NOTIZEN
156
Density of water as a function of temperature
By G e o r g e
A n t o n o f f
and R o b e r t
J. C o n a n
(Z. Naturforschg. 4 a, 156 [1949]; eingeg. am 29. Dez. 1948)
It w a s s h o w n b y the a u t h o r l o n g a g o 1 that a p l o t
of the d e n s i t i e s of m a n y l i q u i d s v s . t e m p e r a t u r e g i v e s
a c u r v e that is not s m o o t h : but e x h i b i t s i n f l e c t i o n
p o i n t s , or k i n k s at s o m e i n t e r v a l s . T h i s can b e s h o w n
to b e t r u e f o r a n y l i q u i d f o r w h i c h t h e r e e x i s t s
a c c u r a t e e x p e r i m e n t a l data. B u t w a t e r s e e m e d an e x c e p t i o n ; f o r the t e m p e r a t u r e — d e n s i t y c u r v e is p e r f e c t l y s m o o t h a c c o r d i n g to f i g u r e s g i v e n in t a b l e s
used at the p r e s e n t time.
It is o b s e r v e d that m o s t p e o p l e p r e f e r not to b e l i e v e
in t h e s e k i n k s . O n e r e a s o n is that t h e y a r e not
p r e d i c t a b l e on the b a s i s of the c u r r e n t t h e o r i e s .
mal p l a c e , the e x p e r i m e n t a l e r r o r s a r e not seen at
all. A n y d e v i a t i o n s f r o m the s m o o t h p a t h m u s t b e d u e
to i n t r i n s i c c a u s e s .
B u t o f all s u b s t a n c e s k n o w n to the a u t h o r , w a t e r
s e e m e d an e x c e p t i o n in that it a l o n e s e e m e d f r e e o f
these discontinuities. H o w e v e r , experiments performed
r e c e n t l y b y the c o - a u t h o r s h o w that this is not t r u e ,
and that k i n k s a r e e a s i l y n o t i c e d in t h e d e n s i t y - t e m p e r a t u r e c u r v e f o r o r d i n a r y d i s t i l l e d w a t e r . A 25-cc.p y c n o m e t e r w a s u s e d in t h e s e m e a s u r e m e n t s , and
d e n s i t i e s d e t e r m i n e d f o r the r a n g e of t e m p e r a t u r e s
f r o m 4 7 ° t o 53 ° C , in a t h e r m o s t a t r e g u l a t e d t o
0,02 ° C . B e t w e e n 47 and 50 t h e r e is a s m o o t h s t r e t c h
of t h e c u r v e , and a n o t h e r b e t w e e n 5 0 ° and 5 3 ° . T h e s e
i n t e r s e c t j u s t a l i t t l e a b o v e 50 ° C , g i v i n g a w e l l
d e f i n e d k i n k ( s e e F i g . 1 ) . B e l o w 47 a n o t h e r s m o o t h
s t r e t c h of the c u r v e b e g i n s , w h i c h is n o t s h o w n on
the d r a w i n g . A figure d r a w n f r o m the data g i v e n in
tlie S m i t h s o n i a n T a b l e s m a y b e seen t o b e p e r f e c t l y
smooth with only a slight curvature.
T h e r e can b e n o d o u b t that the e x p e r i m e n t a l r e s u l t s
w e r e smoothed b y a p p l y i n g the g e n e r a l l y accepted
r u l e s f o r d r a w i n g a r e p r e s e n t a t i v e c u r v e amidst
erratic points due to e x p e r i m e n t a l errors. In this case
it is n o t l e g i t i m a t e to do so b e c a u s e , as e x p l a i n e d
a b o v e , t h e e f f e c t is w e l l a b o v e t h e l i m i t s of e x p e r i m e n t a l e r r o r s , and on a d r a w i n g o f the s c a l e i n d i c a t e d
the e r r o r s do n o t a p p e a r .
F i g . 1. D e n s i t y of w a t e r v s . t e m p e r a t u r e .
A n o t h e r is that the p r e v i o u s e x p e r i m e n t a l i s t s w e r e
n o t a w a r e of t h e s e t h i n g s , and h a v e p e r f o r m e d the
m e a s u r e m e n t s of d e n s i t i e s at r e g u l a r i n t e r v a l s of
t e m p e r a t u r e . B u t t h e k i n k s , or p l a c e s of d e v i a t i o n
f r o m t h e s m o o t h p a t h f r e q u e n t l y f a l l in b e t w e e n the
o b s e r v e d p o i n t s , and t h u s r e m a i n u n n o t i c e d . S o m e
may attribute these effects to conditions which cause
e x p e r i m e n t a l e r r o r s of m o r e or less s y s t e m a t i c c h a r a c ter. T h i s v i e w , in the l i g h t of the p r e s e n t data, s e e m s
absurd.
