Caustic soda

The soda that we use...

Technical data sheet:

Sodium hydroxide (NAOH)
INCI name:
sodium hydroxide
CAS
number
: 1310-73-2
appearance: solid microbeads purity >= 99%Origin
: BelgiumSupplier
: France

Composition & description

Caustic soda is also known as Sodium Hydroxide or Sodium Hydrate. Its primary form is solid and crystalline but it is also marketed in liquid form (diluted with water). Sodium hydroxide is a highly corrosive basic substance (metal, skin) and must be handled with care. Its handling is forbidden to people under 18 years old in professional environment.

Properties

Cleaner, reagent, pH adjusterWe
use soda as a reagent in the cold saponification process.
Saponification is a chemical reaction that occurs when a base (soda for a solid soap and potash for a soft or liquid soap) is combined with a fatty substance (oils, butters, etc.).
Fats are made up of a composition of fatty acids and glycerols. The chemical reaction corresponds to the hydrolysis of an ester in a basic medium which leads to the formation of an alcohol and a carboxylate ion.

Put more simply and keeping in mind that nothing is lost but everything is transformed...

the chemical reaction fat + soda transforms fats into soap + glycerin.
Saponification is a total and exothermic chemical reaction which means that it produces heat and that it continues until one of the reactants is totally exhausted. This last point is important because by over-greasing, i.e. by putting a volume of fat greater than that necessary to carry out the reaction, we ensure that no residual traces of soda remain in the soap. The soap will be all the milder for it.

Note that all cold process soaps use either soda (solid soaps) or potash (liquid soaps). If sodium hydroxide does not appear in the list of regulatory ingredients (INCI list for International Nomenclature of Cosmetic Ingredients), it is because the manufacturer has chosen not to indicate the list of ingredients used but the composition of the soap after saponification. For example, for coconut oil you will not find "cocos nucifera oil" but "Sodium Cocoate" (saponified coconut oil) and in doing so, you will not have any mention of "sodium hydroxide" since it will have been consumed by the saponification.