74 LABORATORY EXERCISES 



c. Get a piece of new, unbleached muslin. What is its 

 color? Why has it a color? Try to remove the color by means 

 of bleaching powder solution and dilute hydrochloric acid, as 

 you used these in b. Finally rinse the muslin thoroughly, and 

 let it dry. What is the result? 



d. Make an ink spot on a piece of white muslin. Try to re- 

 move the spot by soaking it first in bleaching powder solution and 

 then in dilute hydrochloric acid. What are "ink eradicators"? 



Would it be a good plan to try to remove ink from a colored 

 fabric by means of bleaching powder solution and dilute 

 hydrochloric acid? Tell why. 



EXERCISE 71 

 HOW TO REMOVE STAINS 



Apparatus and Materials. Piece of black cloth, candle or lard, 

 benzine or gasoline, blotting paper, white cloth, rusty iron, hydro- 

 chloric acid, white paint, grass or leaf, alcohol. 



a. Make a spot, with candle grease or lard, on a piece of 

 black goods. Remove it by putting a few drops of benzine or 

 gasoline on the spot and rubbing it with a black cloth. A piece 

 of clean blotting paper or a pad of cloth may be placed under the 

 spot to absorb the liquid and the grease it has dissolved. Try 

 the operation more than once, if necessary. 



6. Rub a white cloth with a rusty can or nail until you get a 

 decided stain. You can get a still deeper stain by putting a 

 drop of ferrous sulphate (copperas) solution on the cloth and 

 letting it dry. Soak the stain in dilute hydrochloric acid (5 cu. 

 cm. of concentrated acid to 50 cu. cm. of water) for about 5 

 minutes; then rinse it thoroughly with water. If the stain is 

 not removed, try a second time. 



In the household, lemon juice and salt are used to remove 

 rust stains. This mixture acts like dilute hydrochloric acid. 



