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: Seventy percent of rats given 250 ppm quinacrine hydrochloride and 1 , 000 ppm sodium nitrite simultaneously in the diet had thrombosis of the atria of the heart , while untreated control rats in this laboratory did not have atrial thrombosis .
### Output Text:
Seventy percent of rats given 250 ppm <span class="chemical">quinacrine hydrochloride</span> and 1 , 000 ppm <span class="chemical">sodium nitrite</span> simultaneously in the diet had thrombosis of the atria of the heart , while untreated control rats in this laboratory did not have atrial thrombosis . 