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: 6 h after the administration of amiloride , a reduction was observed in the lithium content of the renal medulla but not in the other organs studied .
### Output Text:
6 h after the administration of <span class="chemical">amiloride</span> , a reduction was observed in the <span class="chemical">lithium</span> content of the renal medulla but not in the other organs studied . 