96 WATER 



b. Put a little cold water in one glass and the same 

 amount of hot water in another glass. Now see how 

 much sugar will dissolve in the cold water and how much 

 in the hot water. When a solvent holds all of a solid it 

 can, the solution is said to be saturated for that temper- 

 ature. Which solution becomes saturated first, the hot 

 one or the cold one? Which is better for dissolving 

 solids, cold water or hot water? 



c. Fill a glass one-fourth full of cold water, take its 

 temperature, and then add half as much sal ammoniac ^ 

 there is water. Stir rapidly and immediately take its 

 temperature. What is another oddity of solution? Can 

 you explain (b.) above, now that you have done (c.) ? 

 Do you think that the solution is saturated? Why? 



d. Put a little dry baking soda and a little dry 

 cream of tartar into a dry glass. Nothing will happen. 

 Now add some water. What happens? Solution per- 

 mits the action of one material upon the other. The 

 gas is carbon dioxide and it is this gas which makes 

 soda biscuits rise- 



Water owes its power of removing dirt to the fact 

 that it can dissolve so many substances, but there are 

 many kinds of material which water cannot dissolve. 

 Fortunately for us there are other solvents which can 

 dissolve some of these. Two common examples of spe- 

 cial solvents are alcohol and gasolene. We should be 

 very careful when we are using either of these solvents. 



