Soap

• Soap is a common emulsifier made by combining fatty acids and a strong base like sodium or potassium hydroxide. The resulting salt is water-soluble but also has a fat-soluble or lipophilic portion that can stabilize oil-water emulsions, dissolving grease on your plates or on your skin. Soap molecules can also combine with calcium or magnesium ions in hard water to form insoluble precipitates like the soap scum you find on taps or in your bathtub.
  
  

Alkyl Sulfates

• Like soaps, alkyl sulfates are water-soluble molecules with a lipophilic chain or tail. The difference lies in the nature of the hydrophilic or water-soluble part. A soap molecule has a type of chemical group called a carboxyl group at its tip, while an alkyl sulfate is tipped with a sulfate group. Unlike soaps, these molecules do not form insoluble precipitates with calcium or magnesium, so they are common emulsifiers in dishwashing liquids and other commercial products.
  
  

Alkylbenzenesulfonates

• Alkylbenzenesulfonates are among the most common emulsifiers in household products like laundry detergents. These molecules feature a straight carbon chain attached to a benzene ring with a highly water-soluble sulfonate group attached to it. Like the alkyl sulfates, they dissolve in water and promote formation of emulsions with oils, fats and greases. They also share another feature in common with alkyl sulfates and soaps -- the water-soluble part of the detergent molecule bears a negative charge. Consequently, these and other similar emulsifiers are sometimes called anionic detergents.
  
  

Cationic & Nonionic Surfactants

• Some cleaning products employ emulsifiers that feature a positive charge on the water-soluble part of the molecule. You can find these compounds in various laundry detergents and fabric softeners; they are collectively known as cationic surfactants. Fatty alcohols like cetyl and stearyl alcohol have a more moderately water-soluble region that does not bear a net charge and are called nonionic surfactants. Fatty alcohols of this type are found not only in laundry detergents but also in various personal care products.