I edited this question because the OP originally had Al2O3, with no numbers subscripted, instead of Al2O3.
When I reformatted the chemical using
The correct formatting appeared in the body of the text but not the title. The title displayed
Al<sub>2</sub>O<sub>3</sub>, not Al2O3.
To get the chemical displayed in the title with the numbers subscripted I had to use conventional MathJax formatting,
Does anyone know why using the
<sub> </sub> pair will not work in titles?