73 



Put a pinch of the heated soda into hard water and see whether 

 it softens the water. Has the heat changed the character 

 of the baking soda? What do we call baking soda after 

 it has been strongly heated and changed in character ? 



EXPERIMENT 66. BLEACHING POWDERS 



For this experiment, the pupil should bring from home 

 pieces of colored gingham or calico, flannel and silk; also 

 small pieces of unbleached muslin. 



(a) Put a teaspoonful of bleaching powder in a tumbler 

 of cold water, and after a fair amount of it has dissolved, 

 filter off the clear solution. Dip a piece of colored ging- 

 ham in the filtered bleaching solution, remove it, and state 

 whether or not its color has been affected. 



(b) Add a small amount of vinegar to the bleaching 

 solution, and then quickly dip into the tumbler a fresh 

 piece of gingham. What occurs ? 



Is the result the same in (a) as in()? Can you suggest 

 any reason for the change? Why must the cloth be im- 

 mersed in the bleaching solution as soon as the vinegar 

 has been added ? 



(c) Into a bleaching solution to which acid has been 

 added, as in (b), dip a piece of flannel or silk. What is the 

 result ? 



Repeat (a), (b), for unbleached muslin. 



EXPERIMENT 67. THE REMOVAL OF STAINS 



For this experiment the pupil should bring from home 

 samples of white and colored cloth, and a piece of black 

 silk. 



