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 purpose of this report is to describe two cases of a disulfiram - like syndrome following occupational exposure to hydrogen cyanamide .
### Output Text:
The purpose of this report is to describe two cases of a <span class="chemical">disulfiram</span> - like syndrome following occupational exposure to <span class="chemical">hydrogen cyanamide</span> . 