Soaps, preparation, classification, use and mechanism

1. Dr. Surendran Parambadath
(M.Sc, M.Phil, M.Tech, Ph.D)
Asst. Prof in Chemistry
TM Jacob Memorial Govt. College
Manimalakunnu

3. SOAPS
Soaps (Surfactants) are the sodium or
potassium salts of higher fatty acids, like
stearic, palmitic and oleic acids.

4. For effective cleaning action of soaps, its fatty acid unit must contain 12 to 18
carbon atoms.
Fatty acid contains <12 carbon atom: Highly soluble in water
Fatty acid contains >22 carbon atom: Insoluble in water
Advantages of soap: Excellent cleansers in soft water, non-toxic, derived from
renewable sources and biodegradable.

5. Calcium or Magnesium Soap: Lubricant and driers
Lead Soap: Adhesives
Iron, Nickel and Zinc Soap: Water proofing leather and canvas
Aluminium and Chromium Soap: Sizing papers

6. Types of Soaps
1. Hard Soaps/Washing Soaps
The sodium salt of fatty acids prepared by the saponification of
cheap oils or fats with caustic soda, are known as hard soap.
This contain free alkali.
Usually contain sodium silicate and white clay as fillers
Cheap perfume

8. 2. Soft Soap or Toilet soap
The potassium salts of fatty acids prepared by the saponification
of the best quality oils and fats with calculated quantity of
caustic potash are called soft soaps.
They usually contain a number of additives such as dyes,
perfumes, creams, oils and a bactericide.
These soaps are more expensive, soft in consistency, produce a
soft lather and are more soluble.
They do not injure the skin because they contain no free alkali.
Soft soaps include toilet soaps ,liquid soaps ,shaving creams,
shaving sticks, shampoos etc.

9. Toilet soaps containing bactericidal ingredients (usually, carbolic
acid or its derivates) are called medicated soaps.
Medicated soaps or antibacterial soaps

10. Transparent Soap
Transparent soap is a clear soap with high glycerin (glycerol) content,
often referred to as glycerin soap.
Transparent soap is less drying than opaque soap and can have
additional emollient oils such as Shea butter or jojoba oil added to it.
It is basically partly soap and partly solvent.
Sodium hydroxide causes big crystals to form in soap and that is why
the soap becomes opaque.
In order to make it transparent, one has to dissolve the soap in enough
solvent to make the crystals so small that light will freely pass through
the soap which makes it look transparent.
The solvent used can be glycerol, alcohol or glycerol-alcohol mixture.

12. Baby Soap
Baby soaps are not much different from ordinary soaps, but they
are comparatively of high purity.
Baby’s skin is soft and sensitive. Hence the oil used for making baby
soap should be clean and bleached.
No pigments are allowed in baby soap, and fragrance materials added
should be bare minimum.
Free alkali content present in baby soap should not exceed 0.05
percent.
Ordinary soap may contain rosin and metallic impurities such as
nickel.

14. Liquid Soap
A liquid soap tends to be more effective than flake soap, and there is a
smaller chance of residue being left on clothing with liquid soap.

15. Preparation of Liquid Soap
Generally from coconut oil, caustic potash (24 %), borax, glycerin,
sugar and water.
The coconut oil is heated in a jacketed kettle at about 50 oC and then
agitated with potash Iye. Now borax, sugar and glycerin are added and
the mixture is stirred with a known quantity of water.
The mixture is filtered and perfumes as well as coloring matters are
added.

17. Total Fatty Matter (TFM) and grades of soap
• Soaps are graded in terms of total fatty matter or
TFM. Bureau of Indian standards(BIS) has
categorized bath or toilet soaps as ‘normal’, ‘baby’,
‘transparent’, and ‘antibacterial’ soaps.
• TFM or total fatty matter is a measure for identifying
the amount of fatty matter present in soaps.
• A known weight of the soap is dissolved in water and
the solution is treated with dilute sulphuric acid.
The soap decomposes to sodium sulphate and fatty
acids.
• The fatty acids so formed can be estimated.

19. Grade TFM Moisture Free salt (Nacl)
I Above 80 Max:13.5 Max:0.7
II 65-80 13-15 0.8
III 55-65 15-20 1.5

20. Bathing Bars
The bathing bar shall be a product containing acceptable surface
active agents which could be used for bathing purposes.
One or more of the following surfactants, confirming to the
relevant Indian standards, can be used:
Soap of fatty acids, fatty acid ester sulphonates, fatty
alkanolamide, fatty alcohol ethoxylates, sarcosinates, taurids, fatty
isothionates, aipha olefin sulphonates, alcohol sulphates and
amphoteric such as betaines.
In addition to surfactants and perfumes, the bathing bar may
contain other ingredients such as electrolytes, bar structuring
and processing aids, coloring matter, permitted antioxidants,
preservatives, permissible germicides, super fatting agents,
humectants and such additional substances that are declared on
the label.

23. Types Of Bathing Bars
There are two types of bathing bars:
(1) made up of partial soap and partial synthetic
detergent (syndet),
(2) made up of wholly synthetic detergent.
The first type is usually known as combination bars or
combars. These contain 50 percent TFM and 30-35
percent mineral matter like talc and kaolin.

24. Cleansing
or
Detergent action of Soap

28. https://www.youtube.com/watch?v=kG8dlCUd8oc