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: CONCLUSIONS : Based on the results , S - 53482 and S - 23121 were teratogenic when administered dermally to pregnant rats as were the compounds administered orally .
### Output Text:
CONCLUSIONS : Based on the results , <span class="chemical">S - 53482</span> and <span class="chemical">S - 23121</span> were teratogenic when administered dermally to pregnant rats as were the compounds administered orally . 