STI:E.IC‘E
803
T E S Y I O S O F OILS
THE SCRFACE TESSIOS OF
on,s
-4LFRED H,ILPCRS School of P h a m a c y , Ditqriesrie I - n i ~ e r s i t i l ,I’itfsl~itrgh, I’ennsijlvania Keceic erl SoLernber 20, 1948
I n the course of a n inw-tigatioii of emul4on. in pi’ogw\- at our Inboratoriez it became necessary to obtain the surface tension of a >cries oi fixed oil, 0ve1’:1 wide range in temperature. -1 search of the literature revealed relativcly feu studies made of the surface tension of oils. Canals and conorlcers (1, 2 , 3) reported the surface tension of a series of oils over a limited temperature iange and suggested an equation for the derivation of the surface tension ior any temperature. I n a subsequent study of olive oil (4), extended over a grcater temperature range, this formula was modified to conform \t ith the enlarged data. S o further investigation of the surfaee tension of any of the other oils over the e-dended temperature range was made. I t should lie noted that the equation for the derivation of the surface tension from the temperature ]vas cledwed from a series of experiments at temperatures from approximately 5” to 40°C. The revised formula v a s derived from a aeries of experiments carried oiit ovcr a temperature range from 5’ to 150°C. Wnchester (17) reported that below 130°C.the surface tension of oils decreases linearly tvith the rise in temperature and increases vith the rise in molecular \\ eight. Kaufmann and Kirsch (11) determined the surface tension of a number of Cats and oils. They did not investigate the effects of temperature and for the most part their study \vas made at room temperature (ZOOC.). It might be rioted that some of the values reported by Canals ( I , 2, 3, 4) and those reported iy IGwfmann and Iiirach (11) are at variance. L-nlilce the different organic compounds the fixed oil, are mixtures, and hamdes of the same oil, labeled ”pure,” are actually of different composition. While hese differences of composition are generally consideied to be of minor imporance, it is important to note the physical and chemical propertie.; of thc oil n order to characterize it. Such characterization i i notahly absent in many of he reported wrface tention 5tudieY. ~~~~~~~~~~~r I L
The oils used in thi. atutly I\ ere obtained commercially :uicl cle,ignnted the best” grade. The phyiical and chemical properties oi t1ie-e oil, (see table 1) re in agreement vith the recorded data (10) :tnd comply ~ i t hthe standards f the C7nzted States Pharnzacopoeia S I I I . The surface tension of the oils 71 :IS determined 11)- the capillary-ri5e method 7 . 14, 15) and the drop-neight method (G, 7 , 12, 13). The thcorctical and ractical aspects of theye technique5 have been adequately di5cussed by other ivestigators (G, 7, 13, 14). capillary tube uith R diameter of appro\imately 0.3 mm. \ \ a i used for the
896
.1LFRED H.\LPER1\;
capillary-ribe method. The radius of the tube \\-a. determined by mean5 of mercury ( 5 ) and nlw calculated from the surface tenqion of Ti-ater and henzene TIBLE 1 The physical a n d chemical properties o j the oils 01L
___-
-
____ ____
~
Almond o i l . . . . . . . . . . . . . . . . Castor oil . . . . . . . . . . . . . . . . . . Coconut, o i l , . . . . . . . . . . . . . . . . . . . Cod liver o i l . . . . . . . . . . . . . . . . . . . Corn o i l . . . . . . . . . . . . . . . . . . . . . Cottonseed o i l . . . . . . . . . . . . . . . . . . . Olive o i l . . . . . . . . . . . . . . Peanut oil. . . . . . . . . . . . . Liquid petrolatum*. . . . . . . . . . . . . .
0.9172 0.0630 0.8211 0.9246 U.9170 0.9231 0.9155 0.91G5 0.S464
1.4631 2.1 1.4711 3.0 1. ~ 0 0 4 . 2 1.4731 0.9 1.4i61 1.4 1.4650 0.3 1.461; 1.1 1.4627 0 . i:
98.1
~
84.0 8.2 163.4 116.6 107.3 83.9 91.2 2.6
'
193.2 lS0 6 256 4 1% 5 190.9 194..i 196.-1 100.3
______~~____~.
* Kinematic viscosity
=
32 centistokes at 37.6'C.
