g . 1: The Anomaly i n the C i s Decahydronaphthalene S p e c i f i c Heat Curve at 50°C. fo r de te rmin ing the s p e c i f i c hea t . When she used the a d i a b a t i c method she obtained i n d i c a t i o n s of an anomaly, but the r e -s u l t s by t h i s method were very i n c o n c l u s i v e . B . E . M c L e l l a n had p r e v i o u s l y measured the s p e c i f i c heat of c i s and t r ans 5 decahydronaphthalene by the a d i a b a t i c method. He found tha t whereas the change i n the s p e c i f i c heat w i t h temperature f o r the t r ans isomer fo l l owed a s t r a i g h t l i n e , tha t fo r the c i s isomer fo l lowed a wavy cu rve . G. P . Davies had obta ined a somewhat s i m i l a r curve fo r the c i s i s o m e r . 6 B . A . D u n e l l has r e c e n t l y measured the v a r i a t i o n o f the d i e l e c t r i c con-stant of the c i s isomer w i t h temperature , and appears t o have found abrupt changes i n the slope of the d i e l e c t r i c constant 5 M c L e l l a n , D . E . , M . A . S c . t h e s i s , pp. 15-23. 6 D a v i e s , G. P . , M . A . S c . t h e s i s , pp. 16-22. (3) versus temperature curve between 50 and 60° c . The very l eas t tha t can be S 8 l d of the c i s isomer i n the l i g h t of the above evidence i s that i t c e r t a i n l y behaves abnormal ly . OBJECT OF THE RESEARCH The genera l object o f the present r e s e a r c h was to attempt to conf i rm the work of the p rev ious i n v e s t i g a t o r s o f the s p e c i f i c heat o f c i s decahydronaphthalene by u s i n g the i s o t h e r m a l method f o r measuring i t . More p a r t i c u l a r l y we wished to o b t a i n a more q u a n t i t a t i v e p l o t than that o f Miss Robinson fo r the anomaly b e l i e v e d to e x i s t i n the s p e c i f i c heat curve « t about 5 0 ° C , and to determine the change i n the en tha lpy or heat content H o c c u r i n g w i t h the t r a n s i t i o n . Much of the genera l objec t has been a t t a i n e d . However more i n v e s t i g a t i o n i s necessary to conf i rm the presence o f the anomaly and to determine the cor responding change i n en tha lpy . METHODS OF SPECIFIC HEAT DETERMINATION Comparison o f A d i a b a t l c "and I so thermal Methods Two methods of measuring s p e c i f i c heat have been men-t i o n e d . These are the a d i a b a t i c method o f W i l l i a m s and D a n i e l s and the i s o t h e r m a l method o f which W. P. ?/hite i s the c h i e f advocate . I n both a measured amount of heat i s added to a 7 D u n e l l , B . A . , M . A . S c : t h e s i s , p . 33 and f i g . 16. (4) weighed amount of the substance of which the heat c a p a c i t y i s to be determined. In both the r i s e o f temperature which r e s u l t s i s observed. I n the a d i a b a t i c method the r e g i o n surrounding the substance i s kept always at the same temp-era tu re as the substance, so that no lo s ses o f heat can occur by conduct ion or r a d i a t i o n . The s p e c i f i c heat i s t hen g iven very s imply as S = Q where S i s the s p e c i f i c heat o f the substance Q i s the heat added AS i s the observed r i s e i n temperature w i s the weight of the sample of the substance I n the i so the rma l method no e f f o r t i s made to keep the r e g i o n surrounding the substance at the same temperature as the sub-s tance . We w i l l suppose tha t we have a c a l o r i m e t e r c o n s i s t -i n g o f a conta iner f o r our substance immersed i n a l i q u i d s t i r r e d so that a l l o f i t i s at the same temperature . Then, i f the temperature o f the con ta ine r i s d i f f e r e n t from that of the surrounding l i q u i d j acke t ,hea t w i l l be l o s t to or gained from t h i s j a c k e t . When we are de te rmin ing the s p e c i f i c heat o f our substance and add our measured q u a n t i t y of heat t o i t , we w i l l observe a r i s e i n temperature of the substance, but t h i s r i s e i n temperature w i l l not be the r i s e which would have r e s u l t e d without heat t r a n s f e r to or from the j a c k e t . I n the i s o t h e r m a l method then we must co r r ec t f o r t h i s t r a n s -fe r of heat before we can apply a formula such as the one (5) g iven f o r the a d i a b a t i c type o f d e t e r m i n a t i o n . The I so thermal Method The i s o t h e r m a l method depends f o r i t s accuracy on the method used f o r de t e rmin ing the heat t r a n s f e r c o r r e c t i o n mentioned above. S ince the substance i n the con ta ine r i m -mersed i n the l i q u i d o f the jacket i s u s u a l l y h o t t e r than that l i q u i d , heat i s l o s t t o i t , and the substance does not undergo as l a rge an inc rease i n temperature when the measured amount of heat i s added, as would be the case i f no heat were l o s t . The heat t r a n s f e r c o r r e c t i o n then i s u s u a l l y a c o o l i n g c o r r e c t i o n . The method of de t e rmin ing the c o o l i n g c o r r e c t i o n 8 used i n t h i s r e s e a r c h i s one desc r ibed by W. P. Whi t e . Suppose that our con ta iner ho lds a l i q u i d o f which we des i r e to know the s p e c i f i c hea t . Suppose tha t our conta iner i s immersed i n a jacket l i q u i d , and fu r ther suppose that both l i q u i d s are p r o p e r l y s t i r r e d so tha t no temperature g rad ien t s e x i s t w i t h i n them. Then i f we add a measured q u a n t i t y o f heat to the l i q u i d i n the c o n t a i n e r , and i f we read the tem-perature of t h i s i n n e r l i q u i d and o f the jacket l i q u i d as we are adding the hea t , and afterward as the inner l i q u i d i s c o o l i n g o f f by l o s i n g heat to the jacket l i q u i d , we may p l o t a graph something l i k e the f o l l o w i n g one, where temperatures 8 Whi te , W. P . , Phy. Rev. 3 1 , pp. 545-548. (6) are shown as o rd ina t e s and t imes as a b s c i s s a e : 0 "H" 2 ^ 3 4-Time - minutes P i g . 2 ; T y p i c a l Hea t ing and C o o l i n g Curve f o r the I so thermal Method. At t ime zero the a d d i t i o n of heat was begun. At t ime X the a d d i t i o n of heat was stopped, but the temperature of the l i q u i d continued t o r i s e because of lags i n the h e a t i n g de-v i c e s . At t ime 2 the temperature reached a maximum. Time 4 i s any l a t e r t i m e . Now l e t ©o be the inne r l i q u i d temperature at t ime 0 0 Z be the i n n e r l i q u i d temperature at t ime 2 and so on . A l s o l e t T-^  be the t ime i n t e r v a l from t ime 0 to 2 T 3 be the t ime i n t e r v a l from time 2 to 4 cp be the temperature d i f f e r e n c e between the i nne r (7) l i q u i d and jacket l i q u i d at any time T w be the temperature f a l l per minute due to the com-bined e f f e c t of evapora t ion and s t i r r i n g <fm be J"ij> dT where m stands f o r any t ime i n t e r v a l Tm I t i s apparent then that equals the area under the i n n e r l i q u i d temperature curve down t o the jacket l i q u i d temperature curve between the two absc issae forming the boundaries o f the t ime i n t e r v a l Tm. Now the heat dQ l o s t i n any element o f t ime dT d u r i n g the experiment , because of the inne r l i q u i d be ing h o t t e r t h a n the jacket l i q u i d , i s g iven by dQ = c <pdT (1) where c i s a constant o f p r o p o r t i o n a l i t y . T h i s statement assumes that Newton's law of c o o l i n g h o l d s , that i s , i t assumes that the r a te of l o s s of heat i s p r o p o r t i o n a l t o the temperature d i f f e r e n c e between the two l i q u i d s . Then i n any pe r iod o f t ime Tm the t o t a l amount of heat l o s t i s / d Q : It C <pdT Qm z o J dT a c fm (2) or Qm oc cp m Thus the t o t a l amount o f heat l o s t by the inner to the jacket l i q u i d d u r i n g a t ime i n t e r v a l i s p r o p o r t i o n a l to the area bounded on the l e f t and r i g h t by the absc i ssae which are the boundaries of the t ime i n t e r v a l , and on the bottom and the (8) top by the two l i q u i d temperature cu rves . Now cons ider t ime i n t e r v a l T^ . The t o t a l l o s s of temperature by the l i q u i d o f which we are de t e rmin ing the s p e c i f i c heat i s g iven by The l o s s of temperature caused by the combined e f f ec t o f evapora t ion and s t i r r i n g i s