180 
From the plot one obtains the following values: 
Surface tension at 0° C.—75.5 dynes per cm. 
Surface tension at 18° C.=72.6 dynes per cm. 
Surface tension of 80° C.=62.6 dynes per cm. 
Temperature coefficient—.161 dynes per cm. 
T. Prector Hall’ gives the following values: 
Tension at 0° C.=75.48 dynes. 
Tension at 18° C.=72.96 dynes. 
Tension at 80° C. (calculated )—64.28 dynes. 
Temperature coefficient—.14 dynes. 
Hall tabulates the results of nineteen different investigations by 
fourteen investigators giving a mean of all of Tension=75.4 dynes at 0° C. 
und temperature coefficient ranging from .141 dynes to .204 dynes per cm. 
Hall adopts .14 dynes as the most probable value. 
It will be observed that the author’s result for the tension at zero 
temperature agrees with the results obtained by others, but that his values 
at higher temperatures are considerably lower, giving a much larger tem- 
perature coefficient. The differences are entirely too large and too regular 
to be attributed to experimental errors. 
Hall claims that absorbed gases tend to raise the surface tension of 
water and to increase the temperature coefficient. He claims also that the 
surface tensions of different samples of water are not the same. The 
author rather inclines to the view that the smaller values obtained at 
higher temperatures in this investigation are due to the fact that the 
measurements were made on water in contact with air saturated with 
watery vapor, while the conditions under which most of the other investi- 
gations have been made give the tension of water in contact with moist 
air, but not saturated air. Perhaps the actual temperature of the film 
under such conditions is not given correctly by a thermometer placed in 
the liquid. Evaporaticn into the air lowers the temperature of the surface 
film—possibly considerably below the temperature of the body of the 
liquid. Whatever the actual magnitude of this effect may be, it tends al- 
ways to give too high values for the surface tension at high temperatures— 
the drier the air the higher the values. 
2 New method of measuring surface tension. Philosophical Magazine, Novem- 
ber, 1898, Vol. 36, p. 412. 
