They will turn red litmus paper blue . They will react with acids to form a salt and water , see Neutralization . Uses of Alkalis .
Sodium hydroxide is used in the manufacture of paper , soap and ceramics .
Indigestion may be caused by too much hydrochloric acid in the stomach . Indigestion tablets contain a base such as magnesium oxide , or calcium carbonate to neutralize the acid . A bee sting is acidic . It may be neutralized by a weak alkali such as ammonia solution .