What solvent is used in Ninhydrin preparation to prevent ink runnage on paper?

The use of Freon 113 in the preparation of Ninhydrin is specifically advantageous for its property of preventing ink runnage on paper. This is crucial because when developing latent prints on documents that may contain written or printed text, the solvent chosen must minimize the risk of the ink being dissolved or smudged, which could obscure critical information or the latent prints themselves.

Freon 113 has a lower affinity for water and does not readily interact with the ink, allowing for the successful visualization of fingerprints without compromising the integrity of the written content on the paper. Its volatility further aids in quickly evaporating the solvent after application, which also helps maintain the clarity of both the latent prints and any existing ink on the paper.

In contrast, the other solvents listed have varying degrees of interaction with inks; some may lead to bleeding or runnage, which would interfere with the examination and analysis of latent fingerprints. Therefore, Freon 113 is specifically chosen for its effectiveness in preserving the quality of the paper while allowing for the development of latent prints using Ninhydrin.