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: In 80 cases insufficient information was available for adequate comment and in 29 a relationship to the administration of clioquinol could be excluded .
### Output Text:
In 80 cases insufficient information was available for adequate comment and in 29 a relationship to the administration of <span class="chemical">clioquinol</span> could be excluded . 