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: Wilson ' s disease is an autosomal recessive disorder of hepatic copper metabolism with consequent copper accumulation and toxicity in many tissues and consequent hepatic , neurologic and psychiatric disorders .
### Output Text:
Wilson ' s disease is an autosomal recessive disorder of hepatic <span class="chemical">copper</span> metabolism with consequent <span class="chemical">copper</span> accumulation and toxicity in many tissues and consequent hepatic , neurologic and psychiatric disorders . 