Exchange and Movements oj Gases and Liquids. 49 



which osmose also plays an important part. The nature of the 

 latter process may be illustrated by the following demonstrations : 

 44. Osmose. Smooth the ends of a section of glass tub- 

 ing a meter long, with an internal diameter of five millimeters, 

 and fit to one end a rubber stopper with one perforation. Soak 

 a section of dialyzer tubing 20 cm. in length in water for a 

 few minutes. Pleat one end into a compact mass, then fold 

 back, and wrap 

 tightly with a small 

 strong cord. Re- 

 move the stopper 

 from the tube, and 

 slip the open end of 

 the dialyzer tubing 

 over the stopper, 

 wrapping tightly with 

 cord. Now fill the 

 dialyzer tube with a 

 saturated solution of 



sugar, 



and re-insert 



the long tube in the 

 perforation in the 

 stopper. Support the 

 tube in an upright 



position, with the 



Fig. 26. Osmometer consisting of a lamp 

 chimney C over the lower end of which a piece 

 of bladder or parchment is fastened. The lamp 

 chimney is supported by a large stopper K in a 

 glass cylinder containing water. After Oels. 



dialyzer suspended in 



a large cylinder of distilled water. Note the gradual rise of the 

 liquid in the glass tube, due to the fact that sugar has drawn 

 water into the dialyzer by osmotic force, and that the increased 

 volume is forced up into the upright tube (Fig. 25). 



Make a second preparation exactly similar to the first, but 

 fill the dialyzer with a solution consisting of one part concen- 

 trated sugar solution and one part distilled water. Compare 

 the height to which the liquid rises in the glass tube in both 

 4 



