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: Of the remainder , a relationship to clioquinol was considered probable in 42 and possible in 69 cases .
### Output Text:
Of the remainder , a relationship to <span class="chemical">clioquinol</span> was considered probable in 42 and possible in 69 cases . 