The relation for the free energy of micellization in      case of ionic a well    a nonionic  safectants has     been updated by including    the  effect of ionic strength and  the size  of the  ions  used.  For   the verification of  the  final  relation and  to  compare  the results  one  gets through  differed     techniques   like    viscometry,   light    absorption\transmission,      surface   tension   and  conductance  have   been  employed   to  determine   critical  micelles   concentration (CMC)   of  sodium dodeoyl sulphate   and  sodium tetradeoyl adphde    safactanta   It is  found  that when the electrolyte   concentration is  very  low  the  viscometry does not give   reliable   results  where   a light     absorption/transmission    does.    The   surface    tension   measurement   and   conductance  measurement  give   reliable   and   reproducible    results  at   any   electrolyte concentration     and temperature.   A new   way  of interpretation of conductivity data has also been proposed, through  which  one  can  get  better remits  even  in  the presence  of high   ionic strength. The  results no  obtained  show   the   decrease  in  CMC    with  the   increase  in   electrolytes   concentration andapproaches   to a  constant value.   This decrease  is in the order of Na+>K+> Li+     . This trend isexplained    in  terms  of change   in  shape  of   the micelles,  specific    absorption of electrolytes, variation in  double   layer thickness  and hence variation in  the free  energy  of the  system and hydrodynamic    radius  of   the  ions  used.  It  is  also   found  that the  CMC   decreases    with  the  increase  in   temperature  of  the  system,    which  is   explained  in  terms   of  solubility   of  thesurfactants, change in shape of the micelles    and free  energy of the system with the temperature.  Further these variation are in accordance with the equation derived by us.