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: This toxicity appeared in patients receiving the higher doses of desferrioxamine or coincided with the normalization of ferritin or aluminium serum levels .
### Output Text:
This toxicity appeared in patients receiving the higher doses of <span class="chemical">desferrioxamine</span> or coincided with the normalization of ferritin or <span class="chemical">aluminium</span> serum levels . 