12 LABORATORY EXERCISES 



why. If you do not succeed the first time, dry the needle and 

 the fork carefully, and try again. 



EXERCISE 8 

 CAPILLARY ACTION 



Apparatus and Materials. Bunsen burner, glass tube about 15 cm. 

 long, colored water or ink, two glass vessels (beakers or water glasses), 

 strip of cotton cloth (or of blotting paper), concentrated salt brine. 



a. Heat the middle of a piece of glass tubing in a Bunsen 

 flame until it is soft enough to be drawn out. You will need 

 to hold both ends of the tube in your hands, and to turn the tube 

 rapidly at first so that it can be heated evenly. Do not draw 

 the tube out until its walls have almost melted together. Then 

 remove the tube from the flame, and draw it out at once. In 

 this way you can get a long tube of a .very small diameter 

 (a capillary tube). 



6. When the tube is cool, break it carefully at its narrowest 

 part, and then dip the small end into a dish of colored water, 

 or into ink. Note how the liquid ascends into the tube. What 

 is the shape of the liquid surface in the capillary tube? If 

 different parts of the tube are of different diameters, break 

 the tube so as to get two capillary tubes, one of a considerably 

 larger diameter than the other. Dip both into the liquid. In 

 which one does the water ascend to the greater height? 



c. Try the experiment shown in Fig. 25, 32, of the text. 

 Use a wet cotton cloth, a wet strip of blotting paper, or a wet 

 string. 



d. Into a clean, dry water-glass pour carefully about 10 cu. 

 cm. of a concentrated salt brine. Pour the salt solution down 

 the side of a glass tube or rod (c/. 84, Fig. 68, of text) so that 

 the solution does not wet the sides of the glass above the liquid 

 level. Mark the level of the liquid by means of a piece of paper 