g iven by wT 3 Let us c a l l the l o s s of temperature caused on ly by the d i f f e r -ence i n temperature of the jacket and con ta ine r the d i r e c t temperature l o s s . Then the d i r e c t l o s s i n i n t e r v a l T 3 i s ( 9 t - 9 J - wT 3 (3) Now l e t be the d i r e c t heat l o s s i n p e r i o d 1 and Q3 be the d i r e c t heat lo s s i n pe r iod 3 Then from the d i s c u s s i o n above (equa t ion 2) Q l r c cp, Q 3 = c cp 3 or Q 1 V. (4) Now i f we l e t t Q-^  be the d i r e c t temperature l o s s i n pe r iod 1 (9) t Q 3 be the d i r e c t temperature l o s s i n pe r iod 3 then because Q l = Q l ' (5) Q3 Q3 we can conclude that 1 (6) V 9V Now by equat ion ( 3 ) Q3 r ( © z - e ^ ) - * T 3 (7) Then by equa t ion (6) the d i r e c t heat l o s s i n pe r iod (1) i s g iven by Q l = J L (<v- V V , T 3 ) ( 8 ) Thus the t o t s l l o s s o f temperature i n pe r iod T-^  i s g iven by t» = ( e x - e ^ - wT3)-» wT (9) % and t h i s exp re s s ion i s the c o o l i n g c o r r e c t i o n d e s i r e d . We merely add t h i s c o r r e c t i o n to the observed r i s e i n temperature, The r e s u l t i s the Ae which may be s u b s t i t u t e d i n the exp re s s ion R Q (*©)( w ) which was mentioned when the a d i a b a t i c method was be ing d i s c u s s e d . (10) We can make some changes i n equa t ion (9) to make i t . somewhat more convenient t o use . Suppose we r e p l a c e Jfi by % = 1 4 t - % % % Then equa t ion (9) becomes •» wT 1 f3 n = ^- vVl_-JkVe2- e 4 " w T 3 l 4 w ( T i ' T z ) (10> I n our work the areas 9? f3 were determined w i t h the a i d o f a p l a n i m e t e r . T-^  and T^ were t aken of the same l eng th so tha t the f o u r t h term of exp re s s ion (10) van i shed . For reasons to be g iven l a t e r w was taken as z e r o . Thus the express ion f o r \ which we used was \ = e 2 - ( I D % APPARATUS Apparatus o f Previous I n v e s t i g a t o r s The apparatus used i n t h i s r e s e a r c h was e s s e n t i a l l y the same as that used by p rev ious i n v e s t i g a t o r s i n t h i s l a b o r a t o r y . The d e s i g n o f the c a l o r i m e t e r i s s i m i l a r t o Q tha t of W i l l i a m s and D a n i e l s . M c L e l l a n g ives a very 9 W i l l i a m s and D a n i e l s , J . Am. Chem. S o c , 46 , pp. 903-917. (11) adequate d e s c r i p t i o n o f the exper imenta l s e t u p . ^ Miss R o b i n -son modif ied the apparatus by the a d d i t i o n of a lead weight to the outer copper con ta iner f o r the sample cup to make i t l e s s buoyant and reduce upward pressure on the s t i r r i n g s h a f t . 1 1 She a l s o added 5% water to the g l y c e r i n e ba th and so cut down the v i s c o s i t y of the g l y c e r i n e to reduce tem-pera ture g rad ien t s i n the b a t h . She r ep l aced the v a r i a b l e r e s i s t a n c e s c o n t r o l l i n g the e l e c t r o l y t i c bath h e a t i n g w i t h a v a r i a b l e t ransformer ( V a r i a c type 100Q) and d i s c o n t i n u e d 12 the use of the p h o t o e l e c t r i c c e l l r e l a y desc r ibed by Graham. M o d i f i c a t i o n s to the Apparatus d u r i n g T h i s Research The apparatus was used by us w i t h l i t t l e m o d i f i c a t i o n . However, changes were made i n the thermopi le and the g l y c e r i n e ba th s t i r r i n g , and a l s o c e r t a i n sma l l m o d i f i c a t i o n s i n the pa r t s o f the w i r i n g system concerned w i t h the de t e rmina t i on of the temperature d i f f e r e n c e between the decahydronaphthalene and the b a t h . The c i r c u i t s used are shown f o r convenience under the heading EXPERIMENTAL PROCEDURE i n f i g u r e s 9 and 10, pages 3( and 3 2 . Accompanying photographs show the assembled apparatus and the e x t e r i o r o f the c a l o r i m e t e r , o f which pa r t s of the 10 M c L e l l a n , op. c i t . , pp. 2 -10 . 11 Robinson , op. c i t . , pp. 16-18. 12 Graham, H . M . , M . A . S c . t h e s i s , pp. 6 -8 . P i g . 3 : Views o f the Assembled Apparatus F i g . 4: Views of the E x t e r i o r of the Ca lo r ime te r (14) Thermopile Our o r i g i n a l i n t e n t i o n was to use Mis s R o b i n s o n ' s thermopi le to t e l l us the decahydronaphthalene temperature w i t h re fe rence to tha t o f the g l y c e r i n e b a t h . The temperature o f the l a t t e r was to be determined by a p la t inum r e s i s t a n c e thermometer. Since the anomaly mentioned e a r l i e r i n t h i s repor t occurs over on ly a smal l temperature range , i t was planned that on ly s m a l l amounts o f heat would be added t o the l i q u i d c i s decahydronaphthalene i n the i nne r c o n t a i n e r . The r e s u l t i n g s m a l l temperature r i s e was to be observed, the c o o l i n g c o r r e c t i o n made, and the s p e c i f i c heat determined as p r e v i o u s l y d e s c r i b e d . The i s o t h e r m a l method g ives the average s p e c i f i c heat between the i n i t i a l and f i n a l sample tempera tures . Because o f the s m a l l heat e f f ec t i nvo lved i n t h i s anomaly i t would disappear a l t oge the r i f the average were taken over a much l a rge r temperature range than that occupied by the an-omaly i t s e l f . The height of the peak of the curve would be very much reduced i f the average were t aken over the tem-perature range of the anomaly. Thus the temperature ranges which we wished to use were very s m a l l , l e s s than h a l f a degree i n f a c t , and the thermopi le had to be capable o f d i f f e r e n t i a t i n g between two temperature d i f f e r e n c e s to an accuracy of the order o f i 0 . 0 0 1 ° C . Since a l l our r e s u l t s were t o depend on the accuracy of the t h e r m o p i l e , i t was decided to begin work by a c c u r a t e l y c a l i b r a t i n g i t . An apparatus was set up as shown i n the accompanying ske tch : (15) th«rmopC(c te«j hdx+ i n ^ el eme-nt" " C o p p e r - T a p K P i g . 5: Apparatus f o r C a l i b r a t i n g a Thermopile A dewar f l a s k was p laced i n the g l y c e r i n e ba th which was l a t e r used i n the s p e c i f i c heat d e t e r m i n a t i o n s . In a d d i t i o n to the equipment shown above, there was a p la t inum r e s i s t a n c e t h e r -mometer i n the dewar and another i n the b a t h . Some t r a n s decahydronaphthalene was used as the l i q u i d i n the dewar f l a s k , With the v a r i a b l e t ransformer i n the A . C . c i r c u i t c o n t r o l l i n g the g l y c e r i n e bath temperature , and the v a r i a b l e r e s i s t a n c e i n the D . C . c i r c u i t p r o v i d i n g current t o the dewar f l a s k r e s i s t a n c e c o i l , qu i t e s a t i s f a c t o r y temperature c o n t r o l was o b t a i n e d . ( 1 6 ) The f o l l o w i n g t a b l e shows a s e r i e s o f c a l i b r a t i o n r ead ings taken w i t h the appara tus . I t i s worthy o f note that p r i o r to the f i r s t t a b l e d r e a d i n g there e x i s t e d a 5° d i f f e r -ence i n temperature between the l e g s - o f the t h e r m o p i l e . Temp. (Temp. j D i f f . , Mean Ver&tage Vol tage Ave . j ~^Ave . G l y c e r i n e Cup Bath °C . °C . I n Tgmp. o. Tgmp. C . Gen. /L V Gen. per Deg. A V / ° C . Mean Temp. °C Vol tage per ° C . 34.586 33.533 1.053 34.060 292.5 277.8 34.581 33.488 1.093 34.034 310.3 283.9 34.581 33.473 1.108 34.027/ 322.0 290.6^ 34.576 33.458 1.118 34.017 325.6 291.2 V 34.025 290.9 34.591 33.468 1.123 34.030 326.7 290.9 J 35.872 33.528 2.344 35.862 33.548 2.314 37.160 33.588 3.572 37.155 33.598 3.557 39.300 33.698 5.602 39.290 33.708 5.582 39.250 39.006 0.244 39.250 38.961 0.289 39.240 38.861 0.379 39.240 38.771 0.469 34.700 573.5 244.7 34.705 566.2 244.7 35.374 815.3 228.2 35.377 817.3 229.8 36.499 1230.3 219.6 36.499 1225.4 219.5 39.128 122.5 502.0 39.106 179.6 621.4 39.051 220.5 581.8 39.006 247.3 527.3 34.702 244.7 35.376 229.0 36.499 219.5 (17) When a s h i f t i n temperature d i f f e r e n c e was made some 15 minutes were a l lowed f o r e q u i l i b r i u m to be reached . The r e -s u l t s have been p l o t t e d on the accompanying graph. 800 • o 1 : • i -. i i O 1 2 3 . 4 S Temptratuft Dlff*«"*«ce between °C. P i g . 