Soaps : What is in it actually??

In our everyday lives, we would use one type of chemical to clean the house, car, furniture and even ourselves. This chemical that I’m talking about is soap. We use soap to clean and it tends to remove almost any stains, but what exactly is the chemical that makes its cleaning properties so popular in our everyday lives? 

Soap, actually, is a salt of a fatty acid which is obtained by treating vegetable or animal oil fats with a strong alkali solution. Fats and oils are composed of triglycerides: three molecules of fatty acids attached to a single molecule of glycerol. The alkaline solution brings about a chemical reaction known as saponification. In saponification, the fats are first hydrolysed into free fatty acids, which then combine with the alkali to form crude soap. Glycerol is then liberated and is either left in or washed out and recovered as a useful by-product according to the process employed. Soaps are key components of most lubricating greases, which are usually emulsions of calcium or lithium soaps and mineral oil.

simplified structures of Na stearate, a typical soap

When used for cleaning, soap serves as a surfactant in conjunction with water, which helps to lossen the grease stains on fabrics or on any surfaces. The cleaning action of this mixture is attributed to the action of micelles, tiny spheres coated on the outside with polar hydrophilic (water loving) groups, encasing a lipophilic (fat loving) pocket that can surround the grease particles, causing them to disperse in water. The lipophilic portion is made up of the long hydrocarbon chain from the fatty acid. In other words, where oil and water normally do not mix, the addition of soap allows oils to disperse in water and be rinsed away. Synthetic detergents operate almost similar to soap.

The ingredients of soap is mostly alkaline and helps in making the grease stains easier to be removed and to prevent any unwanted smells from the grease and oil stains. Below is a table of ingredients and its properties.

Ingredient	Primary Functions	Typical Examples
Abrasives	Supply smoothing, scrubbing and/or polishing action	Calcite Feldspar Quartz Sand
Acids	Neutralize or adjust alkalinity of other ingredients	Acetic acid Citric acid Hydrochloric acid Phosphoric acid Sulphuric acid
Alkalis	Neutralize or adjust acidity of other ingredients Make surfactants and builders more efficient Increase alkalinity	Ammonium hydroxide Ethanolamines Sodium carbonate Sodium hydroxide Sodium silicate
Antimicrobial agents	Kill or inhibit growth of microorganisms that cause diseases and/or odour	Pine oil Quaternary ammonium compounds Sodium hypochlorite Triclocarban Triclosan
Antiredeposition agents	Prevent soil from resettling after removal during washing	Carboxymethyl cellulose Polycarbonates Polyethylene glycol Sodium silicate
Chlorine bleach	Also disinfects	Sodium hypochlorite
colourants	Provide special identity to product Provide bluing action	Pigments or dyes
Corrosion inhibitors	Protect metal machine parts and finishes, china patterns and metal utensils	Sodium silicate
Enzymes	Proteins classified by the type of soil they break down to simpler forms for removal by detergent Cellulase reduces pilling and greying of fabrics containing cotton and helps remove particulate soils.	Amylase (starch soils) Lipase (fatty and oily soils) Protease (protein soils) Cellulase
Fabric softening agents	Impart softness and control static electricity in fabrics	Quaternary ammonium compounds
Fluorescent whitening agents	Attach to fabrics to create a whitening or brightening effect when exposed to daylight Also called optical brighteners.	Colourless fluorescing compounds
Fragrances	Mask base odour of ingredients and package Cover odours of soil Provide special identity to product Provide pleasant odour to clothes and rooms	Fragrance blends
Hydrotropes	Prevent liquid products from separating into layers Ensure product homogeneity	Cumene sulphonates Ethyl alcohol Toluene sulphonates Xylene sulphonates
Opacifiers	Reduce transparency or make product opaque Provide a special effect	Polymers Titanium dioxide
Preservatives	Protect against natural effects of product aging (for example, decay, discolouration, oxidation and bacterial attack)	Butylated hydroxytoluene Ethylene diamine tetraacetic acid Glutaraldehyde
Solvents	Prevent separation or deterioration of ingredients in liquid products Dissolve organic soils Clean without leaving residue Solvents used in cleaning products are water soluble	Ethanol Isopropanol Propylene glycol