Dead organs are generally stored in formalin. Formalin is

Formalin is the common name for an aqueous solution of formaldehyde gas [2]. In its purest form, formaldehyde is a colorless, pungent gas, but it is most frequently utilized in laboratories and medical settings as a liquid solution. A standard commercial formalin solution typically contains approximately 37% to 40% formaldehyde by weight in water [2]. It is widely used for the preservation of biological specimens, dead organs, and tissues because it acts as a fixative, cross-linking proteins to maintain cellular structure and prevent decay. To prevent the polymerization of formaldehyde into paraformaldehyde, stabilizers like methanol (usually 10-15%) are often added to the solution [3]. While it can naturally oxidize into formic acid over time, the primary constituent that defines formalin is aqueous formaldehyde.

Sources

1. [1] https://wwwn.cdc.gov/Tsp/MMG/MMGDetails.aspx?mmgid=216&toxid=39
2. [2] https://www.sciencedirect.com/topics/medicine-and-dentistry/formaldehyde
3. [3] https://www.ncbi.nlm.nih.gov/books/NBK493462/