anchor.diff:                  let f2  = "H2O" |> parseFormulaString 
                   let res = substract f1 f2 |> toString 
                   Expect.equal res "H0.00 O0.00" "Substraction of formulas failed"
  -
           ]
       
       open BioFSharp.Mass  
  
positive.code:                     Root   = Isotopes.Table.Na23.NatAbundance 
                      }
                  let Na' = createMono "Na" (Isotopes.Table.Na23,Isotopes.Table.Na23.NatAbundance) 
                  Expect.isTrue (Na=Na') (sprintf "%A <> %A, check parameter order 'create'" Na Na')
  
              testCase "test_createDiIsotopic" <| fun () ->
                  let H = { 
  
negative.code:                     RelAtomicMass = 1.007947
                      }
                  let H1' = create "H" 1 1 1.00782503207 0.999885 1.007947
                  Expect.equal H1 H1' "Record initialization via function differs from initialization via record expression. Check parameter order of 'create'" 
          ]
      
      open BioFSharp.Elements
  