EXERCISES 205 



on cloth should be washed out at once with water, and the spots treated 

 with a solution of baking soda, borax, etc. Ammonia should rarely 

 be used to neutralize acid spots on colored goods; it may react with the 

 dye, as well as with the acid we wish to neutralize. 



231. Summary. Acids are the sour substances present in fruit, 

 vinegar, pickles, etc. They are either organic or inorganic. Inorganic 

 acids are also called mineral acids. 



Acids act upon coloring matter, metals, carbonates of metals, bases, 

 and fabrics, especially upon cotton and linen. 



Alkalies are the strongest bases. They turn litmus blue, destroy 

 skin and flesh, saponify fats, neutralize acids, and destroy fabrics, 

 especially wool and silk. 



Neutralization is the chemical action between an acid and a base. 

 After neutralization the solution contains a salt. 



Testing for salts consists in finding the metal present in them, and 

 the acid to which they are related. 



Washing of clothing is for the purpose of removing dirt, opening the 

 pores of the cloth, and destroying bacteria. 



Soap is the sodium salt of certain fatty acids; it is made by the boil- 

 ing of alkalies with fat, and is soluble in water. 



Soft water and soap give alkali and organic acid in mild form. Hard 

 water first gives a lime-soap scum. Hard water is " softened " by soap, 

 soda, borax, ammonia water, etc. 



Cotton and linen consist of long hollow fibers of cellulose. 



Wool consists of short, thick cells having overlapping scales. 



Silk and wool can be dyed directly more easily than cotton and linen. 



Mordants are substances used to unite the dye to the fabric. 



Paint generally consists of linseed oil, turpentine, a pigment, and 

 lead white, or some other substance with " covering" power. 



Stains are removed sometimes by physical, and sometimes by 

 chemical means. 



232. Exercises. 



1. If you have spilled dilute hydrochloric acid upon woolen cloth- 

 ing, what should you use to neutralize the acid and to restore the color? 

 Would caustic soda do? Why? 



