Determination of the Surface Tensions of Liquids. Ill 



temperature of the bath-liquid contained in the beaker, the 

 other that of the liquid undergoing investigation in the test 

 tube O. 



Some of these pieces require a more detailed description. 



The immovable part of the gibbed plate has a scale fastened 

 along its side divided into fortieths of an inch, while its mova- 

 ble part has a pointer playing over this scale. Back of the 

 gibbed plate is fixed the bearing P in which the screw EF 

 turns ; the clamps CC are attached to the fixed portion of the 

 gibbed plate, also another pointer for the milled head of the 

 screw. 



The micrometer screw demands a specially detailed descrip- 

 tion, inasmuch as the accuracy of the results obtainable by the 

 apparatus depend mainly upon the accuracy of its construc- 

 tion. The one I use has forty threads to the inch, is about 

 four inches long, and of good diameter, so as to give absolute 

 motion, the adjustable split-bearing P taking up all lost motion. 

 Great pains were taken in turning it, and I have been unable 

 to detect any irregularities in its construction, indeed, the 

 screw furnished by the makers is even more accurate than is 

 really necessary. The milled head E (about SS"""" in diameter) 

 is divided into 100 parts, thus giving a direct reading of 

 ^0"^ of an inch, and even less than that, since it is easy to 

 estimate fractions of a division. 



Three capillary tubes were employed in working with the 

 apparatus : 



A with a bore of about rs™"'. 

 B " " " " " 0-5 '^ 



Q <c U U U ii Q.-|^ << 



From the nature of the method it is not at all necessary to 

 know the exact dimensions of the tubes ; all that is required is 

 that the bore be approximately circular and the edges sharp. 

 To prepare the capillary tubes, a stock of tubing is examined 

 and tubes of the desired dimensions selected. Pieces are 

 broken off from these tubes until it is found that the ends pre- 

 sent plane surfaces perpendicular to the axis of the tube. If 

 the clamps happen to be too large for the tubes, a filling of 

 sheet lead may be employed. 



The liquid serving as bath, and contained in the beaker, may 

 be water or glycerine ; it is heated by means of a Bunsen 

 burner and kept in motion by means of a stirrer (not shown, 

 however, in the figure). Besides this kind of a bath, much 

 use was made of a vapor jacket, for keeping the temperature 

 uniform during a determination. The test-tube O was fitted 

 into a considerably larger tube by means of a cork through a 

 second perforation of which passed a long glass tube, acting as 

 a condenser. On boiling liquids or mixtures of liquids in the 



