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: It was characterized by the onset of fever , diarrhea , shock , pulmonary edema , acute renal failure , metabolic acidosis , weight gain and leukocytosis .
### Output Text:
It was characterized by the onset of fever , diarrhea , shock , pulmonary edema , acute renal failure , metabolic acidosis , weight gain and leukocytosis . 