iy) 
III.—On the Electrical Conductivity of Certain Saline Solutions, with a Note on 
the Density. By J. A. Ewtne and J. G. MacGrecor, B.A. Communi- 
cated by Professor Tarr. (Plate IT.) 
(Read April 21, 1873.) 
I. Note on the Density. 
In preparing solutions of various salts with a view to determine their 
electrical conductivity, we found it of importance to know both the amount of 
salt in each solution, and its density. We prepared the solutions by mixing 
known weights of the salt under examination with known volumes of distilled 
water, and then measured their densities as soon as solution was complete by 
weighing a glass bulb in the liquid. We employed a balance which weighed 
to a milligramme with a kilogramme in each pan, and to give the results 
as great accuracy as possible we corrected for the upward pressure of the 
air displaced by the weights. The weight of the bulb itself was about eighty 
grammes. When not in use it was kept immersed in distilled water, in order 
to prevent change in its weight or volume being caused by impurities adhering 
to it. The temperature at which the densities were taken was 10° centigrade. 
The following table shows the connection between the density and the com- 
position of solutions of pure sulphate of zinc. The third column gives the 
volume to which unit volume of the original water was extended after the salt 
was dissolved. 







I. at Bie) i Une iF II. Ill. 
Ratio of ZnSO,+ ety tele ht | Ratio of volume || Ratio of ZnSO + Density — weight Ratio of volume 
7H,0 to water Cea of solution to 7H,0 to water . ae Ge eon solttion to 
in solution. G@iammiogs volume of water. in solution. Tee * | volume of water. 
1 to 40 10140 10108 1 to 2 12186 1°2308 
a0 1:0187 10144 iene 1:2709 13114 
eee) 1°0278 10216 1 ,, 1-361 12895 1:3455 
hes, UO) 1:0540 10436 ee ok 1°3530 1:4782 
Lahey 1:0760 1:0622 dioctaliental 14053 16011 
LP eo 11019 10893 eee oe. 
1°4220 16385 
Teo 11582 11512 Saturated 
Ih ey eee 1°1845 11819 





The increase of volume due to the dissolution of the salt, that is to say, the 
decimal part of the numbers in column IIL, is given as a curve in fig. 1, along 
with the ratio (expressed as a decimal) of salt to water in the solutions. It 
VOL. XXVII. PART I. O 
