In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: It was " serious " for almost 2 / 3 of the patients ( 62 . 5 % ) and its outcome favourable in most of the cases ( 82 % ) .
### Output Text:
It was " serious " for almost 2 / 3 of the patients ( 62 . 5 % ) and its outcome favourable in most of the cases ( 82 % ) . 