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:

Influence of cold pre-fermentation treatments on the major volatile compounds of three wine varieties. The volatile compounds of wines made from three grape varieties (Monastrell, Cabernet Sauvignon and Syrah) using three pre-fermentation techniques (grape freezing, dry-ice and cold maceration) and a control treatment were measured. The different winemaking practices, which are intended to increase the aromatic properties of wines, produced results that depended on the variety concerned. For example, freezing the Cabernet Sauvignon and Syrah grapes produced different results compared with the respective controls, whereas few changes were found on freezing the Monastrell wine. Differences were significant in the case of some volatile compounds. Linear discriminant analysis allowed some grouping of the varieties at sampling but not of the pre-fermentation techniques used.
{"Chemical": ["dry-ice"]}