A: Converting from Ca_pct to CaO_pct:

1. Make sure that Ca_pct is aliased in the Data>Column Properties dialog

2. Select Calculation>New Geochem Calculation

3. In the Input Columns drop-down list see how CaO_pct is bolded as well as Ca_pct. Even if you only have Ca_pct in your dataset all of the bolded elements are ones that ioGAS can automatically convert between as it knows your input element/units column. So, from the Input Columns list choose CaO_pct

5. If you don’t want to use the CaO_pct column in another expression remove the Output Columns line using the MINUS button on the right hand side

6. Check the Make Input Columns box

7. Click Calculate All and the CaO_pct column should be added to your dataset.