CHEMICALS FOR CONSUMERS
SOAP & DETERGENT
Soap
~Soap = sodium salts (RCOO-Na+) / potassium salts (RCOO-K+) of long-chain fatty acids
~Alkalis react with fatty acids –> soap
~Fatty acids = animal fats or vegetable oils
~Soap preparation: hydrolysing fats or oils under alkaline condition
~Saponification – alkaline hydrolysis
~Saponification process – boiling fats / oils with concentrated sodium hydroxide solution or concentrated potassium hydroxide solution to produce glycerol + salts of fatty acids (soap)
~Saponification steps: 1. Hydrolysis of fats / oils –> glycerol + fatty acids. 2. Neutralisation of fatty acids + concentrated alkali –> soap + water
~Overall equation: Fats / oils + alkali –> glycerol + soap
~Sodium chloride – reduces the solubility of soap in water
Liquid soap | Solid soap |
Sodium hydroxide + saturated oils (coconut oil) | Potassium hydroxide + unsaturated oil (sunflower oil / olive oil) |
Uses: bathing purposes | Uses: shaving cream |
Detergent
~Detergent = sodium salt of sulphonic acid
~Alkalis react with sulphonic acid –> detergent
~Common detergent: sodium alkyl sulphate & sodium alkylbenzene sulphonate.
~Detergent preparation: 2 processes – 1. Sulphonation. 2. Neutralisation.
~Sulphonation: Petroleum fraction (long chain hydrocarbon compounds) converted into sulphonic acid with the present of concentration sulphuric acid. Water molecule is removed.
~Neutralisation: sulphonic acid neutralised with sodium hydroxide to form detergent (water molecule is formed).
~Other type of detergents: 1. Anionic detergent (dishwashing liquid detergent). 2. Cationic detergent (hair conditioner). 3. Non-ionic detergent (car washing detergent).
~Soap and detergent are surfactants. Surfactants are organic compounds that lower the surface tension of a liquid.
~Surfactants act as emulsifiers and foaming agents.
~Anion soap consists of carboxylate ion (hydrophilic = soluble in water) and long hydrocarbon tail (hydrophobic = soluble in grease /oils).
~Anion detergent consists of sulphate ion / sulphonate ion (hydrophilic = soluable in water) and long hydrocarbon tail (hydrophobic = soluble in grease / oils).
1.Soap or detergent is added to water.
2.This has lower the surface tension of water and increases the wetting ability of water.
3.Hydrophilic part of the anion dissolves in water.
4.Hydrophobic part dissolves in grease.
5.Scrubbing helps to pull the grease free and break the grease into small droplets.
6.These droplets do not coagulate and redeposit on the surface of the cloth. It is because therepulsion between negative charges on the surface.
7.The droplets are suspended in water forming an emulsion.
8.Foam produces to float the emulsion.
9.Rinsing helps to remove these droplets.
The effectiveness of the cleansing action of soap and detergent
Condition | Soap | Detergent |
Hard water (contain calcium & magnesium ion) | Form an insoluble precipitate = soap scum (formation of soap scum causes wastage of soap) | Detergent is effective cleaner. Form soluble substances = calcium or magnesium salts (do not form scum) |
Soft water (do not contain calcium & magnesium ion) | Soap is effective cleaner. | Detergent is effective cleaner. |
Acidic water (contain hydrogen ion) | Form insoluble long-chain fatty acids (reduces the amount of soap used for cleaning) | Detergent is effective cleaner. Form soluble substances (Do not form scum) |
Environment | Soap is biodegradable | Soap is non-biodegradable |
Additives in detergent
Additives | Function | Example |
Biological enzyme | Remove protein stains | Amylase, lipase & protease |
Foam control agent | Control foaming in detergent | Silicones |
Builder | Enhance the surfactant efficiency | Sodium phosphate |
Filler | Make the solid detergent dry and enable the liquid detergent to be poured easily | Sodium silicate |
Fragrance | Add fragrance | - |
Optical brightener | Add brightness by convert UV radiation to blue light and whiteness | Fluorescent dye |
Stabilising agent | Lower the production of foam | Silicones |
Suspension agent | Prevent the dirt particles removed from redepositing onto cleaned fabrics | Sodium carboxymethylcellulose |
Whitening agent | Bleach stains | Sodium hypochlorite |
Food Additives
~Food additive = a natural / synthetic substance that is added to food to
prevent spoilage
~extend food storage life
~improve food appearance
~improve food taste
~improve food texture
A. Preservatives
~Function:
slow down / prevent the growth of microorganisms / bacteria / fungi
extend food storage life
Example:
Preservatives | Functions | Example | Side effect |
Salt | Draws the water out of the cells of microorganisms. Retards the growth of microorganisms. | Salted vegetables | Increase the risk of cardiovascular diseases |
Sugar | Draws the water out of the cells of microorganisms. Retards the growth of microorganisms. | Fruit jam | Tooth decay, diabetes and obesity |
Vinegar | Inhibits the growth of microorganisms. | Pickled cucumber | |
Sodium nitrite / sodium nitrate | Slows down the growth of microorganisms. Stabilise red colour in meats. | Sausage | Carcinogenic |
Benzoic acid / sodium benzoate | Slows down the growth of microorganisms. | Tomato sauce | |
Sulphur dioxide | Slows down the growth of microorganisms. | Grape juice | Asthma and allergies |
Food Additives
B. Antioxidant
Function:
~prevent oxidation (causes rancid fats and brown fruits)
Examples:
Food Additives
C. Flavouring
Functions:
~improve the taste
~improve the smell
~restore taste loss due to food process
B. Antioxidant
Function:
~prevent oxidation (causes rancid fats and brown fruits)
Examples:
Antioxidant | Functions | Example | Side effect |
Vitamin E | Prevent oils from turns rancid | Palm oil & sunflower oil | No |
Vitamin C | Preserve the colour of fruit juice and the formation of nitrosamines | Fruit juice & cured meat | No |
Sodium citrate | Stop rancidity in fats | Ice-cream | - |
BHA (Butylated hydroxyanisole) BHT (Butylated hydroxytoluene) | Retard rancidity in fats, oils and oil-containing foods | Margarine & cereal | Carcinogenic |
Food Additives
C. Flavouring
Functions:
~improve the taste
~improve the smell
~restore taste loss due to food process
Examples:
Flavouring | Functions | Example | Side effect |
MSG (monosodium glutamate) | Bring out the flavor | Salad dressing & canned soup | Headache, thirsty, nausea & chest pain. |
Aspartame (non-sugar sweetener) | Sweeten food (about 180 – 200 times than sugar) | Soft drinks & diet drinks | Increase the risk of leukaemia, cancer and neurological problems |
Synthetic essences (esters) | Produce artificial flavours = natural flavour. Cheaper to use than the real fruits | Methyl butanoate (apple flavour) & octyl ethanoate (orange flavour) | - |
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