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:

History of scorpion antivenom: One Arizonan's view. This paper was originally presented as the Elsevier Lecture in July, 2012 at the International Society on Toxinology/Venom Week combined meeting in Honolulu, Hawaii. In it, the author addresses the ancient history of venom and immunity, from the Silurian Era to the 1890s; the development of the first antivenoms; the impact of shifting political and economic pressures; the special case of Arizona; the relative stability of the 1960s through 1990s; the transition to regulatory compliance that took place at the time of the author's own research; and concluding thoughts regarding the instability of apparent success.
{"Chemical": []}