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: PURPOSE : We evaluated the safety of indocyanine green for use in fundus angiography .
### Output Text:
PURPOSE : We evaluated the safety of <span class="chemical">indocyanine green</span> for use in fundus angiography . 