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: Radiological studies were mostly angiographies performed with both ionic and non - ionic contrast material , at an average dose of 245 ml .
### Output Text:
Radiological studies were mostly angiographies performed with both ionic and non - ionic contrast material , at an average dose of 245 ml . 