BLEACHING 73 



e. Soak a piece of the cotton cloth in the mordant of a; let 

 it dry for 5 minutes; then boil it in the picric acid solution for 

 2 minutes. Rinse the cloth, and let it dry. Is the color fast 

 now? Which material is dyed directly by picric acid? Which 

 indirectly f 



f. . Boil a piece of the washed cotton cloth in a solution of 

 sugar of lead (5 cu. cm.) ; then leave it for 2 minutes in a boiling 

 solution of potassium dichromate. Rinse the cloth, and let it 

 dry. What is the result? 



Paste all the dyed materials in your note book, giving them 

 the proper labels. 



EXERCISE 70 

 BLEACHING 



Apparatus and Materials. Bleaching powder, hydrochloric acid, 

 colored cheesecloth or mosquito netting, unbleached muslin, ink, glass 

 or porcelain dishes (beakers or cups). 



a. Make a bleaching solution out of about 5 cu. cm. (a tea- 

 spoonful) of bleaching powder (chloride of lime) and 100 cu. cm. 

 of water. Stir this for 5 minutes; then either filter it or pour 

 off the clear solution. Note the odor of bleaching powder and 

 of its solution. 



Get ready also some rather dilute hydrochloric acid (5 cu. 

 cm. of concentrated acid and 50 cu. cm. of water). 



6. Into the bleaching powder solution put a small piece of 

 cheap, colored cheesecloth or mosquito netting (use pink, green, 

 or blue, if possible) . Let it remain in the solution for 2 minutes, 

 and note whether the color is altered. Now take the colored 

 material out of the bleaching powder solution and dip it into the 

 dilute hydrochloric acid. How does this affect the color? If 

 the color is still unchanged, try dipping the cloth once more into 

 the first solution and leaving it a longer time before you put it 

 into the dilute hydrochloric acid. Give the results. 