TXBLI: 2 The surjuce tension o j o i l s
NETHOD..
. . . ., l
20 30 40 50 60 70
80 91 82 101 104 111 113 122 130
Drop
Drop
weight
ireigiit
35,s 34.9 34.0 33.2 32.5 31.7 30.8 20.9
39.0 3S.3 37.S 37.0 36.4 35.9 35.2
-
34.9 34.3 33.9 33.0
20.0 25.3 27.5 I 26.6
--
Capillary rise
Calrjtiary riie
Droii weigiit
Capjllary
33.4 32.6 :31.S 31.0 30.2 2.3 25.4 2'7 , S
3S.2 37.1 36.2 35.3 34.4 33.3 3'2.1 30.9
313 A 32.4
3.5.4 34.7 3-1.1 83.4 32.7 32.0 31.3
-
-
-
-
-
30 1
26.0 23.5
36.5 25.8
-
-
29.0
24.9
30.5 23.6 25.9 28.2 27.5
I7ro.3 n-cigiit
'
31.3 30.4 29.2 25.3 ";.2
-
-
-
24.9 24.0
27.5 27.0
24.0 23.2
nror>
Cap,il!ary rise
\i--right
35.8 33.1 3-1.4 33,s 33.1 32.7 32.0 31.5
35.5 31.S 33.9 33.2 32.5 31.7 30.9
33.1 32.2 31.3 30.4 29.6 28.7 27.6
-
-
-
29.9
36.S
rise
30.9 30.0 29.2
1
-
29.4
-
25.7 -
24.7
2S.6
-
27.9 27.2
24.0
23.1
-
at 20°C. obtained from a serif? of control experiments. The difference in the qize of the radius calculated hy these methodz IT-as 00004 mm. The height of the column \ \ a i measured v \ i t h a cnihetometer and the corrections for the nieni\cus (7, 14. 13) innde. The wrface tension determined by this method
SURFACE TESSION OF OILS
89i
was calculated from the equation proposed by Harkins and Bron-n. At least eight readings of the column height were made for each determination (table 2 ) . The apparatus described by Morgan (12) n-as used t o determine the surface tension by the drop-n-eight method. A capillary tube n-ith a bore of 0.213 mm. and outer diameter of -1.67 mm. T ~ used S and the dropweight correction ( 7 , 8 ) applied. The surface tension of the oils n-as calculated in the u ~ a manlier l from the mean of five runs (table 2 ) . SUMMARY
The surface tension of nine fixed oils n-as determined tiy means of the capillaryrise and the drop-n-eight methods over a temperature range from 20’ to 130°C. The surface tension of these oils decreases with the increase in temperature. REFERESCES
CASALS,E., ASD R A X ~ H E S I S A R,A S . ~ I V OJ.: pharm. chim. 16, 431 (1932,. C a s a ~ sE., , AND RAXAHESISA, R A S A I V OJ. : pharm. rhim. 17, 505 119301. CASALS,E . , A N D R A ~ I A H E S I SRASAIVO: A, J. ph:irm. c h i m 18, 436 (1933). CASALS, E., ASD FLOES, AI, E . : J. pharm. chim. 20, 241 (1934). HARKISS,W. D. : Physical 3lethotls o,i Organic Chemist,y, edited by h.Weissberger, pp. 158-76. Interscience Publishers, Inc., S e n . Tork (19451. (6) HARKISS, JT. D., ASD BROII-S,F . E . : J. d m . Cheni. Soc. 38, 246 (1916:. (7) HARKISS, TIr.D . , ASD BROM-S, F. E.: J. .lm.Chem. SOC.41, 409 (1919). ( S i H A R K I K SIT. , D., ASD HL-MPHRET, E. C . : J. - h i . Chem. Soc. 38, 226 (19161. (9) HARKISS,IT. D., ASD JORDAS, H. F . : J. h m . Chem. Soc. 52, 1753 (1930:. 10) HILDITCH,T. P.:The Chemical Constit~ctionof the Natural F a f s . John Wiley and (1) (2) (3) (4) (5)
Sons, Inc.,
SeJy
York (194Oi.
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