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: Part B , for eight different rats in each group blood - brain barrier permeability was evaluated by measuring the amount and extent of extravasation of Evans Blue dye .
### Output Text:
Part B , for eight different rats in each group blood - brain barrier permeability was evaluated by measuring the amount and extent of extravasation of Evans Blue dye . 