6: Graph Showing the V a r i a t i o n i n E . M . F . per Degree D i f f e r e n c e i n Thermopile Leg Temperatures w i t h the Magnitude o f That D i f f e r e n c e The r e s u l t s i n d i c a t e t h a t , separated as i t was from the bath by the s t ano lax and g l a s s bu lb surrounding i t , the the rmopi le had a memory f o r the i n i t i a l compara t ive ly h i g h temperature d i f f e r e n c e o f 5°C. between the l e g s . Such a t he rmop i l e was o b v i o u s l y unsu i ted to our purposes , because, i n the measuring o f the s m a l l temperature changes o f the decahydronaphthalene, o n ly sma l l temperature g rad ien t s would be at work i n the g l a s s and s t ano lax sur rounding the thermo-p i l e l e g p laced i n the decahydronaphthalene. These temperature g rad ien t s were to be , i f any th ing , l e s s than those encounter-(18) ed i n the above exper iment , where c e r t a i n l y very v a r i a b l e c a l i b r a t i o n s o f the thermopi le were o b t a i n e d . S i m i l a r r e -s u l t s were obta ined u s i n g a d i f f e r e n t potent iometer and a newly cons t ruc ted copper -cons tan t in t h e r m o p i l e . We were forced to the c o n c l u s i o n that such a t h e r m o p i l e , where the element was enc losed i n s t ano lax and g l a s s , was e n t i r e l y u n -s u i t e d t o the de te rmina t ion of the s p e c i f i c heat by the i s o t h e r m a l method, at l e a s t where sma l l temperature g rad i en t s were i n v o l v e d . However, i t seemed that i t would be p o s s i b l e d u r i n g s p e c i f i c heat d e t e r m i n a t i o n s , t o m a i n t a i n the g l y c e r i n e bath at a constant temperature f o r a pe r iod s u f f i c i e n t l y long so tha t the l e g o f the the rmopi l e immersed i n i t cou ld reach s e n s i b l y the same temperature as the b a t h . I t was then apparent that i f i t were p o s s i b l e t o somehow make the thermo-p i l e l e g i n the decahydronaphthalene reac t wi thout l a g , we would have a s a t i s f a c t o r y arrangement f o r our purposes. A new coppe r - cons t an t in the rmopi le was cons t ruc ted and p laced i n a g l a s s U tube s i m i l a r t o the one used p r e v i o u s -l y except that the g l a s s l e g on the decahydronaphthalene s ide was cut away approximate ly at the ca lo r ime te r l i d l e v e l as shown i n the f o l l o w i n g d iagram. The the rmopi le w i r e s on the decahydronaphthalene s ide were i n s u l a t e d from one another by s l i d i n g over each separate wi re of the f i v e j u n c t i o n s a f i n e l y drawn out g l a s s t ube . The j u n c t i o n s were then s o l d e r e d t o -gether , wrapped at t h e i r bases w i t h s i l k thread to keep them apar t , and then i n s u l a t e d w i t h g l y p t a l v a r n i s h baked on over n igh t i n an oven kept at 60°C. The j u n c t i o n s i n the g l a s s • (19) / l sect ion drunjinj ) P i g . 7: The Copper -Cons tan t in Thermopile w i t h Glass Removed from one Leg tube had p r e v i o u s l y been t r ea t ed s i m i l a r l y . E g y p t i a n adamant cement was used to s e a l the thermopi le w i r e s i n t o the stump of the g l a s s tube on the decahydronaphthalene s i d e . T h i s change i n the amount o f g lass present i n the c a l o r i m e t e r , and the removal o f the s t ano lax p r e v i o u s l y i n the g l a s s l e g on the decahydronaphthalene s ide o f the t h e r m o p i l e , meant that the water equ iva len t o f the ca lo r ime te r had to be r e -determined. The new coppe r -cons t an t in thermopi le assembly desc r ibed above was c a l i b r a t e d by p l a c i n g one l eg i n a water-snow m i x -t u r e , and the other i n a water b a t h . The f o l l o w i n g r ead ings (20) were obta ined a f t e r some time had elapsed fo r the at tainment o f " e q u i l i b r i u m c o n d i t i o n s . E . M . P . Water Ba th E . M . P . per Degree . Time Temp. /*• V ° C . / t V / ° C . 4 .245.7 21 .3 200.0 2:31 P . M . 4 .224 .8 21 .0 200.5 4 ,088 .8 20.6 198.6 2:45 P .M. 13 Acco rd ing to the Leeds and Nor thrup Co. a 5 j u n c t i o n copper -cons tan t in thermopi le should show an e .m. f . o f (0 .04) (1000) (5) B 2 0 0 / a V / ° C . i n the range where the d i f f e r e n c e i n temperature between the legs i s from 0 to 30°C . I t was decided t o use the t a b u l a t e d f i g u r e of 200 jUV/°G. f o r the t h e r m o p i l e . The the rmopi le was checked w i t h both legs i n a s t i r r e d water bath at room temperature . The f o l l o w i n g r e s u l t s were ob ta ined! Time E . M . p f ^ a V Time E.M.F'f /x.V 1.49 P . M . 1.0 1.57 P . M . . * 0 .7 1.52 * 0 .9 1.58 - 0.2 1.55 - 0 .8 2 .20 * 0 .3 * Measured by Type K po ten t iomete r . 13 Standard Convers ion_Tables f o r L . and N . Thermocouples, p, (21) G l y c e r i n e Ba th S t i r r i n g One o f the h i g h speed shaf ts used by Mis s Robinson was removed from the g l y c e r i n e ba th , which was then s t i r r e d by a s i n g l e shaft o n l y . The bath was then exp lo red at 30°C . w i t h a p la t inum r e s i s t a n c e thermometer. Even at t h i s low temperature the maximum temperature d i f f e r e n c e found i n the ba th was between 1 and l | r hundredths of a degree c e n t i g r a d e . CALIBRATION OP THE APPARATUS Heat of S t i r r i n g and Evapora t ion The f o l l o w i n g method f o r o b t a i n i n g the combined heat of s t i r r i n g and evapora t ion was d e r i v e d by r eason ing s i m i l a r t o tha t employed by W. P. White i n o b t a i n i n g the c o o l i n g c o r r e c t i o n . The l i q u i d i n the i nne r c a l o r i m e t e r con t a ine r was a l lowed to c o o l w h i l e be ing s t i r r e d by the 717 r . p . m . synchronous s t i r r i n g motor . A graph s i m i l a r t o the f o l l o w i n g was ob ta ined : "Time " minutes P i g . 8: Graph f o r Dete rmin ing the Heat o f S t i r r i n g (22) Dur ing the t ime i n t e r v a l the l i q u i d temperature f e l l from Gi to e 3 . Dur ing the t ime i n t e r v a l Tg the l i q u i d temperature f e l l from 0, t o ©a . The remainder of the nomenclature f o l l o w s that used i n the c a l c u l a t i o n of the c o o l i n g c o r r e c t i o n . The * d i r e c t l o s s o f temperature i n p e r i o d T^ i s g i v e n by i Q = e, - a, - i f T x ( l ) r and i n p e r i o d T 2 i s g iven by - 0, - 6 Z -wTg. (2) Prom the d i s c u s s i o n of the c o o l i n g c o r r e c t i o n (equa t ion 6, p . 9 ) where (j? and (f? are the areas between the curves f o r the jacket and the inne r con ta iner o f the c a l o r i m e t e r cor responding to the time i n t e r v a l s T and T r e s p e c t i v e l y . Then i f we sub-1 d> s t i t u t e equat ions (1) and. (2) i n equat ion (3) and c ross m u l t i p l y we o b t a i n the r e s u l t e, - e - wT. z y. ( e, - e - wT_) (4) When we p lo t the graph we can s e l e c t and read o f f © . , 0 2 . , Q3 , T , and T 0 . We can determine cp4 and < £ w i t h the p lan imete r 1 2 or by count ing squares . The s u b s t i t u t i o n of the va lues i n equat ion (4) leaves us w i t h a simple equa t ion for w. C a l c u l a t i o n s o f the heat of s t i r r i n g were made f o r the c o o l i n g pe r iods of four s p e c i f i c heat runs on decahydro-(23) naphthalene. The r e s u l t s are t a b l e d below: C i s Decahydronaphthalene S p e c i f i c Heat Run No. 28 29 30 32 Heat of S t i r r i n g and Evapora t i on w - deg C . / m i n . * 0.00003 4 0.0003 - 0.0007 - 0.005 ( R e c a l l tha t w i s the temperature f a l l per minute due t o the combined e f fec t o f evapora t ion and s t i r r i n g ) . The r e s u l t s obta ined are o b v i o u s l y not very p r e c i s e . I n the c a l c u l a t i o n s q u a n t i t i e s of very c l o s e l y the same magnitude are sub t r ac t ed one from the o the r , so tha t sma l l e r r o r s i n these q u a n t i t i e s produce la rge e r r o r s i n the f i n a l answer. The f o l l o w i n g specimen c a l c u l a t i o n serves t o i l l u s t r a t e t h i s f a c t : Heat o f S t i r r i n g & E v a p o r a t i o n , Run 28 . 0, - 0 . 1 9 9 6 ° C . e, = 0.1520 0,-e 3s 0.0476 0, = 0 . 1 9 9 6 ° C . Qz - 0.1781 0 r e l S 0.0215 # # 1650 -2 .212 % " ' 746 T-L a 17.7 m i n . Tg - 7.3 m i n . e , - © j - wTi = f, ( e, - e A - WT 2 ) (24) 0.04760 - 17.7 w = 0.04756 - 16.148 w - 1.552 w = - 0.00004 w s 4 0 . 