It w o u l d not b e e a s y t o r e p e a t t h e w o r k
of
R a m s e y and S i d n e y Y o u n g 2 , f o r t h i s r e q u i r e s
c o m p l i c a t e d apparatus and takes m u c h time. H o w e v e r ,
t h e r e is an e a s y m e t h o d of d e m o n s t r a t i n g t h e s e
p h e n o m e n a at m o d e r a t e t e m p e r a t u r e s 3 . T h e a u t h o r
t o o k p r o p y l a l c o h o l , w h i c h was. purified b y the proced u r e of S i d n e y Y o u n g , and d e t e r m i n e d its d e n s i t y in
a p y c n o m e t e r at v a r i o u s t e m p e r a t u r e s b e t w e e n 2 0 °
and 80 ° C . T h e c u r v e so o b t a i n e d s h o w e d a k i n k in
t h e s a m e p l a c e as it had a p p e a r e d in the data of
S i d n e y Y o u n g . O t h e r l i q u i d s also s h o w k i n k s in this
r e g i o n of t e m p e r a t u r e : b e n z e n e has a k i n k at 4 5 ° C ,
etc. T h e t e m p e r a t u r e w a s c a r e f u l l y r e g u l a t e d d u r i n g
t h e s e e x p e r i m e n t s , and b y w e i g h i n g a 2 5 - c c . - p y c n o m e t e r the d e n s i t y m a y b e d e t e r m i n e d to f i v e d e c i m a l
p l a c e s . B u t such is not n e e d e d , f o r the t h i r d d e c i m a l
is s u f f i c i e n t t o d e m o n s t r a t e the k i n k s . A n d if the
c u r v e is p l o t t e d on g r a p h p a p e r in such a w a y that
a f r a c t i o n of a m i l l i m e t e r r e p r e s e n t s the f o u r t h d e c i -
T h i s is n o t t h e o n l y case w h e r e the figures g i v e n
in t a b l e s s h o w t h e m s e l v e s a d u l t e r a t e d , and e s p e c i a l l y
in t h e stud} 7 o f l i q u i d s t h e r e a r e s o m e c a s e s w h e r e
the e n t i r e e x p e r i m e n t a l w o r k o u g h t to b e d o n e a f r e s h .
G . A n t o n o f f , P h i l o s . M a g . J. Sei. 1, 256 [1925].
Sidney Y o u n g ,
P r o c . R o y . S o c . D u b l i n 12,
374 [19101.
3 G. A n t o n o f f ,
J. p h y s i c . C h e m . 48, 80 [1944J.
1
2
Über das dielektrische Verhalten des Diphenyläthers in Mischungen mit unpolaren Flüssigkeiten
Von H e r m a n n
Hart mann
und P a u l
Henschel
I n s t i t u t f ü r physikalische Chemie
der U n i v e r s i t ä t F r a n k f u r t a. M.
(Z. Naturforschg. 4 a, 156—157 [1949]; eingeg. am 26. Januar 1949)
D i e M o l p o l a r i s a t i o n d e s D i ä t h y l ä t h e r s in M i s c h u n g e n d i e s e s S t o f f e s mit u n p o l a r e n F l ü s s i g k e i t e n ist
v o n der Konzentration nahezu u n a b h ä n g i g 1 . Diäthylä t h e r l ä ß t ich a l s o w e d e r in die G r u p p e der S t o f f e ,
die in L ö s u n g s t ö c h i o m e t r i s c h d e f i n i e r t e A s s o z i a t e
bilden, n o c h in die der D i p o l s c h w a r m b i l d n e r eindeutig
e i n o r d n e n 2 . D i e s e r S a c h v e r h a l t hat u n s v e r a n l a ß t ,
das d i e l e k t r i s c h e V e r h a l t e n d e s D i p h e n y l ä t h e r s in
M i s c h u n g e n mit u n p o l a r e n F l ü s s i g k e i t e n zu unters u c h e n , u m v i e l l e i c h t auf d i e s e m W e g E i n b l i c k in die
G r ü n d e f ü r das m e r k w ü r d i g e d i e l e k t r i s c h e V e r h a l t e n
d e s D i ä t h y l ä t h e r s zu g e w i n n e n .
P.
H.
Chem.
[1942],
1
2
Deby
H a r t
47. 856
53, 37,
e , P o l a r e M o l e k e l n , L e i p z i g 1929, S. 48.
m a n n , Z. Elektrochem. angew. physik.
[1941]; Z . p h y s i k . C h e m . , A b t . B 51. 309
49. 54 [1942].
Unauthenticated
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