378 Proceedings of Royal Society of Edinburgh. [sess. 
Acetic Acid. 
Barometer. 
Temp, of 
Room. 
Ice present. 
Concentra- 
tion. 
Depression. 
Depression for 
decinormal 
solution. 
763 mm. 
13° 
18*5 g. 
0*0970 
0*1848 
0*1905 
758 
15 
18 
0*09668 
0*1840 
0*1903 
763 
15 
18 
0*09757 
0*1856 
0*1902 
772 
15 
20 
0*1000 
0*1907 
0*1907 
771 
15 
15 
0*09337 
0*1775 
0*1903 
769 
15*5 
17*5 
0*0974 
0*1853 
0*1903 
763 
15*5 
18 
0*0970 
0*1844 
0*1901 
Mean 0*1903 
The last column shows the extremely uniform character of the 
results obtained under a very considerable variety of conditions. 
The extreme difference of the depressions is only 0‘0006°, and the 
greatest divergence from the mean is only 0*0004°, the divergence 
from the mean in six observations out of the seven being 0*0002° 
or less. 
If we take the ionisation of decinormal acetic acid to he 0*012, 
we obtain the number 0*188 as the depression which would he 
shown by acetic acid if it were undissociated in decinormal solution. 
The equivalent depression for acetic acid, i.e ., the value of the 
depression divided by the concentration, would thus for the undisso- 
ciated compound he 1 *88. The mean value found by Loomis for 
nine non-electrolytes of small molecular weight is 1 *85, the 
greatest value being 1*87 and the smallest 1*81. 
Comparison with other Observers. 
When we compare our depressions for strong electrolytes with 
those of other observers, we find that there is on the whole an 
excellent agreement. The comparison is best made by ascertaining 
the equivalent depressions for the various solutions, and then by 
interpolation reducing these values to the equivalent depression 
for exactly 0*05 normal solution. 
Depression. 
0*1847 
0*1870 
Hydrochloric Acid. 
Concentration. 
0*0514 
0*0522 
Equiv. 
Depression. 
3*593 
3*583 
Equiv. Depr. 
for N/20. 
3*594 
3*585 
Mean, 3*590 