0 0 0 0 3 ° C . / t n l n . The on ly c o n c l u s i o n which can be drawn from these r e s u l t s i s that the heat o f s t i r r i n g and evapora t ion i s so s m a l l t ha t i t i s very d i f f i c u l t t o measure i t at a l l a c c u r a t e l y . I n equa t ion (10) page 10, the c o o l i n g c o r r e c t i o n equa t ion , f ; occurs t w i c e . I f <p. i s taken equa l to<g„ and T-^  equa l t o T^ , w w i l l have no e f f e c t whatever on the c a l c u l a t i o n s . I n our work we were c a r e f u l t o have T-^  equal to T^ , but perhaps not qu i t e enough t r o u b l e was taken w i t h the adjustment of the i n i t i a l temperature o f the l i q u i d i n the i nne r c o n t a i n e r , w i t h the r e s u l t tha t ^, - was u s u a l l y a f r a c t i o n o f the order o f l/fi* However, itoe e f f e c t ^ i n the equa t ion may be s t i l l qu i t e s m a l l . For example i f w equa l l ed 4 0 . 0 0 0 3 ° C , i f T 3 was 900 seconds or 15 m i n . , and i f the l i q u i d i n the inne r con ta ine r were heated through 0 . 1 5 ° C , t h e n the e f f ec t on the change i n temperature of the l i q u i d would be of the order o f 1 ( 1 5 ) ( 0 . 0 0 0 3 ) Y 100$ s 1% 3 0.15 i f we apply equa t ion ( 1 0 ) , p . 10. The runs i n which the heat o f s t i r r i n g was determined were qu i t e s i m i l a r t o the example immediately above, so that i f from the c o o l i n g curves o f such runs the heat of s t i r r i n g could not be obta ined any more a c c u r a t e l y than we have been able to do so , i t i s conve r se ly unnecessary to i n c l u d e the heat o f s t i r r i n g as a c o r r e c t i o n (25) i n c a l c u l a t i n g the c o o l i n g c o r r e c t i o n tin such r u n s , at l e a s t u n t i l the measurements i n v o l v e d , , p a r t i c u l a r l y those of tem-perature , , can he made much more a c c u r a t e l y than i s p o s s i b l e at p re sen t . I n other runs the decahydronaphthalene was hea t -o ed through approximate ly 1.5 C . i n approximate ly the same t i m e . I n these runs the heat of s t i r r i n g cou ld be 10 t imes as la rge wi thout an inc rease o c c u r i n g i n the percentage e r r o r caused by n e g l e c t i n g i t . S i n c e , a l s o , we were more i n t e r e s t e d i n the r e l a t i v e va lues than i n the absolute va lues of the s p e c i f i c heat , we decided to assume a value of zero f o r the heat of s t i r r i n g . Water Equ iva len t o f the Ca lo r ime te r Because of the changes i n the the rmopi le a l ready descr ibed , , i t was necessary t o redetermine the water e q u i v a -l en t o f t he c a l o r i m e t e r . The i nne r con ta iner was f i l l e d w i t h C . E ; . t o l u e n e . A procedure s i m i l a r to that, used fo r i so the rmal , de te rmina t ions of the s p e c i f i c heat ofF decahydro-naphthalene was c a r r i e d out,, the to luene be ing heated through a temperature range of approximate ly 1 . 3 ° C . i n 700 seconds. The s p e c i f i c heat o f to luene i s known between -&0° and 1 0 0 ° C . 1 4 so tha t i t was: p o s s i b l e to c a l c u l a t e the water e q u i v -a len t o f the c a l o r i m e t e r . The f o l l o w i n g t a b l e summarizes, the resu l t s^ ob ta ined : 14 I n t e r n a t i o n a l C r i t i c a l Tab l e s , V o l . V , p . 115. tan No. Weight Hea t ing Cor rec ted Average Wat er Toluene Time R i s e i n Toluene Equ iva l en t gms. sees . Temp, o f Temp. j o u l e s / d e g . Toluene deg. C . deg. C. 8 140.23 640 1.2409 19.08 19.48 9 140.23 645 1.1994 19.85 30.16 10 140.23 674 1.284 21.68 22.87 11 140.23 685.5 1.301 21.74 24.04 12 135.61 944 1.865 21.12 21.32 13 135.61 832 1.6133 22.84 26.29 14 135.61 690 1.3292 24.42 27 .63 15 135.61 925 1.737 24.61 34.13 Average 21.92 25.74 At f i r s t s i gh t the d i s c r e p a n c i e s i n the r e s u l t s f o r the i n d i v i d u a l runs seem q u i t e l a r g e . However, percentage e r r o r s i n the r e s u l t s are magnif ied over those o f the read-i n g s , as a r e s u l t of the n e c e s s i t y o f s u b t r a c t i n g i n the c a l c u l a t i o n s two q u a n t i t i e s o f magnitude of order 300 to get one of order 30 . The f o l l o w i n g specimen c a l c u l a t i o n taken from run 11 w i l l serve to i l l u s t r a t e t h i s f a c t : Let Q. be the water equ iva l en t o f the c a l o r i m e t e r , -at be the t o t a l temperature r i s e o f the to luene ( c o o l i n g c o r r e c t i o n "n. a p p l i e d ) , S be the s p e c i f i c heat of the to luene at i t s average temperature , and w be the weight, of the to luene (27) Then (a t ) Q - t o t a l heat supp l i ed - heat s u p p l i e d to the to luene - t o t a l heat s u p p l i e d - (w)( A t ) ( S ) . A t B 1 .301°C. t o t a l heat s upp l i ed s 336.14 j o u l e s w = 140.23 gws. S = 1.671 j o u l e s / ° C . S u b s t i t u t i n g i n the fo rmula , use o b t a i n 1.301 Q « 336.14 - 304.86 = 31.28 Q r 31.28 s 24.04 j o u l e s / ° C . 1.301 Now an e r r o r of 1%, say , i n the measurement of the heat added to the t o l u e n e , would mean an e r r o r of approximate ly 3 j o u l e s . Assuming the f i g u r e 304.86 to be c o r r e c t , the e r r o r i n the d i f f e r e n c e shown above would be approximate ly 10$, and t h i s i s a l s o the percentage e r r o r which would r e s u l t i n the water e q u i v a l e n t . Some d i f f i c u l t y was exper ienced i n weighing out the to luene because of i t s v o l a t i l i t y . C l o s i n g the conta iner w i t h a rubber stopper i s u n s a t i s f a c t o r y because the stopper absorbs t he vapor and changes i n we igh t . The best method i s probably to weigh out the to luene i n the i nne r c a l o r i m e t e r con ta iner covered w i t h a square o f f l a t cardboard . By way o f a check two a d i a b a t i c de te rmina t ions of the water equ iva len t were made. The r e s u l t s f o l l o w : (28) C a l i b r a t i n g L i q u i d Length o f Run-seos . Temp. Q j o u l e s / ° C . °C Benzene* 7980 21.90 42 .7 C P . Toluene 7145 23.51 33.62 I n the c a l c u l a t i o n s fo r the a d i a b a t i c method the same mag-n i f i c a t i o n of e r r o r s occurs as i n the c a l c u l a t i o n s f o r the i s o t h e r m a l method. The value of the water equ iva len t used i n c a l c u l a t i n g the s p e c i f i c heat of the decahydronaphthalene was 25.74 j ou l e s per ° C . at 2 1 . 9 ° C , t h i s f i g u r e be ing the average r e s u l t o f the i s o t h e r m a l r u n s . M c L e l l a n had found the water equ iva len t of the unmodified apparatus to be 38 j o u l e s per °G. at 3 0 ° C 5 He made an approximate c a l c u l a t i o n o f the i n -crease i n the water equ iva len t w i t h i n c r e a s i n g temperature , and obtained a f i g u r e o f 0 .01 j o u l e s per degree per degree cent igrade r i s e i n temperature . The cor responding f i g u r e used i n t h i s r e sea rch was 0.007 j o u l e s per degree per degree, c a l c u l a t e d on the assumption of i t s be ing d i r e c t l y p r o p o r t i o n -a l t o the magnitude of the water e q u i v a l e n t . Thus the r a t e o f i nc rease i s g i v e n by 25.74 1 (0 .1 ) = 0.007 j o u l e s per deg . per deg . 37 .9 10 C P . benzene p u r i f i e d by 4 r e c r y s t a l l i z a t i o n s . 15 M c L e l l a n , op . c i t . , p . 12. (29) EXPERIMENTAL PROCEDURE P r e p a r a t i o n fo r a Run Approx imate ly 145 grams o f decahydronaphthalene were weighed out i n the i nne r con ta iner o f the c a l o r i m e t e r . The c a l o r i m e t e r was then assembled, and the ba th and the decahydro-naphthalene were heated to the temperature at which the s p e c i f i c heat was t o be determined. The b a t t e r y was swi tched t o the dummy heater at l eas t h a l f an hour before the beg inn ing o f the run to i n su re tha t any i n i t i a l l y h i g h b a t t e r y e .m . f . would be lowered to a constant v a l u e . The bath temperature was kept as constant as p o s s i b l e fo r a h a l f an hour , up t o as long as 24 hours , before the beg inn ing of the r u n , hand c o n t r o l of the A . C . e l e c t r o l y t i c ba th h e a t i n g by means of a V a r i a c t ransformer b e i n g the most s a t i s f a c t o r y method o f m a i n t a i n i n g t h i s temperature . As the runs progressed we be-came more and more c a r e f u l about the constancy of the ba th temperature , and the l eng th of the p e r i o d o f such constancy before the s t a r t of the r u n i nc rea sed c o r r e s p o n d i n g l y . Procedure d u r i n g the Runs The s p e c i f i c heat de te rmina t ions f a l l n a t u r a l l y i n t o two c l a s s e s , the d i s t i n g u i s h i n g c h a r a c t e r i s t i c be ing the temperature range through which the decahydronaphthalene was heated . I n runs 1-18 we were In t e r e s t ed i n de te rmin ing the (30) s p e c i f i c heat versus temperature curve between 20 and 50°C. As no t r a n s i t i o n p o i n t s were b e l i e v e d t o e x i s t i n tha t range i t was cons idered s a t i s f a c t o r y to heat the decahydronaphthalene through approximate ly 1 . 