CHEMICAL PROPERTIES OF THE SOIL

Soil colloids and Ion Exchange.

    Soil colloids are complex constituent of the soil which determine the physical and chemical properties of the soil.                                                            

           These soil  colloids are made of small particles of humus and clay in the soil. Soil particles less than 0.001mm officialy defined as colloids. 

              The smallest size of soil colloids provide large surface area for chemical reaction to take place. Clay and humus are therefore called colloids. Clay colloids also called mineral colloids while humus colloids called organic colloids.                                                              

                                                  CHEMICAL PROPERTIES OF COLLOIDS

1) Soil colloids are negatively charged, As a negatively charged particles attract postively (cations) charged particles arround it.

                                                                 

     

2) They exhibit ion exchange.

  Ion exchange is a reversible process where by cations or anions are exchanged between solid and solid or between solid and liquid. 

           Colloids (negatively) charged particles hold exchangeable postively particles (cations) which are exchanged with cations which are nearby.  The cations absorbed onto colloids are displaced by ctions from the soil solution.  
                                                                         

       This systme of displacement called ION EXCHANGE.   And cations which are exchanged are called exchangeable cations.