376 



Common Science 



or soda pop into limewater, you get the same milkiness, 

 for the bubbles of carbon dioxid in the charged water 

 act as the carbon dioxid in your breath did. If you 

 pumped enough air through the limewater you would 

 produce some milkiness in it, for there is always some 

 carbon dioxid in the air. 



The purpose of these experiments is only to give you 

 a general notion of how a chemist analyzes things, - 

 by putting an unknown substance through a series of 

 tests he can tell just what that substance contains ; 

 and by accurately weighing and measuring everything 

 he puts in and everything he gets out, he can determine 

 how much of each thing is present in the compound or 

 mixture. To learn to do this accurately takes years of 

 training. But the men who go through this training 

 and analyze substances for us are among the most useful 

 members of the human race. 



Inference Exercise 

 Explain the following : 



551. A little soda used in canning an acid fruit will save sugar. 



552. The fats you eat are mostly digested in the small intestine, 



where there is a large excess of alkali. 

 The dissolved food in the liquid part of the blood gets 



out of the blood vessels and in among the cells of the 



body, and it is finally taken into the cells through their 



walls. 



Ammonia takes the color out of delicate fabrics. 

 Dishes in which cheese has been cooked can be cleaned 



quickly by boiling vinegar in them. 



556. Prepared pancake flour contains baking powder. It keeps 



indefinitely when dry, but if the box gets wet, it spoils. 



557. When water or milk is added to prepared pancake flour to 



make a batter, bubbles appear all through it. 



558. When a roof leaks a little, a large spot appears on the ceiling. 



553- 



554- 

 555- 