5 0 C i n each de t e rmina t ion o f the s p e c i f i c hea t . The b a t t e r y was switched from the dummy heater to the decahydronaphthalene heater and the stopwatch s t a r t e d s imu l t aneous ly . With the type K poten t iometer , r ead ings of the IR drop across the standard ohm, and the IR drop across? the ohm, decahydronaphthalene hea te r , and leads were t a k e n . Each vo l tage was read tw ice d u r i n g the f i r s t r uns , but as i t was found that each p a i r of r ead ings was almost always i d e n t i c a l , and tha t any tendency o f the vo l t ages to vary could be noted when the read ings were b e i n g t aken , the p r a c t i c e o f t a k i n g double read ings of each vo l t age was d i s c o n t i n u e d , s i n g l e r ead ings o f each s u f f i c i n g . Concurrent r ead ings of the tem-perature d i f f e r e n t i a l between the ba th and the decahydronaph-tha lene were taken by r e a d i n g the thermopi le vo l t ages w i t h a Leeds and Northrup type number 8662 po ten t iomete r . ( S e r i a l numbers 553 ,553 and 634,358 were the ins t ruments u s e d ) . I t i s worthy of note i n pas s ing tha t most potent iometers seem to have a sma l l zero e r r o r , so tha t i t i s wrong to assume tha t when a the rmopi le reads zero as shown by a s e n s i t i v e galvanometer connected t o i t s l eads , a potent iometer connected to i t s leads would a l s o read e x a c t l y z e r o . Dur ing these runs the b a t t e r y r e s i s t a n c e box was set at about 15 ohms so tha t the hea t ing t ime was o f the order of 800 seconds. At the c o n c l u s i o n of the h e a t i n g pe r iod a c o o l i n g p e r i o d of the same l eng th was used , r ead ings of the temperature d i f f e r e n t i a l (31) be ing continued w i t h the L . and N . po ten t iomete r . The w i r i n g system i n use d u r i n g runs 1-18 was that of M c L e l l a n f o r the 16 b a t t e r y c i r c u i t . The w i r i n g used i n the thermopi le c i r c u i t i s shown below: 1" ) = y l j I $wt+eb- -for gnorf rng thermopile When not in use P i g . 9: Thermopile C i r c u i t Runs 1-18 When run 18 had been completed the next s tep which we wished to ca r ry out was to p l o t the anomaly i n the s p e c i f i c heat curve b e l i e v e d to e x i s t at about 50°C. For t h i s purpose we wished to heat the decahydronaphthalene through on ly a very s m a l l temperature range f o r reasons a l ready e x p l a i n e d . A c c o r d i n g l y , i n runs 18-36, a r e s i s t a n c e o f about 65 ohms was used i n the b a t t e r y r e s i s t a n c e box so that the decahydro-naphthalene was heated through about 0 . 1 5 ° C . i n some 900 seconds. The w i r i n g from the thermopi le was a l t e r e d so that the type K. potent iometer was used fo r the read ings of tempera-t u r e d i f f e r e n t i a l as w e l l as those o f current and vo l t age t o the decahydronaphthalene hea t e r . I n the runs before 19 the use of» two potent iometers meant tha t few changes i n the L6 N. P o t e n t iometer T y p e 8 6 6 2 16 M c L e l l a n , op. c i t . , p . 9 . (32) V a r i a c s e t t i n g c o n t r o l l i n g the bath temperature were made. However i n these runs the r e s u l t s seemed reasonable and the changes o f a few hundredths o f a degree i n the ba th tempera-t u r e which occured d u r i n g the runs d i d not seem to be ad-v e r s e l y a f f e c t i n g the r e s u l t s . However i n the runs a f t e r 19, very e r r a t i c r e s u l t s were ob t a ined , and i n an e f f o r t t o o b t a i n the p rev ious smooth curve type o f r e s u l t s , i n runs 27-36 very c lose c o n t r o l o f the V a r i a c s e t t i n g was ma in t a ined , so tha t f o r most o f these runs the maximum change i n the bath tem-pera ture o c c u r i n g was l e s s than 0 . 0 1 ° C . Except fo r the above d e t a i l s the procedure i n runs 19-36 was the same as that i n runs 1-18. The f o l l o w i n g w i r i n g diagram shows the b a t t e r y and thermppi le c i r c u i t s i n use d u r i n g runs 19-36: Volt-B o x 1 i ItyVVWVV/VvJ D e d a h y d r o n a phtha.tc.ne heartng coil B a t t e r y R e s i s t a n c e Box /Wire ^or Shorting -thermopile. ^ - — A " Cu- S w f t e h Galy* +ype P H° - Hone Pter. 14 see. coo.* ? 6V- Batt«ry 6 6 Tnemo pile C e l l Per S,% cp.fty.. 5CJ Ub SAC. P i g . 10: Thermopile and B a t t e r y C i r c u i t s Runs 19-36 (33) Prom and i n c l u d i n g run number 27 galvanometer number 81126 was used w i t h the potent iometer i n de te rmin ing the d i f f e r e n c e in A temperatures o f the decahydronaphthalene and the g l y c e r i n e ba th , because i t had a sma l l e r pe r iod o f o s c i l l a t i o n than the Leeds & Northrup type P galvanometer which had been used p r e -v i o u s l y , and hence f a s t e r response was obta ined to changes i n the temperature d i f f e r e n c e b e i n g measured. The i d e a l g a l -vanometer fo r t h i s purpose should have as short a p e r i o d as p o s s i b l e , so tha t sucess ive read ings can be made q u i c k l y , a c r i t i c a l damping r e s i s t a n c e approximate ly equal to the r e -s i s t ance o f the c i r c u i t i n which I t i s be ing used so that i t does not o s c i l l a t e about a g iven r e e d i n g , and a f a i r l y h i g h s e n s i t i v i t y , say 0 .5 jut. V. per mm. so as to permit the accura te measurement o f the sma l l vo l t ages (10-40 jl V.) produced by the 5 j u n c t i o n the rmopi le w i t h s m a l l temperature d i f f e r e n c e s ( 0 . 0 5 - 0 . 2 0 ° C . ) between i t s l e g s . Readings and C a l c u l a t i o n s The f o l l o w i n g pages show a t y p i c a l set o f r ead ings and c a l c u l a t i o n s : Readings for Run 30 J u l y 7, 1946 Ba th r e s i s t a n c e thermometer r e a d i n g f o r d i f f e r e n c e between R and N : R = 2.9882 R z a 0.00005 N = 2U98455 N z = 0.0002 R-K - 365 ; .... . _ . (34) Readings showing the ba th temperature befoperand d u r i n g the r u n : Time V a r i a c Rdg. P . M . on A . C . Hea t ing f o r Bath v o l t s 12:40 54 12:45 t o 52 12:57 t o 51 1:07 t o 50 1:09.5 to 50.05 1:16 50.05 1:27 t o 50.0 1:40 t o 49.95 1:42 49.95 1:43 49.95 1:45 49.95 1:46 t o 49.97 1:50 49.97 1:51 t o 50.0 ( s t a r t o f the run 1:52 sees . 50.0 0) 50.0 53 50.0 133 to 49.98 241 49.98 318 to 49.95 Res . Therm. Amount Amount N Ba th Temp, Ba th Temp. Reading above N above N mms. g a l v o . C . s c a l e 2.9842 + 1 2.9844 * 0 .5 2.9845 • 1 2.9846 - 0 .3 2,9846 - 0.75 2.9845 * 0 .3 2.9846 4 1 2.9847 0 2.9847 - 0 .5 2.9847 - 1 2.9847 - 1 2.9847 - 1.2 2.9846i 0 2.9846 - 0 .25 P . M . ) 2.9846 2.9846 - 0 .5 - 0.0042 2.9846 0 0 .0 2.9846 + 0.25 4 0.0021 2.9846 * 0 .3 4 § . 0 0 2 5 2.9846 4 0 .3 * 0.0025 (35) Time sees . V a r i a c Rdg. on A . C . Hea t ing fo r Bath v o l t s Res . Therm. N Reading Amount Bath Temp. above N mms. g a l v o . s ca l e Amount Bath Tern] above N ° C . 438 49.95 2.9846 - 0.2 - 0.0017 498 49.95 2.9846 t 0 .1 •» 0.0008 582 49.95 2.9846 0 " 0 678 49.95 2.9846 4 0 .1 4 0.0008 720 49.95 2.9846 0 0 814 49.95 2.9846 0 0 874 49.95 2.9846 0 0 977 49.95 2.9846 0 0 1077 49.95 2.9846 0 0 1151 49.95 2.9846 0 0 1313 49.95 2.9846 0 0 1405 49.95 2.9846 0 0 1550 t o 49.93 2.9846 4 0 .2 4 0.0017 1652 49.93 2.9846 4 0 .2 4 0.0017 1752 49.93 2.9846 " 0 0 1805 49.93 2.9846 0 0 1918 49.93 2.9846 0 0 2008 49.93 2.9846 0 0 2157 49.93 2.9846 0 0 2295 49.93 2.9846 0 0 2442 t o 49.92 2.9846 * 0.2 4 0.0017 2537 49.92 2.9846 4 0.3 4 0.0025 2620 49.92 2.9846 4 0 .4 -f 0.0033 ( S e n s i t i v i t y of the galvanometer, 1.2 mm'. = 0.010°C : .) Readings taken w i t h the (36) potent iometer d u r i n g the r u n : Time sees, 0 95 182 399 517 769 953 1223 1250 1258 1288 1341 1460 1519 1697 1884 2007 2227 2394 2577 Vol tage Read /jl V. 16.05 18.4 21 .3 39.6 43.6 51.1 heat o f f 51 .8 51.95 51.5 49.95 49 .1 47.2 45 .3 44 41.9 40.25 38 .2 Vol tage \ Cor rec ted f o r Zero E r r o r /JL V . 