I simply want to calculate the bulk modulus of water at 50C and increasing pressures. I think I am correctly calculating the new specific volume from the original conditions at 25C and 1atm to 50C and higher pressures.  I am rightly getting a decrease in specific volume with increasing pressure at constant temperature (Column5). Here is the spreadsheet:![enter image description here][1]

  [1]: https://i.sstatic.net/JU2iU.jpg

I derived Column 7 from the slope of the line in the chart below the spreadsheet. When I multiply the slope(Column 7) by the -1/V (v is Column 5) I get the new water compressibility  (Column 8) and converting to Bulk Modulus (Column 9).  Oops, bulk modulus should be increasing with pressure at a constant temperature, not decreasing.  Where did I go wrong?