What is Saponification Number ? Discuss the Factors that Affects the Saponification Number.
The term saponification comes from the Latin word sapo meaning soap. Saponification is a chemical process of producing soap by hydrolyzing fats or oils with an alkali.
The saponification number or saponification value is defined as the amount of potassium hydroxide in milligrams required to completely saponify one gram of fat or oil. Saponification value is a measure of the average molecular weight of fatty acids present in a fat or oil. Higher saponification number indicates a higher proportion of shorter-chain fatty acids, while a lower number suggests longer-chain fatty acids.
For example, one mole of glycerol tripalmitate (molecular weight = 807) requires 168,000 mg of KOH for saponification. Therefore, one gram of fat will require 168000/807 mg of KOH. Hence the saponification number of glycerol tripalmitate is 208.
Saponification Value Formula
where,
Blank = The volume of HCl solution for the blank run
Sample = Volume of HCl the sample to test
Molarity = Molarity of HCl solution
56.1 = Molecular weight of KOH
Weight = Weight of the sample.
Saponification Number Calculator
| Saponification Number of Common oils and Fats | |
|---|---|
| Oil / Fat | Saponification Value |
| Beeswax | 60-102 |
| Canola oil | 182-193 |
| Canola oil | 182-193 |
| Cocoa butter | 192-200 |
| Coconut oil | 248-265 |
| Fish oil | 179-200 |
| Lard | 192-203 |
| Olive oil | 184-196 |
| Shea butter | 170-190 |
| Soybean oil | 187-195 |
| Sunflower oil | 189-195 |
Factors Affecting Saponification Number
There are number of factors that can affects the saponification number. Some of them are discussed below-
Composition of Fatty Acid
The types and chain lengths of fatty acids present in the oil significantly affect the saponification number. Oils with shorter-chain fatty acids (e.g., coconut oil) have higher saponification values because they require more alkali to saponify a given weight of fat compared to oils with longer-chain fatty acids (e.g., olive oil).
Presence of Unsaponifiable Matter
Oils that contain high levels of unsaponifiable substances such as sterols, tocopherols, lipopigments, and hydrocarbons can lower the effective saponification number, as these components do not react with alkali during saponification.
Unsaponifiable substances are a component of fats and oils that doesn't form soap when treated with alkali. It is made up of substances like sterols, tocopherols, lipopigments, and hydrocarbons. Unsaponifiable substances are insoluble in water but soluble in organic solvents.
Free Fatty Acids
The presence of free fatty acids in the oil can also affect the saponification number. Higher concentrated oils of free fatty acids require less alkali for saponification, leading to a lower overall saponification value.
Molecular Weight of Triglycerides
The average molecular weight of triglycerides in the oil is inversely related to the saponification number. Lower the molecular weight of triglycerides, higher the saponification numbers.
Conditions of Reaction
Factors such as temperature, reaction time, and the concentration of the alkali used can also affect the efficiency and extent of the saponification reaction, thereby affecting the measured saponification number.
