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: Thermal enhancement ratios estimated for " acute " hematological changes were 1 . 3 , whereas those estimated for " late " damage ( based on morphological cardiac and renal lesions ) varied between 2 . 4 and 4 . 3 .
### Output Text:
Thermal enhancement ratios estimated for " acute " hematological changes were 1 . 3 , whereas those estimated for " late " damage ( based on morphological cardiac and renal lesions ) varied between 2 . 4 and 4 . 3 . 