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DENSITY AND SURFACE­TENSION

MEASUREMENTS OF PURE POLYPHENYLS

AND SOME POLYPHENYL MIXTURES

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1963

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ORGEL Program

Joint Nuclear Research Genter Ispra Establishment - Italy

Heat Transfer Department mm

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Neither the Euratom Commission, its contractors nor any person acting on their behalf

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U

E.C.2, ι! » V

giving the reference: «EUR 165.e ­ Density­and surface­tension measurements of pure polyphenyls and some poly­pheny! mixtures»

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EUR 1 6 5 . e

DENSITY AND SURFACE-TENSION MEASUREMENTS OF P U R E P O L Y P H E N YLS AND SOME P O L Y P H E N YL M I X T U R E S by G. FRIZ and H. VOSSEN.

European Atomic Energy Community - EURATOM. ORGEL Program. Joint Nuclear Research Center. Ispra Establishment (Italy). Heat Transfer Department. Brussels, February 1963 - pages 7 + figures 5.

The note presents two simple capillar}- methods for determining the density and the surface tension of polyphenyls.

Density is determined by measuring the length of a liquid thread and weight difference. Above the boiling point a sealed capillar}' is used. Surface tension is measured by the horizontal capillary method with optical observing of the liquid surface a t the capillary end. Results are presented for Diphenyl-, Terphenyl-isomers and two industrial mixtures.

EUR 1 6 5 . e

DENSITY AND SURFACE-TENSION MEASUREMENTS OF P U R E POLYPHENYLS AND SOME P O L Y P H E N Y L MIXTURES by G. F R I Z and H. VOSSEN.

European Atomic Energy Community - EURATOM. ORGEL Program. Joint Nuclear Research Center. Ispra Establishment (Italy). Heat Transfer Department. Brussels, February 1963 - pages 7 + figures 5.

The note presents two simple capillary methods for determining the density and the surface tension of polyphenyls.

Density is determined by measuring the length of a liquid thread and weight difference. Abo\-e the boiling point a sealed capillar}' is used. Surface tension is measured by the horizontal capillary method with optical observing of the liquid surface a t the capillar}' end. Results are presented for Diphenyl-, Terphenyl-isomers and two industrial mixtures.

í j a n - í o o s n s í i i l j ^ l í í i l l » * » !

EUR 1 6 5 . e

DENSITY AND SURFACE-TENSION MEASUREMENTS OF P U R E POLYPHENYLS AND SOME P O L Y P H E N Y L MIXTURES by G. FRIZ and H. VOSSEN.

European Atomic Energy Community - EURATOM. ORGEL Program. Joint Nuclear Research Center. Ispra Establishment (Italy). Heat Transfer Department. Brussels, February 1963 - pages 7 + figures 5.

The note presents two simple capillary methods for determining the density and the surface tension of polyphenyls.

Density is determined by measuring the length of a liquid thread and weight difference. Above the boiling point a sealed capillary is used. Surface tension is measured by the horizontal capillar)- method with optical observing of the liquid surface a t the capillary end. Results are presented for Diphenyl-, Terphenyl-isomers and two industrial mixtures.

E U R 1 6 5 . e

EUROPEAN ATOMIC ENERGY COMMUNITY - EURATOM

DENSITY AND SURFACE-TENSION MEASUREMENTS OF PURE POLYPHEN YLS

AND SOME POLYPHENYL MIXTURES

by

G. FRIZ and H. VOSSEN

1963

ORGEL Program

Joint Nuclear Research Center Ispra Establishment - Italy

Heat Transfer Department

C O N T E N T S

1. INTRODUCTION 2

2. MEASUREMENT OF DENSITY 2

2, 1. Apparatus and procedure of measur ing 2 2. 2. Est imation of accuracy, resu l t s 4

3. MEASUREMENT OF SURFACE TENSION 4

3. 1. Apparatus and procedure of measur ing 4 3. 2. Est imation of accuracy, resu l t s 5

