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: The mean BIS score corresponding to the first word recalled after the procedure was completed was 91 . 2 ( 95 % CI = 88 . 1 to 94 . 3 ) .
### Output Text:
The mean BIS score corresponding to the first word recalled after the procedure was completed was 91 . 2 ( 95 % CI = 88 . 1 to 94 . 3 ) . 