Hello Tomasz,
Could you please provide a hint why parsing formulas failed? The message
"Failed to parse: 3 H_2O + 2Fe{} \rarrow Fe_2O_3 + 3 H_2"
isn't very helpful. Better might be:
"Failed to parse: 3 H_2O + 2Fe{} \rarrow Fe_2O_3 + 3 H_2"
^^^^^^^ unknown object
Or perhaps highlight the failed token in red.
Best regards,
JeLuF