You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Innovation and originality in the strategies developed by bacteria to get access to iron. Pumping iron: Raymond's group has identified and described the molecular details of an ABC transporter. Together with a binding protein at the cell surface, it is able to extract an unstable form of ferricitrate.
{"Chemical": ["iron"]}