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 patient with nitrazepam overdose and two of those with chlormethiazole intoxication conformed to the criteria of ' alpha coma ' , showing non - reactive generalized or frontally predominant alpha activity in the EEG .
### Output Text:
The patient with <span class="chemical">nitrazepam</span> overdose and two of those with <span class="chemical">chlormethiazole</span> intoxication conformed to the criteria of ' alpha coma ' , showing non - reactive generalized or frontally predominant alpha activity in the EEG . 