Solution and Chemical Action 369 



gingerbread. She had also baking soda, caustic soda, lemons, 

 oranges, vanilla, salad oil, vinegar, and lye. Was there any 

 way in which she might have made the gingerbread light 

 without spoiling it? 



Inference Exercise 

 Explain the following : 



541. Harness is oiled to keep it flexible. 



542. When you pour nitric acid on copper filings, there is a 



bubbling up of gas. 



543. The flask or dish in which the action takes place becomes 



very hot. 



544. The copper disappears and a clear green solution is left. 



545. In making cream of tomato soup, soda is added to the to- 



matoes before the milk is, so that the milk will not curdle 

 How does the soda prevent curdling ? 



546. The soda makes the soup froth up. 



547. A wagon squeaks when an axle needs greasing. 



548. Seidlitz powders are mixed in only half a glass of water. 



549. The work of developing photographs is all done with a ruby 



light for illumination. 



550. Coal slides forward off the shovel into a furnace when you 



stop the shovel at the furnace door. 



