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 a further series of experiments , haloperidol ( 0 . 2 mg / kg i . p . ) was used in order to block the dopaminergic activation and to estimate the real degree of the tolerance to the rigidity without any dopaminergic interference .
### Output Text:
In a further series of experiments , <span class="chemical">haloperidol</span> ( 0 . 2 mg / kg i . p . ) was used in order to block the dopaminergic activation and to estimate the real degree of the tolerance to the rigidity without any dopaminergic interference . 