REMOVAL OF GREASE 235 



red litmus paper turns blue, nor blue paper red, in the 

 presence of this combination. Such a mixture as this is 

 said to be neutral. In cleaning we make use of neutral- 

 ization, by using acids to remove stains caused by bases, 

 and by using bases to remove stains caused by acids. 



Experiment. Removal of spots and stains. 



Materials: Strips of white cotton cloth. Congo red solution. Sodium 

 carbonate. Lemon. Ammonia. Acetic acid or white vinegar. 

 Salad oil. Lard. Butter. Alcohol. Gasoline. Carbon tetrachlo- 

 ride. Oxalic acid. Black ink. Red ink. Test tubes. 



Adds and alkalies: Dye one strip of white cloth in Congo red. A sec- 

 ond in Congo red to* which is added a pinch of sodium carbonate. 

 Dry them. What are the colors? 



Let a drop of lemon juice (an acid) fall on the blue cloth. Result. 

 Try to restore the color with ammonia. Let a drop of ammonia fall 

 on the red cloth. Result. Try to restore the color with acetic acid 

 or vinegar. 



Acids and alkalies have opposite properties and each tends to 

 destroy the other. 



Grease spots: Dirt held by oil or grease can only be removed by the 

 removal of the oil or grease. Test the solubility of salad oil, lard, 

 and butter in water, alcohol, gasoline, carbon tetrachloride. Results? 

 Suggest a good way to remove grease spots from clothing. What 

 danger is there in using gasoline? 



Fruit and ink stains : Try cold water, then hot water. Oxalic acid will 

 remove black ink containing iron. White cotton or linen may be 

 treated with Javelle water. The cloth must be thoroughly washed 

 in dilute ammonia afterwards. 



NOTE : Use alcohol for grass stains ; dilute hydrochloric acid for 



. rust ; turpentine for paint ; benzole for tar, and sulphurous acid or 

 hydrogen peroxide for bleaching white woolens, silks, and linens. 



Removal of grease. An easy way to remove grease 

 from clothing is to cover the grease spot with blotting 

 paper and press with a hot iron. The grease is melted 

 by the heat and absorbed by the blotter, which draws the 

 liquid up into it by capillary attraction. Grease and oils 



