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: Auditory deterioration and improvement , demonstrated serially in individual patients receiving and not receiving deferoxamine , respectively , provided convincing evidence for a cause - and - effect relation between deferoxamine administration and ototoxicity .
### Output Text:
Auditory deterioration and improvement , demonstrated serially in individual patients receiving and not receiving <span class="chemical">deferoxamine</span> , respectively , provided convincing evidence for a cause - and - effect relation between <span class="chemical">deferoxamine</span> administration and ototoxicity . 