ELECTRICAL CONDUCTIVITY OF CERTAIN SALINE SOLUTIONS. 65 
2°66 
1578 — D © 
This equation applies to all solutions, from that of density 1:2891 to that of satu- 
ration. The curve shews that throughout all the solutions, from that of density 
1:16 to the saturated one, there is only a comparatively small variation in resist - 
ance, not greater than 15 per cent. This result is important from a practical 
point of view, as it proves that in a galvanic cell any one of a wide range of solu- 
tions of this salt may be employed with approximately equal advantage, so far 
as conductivity is concerned. 
Our next salt was sulphate of copper, which was carefully purified before 
use. Eleven solutions were tested, containing from 1 part in 40 to 1 in 2°597, 
which is the ratio of saturation. 
R = 396 — 16 D + 
SULPHATE OF CoPpPER. 











I, Il. WN IV, I. Ii. Ill. eve 
eee ee ee ee SS | Be oa 
1 to 40 1:0167 9500 164°4 I to 4:146 1:1386 2020 35-0 
i 0. 1:0216 7790 134'8 Is, 4 1:1432 1970 34-1 
i, 20 1:0318 5700 98°7 Woy BAYT 1:1679 1830 oer 
Wy WM) 1:0622 3410 59-0 E5502 1:1823 1770 30°6 
a 1:0858 2730 47:3 |11,, 2°597 
! 1-205] 1690 29:3 
ee 11174 2200 38'1 Saturated 



The resistances were in this case measured in asecond tube, of the same 
form as the first, but of slightly different dimensions. The numbers in column 
IV. are obtained from those in column III., by multiplying by 01731, a coefficient 
which was determined by a careful calibration of the tube.* The conductivity 
here increases steadily up to the point of saturation. It appears that a satu- 
rated solution of sulphate of copper has almost exactly the same resistance as 
the solution of sulphate of zinc of maximum conductivity. 
This set of experiments is also presented in the form of a curve (fig. 3). 
As before, the excesses of density over unity are taken as the horizontal, and 
the resistances as the vertical ordinates. The horizontal scale (that of densities) 
is twice as great as that of fig. 2. 
We find that in this case also the curve is an hyperbola, not rectangular, the 
lower asymptote being inclined upwards as before. It is considerably more 
* Comparing this number with that already given for the first tube (022301), it appears that the 
ratio of the resistance in the first to that in the second tube is 1 to 1°29, a ratio exactly the same as 
one which we obtained experimentally by measuring the resistance of several solutions in both tubes. 
