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: After angiography by the venous route in patient n degree 1 a biphasic reaction with an immediate reaction ( dyspnea , loss of consciousness ) and delayed macro - papular rash appeared , whilst patient n degree 2 developed a generalised sensation of heat , persistent pain at the site of injection immediately and a generalised macro - papular reaction after 24 hours .
### Output Text:
After angiography by the venous route in patient n degree 1 a biphasic reaction with an immediate reaction ( dyspnea , loss of consciousness ) and delayed macro - papular rash appeared , whilst patient n degree 2 developed a generalised sensation of heat , persistent pain at the site of injection immediately and a generalised macro - papular reaction after 24 hours . 