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: The data indicate that audiovisual toxicity is not an infrequent complication in hemodialyzed patients receiving desferrioxamine .
### Output Text:
The data indicate that audiovisual toxicity is not an infrequent complication in hemodialyzed patients receiving <span class="chemical">desferrioxamine</span> . 