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: Clinical trials of aminoglycosides in seriously ill patients indicate that the relative risk for developing acute renal failure during therapy ranges from 8 to 10 and that the attributable risk is 70 % to 80 % .
### Output Text:
Clinical trials of <span class="chemical">aminoglycosides</span> in seriously ill patients indicate that the relative risk for developing acute renal failure during therapy ranges from 8 to 10 and that the attributable risk is 70 % to 80 % . 