SOLUTION 41 



water the invisible particles of which they are composed begin 

 to spread through the water until they are equally distributed. 

 This is the law of solution. Just as a ball thrown up in 

 the air returns to earth in response to the law of gravity, 

 so the particles of a solute become equally distributed 

 throughout their solvent, in response to the law of solution. 

 The lemonade in a glass is just as sweet at the top as it is 

 at the bottom. The particles of sugar are equally dis- 

 tributed throughout it. 



Now let us see why solutions are so important in life as 

 well as in lemonade. You know about digestion. You 

 know that it is the process of changing food from solid 

 to liquid form. This means that the food absorbed by our 

 blood is a solution. Blood itself is a solution. In plant 

 life, solutions are just as important as in animal life. All 

 that the roots take in from the soil is in the form of solu- 

 tion, and the nourishing sap that moves inside the plant 

 is simply water with various substances dissolved in it. 

 And, finally, inside the bodies of plants and animals, all 

 the processes that belong to life itself are processes that occur 

 in solutions. 



You must distinguish between solution and suspension. 

 When we wash our hands we may say that the soapy water 

 dissolves the dirt, but if the water itself turns dirty, that 

 shows that we have a case of suspension and not of solu- 

 tion. Suspension is the floating in a liquid of fine particles 

 of a solid or of another liquid. Streams that are muddy 

 in flood time gradually become clear. The mud suspended 

 in them is called sediment because it gradually "settles." 

 It slowly sinks to the bottom. But the solutes in solutions 

 do not sink to the bottom. The salt in sea-water never 

 settles. It becomes a solid only when the water evaporates. 



