17 4:34 PM

1 downloads 0 Views 1MB Size Report
Since Arnim, is constant, (Ab/b)c and (Ab/b)c must be different. If there is a cooperative motion of a small number of ions we can write. {Ablb) c= (n b>u-nbu)l(n.
# = 4 0 G . Parameter ist die Entfernung x der Außenspulen II und III von der Mittelspule I. Die Ergiebigkeit ist hier (v = 2 0 m / s ) % = 0,18//V/A. (7 b) Das beschriebene Verfahren gestattet die Messung der über den Querschnitt gemittelten Geschwindigkeit v bei bekannter elektrischer Leitfähigkeit o. Ist das LeitfähigThe Electrical Conductivity of Solid and Molten 6 L i 2 S 0 4 and 7 L i 2 S 0 4 ARNOLD

KVIST

Department of Physics, Chalmers Institute of Technology, Göteborg (Z. Naturforschg. 21 a, 487 [ 1 9 6 6 ] ; received 3 February 1966)

The electrical conductivity of L i 2 S 0 4 with different concentrations of 8 Li and 7 L i has been measured from 5 7 5 to 9 3 0 ° C . The ratio of the specific conductivity of 6 L i 2 S 0 4 and 7 L i 2 S 0 4 is 1.042 + 0 . 0 0 2 and within the experimental errors independent of the temperature. A comparison with the mass effect found in electromigration experiments show that there is a cooperative motion of the cations in a - L i 2 S 0 4 .

In the cubic high temperature modification of lithium sulphate, the cation is highly mobile and for this reason the electrical conductivity is almost the same as in the molten salt 1 . The transference number of the cation in a-Li 2 S0 4 is unity 2 and the cations are moving in a pseudo-lattice of sulphate ions. Deviations from the N E R N S T - E I N S T E I N equation found by K V I S T and L U N D E N 1 can be explained by assuming a coupled transport mechanism. The mass effect /u is defined as the ratio of the relative difference of the mobilities and the relative difference of the masses of the two cations Ab /Am + (1) ^ - b ! m —+ L U N D E N 2 hat from electromigration experiments in a-Li 2 S0 4 calculated the mass effect of 6 Li and 7 Li and obtained the value — ^u-nbu)l(n b) = ( & ' L i - H i ) / & • 11 is the mean value of the number of ions taking part in the same movement. In natural lithium sulphate the number of 6 Li ions is small compared with the number of 7 Li ions and this gives (Ab/b)e = (Hi + (n -1) fc'Li - n Hi)/ (n b) = (Ab/b) Jn . The mean value of the number of ions taking part in the same movement is thus 2.0. The difference in electrical conductivity of molten 6 LiCl and 7 LiCl has recently been discussed by L E N K E a n d

KLEMM

4

.

I wish to thank Dr. A . LUNDEN for helpful discussions during this work. This work was supported by "Chalmerska Forskningsfonden".

T

cm 96.2

915.0 904.8 871.3 822.8 806.4 768.2 756.5 716.5 702.0 646.2 624.4 100.0 889.5 880.5 873.8 864.8 861.0 840.8 823.2 789.2 771.4 747.6 714.6 687.8 679.8 634.2

a

T

*

°C

ß-icm-

°C

% «Li

12.6

4.646 4.582 4.402 3.025 2.887 2.565 2.463 2.053 1.958 1.495 1.318 % 7 Li 4.321 4.276 4.236 4.199 4.169 3.011 2.872 2.587 2.448 2.251 1.978 1.763 1.690 1.339

906.5 892.2 866.2 856.8 820.0 802.5 784.2 730.8

%

1

«Li 4.424 4.356 4.194 3.587 2.857 2.718 2.562 2.117

12.6 929.5 910.8 891.0 838.0 832.0 811.3 802.5 786.8 730.0 714.4 691.5 670.4 630.8 610.0 582.2 579.2

%«Li 4.539 4.451 4.340 3.017 2.968 2.797 2.718 2.594 2.099 1.973 1.793 1.614 1.308 1.146 0.946 0.913

Table 1. The electrical conductivity of L i 2 S 0 4 with different concentrations of 6 Li. Melting point of L i 2 S 0 4 : 8 6 0 ° C . 3

A . K V I S T a n d A . RANDSALU, t o b e

4

R . LENKE a n d A . KLEMM, Z . N a t u r f o r s c h g . 2 0 a , 1 7 2 3

published. [1965],

Unauthenticated Download Date | 6/30/17 4:34 PM