Which chemical has been known to effectively develop print impressions on human skin?

Iodine is known to effectively develop latent prints on non-porous surfaces, including human skin. When iodine crystals are heated, they sublime and produce vapors that can adhere to the fatty and oily residues present in latent fingerprints. This process allows for the visualization of the prints, enabling forensic investigators to analyze and potentially identify individuals based on their unique fingerprint patterns.

In contrast, while ninhydrin is a well-known chemical for developing prints on porous surfaces like paper, it is less effective on skin. Calcium carbonate does not have applications in developing prints, and cyanoacrylate, although useful for non-porous surfaces, can be less effective for skin due to its specific chemical interactions. Therefore, iodine stands out as the appropriate choice for developing prints on human skin.