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: CONCLUSION : In this preliminary report , divalproex sodium was a superior alternative to lithium in bipolar patients experiencing cognitive deficits , loss of creativity , and functional impairments .
### Output Text:
CONCLUSION : In this preliminary report , <span class="chemical">divalproex sodium</span> was a superior alternative to <span class="chemical">lithium</span> in bipolar patients experiencing cognitive deficits , loss of creativity , and functional impairments . 