Tite Surrace Tension TEMPERATURE CORFFICIENT. 
By ARTHUR L. FOLEY. 
Some fifteen years ago the author described a method of finding the 
surface tension of liquids by determining with a balance the force required 
to pull a frame of mica from the liquid.! A mica frame, cut in the form 
shown in Fig. 1 is suspended from one arm 
re) of a sensitive balance and the lower edge 
lebetilede dttclrte i.e tele my 
(a-b) of the upper strip of mica is brought 
into contact with the liquid. The liquid is 
then gradually lowered while the pointer of 
Fig. 1. the balance is kept at the turning point by 
adding weights to the other pan. Eventually 
the downpull of the liquid and film is exceeded by the weights on the other 
arm of the balance, the mica frame is pulled suddenly upward, and the 
film breaks. The frame is then weighed while still in the liquid. The 
difference between the two weights gives what is called the maximum 
weight, from which the method takes its name. 
The surface tension is given by the equation 
awe: 4 dPt*g _—itg 
~ 2(1—t) © 40+) 4(1-+t) 
Where T=surface tension in dynes. 
Ni dal*t® - 4w (lt) id. (1) 
w=maximum weight. 
l=length of frame (between legs). 
t=thickness of frame. 
d=density of liquid. 
g=acceleration due to gravity. 
When the frames are thin one may use the simple equation 
SS 
T=)" (2) 
The maximum weight can be determined again and again with sur- 
prising uniformity. Even when one uses mica frames differing greatly in 
‘Proceedings of the Indiana Academy of Science, 1895, p. 67. 
Physical Review, Vol. 3, No. 5, 1896, p. 381. 
