Fats and oils + NaOH ⇒ soap + glycerin
There is no water in the chemical reaction formula.
So you can use an extremely thick caustic soda solution.
The saturated concentration of caustic soda was 19 mol / liter
Seemingly,
You can solute by 100 grams of NaOH in 100 grams of water.
In terms of molar ratio,
It is saturated at about 1: 3 with NaOH: H 2 O,
We use 1: 5 molar ratio (1: 2 by weight ratio) for soap making.
Now,
When oil and fat and caustic soda aqueous solution are heated slightly and mixed, the reaction proceeds naturally.
Chemical reaction,
If the free energy is minus, proceed.
Free energy is Enthalpy (minus for exothermic reactions) - Absolute temperature * Entropy (plus if clutter increases)
In response to this relationship, reactions that increase exothermic reactions or disorder will progress naturally.
Here,
In the saponification reaction, the calorific value is small. It seems to be about 40 KJ / mol.
If the amount of fat or oil of about 500 grams is 1 mole,
Because it is 40 kJ, it is about 10 kilocalories.
It's heat enough to raise 1000 grams of water by 10 degrees.
Because it is not 1 kilogram of fats and oils and alkali, it is calculated to rise by 10 ℃ or more with fever.
However, it is easy to cool down when the surroundings are cold, insulation is said to be important.
Also the clutter has not changed so much.
that is
1) Nucleophilic attack of oil promoted to base by water is caused.
2) One of the double bonds between carbon and oxygen of the ester is broken.
3) It goes through a state where there are four bonds centered on carbon.
4) The oxygen of the ester and the glycerin moiety are eliminated and a double bond between oxygen is born again and a carboxylic acid is generated.
5) Hydrogen is transferred from carboxylic acid to glycerin moiety.
6) Carboxylic acid makes salt with sodium, glycerin is completed.
Here, since 1) to 4) are equilibrium reactions, increasing the temperature raises the reaction rate.
And 5) When the sodium salt of 6) is made, it is soap, it does not react nucleophilically,
Glycerin is a very weak acid, while carboxylic acid is an acid,
Only relatively strong acid carboxylates are preferentially made.
And since the soap never returns again, the reaction naturally proceeds irreversibly.
For reaction rate,
The process of increasing the contact area where the first water and oil mix,
Followed by saponification progress.
In particular, the reaction in the second half proceeds at such a rate that the half life is constant.
The reaction rate gradually declines as the concentration decreases.