subroutine heden(val,eval)

      implicit none

      integer i,n
      parameter(n=34)
      double precision temp(n), den(n)
      double precision val,eval,slop,y_int

      data temp/ 0.2, 0.3, 0.4, 0.5, 0.6,
     &           0.7, 0.8, 0.9, 1.0, 1.1,
     &           1.2, 1.3, 1.4, 1.5, 1.6,
     &           1.7, 1.8, 1.9, 2.0, 2.1,
     &           2.2, 2.3, 2.4, 2.5, 2.6,
     &           2.8, 3.0, 3.2, 3.4, 3.6,
     &           3.8, 4.0, 4.2, 4.4/  ! (K)
      data den/ 0.1450, 0.1450, 0.1450, 0.1450, 0.1450,
     &          0.1450, 0.1450, 0.1450, 0.1450, 0.1450,
     &          0.1450, 0.1450, 0.1450, 0.1451, 0.1451,
     &          0.1452, 0.1453, 0.1454, 0.1456, 0.1458,
     &          0.1460, 0.1457, 0.1453, 0.1448, 0.1442,
     &          0.1429, 0.1412, 0.1392, 0.1369, 0.1343,
     &          0.1315, 0.1284, 0.1251, 0.1216/ ! (gm/cm^3)
*
      do i=1,n-1
         if(val.lt.temp(1).or.val.gt.temp(n)) then
            write(*,*) val,temp(1),temp(n)
            write(*,*) 'The value is out of range ... heden code'
c            stop
         elseif(val.eq.temp(i)) then
            eval = den(i)
         elseif(val.eq.temp(i+1)) then
            eval = den(i+1)
         elseif(val.gt.temp(i).and.val.lt.temp(i+1)) then
            slop = (den(i+1)-den(i))/(temp(i+1)-temp(i))
            y_int = den(i) - slop*temp(i)
            eval = slop*val+y_int
         else
            continue
         endif
      enddo

      return
      end