ELECTRICAL CONDUCTIVITY OF CERTAIN SALINE SOLUTIONS. 67 
Mrxep Souvurions. 









: Specificresistances at 10 °C when mixed with equal volumes of solutions 
Solutions of CuSO, + 5H,0. of ZnSO, + 7H,0. B. A. Units. 
iE ] |) with | with Mm i 
: 5 With N With O With P 
Specific (Saturated) Density Teneiey, Density Density, 
N Dansk resistance at Density =1°2895. —~1-1595 ~1-0760 10278 
eee WB 10° C. =1:4229, |Sp. resistance| «stance | Sp. resistance| Sp. resistan 
B. A. U. Sp. resistance =29"1 P ae cad Leis O77. 
=33'2? (minimum). ra : s : — : 
| A 11605 32°2 27°3 28°2 31°8 37:9 45°3 
1:0858 47°3 27°5 29°6 34°3 46°7 59°3 
C 10318 98°7 27°9 31:3 42°0 64°5 101°6 









From this it appears— 
1st, That invariably the resistance of the mixture is less than the mean 
resistance of the components, being in many cases less than that of either. 
2d, That in mixtures, consisting of equal volumes of the solutions of these 
two salts, the maximum of conductivity is reached when a saturated solution 
of sulphate of zinc is mixed with a solution of sulphate of copper. What the 
strength of this copper solution is, appears to affect the result but little (AL, 
BL, and CL being of very nearly equal resistance). The least resistance of all 
is given when both solutions are saturated. We have also represented these 
results 'in a graphic form (fig. 4). The vertical ordinates are the specific 
resistances of the mixtures; the horizontal ones are the excesses over unity 
of the densities of the solutions of sulphate of zinc, with which the three 
solutions of sulphate of copper are mixed. The three curves correspond to the 
three solutions of sulphate of copper, and are lettered A, B, and C, after them. 
The points where these curves cut the axis, along which resistances are mea- 
sured, of course represent the resistances got by mixing the copper solutions 
with equal volumes of solution of sulphate of zinc, whose density = 1, that is, 
with equal volumes of pure water. These points are calculated, from the curves 
of density and resistance already given, for cupric sulphate alone. (Figs. 1 
and 3.) They are— 
A, diluted with an equal volume of water, sp. res. = 49°5 
B, ” ” ” . = 78:7 
C; ) 3) 3? = 147°0 
The other points on the curves are determined by experiment. By the help 
of these curves it would be possible to determine, at least approximately, the 
resistance of any mixture of equal volumes of solutions of these two salts. 
We endeavoured to account for the increased conductivity of the mixtures 
in the following manner :—We had data by which we could calculate the amount 
of water, of cupric sulphate, and of zincic sulphate in each mixture. Now, 
VOL. XXVII. PART I. S 
