Solution and Chemical Action 365 



538. The clothes will be easier to iron if dampened. 



539. The creases made in ironing the clothes will reappear even 



if you flatten the creases out with your hand. 



540. After they have been worn, washed, and ironed a number 



of times, clothes are thinner than they were when they 

 were new. 



SECTION 57. Effervescence. 



What makes baking powder bubble ? 

 What makes the foam on soda water ? 



Did you ever make soda lemonade? It is easy to 

 make and is rather good. Try making it at home. 

 Here are the directions : 



Experiment 112. Make a glass of ordinary lemonade (half 

 a lemon, i^ teaspoonfuls of sugar ; fill the glass with water). 

 Pour half of this lemonade into another cup or glass. Into 

 the remaining half glass stir half a teaspoonful of soda. 

 Drink it while it fizzes. Does it taste sour? 



When anything fizzes or bubbles up like this, we say 

 that it effervesces. Effervescence is the bubbling up of 

 a gas from a liquid. The gas that bubbled up from 

 your lemonade was carbon dioxid (CO 2 ), and this is 

 the gas that usually bubbles up out of things when they 

 effervesce. 



When you make bread, the yeast turns the sugar into 

 carbon dioxid (CO 2 ) and alcohol. The carbon dioxid 

 tries to bubble up out of the dough, and the bubbles 

 make little holes all through the dough. This makes 

 the bread light. When bread rises, it really is slowly 

 effervescing. 



How soda water is made. Certain firms make pure 

 carbon dioxid (commercially known as carbonic acid 



