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: Rats treated with 500 ppm quinacrine hydrochloride in the diet all developed a high incidence of left atrial thrombosis .
### Output Text:
Rats treated with 500 ppm <span class="chemical">quinacrine hydrochloride</span> in the diet all developed a high incidence of left atrial thrombosis . 