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 fact the concentration of free DPH was normal , the patient presented a retarded morbilliform rash during DPH treatment , the protidogram was normal , and an intradermic DPH injection had no local effect .
### Output Text:
In fact the concentration of free <span class="chemical">DPH</span> was normal , the patient presented a retarded morbilliform rash during <span class="chemical">DPH</span> treatment , the protidogram was normal , and an intradermic <span class="chemical">DPH</span> injection had no local effect . 