===================================================================================
Pressure of vapor-saturation
===================================================================================

The dissolved volatile content of a melt in equilibrium with a vapor can be used as a barometer because the sum of the partial pressures of all the vapor species must equal the total pressure (e.g., Anderson et al., 1989; Blundy & Cashman, 2009).
This is the pressure of vapor saturation (P\ :sup:`v` :sub:`sat`) barometer and is often applied to melt inclusions to calculate magma storage depths (e.g., Black and Andrews, 2020; Camejo-Harry et al., 2019, 2018; Colman et al., 2015; Wanless et al., 2015; Wieser et al., 2021) and sub-aqueous matrix glasses to calculate eruption depths (e.g., Belgrano et al., 2021; Coombs et al., 2006; Lund et al., 2018; Seaman et al., 2004).

VolFe calculates P\ :sup:`v` :sub:`sat`, the melt speciation, and the vapor composition for a melt of given temperature and melt composition (including volatiles and f\ :sub:`O2`).

This calculation was outlined in detail `Hughes et al. (2024) <https://doi.org/10.2138/am-2022-8739>`_ (schematic of the calculation shown in the figure below; `Hughes et al., 2025 <https://doi.org/10.30909/vol/imvc1781>`_).

.. figure:: figures/pvsatcalc.png

In these examples we will show you how to run this calculation for:

- :doc:`Example 1a <Examples/1a. pvsat 1MI_df>`: One analysis entered as a DataFrame using default options.

- :doc:`Example 1b <Examples/1b. pvsat csv>`: Multiple analyses in a csv file using default options.

- :doc:`Example 1c <Examples/1c. pvsat user_opt>`: Multiple analyses in a csv file using user-specified options.

- :doc:`Example 1d <Examples/1d. pvsat X>`: Changing the identity of the volatile species "X".

- :doc:`Example 1e <Examples/1e. pvsat error>`: Including uncertainties on inputs into the calculation outputs.