15.65 18.0 20.9 39.2 43.2 50.7 51.4 51.55 51.1 49.55 48.7 46 .8 44.9 43.6 41 .5 39.85 37 .8 ' D i f f e r e n c e Vol tage i n Temperature Read o f Ba th & Cup v o l t s ° C . 0.0782 0.090 0.1045 (heater v o l -t age) 0.0135525 (s tandard ohm) 0.085782 0.196 0.216 0.2535 0.257 0.2578 0.2555 0.2478 0.2435 0.234 0.2245 0.218 0.2075 0.1992 0.189 (38) Room temperature r e a d i n g s : Time 211 sees. 1428 Aug. 27 , 1946. C a l c u l a t i o n of S p e c i f i c Heat o f Decahydronaphthalene Run 30 Average temp, o f ha th s 45.990 Room temp, s 20 .0 D i f f e r e n c e = 25.990 Di f f e r ence 4- 2 - 12.995 Temperature f o r l ead r e s . - 32.995 Res i s t ance o f leads - 0.18063 I n i t i a l temp, o f ba th = 45.9858 I n i t i a l d i f f . cup & bath = 0.0782 I n i t i a l cup temperature - 46.0640 Ba th temp, at max. swing = 45.990 D i f f . bath-cup at max. swing = 0.2578 Max. temp, of cup - 46.2478 I n i t i a l p l u s max. cup t . z 92.3118 Average cup temp. s 46«1559 Heater v o l t s = 0.0135525 x 50 a 0.677625 v . Heater current = 0.085782 a . Temp. 19.9 19.7 IR drop across leads - (0.085782)(0.18063) r IR drop across ohm = T o t a l IR drop not a p p l i c a b l e z T o t a l vo l t age z Not a p p l i c a b l e r Net vo l t age = Heat imput / sec . r (0.576348)(0.085782) = T o t a l heat imput = (0.0494403)(1250) = (39) 0.015495 0.085782 0.101277 0.677625 0.101277 0.576348 0.0494403 wat t s 61.800 j ou l e s - 2598 - f t = 2 0 2 0 %-% r 578 e t - e * ( e x - © A ) ^ 4, - % t . + :_578 . + 0.2225 2598 / = - 0 . 0 ( " %) ( <P. - ^ ^ - - ( 0 . 0 6 5 9 ) (0.2225) 014663 6a = 0.2578 - e = 0.1919 4 . '" © 4 = 0.06590 4( e a - frj,^<p. -<£ j ="0.01466 \ s 0.05124 4 6i - e o = 0.1838 t o t a l temperature - 0.23504 " A t r i s e wt - A t heat i n (146 .64 ) (0 .23504) (C p ) = 61 .8 ( 3 4 . 4 6 ) ( C p ) - 61 .8 ( ° p ) = 55.71 34.46 ^ = 0.2578 - e 0 = 0.0740 e a - © o = 0.1838 A t W.E. - (0 .23504)(25.91) - 6.090 = 55.71 1.6166 (40) RESULTS Runs 1-18 ( 1 . 5 ° C . Temperature R i s e ) An accompanying t a b l e shows the r e s u l t s o f runs 1-18 o f the s p e c i f i c heat d e t e r m i n a t i o n s . I n the t a b l e temperature and s p e c i f i c heat f i g u r e s g iven past the second dec ima l p lace have l i t t l e meaning. However the ex t ra numbers are i n c l u d e d f o r re fe rence i n case they should ever be r e q u i r e d . An accompanying graph shows a p l o t o f these r e s u l t s , toge ther 17 w i t h the average values o f M c L e l l a n , o f Mead,and of D a v i e s . 18 A few of M i s s Rob inson ' s r e s u l t s are a l s o p l o t t e d . Runs 19-36 ( 0 . 1 5 ° C . Temperature R i s e ) To t e s t whether or not the r e s u l t s o f the runs w i t h the s m a l l temperature r i s e were reasonab le , i t was dec ided to make some runs at temperatures f o r which the s p e c i f i c heat had a l ready been determined. We could not reproduce the r e s u l t s o f runs 1-19 when we used the sma l l e r temperature r i s e , and the re fo re d i d not attempt t o t r ace the anomaly. However, i t i s worthy of note tha t i n run .26 at 5 0 . 2 ° C . an unusua l value o f the s p e c i f i c heat was not o b t a i n e d . A t a b l e f o l l o w i n g shows the r e s u l t s . 17 M c L e l l a n , op . c i t . , p . 2 3 . 18 Robinson , op . c i t . , p . 39« 42 . (41) Date Run M i n . Max. Length Temp. Ave . C i s S p e c i f i c June No. Time V a r n . Hea t ing R i s e D e c a l i n Heat 1946 Ba th Ba th Per iod ( C o o l i n g Temp. j o u l e s / Temp. Temp. sees . c o r r . ° C . gm. / Oons. i n a p p l i e d ) 8 C before Run 6 C . Run 00 . m i n . 15 1 20 0.14 865 1.4716 21.52 1.8135 15 2 20 0.07 880 1.5102 27.03 1.8021 15 3 20 0.02 940 1.6154 32.66 1.7992 15 4* 20 0.06 860 1.5185 37.58 1.7430 17 5 20 0.08 1000 1.6973 25.08 1.8191 17 6 20 0 .08 910 1.5783 43.67 1.7731 17 7 * 20 0.10 930 1.5931 48.82 1.7970 18 8 20 0.06 930 1.5847 28.42 1.7999 18 9* 20 0.01 1000 1.6900 35.64 1.8123 19 10 20 0.06 1050 1.7674 23.80 1.8148 19 11 20 0.04 815 1.3916 30.17 1.7902 19 12 20 0.05 725 1.2241 36.78 1.8131 19 13* 20 0.04 815 1.380 40.79 1.8090 20 14* 20 0 .0 780 1.298 39.72 1.8321 21 15 20 0.06 780 1.372 40.51 1.8306 21 16 20 0.02 740 1.3004 43.36 1.8218 . 21 17 20 0.04 720 1.2457 46.50 1.8457 21 18* 20 0.03 740 1.2666 48.68 1.8565 Weight o f c i s decahydronaphthalene used a 144.173 gm. * Decahydronaphthalene a l lowed to c o o l t o approximate ly 20°C . a f t e r therse r u n s . (42) P i g . 12: S p e c i f i c Heat of C i s Decahydronaphthalene Runs 1-18 1 9-< 3 r > 6 > i s | € » s I w.r. ,, - /» ® -n .- > c i —t 1 7 r l < t o - - i I t 3 t I ? *) 1 w -3 r r 1 — 1 T r i i S a L — i 1 I. to L <? 1 i h a r c h • X c- >< i c s ( J > S Y i d ( A r i i a t * . | T c 1 C c ( n Add f c t" s 0 t hr rr • 2 -a i n A V > L t I i A Y< m »r 1 w No. S36, GRAPH PAPER, SMITH, DAVIDSON a WRIGHT, LTD. (43) Date Run M i n . Max. Length Temp. Ave . C i s S p e c i f l 1946 No. Time V a r n . Hea t ing R i s e D e c a l i n Heat Bath Ba th Per iod ( C o o l i n g Temp. joules , Temp.Temp. sees . c o r r . ° C . gm. / Cons. i n a p p l i e d ) 8 C beforegun ° C . Run C. m i n . June 24 19 120 0.03 750 0.15023 48.77 1.5914 June 24 20* run not c a l c u l a t e d , loose b a t t e r y connec t ions . June 25 21 20 0.07 960 0.16285 48.11 1.8987 June 25 22* 20 0.065 1210 0.20521 49.60 1.9030 June 26 23 20 0.05 1060 0.1928 • 35.83 i; '7568 June 26 24 20 0.065 1185 0.2071 49.99 1.8311 June 26- 25 20 0.035 915 0.1761 50.13 1.6443 June 26 26* 20 0.02 1020 0.1825 50.20 1.7892 J u l y 6 27 60 0.005 1120 0.1969 30.09 1.7391 J u l y 6 28 50 0.004 1030 0.17574 34.66 1.7961 J u l y 6 29* 40 0.010 990 0.18708 39.99 1.6050 J u l y 7 30 65 0 .00? 1250 0.23504 46.16 1.6166 J u l y 7 31 40 0.007 753 0.13852 49.91 1.6559 J u l y 7 32 20 0.008 740 0.13883 50.00 1.6200 Sept . 3 33 120 0.008 1298 0.22528 30.37 1.8261 Sept . 4 34 120 0.008 870 0.15428 35 .78 1.7750 Sept . 5 35 80 0.018 834 0.15097 42.35 1.7324 Sept . 7 36* MO 0.006 849 0.16489 47.93 1.5899 Weight of c i s decahydronaphthalene used , runs 19-26, 144.173 gm., runs 27-32, 146.64 gm. and runs 33-36 , 143.833 gm. C i s decahydronaphthalene was a l lowed to c o o l to 2 0 U C . at the c o n c l u s i o n o f the.Be r u n s . (44) At the end o f each r u n marked i n the t a b l e w i t h an a s t e r i s k , g l y c e r i n e was removed from the ba th so that i t s l e v e l was below tha t o f the s m a l l i n v e r t e d cup s e a l on the decahydronaphthalene s t i r r e r sha f t . Even though t h i s p r e -cau t i on was taken a sma l l amount o f g l y c e r i n e was found i n the decahydronaphthalene con ta iner at the c o n c l u s i o n of run 26. I n assembling f o r the next set of runs , care was t aken to wrap the decahydronaphthalene s t i r r i n g shaft w i t h a s m a l l q u a n t i t y of va lve pack ing at the po in t where the shaft en te r s the copper s leeve connected t o the g l y c e r i n e side of the l i d . When the decahydronaphthalene was removed from the con t a ine r at the end of, runs 32 and 36 no contaminat ion w i t h g l y c e r i n e had occured . The same sample o f c i s decahydronaphthalene was used i n runs 1-26 I n c l u s i v e . A second sample was used i n runs 27-36, but note tha t at the end o f r u n 32 some o f the decahydronaphthalene was removed from the cup. The. decahydronaphthalene used was prepared by vacuum d i s t i l l a t i o n i n a Stedman column and had been f u r t h e r pu r -i f i e d by s e v e r a l c r y s t a l l i z a t i o n s . I t s r e f r a c t i v e i ndex was 1.48116 cor responding t o 100.0$ c i s . At the c o n c l u s i o n o f run 36 the r e f r a c t i v e index was found to be 1.48120. Appa ren t ly no change over from the c i s t o the t r a n s isomer had occured . I t had been supposed that the p la t inum wi re used to t i e the the rmopi le bundle , the nichrome w i r e o f the decahydronaphthalene hea t ing element, or the copper c o n t a i n e r , might have c a t a l y z e d such a change. (45) Up to and i n c l u d i n g run 32 the se ts o f runs between success ive a s t e r i s k s were made i n a s i n g l e day . Between runs 33-36; the s t i r r e r s were shut o f f , and the g l y c e r i n e ba th and the decahydronaphthalene were kept at a constant temperature by the A \ C . ba th h e a t i n g , so that runs 33-36 were made on d i f f e r e n t days , and the d e c a l i n was not a l lowed t o c o o l o f f i n between the r u n s . The graphs on the f o l l o w i n g pages are p l o t t e d fo r the se ts o f runs between the a s t e r i s k s i n the t a b l e on page 43 . The graph on page 50 summarizes the r e s u l t s o f a l l the runs o f the r e s e a r c h . No. 336, GRAPH PAPER, SMITH, DAVIDSON Bt WRIGHT, LTD. (47) P i g . 