m. DIFFUSION AND OSMOSIS 



16. DIFFUSION 



Object. To learn what is meant by diffusion. 



Apparatus. A tall jar or bottle, some crystals of copper sul- 

 phate or potassium bichromate or any other highly colored salt 

 soluble in water. 



Method. Place a few crystals of the salt in the jar and 

 carefully cover it with water, letting it run down the side 

 of the jar very slowly, and do not shake or stir the mixture. 

 Let it stand for some time. What is the result? This 

 tendency of substances to mix is called diffusion. 



Conclusion. State in a sentence what is the meaning 

 of diffusion. 



Note. Gases also have this property and diffuse much more 

 rapidly than liquids. 



17. DIFFUSION 

 Object. Same as in Experiment 16- 



Apparatus. A U-tube, gelatin, litmus solution, hydrochloric 

 acid, caustic soda, potassium bichromate. 



Method. Soak the gelatin until it is soft and melt it 

 over a lamp. Add a drop of potassium bichromate to render 

 it insoluble, then add the litmus solution till it acquires a 

 rich purple color. Pour it into the U-tube until it fills the 

 bend and leave it in a cool place until the gelatin has set. 



30 



