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: Patients who did not receive mannitol were more likely to develop nephrotoxicity : odds ratio [ OR ] = 2 . 646 ( 95 % CI = 1 . 008 , 6 . 944 ; P = 0 . 048 ) .
### Output Text:
Patients who did not receive <span class="chemical">mannitol</span> were more likely to develop nephrotoxicity : odds ratio [ OR ] = 2 . 646 ( 95 % CI = 1 . 008 , 6 . 944 ; P = 0 . 048 ) . 