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: In addition , nonimmunologic binding of normal and patient ' s serum proteins to her own and cephalothin - coated normal red cells was demonstrated .
### Output Text:
In addition , nonimmunologic binding of normal and patient ' s serum proteins to her own and <span class="chemical">cephalothin</span> - coated normal red cells was demonstrated . 