Hello, in chemical equations one sometimes want to write that a substance goes away into the air. Commonly an uprising arrow after the molecule is used to indicate that. With the mhchem package you have to use the ^ for this purpose. But in the math-mode in LyX this is used to upraise a character. Nevertheless the arrow is made as long as the upraising box exists. Unfortunately this box disappears if nothing is inside.
Here is the trick making LyX to do it right: Write \, into the upraising box. Karl