Lets you change chemical plants to a flipped version that has the input pipes swapped. This means that for any recipe with two fluid inputs, you get to decide which fluid goes in which input pipe!
To flip a chemical plant's inputs, place it down and use CTRL+R on it (keys configurable in the controls menu).
To flip the outputs, it's the same deal except the default command is CTRL+O instead.
If you are using Bob's or Angel's mods, this mod will allow you to flip almost all chemistry/refining buildings that have multiple fluid inputs and/or outputs. If you are not using either of those mods, it just lets you flip the normal chemical plant.