code: def dens_floc_init(ConcAluminum, ConcClay, coag, material):
      
      return (conc_floc(ConcAluminum, ConcClay, coag).magnitude
              / frac_vol_floc_initial(ConcAluminum, ConcClay, coag, material)
              )
docs: Return the density of the initial floc.
  
      Initial floc is made primarily of the primary colloid and nanoglobs.