Which of the following chemicals are intercalating agents?

Intercalating agents are substances that can insert themselves between the bases of DNA. This interaction can disrupt normal DNA function and has implications in mutagenesis and cancer development. Quinacrine dihydrochloride is recognized as an intercalating agent due to its ability to fit between the DNA base pairs, causing structural changes in the double helix. This property is leveraged in some laboratory procedures, such as fluorescence microscopy, to highlight specific DNA sequences.

The other options do not possess this intercalating capability. Acetic acid is primarily involved in processes like protein precipitation and does not interact specifically with DNA in a manner consistent with intercalation. Formalin, often used as a fixative in tissue preservation, cross-links proteins and nucleic acids but does not intercalate between the DNA bases. Alcohol is commonly used in DNA extraction and purification but it does not interfere with the DNA structure in the way intercalating agents do. Thus, Quinacrine dihydrochloride stands out as the correct answer in this context.