AQUEOUS SOLUTIONS.—McKAY. 351 
Distilled water was used in making up all the solutions. In 
the case of the very dilute solutions, the conductivity of the 
water used was subtracted from the measured conductivity of 
the solution. The greatest value of this correction was 0.2 per 
cent, 
The combined error in ‘the determination of the conductivity 
and concentration of a double salt solution might be for solutions 
of concentration 0.4 gr.-eq. per litre, 0.8 per cent., for 0.8 solu- 
tions, 0.4 per cent., and for the very dilute solutions, from 
0.02 downwards, 0.8 per cent. The errors in the case of the 
stronger simple solutions micht be 0.2 per cent. greater. The 
error in plotting results and calculating from them by Professor 
MacGregor’s graphical process might be 0.2 per cent. 
Kohlrausch’s values of the molecular conductivity at infinite 
‘dilution, were used in the calculations. They are, for potassium 
sulphate 1270, for magnesium sulphate 1080, expressed in terms 
of 10-* times the conductivity of mercury at 0°C. 
The following table gives the results of the measurements of 
simple solutions, made to secure data for the subsequent calcula- 
tions. The concentrations are given in gramme-equivalents 
per litre at 18°C. The conductivities are for the temperature 
18°C., and are expressed in terms of the conductivity of mercury 
at 0°C. multiplied by 10-* :— 