4 . LITERATURE . . . , 7

5. DIAGRAMS

Fig. 1 Density of Diphenyl and of the Terphenyls Fig . 2 Density of OM1 and OM 2 Fig . 3 Surface tension of Diphenyl and the Terphenyls F ig . 4 Apparatus for density measurements Fig. 5 Apparatus for surface tension measurements

DENSITY AND SURFACE-TENSION MEASUREMENTS OF PURE POLYPHENYLS AND SOME POLYPHENYL

MIXTURES

SUMMARY

The note presents two simple capil lary methods for de te rmin­ing the density and the surface tension of polyphenyls.

Density is determined by measur ing the length of a liquid thread and weight difference. Above the boiling point a sealed bapillary is used. Surface tension is measured by the horizontal capillary m e ­thod with optical observing of the liquid surface at the capillary end. Results a re presented for Diphenyl-, Terphenyl - i somers and two in­dust r ia l mix tu re s .

1. INTRODUCTION

The density of polyphenyls has a l ready been m e a s u r e d severa l t imes (R. 1, 2, 3, 4 , 5 ) . Mostly the boiling point l imited the curves , so that it was des i rab le to extend the p r e s s u r e and t e m p e r a t u r e range . On the other hand the a im was also to m e a s u r e high b o i l e r s , which a r e difficult to obtain in l a r g e r quant i t ies . By reason of th is a μ - m e ­thod was worked out which reques t s only the smal l quantity of about 50 mg substance .

The surface tension was measu red by BOWRING et a l . in 1961 (R. 6) with the ve r t i ca l capil lary method. In I sp ra the hor izonta l ca­pi l lary-method was taken, for this method too reques t s only smal l tes t por t ions . The re su l t s of the two methods cor respond very well .

The measur ing p rogram s tar ted with pure substances of Di­phenyl and of the Te rpheny l - i somers and the indust r ia l mix tures OM1 and OM2 from PROGIL. It will be followed by a p r o g r a m for high-bo i l e r s .

2. MEASUREMENT OF DENSITY

2 .1 . A p p a r a t u s a n d p r o c e d u r e of m e a s u r i n g

The density is measured in two steps with a slight difference. In the lower t empe ra tu r e range an open glass capi l lary (open at one end and closed at the other) is used. It is par t ly filled with the tes t liquid. Fil l ing is done with an injection-needle of g lass which is heated up together with the tes t capi l lary in a special filling furnace, as the polyphenyls a r e solid at room t e m p e r a t u r e .

In a glass furnace with an in ternal aluminium bloc (fig.4) the tes t capi l lary is heated up, and then the length of the liquid th read is m e a s u r e d . After that the difference of weight of filled and empty ca­pi l lary is de te rmined with a μ -balance . Following a cal ibrat ing curve -obtained with water m e a s u r e m e n t s - t he re is a re la t ion be t ­ween volume and length of the liquid th read . Weight-difference and volume give densi ty . A li t t le cor rec t ion must be applied for t e m p e r a ­ture expansion of the glass capi l la ry . The dimension of the g lass ca ­pi l lary a r e :

m a t e r i a l l eng th o u t e r d i a m e t e r i n n e r d i a m e t e r

p y r e x 50 m m

6 m m 1 m m

The c a p i l l a r y l i e s in a b o r e of the a l u m i n i u m - b l o c , which i s s l i t t ed to a l low o p t i c a l r e a d i n g of l eng th with a c a t h e t o m e t e r by o b ­s e r v i n g the c a p i l l a r y in a 4 5 ° - i n c l i n e d m i r r o r . The fu rnace i s i n s t a l l ­ed h o r i z o n t a l l y to a s s u r e good t e m p e r a t u r e d i s t r i b u t i o n . The t e m p e r a ­t u r e i s m e a s u r e d wi th a t h e r m o c o u p l e in a s p e c i a l b o r e of the b l o c . In s e p a r a t e e x p e r i m e n t s it w a s v e r i f i e d tha t c a p i l l a r y - t e m p e r a t u r e and b l o c - t e m p e r a t u r e c o r r e s p o n d wi th in 0, 5 ° C .

