666 Messrs. Narayan and Subrahmanyam on Surface 



To measure the diameter of the bubble a magnified image 

 of it is projected on a graduated paper placed at a distance. 

 The bubble is illumined with an electric glow-lamp arranged 

 on one side of the glass box, and a good definition of the 

 periphery is secured by making the side of the glass box 

 next to the bulb of a ground glass plate. Some screens are 

 also interposed between the lamp and the glass box, and a 

 preliminary observation with a delicate thermometer indicated 

 no temperature changes within the enclosed space. Without 

 disturbing the position of either the lens or the screen, a 

 translucent scale is held horizontally in the position previously 

 occupied by the bubble, and each of the equal divisions of 

 the graduated paper is calibrated. This avoids the necessity 

 for measuring^ and v and the consequent error in calculating 

 the magnification. This, of course, is done at the conclusion 

 of the experiment. 



To make the description clear, a photographic reproduction 

 of the arrangement of the apparatus is given herewith 

 (PL XV.). 



Table I. 



Surface Tension of freshly prepared Sodium Oleate Solution. 



(By the Bubble method.) 



Length of the manometric column 9*10 cm. 



Density of Xylene (Temp. 28°'l C.) ... 0'850 grm. per c.c. 





ISo. of rotations 



Diameter 



Surface Tension. 

 (Dynes per cm.) 



Concentration. 



of the micrometer 

 screw. 



(to be multiplied 

 by 3/5-35). 



Saturated 









solution. 



11 97 



3*35 cm. 



23-50 



0-667 of „ 



10 108 



3-66 „ 



23-53 



0-445 



11 27 



3-47 „ 



2371 



0-297 



12 25 



3-12 „ 



23-23 



0-198 



10 57 



3-60 „ 



2319 



0132 



11 82 



3-33 „ 



23-23 



0-088 



11 33 



344 „ 



23-57 



0-059 



12 66 



3-10 „ 



23-41 



0-039 



12 58 



3-12 „ 



23-50 



0-0909 

 1 00625 

 ! 00476 



| 0-0385 



' 0-0322 



Length of the manometric column: 9'00 cm. 

 Other data precisely the same. 



11 83 3-38 cm. j 



11 199 326 „ 



12 130 3'07 „ 

 12 179 2-98 „ 



No bubbles could be blown. 



23-33 

 23 46 

 23-42 

 2311 



