SPECIFIC GRAVITY OF AQUEOUS SOLUTIONS.—ARCHIBALD. 337 
calculated values based on the values of ionization-coetticients 
for 18° C. I have, however, calculated some of the ionization- 
coefticients, for the different salts, corresponding to 15°C, by 
using the conductivity coefficients given by Kohlrausch, and find 
that the differences between the values for 18° and 15° are not 
large enough to cause any appreciable error in the calculations 
Rother seems to regard his measurements as possibly in error 
by 5 to 8 in the third decimal place. He found the surface. 
tension of the water he used to be 7.357. 
Observations of Specific Gravity. 
The specific gravity observations were all made at 18°C, and 
are referred to water at 18°C. Ostwald’s form of Sprengel’s 
pyknometer was used in making the measurements. It was 
tilled by dipping one arm in the solution to be measured and 
connecting the other by means of a rubber tube with an exhaust 
bottle. When the pyknometer had filled beyond the constant 
volume mark on the stem, it was placed in a water bath provided 
with a mechanical stirrer, which was connected with a water 
wheel driven by the water from a tap. The temperature of the 
bath was not allowed to vary more than a twentieth of a degree 
from 18°. When the liquid column in the arm had remained 
stationary for three or four minutes the meniscus was adjusted 
to the mark, the pyknometer taken from the bath, dipped in 
distilled water, then carefully dried with a linen cloth and 
weighed. From several measurements of the same solution, it 
would appear that the values of the specific gravity might be in 
error by about 5 in the fifth decimal place. 
The Lonization Coefficients. 
For simple solutions, the ionization coefficients, as in former 
papers, were taken to be the ratios of the specific molecular 
conductivity to the specific molecular conductivity at infinite 
dilution. The data for finding them for the simple solutions of 
Potassium, Sodium, and Copper Sulphates will be found in the 
above papers. In the case of the chlorides of Potassium and 
