A Good Helper of Our Life ------ Detergent

  In everywhere no matter is supermarket, grocery store or even a house, you can always see the appearance of detergent. It's not an expensive thing but it is necessary for everyone in everyday life for daily use. However, is that anyone really know what is meant by detergent and how is it form in our life?

  In fact, a detergent is a sodium or potassium salt of alkyl sulphonic acid or alkylbenzene sulphonic acid. According to the Oxford Dictionary, a detergent is a water-soluble cleansing agent which combines with impurities and dirt to make them more soluble, and differs from soap in not forming a scum with the salts in hard water.
   
    Besides, detergents are usually made from synthetic resources such as petroleum fractions. They were developed during the Second World War in response to a shortage of animal fats and vegetable oils. The general formulae for two common detegents are shown below where R represents a long-chain hydrocarbon.

   A long-chain hydrocarbon obtained from petroleum fractions is converted into an organic acid through a series of steps during the preparation of detergents. The organic acid is then neutralised with sodium hydroxide solution to produce a neutral salt which is a detergent.

Preparation of sodium alkyl sulphate

Step 1: Reaction with concentrated sulphuric acid

         

A long-chain alcohol reacts with concentrated sulphuric acid to form alkyl hydrogen sulphate.

                                                                                                                                  

Step 2: Neutralisation with sodium hydroxide solution

The resulting acid is then converted to the sodium salt by a reaction with sodium hydroxide.

Cleaning action of detergent

       

    We all know that detergents are used to clean items by removing bacteria and dirt. However, not many people understand how exactly these cleaners work. Detergents work because they contain surfactants. A surfactant is any molecule that reduces water tension and bonds to dirt. Once the dirt and surfactants are bonded, the rinse water washes the surfactants away, taking dirt and grime with it. Synthetic surfactants bond to particles because they hold a charge. Depending on the surfactant used, when mixed with water it can take on a positive or negative charge. Most surfactants used in detergents become positively charged when mixed with water.

     Basically, detergents are more complex and able to clean better in hard water than soap because they do not produce soap scum. Detergents are usually synthetic compounds that originate from crude oil. To isolate and extract DNA, scientists treat plant or animal samples with a detergent. This breaks down cell membranes, allowing scientists to study the DNA.

    
      Detergents are used for cleaning because pure water can't remove oily, organic soiling. Surfactants lower the surface tension of water, essentially making it 'wetter' so that it is less likely to stick to itself and more likely to interact with oil and grease.

     
      Like soaps, detergents have hydrophobic or water-hating molecular chains and hydrophilic or water-loving components. The hydrophobic hydrocarbons are repelled by water, but are attracted to oil and grease. The hydrophilic end of the same molecule means that one end of the molecule will be attracted to water, while the other side is binding to oil.
    
      Swishing the soapy water around allows the detergent to pull the grime away from clothes or dishes and into the larger pool of rinse water. Rinsing washes the detergent and soil away. Warm or hot water melts fats and oils so that it is easier for the detergent to dissolve the soil and pull it away into the rinse water. Detergents are similar to soap, but they are less likely to form films (soap scum) and are not as affected by the presence of minerals in water (hard water).

   Detergents are cleansing agents that are effective in soft water as well as hardwater. This is because detergents do not form scum with Mg+ and Ca2+ ions foundin hard water. The detergents ions (R –O – SO3- and R – SO3- ) react with Mg+ and Ca2+ ions in hard water.
    
   However, the magnesium salts and calcium salts which are formed are soluble in water. Hence, the scum is not formed and the detergents are still activein hard water and lathers easily.Detergents are synthetic cleansing agents. This means that the structure of the hydrocarbon chain can be modified to produce detergents with specific properties.
  
    Nowadays, different types of detergents have been synthesised for specific uses such as shampoos and dish cleaner.Furthermore, detergents are also effective in acidic water because H+ ion is acidic water do not combined with detergents ions.

    Nowadays, the modern detergent in the market that used for washing clothes contain a few sorts of additives to increase their cleaning power and make them to attractive and saleable. 

a) Whitening agents
   Example: Sodium perborate.
   Function: Through the oxidation process to convert stains into colourless substances.

(b) Biological enzymes
   Examples: Amylases, proteases, cellulases and lipases.

   Function: To remove protein stains such as blood, milk and tomato sauce which are insoluble                               stains in water.

(c) Fillers and drying agents

   Examples: Sodium sulphate and sodium silicate.

   Function: To ensure that the detergent is always in a dry condition, to add to the bulk of the detergent and enable it to be poured easily.

(d) Fragrances
   Function: To make clothes fresh and clean and to add fragrance to both the detergent and fabrics.

(e) Builder
    Example: Sodium tripolyphosphate
    Function: To soften the hard water and increases the pH value of water so that muddy dirt can be removed.

(f) Suspension agents
    Example: Carboxymethylcellulose (CMC)
    Function: To prevent the dirt particles redepositing onto cleaned fabrics.

  

     In the nutshell, there are too many types of detergents in the world and we could not without detergents in our life because detergent is really a good helper in our life in anytime and any place to help us to solve many problems. Cherish what you have in your life and use it properly!