14j S p e c i f i c Heat of C i s Decahydronaphthalene Runs 27-29 1 I: 9 IT' «• Hi ii J h h T I 1 -i ~i • j T ~I 1 8 I, D u *- H t \ i *»:-f- ? ( r i -S i o-7 .a I; :/ i a -J 1 r~ 1 j - 1 j _ 1 1 _ l _ = ~j JL Lfe 9 T 1 7n AC 5 | 1 1 _j_ ~jr~ A D • vervx < e -V l< [L<2 Aim t u f, it i_ _J= i i | T_ l _i~ _ i_ I I 1 I ~_r~ I l_ —fi— j - nr 1 I 1 I No. S36, GRAPH PAPER, SMITH, DAVIDSON & WRIGHT, LTD. S36, GRAPH PAPER, SMITH, DAVIDSON ft WRIGHT. LTD. NO. S36, GRAPH PAPER, SMITH, DAVIDSON & WRIGHT, LTD. (50) P i g . 17: S p e c i f i c Heat of C i s Decahydronaphthalene ! M 1 i 1 i i i i i i L 1 i i i i ! 1 i i i I 1 1 I 1 i i i l i I 1 1 ! 1 1 1 1 M l 1 i 1 1 1 1 1 1 I 1 I 1 1 i 1 1 1 1 i I I I ! 1 1 J _ 1 1 i 1 1 1 1 1 1 1 1 1 1 1 ' 1 i I i 1 J < i> l 1 I •1 1 ! i i 21 • 1 1 1 1 i 1 1 ! 1 1 1 1 1 1 1 1 1 | - 1 1 ! 1 1 1 1 1 1 I i 1 1 1 I 1 1 1 i 1 1 1 1 1 ' 1 1 1 1 1 i 1 1 1 1 1 1 1 1 l 1 1 1 I 0 1 1 1 ! 1 1 <•> 1 1 1 i i I • 1 , 7 1 1 I i i 1' 1 1 1 1 1 i i J 0 ( 1 1 1 < h | 1 1 I i i _ A 1 3 1 i t •T 1 - 1 1 \ 1 T <• i 1 1 1 I 1 <i »i 1 5 < S m is 1 11 10 1 I 11 f i 1 1 1 i ft « | • a t ! V 1 1 a I 3 », 1 1 l 1 1 l ' 1 f\ 1 e It > \ i • i i i * 1 i © 1 1 i I 6 1 I 1 l 1 1 I 0 i 1 1 1 « I I 1 i i 3 1 < i 1 i A 1 1 a — 4 I 1 + l I I I ' 1 a 1 1 1 ' T 1 1 1 i I 1 1 1 1 T 1 1 7 i 1 1 S 4 1 t d i | \ 0 I — -> I I < r i i 1 1 1 I i 1 1 1 i 1 1 1 1 1 1 1 B •» c 1 1 1 1 *• •> 1 I 1 I I 1 1 1 i i i i 1 1 1 t I i 7 ! 1 i i i e 1 1 i i 1 1 \ 9 i i M 1 V i : I 1 1 © 0 I 1 1 1 i 1 i 1 1 1 1 I- 1 1 i i • M M i 1 1 L M M 1 1 1 j 1 1 M I L 1 1 d 0 l i 4 0 1 1 A S C) 1 i i 1 i i i i i 1 1 i 1 1 i I • . I < ,1 iX t 5 1 o 1 1 1 c_ • 1 1 1 ! 1 J (51) DISCUSSION OP THE RESULTS The r e s u l t s obta ined by hea t ing the decahydronaphthalene through a temperature range of 1 . 5 °C . seem, on the whole , t o be reasonab le , at l e a s t i n the temperature range between 30 and 50°C. D e v i a t i o n s from the u s u a l type o f s p e c i f i c heat curve below 3 0 ° C . c o u l d , perhaps, be a t t r i b u t e d to the ex -i s t e n c e o f temperature g r ad i en t s i n the g l y c e r i n e ba th caused by h i g h g l y c e r i n e v i s c o s i t y at these temperatures . However such an e x p l a n a t i o n does not account fo r the low r e s u l t s ob-t a i n e d fo r runs 4 , 6, and 7 . The r e s u l t s of runs where the decahydronaphthalene was heated through a temperature range o f 0 . 2 ° C . were so very e r r a t i c tha t i t seemed u s e l e s s to attempt to p l o t the anomaly i n the s p e c i f i c heat cu rve , at l e a s t w i t h the equipment i n i t s present fo rm. The reasons f o r the e r r a t i c r e s u l t s have not been de termined. I t may be that temperature g r ad i en t s e x i s t f o r very much longer p e r i o d s than was supposed i n the g l a s s bu lb and s t ano l ax sur rounding the s t i l l enclosed the rmopi le e lement . Such g rad i en t s would , of course , be l e s s important i n runs where a l a r g e r temperature change o f the decahydro-naphthalene occured . An e r r o r of 0 . 0 2 ° C . i n the temperature measurements would account f o r the d i s c r e p a n c i e s i n the r e -s u l t s . On the other hand the t r o u b l e may be caused by p e c u l i a r i t i e s of the decahydronaphthalene i t s e l f . I t seems p o s s i b l e tha t the changes i n s p e c i f i c heat noted might be caused by some sort of change i n the a s s o c i a t i o n o f the l i q u i d m o l e c u l e s . (52) When X - r a y s are passed through c e r t a i n l i q u i d s ha lo 20 21 d i f f r a c t i o n pa t t e rns o f the r a y s are o b t a i n e d . ' These pa t t e rns i n d i c a t e some sor t of o r d e r l y s p a t i a l arrangement o f the molecules o f the l i q u i d s , . p r e s u m a b l y i n t o sma l l groups of mo lecu le s , separated by r eg ions where the arrangement of molecules i s more random. These groups o f molecules are c a l l e d c y b o t a c t i c g roups . I n c r e a s i n g the temperature I n the experiments changes the p o s i t i o n o f the d i f f r a c t i o n h a l o , makes the ha lo l e s s i n t e n s e , and a l s o causes i t t o be l e s s w e l l def ined and more spread ou t . I n other words, as would be expected , w i t h i nc rease i n temperature , a more random arrangement o f the molecules r e s u l t s , the groups of molecules probably becoming sma l l e r and some o f them d i s a p p e a r i n g a l -t o g e t h e r . The entropy of the l i q u i d i n c r e a s e s , t h e n , w i t h i n c r e a s i n g temperature . Now i f i n our sample o f decahydro-naphthalene other i n f l u e n c e s than temperature a lone were a f f e c t i n g the degree o f a s s o c i a t i o n o f the decahydronaphthalene molecules i n t o c y b o t a c t i c groups, sudden jumps i n the s p e c i f i c heat might o c c u r . The equa t ion C n s T £!! p dT g ives the r e l a t i o n of the s p e c i f i c heat at constant pressure o f a system to the temperature and the r a t e of change of the entropy w i t h the temperature . Now i f the entropy o f the system, t ha t i s the degree o f a s s o c i a t i o n o f the molecules 20 Stewar t , G. W . , T r a n s . F a r . Soc . 29,, pp . 982-990, 1933. 21 Stewar t , G. W. , Rev . Mod. R r g . 2 , pp . 116-122, 1930. (53) i n t o c y b o t a c t i c groups, changed between two de te rmina t ions o f the s p e c i f i c heat at any one temperature , the r a t e o f change of the new entropy might be d i f f e r e n t from that o f the o l d , and i t f o l l o w s that a d i f f e r e n t value fo r the s p e c i f i c heat might r e s u l t i n the second de t e rmina t ion from that obtained i n the f i r s t . A ques t i on a r i s e s at once, o f course , as t o what could cause a change i n the degree of a s s o c i a t i o n i n t o groups at any one temperature . One suggested p o s s i b i l i t y i s tha t the passage o f t ime might be an i n f l u e n c e i n t h i s a s s o c i a t i o n . To e x p l a i n , f o r example, the r e s u l t s o f runs 33-36 , p l o t t e d on page 49, where the s p e c i f i c heat decreases , seemingly , as the temperature r i s e s , we would have t o suppo:se that as t ime pas-sed between the r u n s , the entropy of the system changed t o a value where dS was smal le r than i t would have been had the dT s p e c i f i c heat been determined almost immedia te ly a f t e r the temperature o f the decahydronaphthalene was changed, a p roced-ure fo l l owed i n a l l the other r u n s . The decrease i n dS be -tween any two po in t s on the s p e c i f i c heat curve would^nave t o be s u f f i c i e n t t o more than counterbalance the cor responding inc rease i n temperature f o r a smal le r s p e c i f i c heat t o be ob-t a i n e d at the h igher temperature than at the lower . The above d i s c u s s i o n i s , o f course , most ly i n the realm o f con jec tu re , and much work would have to be done,to s u b s t a n t i a t e the hypo-t h e s i s , assuming tha t more r e f i n e d methods of temperature measurement s t i l l g ive r e s u l t s which r e q u i r e such an h y p o t h e s i s . (54) CALCULATION OP THE INTERNAL PRESSURE OP CIS DECAHYDRONAPHTHALENE I n order tha t some es t imate cou ld be made o f the a t t r a c t i v e forces between the c i s decahydronaphthalene molecu l and hence an i n d i c a t i o n ob ta ined of the s t a b i l i t y of p o s s i b l e c y b o t a c t i c groups i n the l i q u i d , the i n t e r n a l pressure was c a l c u l a t e d fo r c i s decahydronaphthalene at 2 5 ° C . The i n t e r n a l pressure o f a l i q u i d i s g iven by p. - a 1 v 2 22 assuming van der Wea l s ' equa t ion a p p l i e s . I n t h i s equa t ion a r ep resen t s van der Waa ls ' cons tan t , and v the volume o f a mole of the l i q u i d at the temperature under c o n s i d e r a t i o n . The value of a was c a l c u l a t e d from the c r i t i c a l data fo r c i s 23 decahydronaphthalene es t imated by Davenpor t . A value o f 428°C. was used fo r the c r i t i c a l temperature , and one o f 46 .1 atmospheres f o r the c r i t i c a l p r e s su re . The equa t ion a = 27 R 2 T c 2 g ives the r e l a t i o n o f the constant a to the gas cons tan t , the 24 c r i t i c a l temperature ( o A . ) , and the c r i t i c a l p r e s su re . For 22 G las s tone , S . , Textbook o f Phy. Chem., p . 