344 ON THE SURFACE TENSION AND 
TABLE V. (Continued) —Sprciric GRAVITY. 
Copper and Potassium Sulphate Mixtures. 
ocZonsentiations of | Tonizatign CooMcionts | « spocite Gravity of Mixture, 
z KgSO4. | +CuSO4. | 4 KgSOq4. | 4 CuSO4. |Observed| Calculated | Difference. 
Value. Value. 
.04000 04000 783 427 1.00322} 1.00319 | — 0.0,3 
.05000 .05000 766 410 1.00895) 1.00597 | + 2 
06666 | .06666 749 2080 1.00527} 1.00525 | — 2 
.07500 -07500 743 316 1.00591; 1.00589 | — 2 
.0909 0909 (29 .d09 1.00707} 1.00710 | + 3 
1000 .1000 «122 349 1.00783) 1.00780 | — 3 | 
1666 . 1666 679 300 1.01271) 1.01275 | + 4 
2222 2222 658 .283 1 | 1.01690 | — 4 
Fs 13.5) 3333) .635 .253 1.02503} 1.02510 | + 7 
.4000 .4000 .625 .239 1.08000} 1.08006 | + 
-5000 .5000 .603 226 ee 1.03734 | + 0.031 
It appears from the above Tables IV and V that the differ- 
ences between calculated and observed values are within the 
limits of error, throughout nearly the same range of concentra- 
tion as that of the observations on simple solutions used in 
determining the constants. This range is somewhat greater for 
the Sodium and Potassium Sulphate mixtures than for the Cop- 
per and Potassium Sulphate mixtures, which would seem to 
support the view taken of these mixtures in my previous paper, 
viz., as to the existence of a double salt in the solution. It 
might also be mentioned here, in support of this view, that for 
mixtures of stronger solutions of the Copper and Potassium 
Sulphates than are here given, I have observed a quite noticeable 
change of volume on mixing which is not the case for mixtures 
of solutions of the Sodium and Potassium Sulphates for a like 
concentration. 
As the ionization constants used in the calculations were not 
determined from the observations of these tables, such alternation 