The open c a p i l l a r y - m e t h o d i s work ing up to a t e m p e r a t u r e of about 30°C be low the boi l ing poin t . Then b e g i n s a m a r k a b l e l o s s of t e s t p o r t i o n by v a p o r i s a t i o n .

By r e a s o n s of t h i s , the r a n g e above t h i s t e m p e r a t u r e i s m e a s u r ­ed with a c l o s e d c a p i l l a r y . Half of the c a p i l l a r y i s f i l led with the l iquid and then s e a l e d . The f i r s t m e t h o d gave a b s o l u t e dens i t y da ta be low the boi l ing poin t . S t a r t i ng with one of t h e s e v a l u e s , t he expans ion of the l iquid t h r e a d a l lows c a l c u l a t i o n of d e n s i t y without weigh ing , p rov ided tha t the c a p i l l a r y d i a m e t e r i s suff ic ient ly c o n s t a n t o v e r the l eng th . The l a s t condi t ion w a s t e s t e d b e f o r e .

The m e t h o d r e q u i r e s s o m e c o r r e c t i o n s :

1) The t e m p e r a t u r e - c o r r e c t i o n for d i a m e t e r expans ion .

2) The v a p o u r - c o r r e c t i o n which c o n s i d e r s the fact tha t a c e r t a i n po r t i on of v a p o u r i s f i l l ing the v o l u m e above the l iquid t h r e a d . To c a l c u l a t e t h i s c o r r e c t i o n , e x p e r i m e n t a l v a p o u r -p r e s s u r e da t a and i d e a l gas l aw for the vapour w e r e t a k e n .

3) An op t i ca l c o r r e c t i o n for a d i f f e rence be tween the r e a d i n g and the r e a l pos i t ion of the inne r c a p i l l a r y end, by r e a s o n of l ight r e f r a c t i o n a t the half s p h e r e d top of the o u t e r g l a s s s u r f a c e . Th i s c o r r e c t i o n w a s c a l c u l a t e d , a s s u m i n g the top to be exac t ly a half s p h e r e .

In the r a n g e be low t h e boi l ing point t he two m e t h o d s can be com­p a r e d . The c o r r e s p o n d e n c e of the two m e t h o d s l i e wi th in * 3 %.

2 . 2 . E s t i m a t i o n of a c c u r a c y , r e s u l t s .

The accuracy in the absolute (open capillary) method depends on the following: determination of weight-difference and length of l i ­quid thread, t empera tu re measuremen t and d iamete r change with tem­pe ra tu re . The f irst and the second e r r o r a r e both in the range of 1 %. The tempera ture deviation should l ie within 2 °C , which r e su l t s in a maximum e r r o r of * 2 ° / ° ° · The deviations of the cal ibrat ing points from a straight line show a scat ter ing of * 2 ° / o o , which a r e assumed to come from the f irs t two sources of e r r o r . The equalized curve is expected to be within this range so that the maximum e r r o r is est imat­ed to be in the range of - 0, 5 %.

In the case of closed capi l lary, the vapour -co r rec t ion and op­t ical correct ion a r e together 1 %. If they a r e calculated with an e r ro r of 20 %, we have an e r r o r of 2 ° /oo by r eason of i nco r r ec t calculation. Together with the other effects the maximum e r r o r in density will reach 0, 5 % too. The comparison of both methods in the range below boiling point shows a deviation from the smoothed curve of l e s s than * 3 ° / o o .

The measur ing p rogram s tar ted with the pure substances Di­phenyl, o - , m - , and p-Terphenyi and the mix tu res OM1 and OM 2 of PROGIL. The t empera tu re range extended from the point of fusion up to 41§-420°C. The resu l t s a r e presented in d iagram 1 and 2.