472. 23 Davenport , C. H . , M . A . S c . t h e s i s , pp. 38-39 . 24 Glass tone , o p . c i t . , p . 428. (55) c i s decahydronaphthalene a value of 30 atmospheres was ob-t a i n e d f o r a . Davenport g ives the d e n s i t y o f the c i s isomer as 0.8930 gm. / cc . at 2 5 ° C . 2 5 Based on these da t a , the i n -t e r n a l pressure o f c i s decahydronaphthalene at 25°C . i s 1250 atmospheres. Van der Waa l s 1 a was c a l c u l a t e d f o r benzene and f o r normal hexane from the c r i t i c a l data f o r these compounds. By the same method used above fo r o b t a i n i n g the i n t e r n a l p r e s -sure o f the c i s decahydronaphthalene, the i n t e r n a l pressure of these two compounds was then c a l c u l a t e d . For benzene the value was 2340 atmospheres, and f o r normal hexane 1420 a t -mospheres, bo th r e s u l t s be ing at 25°C . Glass tone g ive s a t a b l e of i n t e r n a l pressures of c e r t a i n l i q u i d s , one of which i s h e x a n e . 2 6 Hexane has the lowest i n t e r n a l pressure on the l i s t . S ince c i s decahydronaphthalene appears t o have an ab-normal ly low i n t e r n a l p ressu re , t hen , the a t t r a c t i o n between the molecules i n t h i s compound must be compara t ive ly s m a l l , so tha t i t seems p o s s i b l e that c y b o t a c t i c groups i n the decahydronaphthalene might be r e l a t i v e l y e a s i l y broken up . SUGGESTIONS FOR FUTURE WORK The f o l l o w i n g suggest ions are submitted f o r p o s s i b l e use i n fu r t he r works 25 Davenport , op . c i t . , p . 2 3 . 26 Glass tone , op . c i t . , p . 472. (56) (1) I n a l l runs u s i n g the i s o t h e r m a l method care should he taken that zero t ime occurs when the decahydronaphthalene i s s u f f i c i e n t l y ho t t e r than the g l y c e r i n e so that <J> equals cp3 when the h e a t i n g and c o o l i n g curve i s p l o t t e d , i n order tha t the heat o f s t i r r i n g w i l l not enter i n t o the c a l c u l a t i o n o f the c o o l i n g c o r r e c t i o n . . (T^ must equal T 3 a l s o o f course . ) (2) The s p e c i f i c heat o f another l i q u i d should be measured1 i n the c a l o r i m e t e r by the present methods to see i f the same spo t ty r e s u l t s are o b t a i n e d . (3) I f the same r e s u l t s were obta ined w i t h another l i q u i d i n d i c a t i o n s would be s t ronger that the temperature measure-ments are at f a u l t . I t would be i n t e r e s t i n g to t r y some runs w i t h the g l a s s bu lb and s tano lax removed from the thermopi le l e g on the g l y c e r i n e s i d e . Dur ing the run the A . C . e l e c t r o -l y t i c h e a t i n g would have to be shut o f f . The bath would then c o o l o f f , but the c o o l i n g would not i n t e r f e r e w i t h the method as long as the ba th temperature could be a c c u r a t e l y determined d u r i n g the r u n . A p la t inum r e s i s t a n c e thermometer w i t h the element encased i n me ta l would be more s a t i s f a c t o r y than the present thermometer, which i s of the quar tz tube t y p e , because of the sho r t e r l a g i n the former. Wi th such a thermometer, and w i t h the g l a s s and s t a n o l a x removed from both l imbs o f the t h e r m o p i l e , temperature l ags should c e r t a i n l y be reduced to an almost n e g l i g a b l e v a l u e . (4) I f more normal r e s u l t s are obtained w i t h another l i q u i d i n d i c a t i o n s that c y b o t a c t i c groups enter i n t o the p i c -tu re would be s t r o n g e r . I t would be i n t e r e s t i n g then t o make an X - r a y d i f f r a c t i o n s tudy of c i s decahydronaphthalene to see (57) what sort o f groups are p resen t , and what happens to them as the temperature i n c r e a s e s . Any such study should i n c l u d e the e f fec t o f the passage o f t ime on the s i z e o f the groups found at a g iven temperature . (5) A study o f Brownian movement i n c i s decahydronaphtha-lene might be o f a s s i s t ance i n g i v i n g an i n d i c a t i o n of the s i z e of c y b o t a c t i c groups i n the l i q u i d . The c o l l i s i o n o f a l a rge group o f molecules w i t h a p a r t i c l e should r e s u l t In a l a r g e r t r a n s f e r o f momentum to the p a r t i c l e than the c o l l i s i o n o f a sma l l group of molecu les w i t h the p a r t i c l e would o c c a s i o n , assuming, o f course , bo th groups t o be moving at the same speed. I f the s i z e of the groups i n a l i q u i d i s p r o p o r t i o n a l to the i n t e r n a l p res su re , the Brownian movement i f l c i s deca -hydronaphthalene might be expected to be l e s s v igorous than that i n l i q u i d s w i t h a h igher i n t e r n a l p r e s su re . A l s o the upward l i m i t o f the s i z e o f p a r t i c l e s capable of Brownian movement i n the decahydronaphthalene should be somewhat sma l l e r than the l i m i t f o r the movement In such other l i q u i d s , because the Brownian movement ceases when the p a r t i c l e s are l a rge enough so that they r e c e i v e equal impacts on a l l s i d e s , and dec reas ing the s i z e and i n c r e a s i n g the number of the s t r i k i n g bodies should decrease the p r o b a b i l i t y o f unequal impac t s . (58) BIBLIOGRAPHY Davenport , C. H . , M . A . S c . t h e s i s , The De te rmina t ion o f the  P h y s i c a l P r o p e r t i e s o f the C i s and Trans Isomers o f  De cahydronaphtha1ene, 1939, D a v i e s , G. P . , M . A . S c . t h e s i s , I n v e s t i g a t i o n o f the S p e c i f i c  Heat of C i s Decahydronaphthalene, 1939. D u n e l l , B.. A . , M . A . S c . t h e s i s , A Method fo r Measur ing the  D i e l e c t r i c Constant o f L i q u i d s , 1946. Glass tone , S . , Textbook o f P h y s i c a l Chemis t ry , D . Van Nostrand C o . , New Y o r k , 1940. Graham, H. M . , M . A . S c . t h e s i s , S p e c i f i c Heat of C i s Decahydro-naphthalene, 1944. I n t e r n a t i o n a l C r i t i c a l T a b l e s , V o l . V, M c G r a w - H i l l Book C o . , New York , 1929. L e s l i e , J . D . , M . A . S c . t h e s i s , Some S tud ie s i n L i q u i d V i s c o s i t y w i t h S p e c i a l Reference to the Isomers of Decahydronaphthalene 1941. M c L e l l a n , D . E . , M . A . S c . t h e s i s , S p e c i f i c Heat and Heat o f T r a n s i t i o n of C i s Decahydronaphthalene, 1943. Robinson , M . , M . A . t h e s i s , The Second Order Phase T r a n s i t i o n o f C i s Decahydronaphthalene, 1945. Standard Convers ion Tables f o r L . and N . Thermocouples. S tewar t , G. W., " X - r a y D i f f r a c t i o n i n L i q u i d s , " Reviews o f Modern P h y s i c s , V o l . 2 , pp. 116-122, 1930. Stewart , G. W., " A l t e r a t i o n s i n the Nature o f a F l u i d from a Gaseous to L i q u i d C r y s t a l l i n e C o n d i t i o n s as Shown by (59) X - r a y s , " T ransac t i ons o f the Faraday S o c i e t y , V o l . 29 , pp. 982-990, 1933. Whi te , W. P . , "Some C a l o r i m e t r i c Methods," The P h y s i c a l Review, V o l . 31 , pp. 545-548, 1910. W i l l i a m s , J . W., D a n i e l s , F . , "The S p e c i f i c Heats of C e r t a i n Organic L i q u i d s at E l eva t ed Temperatures," J o u r n a l o f the American Chemical S o c i e t y , V o l . 46 , pp. 903-917, 1924. 

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