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: Ionizing radiation is capable of inducing the requisite CML - associated t ( 9 : 22 ) translocation ( Philadelphia chromosome ) in appropriate cells in vitro but , thus far , chemicals have not shown this capacity .
### Output Text:
Ionizing radiation is capable of inducing the requisite CML - associated t ( 9 : 22 ) translocation ( Philadelphia chromosome ) in appropriate cells in vitro but , thus far , chemicals have not shown this capacity . 