3 . MEASUREMENTS OF SURFACE TENSION.

3 .1 . A p p a r a t u s a n d p r o c e d u r e of m e a s u r i n g .

F igure (5) shows the principle of the appa ra tus . A capil lary is placed im a furnace in horisontal posit ion. It i s filled about 20 m m with t e s t liquid. A l ight -source with para l le l beam and a te lescope allow optical observation of the flat capi l lary end. A smal l p r e s s u r e pushes the liquid to th is end. Without p r e s s u r e the liquid surface i s curvedas a half sphe re . At a cer ta in p r e s s u r e this surface i s p lane. In th is mo­ment a l l the surface ref lects the light while at higher o r lower pres -s u r e s only a l i t t le spot appea r s . The effect i s ve ry sens i t ive . The p r e s s u r e i s measured with an ins t rument which allows reading of l-2/lOO m m H 2 0 p r e s su re (Minisi

-5-

The requi red liquid portions a re in the range of 50 mg.

The relat ion between surface tension and p r e s su re in the case of full wetting liquids i s very simple:

d , . a = — · Δ ρ (d = diameter of capillary)

4

With a cer ta in contact angle α we have the formula:

σ cos α = — · Δ ρ

The organic liquid was observed in a free capillary and the

contact angle was est imated to be zero , but this is not sufficient for

exact m e a s u r e m e n t s . By reason of this additional measurement s were

done with the bubble ­pressure method, which is independent of contact

angle. The mean resu l t was: both method correspond within ­ 1%.

This work will be repor ted previously.

The capil lary is heated up in a furnace with internal bored copper­cyl inder . Tempera tu re regulation was done by taking a constant tension source with regulating t r ans fo rmator . The tempera ture mea ­surement was effected in the same way as in the density appara tus .

The capil lary was calibrated with tes t l iquids, so that we have a re la t ive method. Test liquids were: water , benzene, glycerine, for­mic acid, carbon te t rachlora tüm and alcohol. Mean values from 5 ta ­bles were taken. They gave a maximum deviation from the best straight line of l e s s than 0, 8 %.

3 .2 . E s t i m a t i o n of a c c u r a c y , r e s u l t s .

The scat ter ing of p r e s s u r e readings at a cer tain t empera tu re

was within the range of * 3 ° /oo . The maximum deviation of the table

values from the straight line were 8 % o . Other sources of e r r o r a r e :

inclination of capil lary and change of diameter with length. The f irst

e r r o r was suppressed by a careful leveling, taking the liquid thread

itself as level indicator . The second source was proved by filling the

capil lary with different quantities of liquid.

-6-

The capillary diameter was found to have sufficient constancy. The tempera ture deviation should be the same as in the density appa­ra tus , which resul ts in a maximum e r r o r of 4 ° /oo . Considering all these sources of e r r o r , we should have an overal l maximum e r r o r of about 1, 5 % for the product

σ · cos a

Assuming α to be zero, we give in d iagram 3 the r e su l t s of the measurements with Diphenyl and the three Terphenyls . The resul ts a re compared with the measuring points of BOWRING (Ref .AEEW-R 41) of I96I, which a re obtained with the ver t ica l capil lary method.

The diagram contents additionally the curve for a specia l Hexa-phenyl which was obtained within the measur ing program of pure high-boi le rs .

LITERATURE

Rl BOWRINGR.W. GARTON D. Α.

R2 ANDERSON Κ.

R3 CORK J. M. et a l .

R4 STONE J. P . et al .

R5 G E R C K E R . H . ASANOVICH G.

R6 BOWRING RW. et al .

AERE R/R 2762

ANL-5121(1953)

Rev. Sc. Ins t r . 1(1950) 563

Ind. Eng. Chem. 50 (1958)

NAA-SR-4484

AEEW-R 41

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