MNc Method Validation

Spread measures agreement among the selected ternary systems. In Example 1, the reference distribution and this calculator's independently optimized distribution both give small spreads, yet their system methane numbers cluster around 74.95 and 74.82, respectively. A small spread therefore does not determine a unique MN′.

Worked examples

Using the reference component distributions in Tables A.5, A.6 and A.8 of ISO 17507-1:2025, this app closely reproduces the intermediate methane numbers. Each example first compares methane numbers calculated from those distributions with the reference values, then compares the final results when the app determines its own distribution through optimization.

Calculator MN means the methane number calculated by this app. In the first table for each example, the app evaluates the within-system volume percentages given in the reference tables using its implementation of the standard’s polynomials, without optimizing the distribution. Those percentages have limited precision. Difference is Calculator MN minus the reference MN.

Select “Use in calculator” to open the example’s gas composition in this app’s calculator. The app finds its own distribution between systems, so the final methane number may differ from the reference value.

After calculating, open “System details” to see each system’s component amounts and methane number. You can also check that the component amounts add up to the original mixture.

Calculating worked examples...

Annex A.10 comparison

This table compares this app's MNc methane numbers with Table A.10, "Additional numerical examples for software validation purposes", from ISO 17507-1:2025.

Each mixture can be expanded with the eye icon to show its composition in volume percent, or loaded into the calculator with the calculator icon.

Calculating Annex A.10 examples...

  1. Reference MNc value from Annex A.10.
  2. This app's MNc minus the reference value.
  3. The spread among the methane numbers of the ternary systems used in the calculator's final result.
  4. Ternary systems used in the final calculated result.
  5. Systems removed from the final weighted result because their contribution fell below the minimum threshold.

Mixture 14 shows a particularly large difference from the reference methane number, and some other mixtures also differ noticeably. The ternary systems selected by this calculator nevertheless agree closely in these mixtures. A small spread between systems therefore does not ensure the same final MNc as the reference. Annex A.10 does not provide the reference system distributions or spreads, so its final values alone do not show how those results were obtained.