### 18.11.6. Error Checks

The following error checking is performed for user state point functions:

- Validation of input and output thermodynamic properties.

- Check if output property can be computed from specified input data.

- For fluid mixtures, the following additional checks are performed:

  - Check if fluid is a mixture.

  - Check if specified components are valid mixture components.

  - Check if all mixture components have been specified.

  - Check if specified mass fractions sum up to unity. Mass fractions are assumed to be in the range between 0 and 1 and no clipping is performed if this is not the case. The user specified mass fractions are renormalized in case they do not sum up to unity with a tolerance of 2%.

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