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: The fourth patient who was unconscious after chlormethiazole administration exhibite generalized non - reactive activity in the slow beta range .
### Output Text:
The fourth patient who was unconscious after <span class="chemical">chlormethiazole</span> administration exhibite generalized non - reactive activity in the slow beta range . 