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The development of synthetic detergents is a significant accomplishment in the field of cleansing.
These soaps have the same desirable properties as regular soaps and can be used in hard water and acidic solutions.
In contrast to soap, which is a salt of carboxylic acids, these are salts of sulphonic acids or alkyl hydrogen sulphates.
The detergents do not precipitate with the \(Ca^{2+}\) and \(Mg^{2+}\) ions found in hard water. As a result, detergents have a better cleaning action than soaps.
Preparation of detergents:
Detergents are made by combining sulphuric acid with a processed hydrocarbon derived from petroleum.
This chemical reaction produces molecules that are similar to the fatty acids found in soap.
The mixture is then treated with an alkali to produce the ‘surfactant molecules’, which do not bind with the minerals in the hard water, preventing the formation of their precipitates.
Aside from a 'surfactant,' modern detergent contains a number of other ingredients. The following list contains a few of them:
  • Sodium silicate, which protects the washing machine from corrosion and ensures that the detergent does not damage it.
  • Fluorescent is a whitening agent that gives clothes a glimmer or shine.
  • Certain stains on cloth can be removed using oxygen bleaches such as 'sodium perborate'.
  • Sodium sulphate is added to stop the detergent powder from caking,
  • Enzymes are used to disintegrate some stains caused by biological substances such as blood and vegetable juice.
  • Certain chemicals that emit a pleasant odour are also added to make the clothes smell nice after being washed with detergent.
Advantages of detergents over soaps:
  • Detergents are superior to soaps because they can be used in both hard and soft water and clean more effectively in hard water.
  • They can also be used in saline and acidic water.
  • They do not leave soap scum in the tub or on the clothes.
  • Detergents dissolve easily, even in cold water, and rinse easily in hard water.
  • They can be used to wash woollen garments, whereas soap cannot.
  • Detergents have a biodegradable linear hydrocarbon chain.
  • They are active emulsifiers of motor grease.
  • Detergents are effective and safe cleaning agents that keep synthetic fabrics bright and white.
Biodegradable and Non-biodegradable detergents:
a) Biodegradable detergents: They have straight hydrocarbon chains that bacteria can easily degrade.
b) Non-biodegradable detergents: They have highly branched hydrocarbon chains that bacteria cannot degrade.
Disadvantages of Detergents:
  • Some detergents with branched hydrocarbon chains are not completely biodegradable by water-based microorganisms. As a result, they pollute the water.
  • Detergents are more expensive than soap.
The cleansing action is similar to what takes place in soap.