Solvent 1+sample                  Some of the sample              Sample become distributed
           +impurities                              moves to solvent                         between 1 and 2 
      Immiscible solvents are mixtures of liquids that are insoluble in each 
    other. Such solvents will form two layers; the upper layer is for the liquid 
    with  the  lower  density  and  the  lower  layer  is  for  the  liquid  with  the 
    higher density.
          The  process  of  extraction  with  immiscible  solvents  is  generally 
    employed  for  the  isolation  of  dissolved  compounds  from  solutions, 
    isolation of solid compounds from mixtures, or removal of undesirable 
    impurities  from  mixtures  (washing).  Some  times  it  is  used  in  organic 
    chemistry laboratories to remove an organic compound from a solution 
    when the use of distillation is not convenient.
    In many cases mixtures of organic compounds can be separated by 
    methods which depend on a difference in their chemical properties. 
    Frequently. one or more compounds of a mixture is transformed into a 
    salt for easy separation. Salts , in general , are water soluble and 
    insoluble in organic solvents.
    For example, for acidic compounds(HA):
      
    For bases (B):
     
    In this experiment , the mixture may be readily separated by virtue of 
    the fact that p-toluidine will react with HCl in water and 2-naphthol 
    will react with sodium hydroxide (NaOH) in water . Thus, if a 
    solution of a mixture of p-toluidine and 2-naphthol in ether is shaken 
    with aqueous HCl the amine will be removed into the aqueous layer 
    as its ammonium salt , whereas 2-naphthol and the impurities will 
    remain dissolved in the ether . 
   With only 2-naphthol and impurities left in the ether, the 2-naphthol then 
   can  be  extracted  as  its  sodium  salt  by  extracting  the  ether  layer  with 
   aqueous NaOH.
   After separation of the aqueous and ether layer , the p-toluidine can be 
   regenerated by basification with aqueous NaOH , while 2-naphthol can be 
   regenerated from its sodium salt by acidification with dilute acid.
   Note:
   When  performing  these  exactions,  you  will  have  two  heterogeneous 
   layers;  an  organic and an aqueous layer. As a general rule, the organic 
   layer will be the top layer, except for organic solvent with heavy halide 
   groups attached (i.e.  CH2Cl2 , CH3CCl3) will be on the bottom layer 
   since they are denser that water.