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: CONCLUSIONS : Urine volume can be reduced by giving lithium once daily and / or by lowering the total daily dose .
### Output Text:
CONCLUSIONS : Urine volume can be reduced by giving <span class="chemical">lithium</span> once daily and / or by lowering the total daily dose . 