User:Enix150/ReagentTables/Marquis

Various colours that represent the whole of the visible spectrum are given by a large number of compounds. Structures that tend to maintain the response to the reagent at the violet end of the spectrum are, in decreasing order of efficacy: ring sulfur (with or without aromatic ring); ring oxygen (with aromatic ring); extra-ring oxygen or sulfur (with aromatic ring); aromatic compounds that consist entirely of C, H, N. Thus, there is a tendency for the response to the Marquis reagent to move gradually towards longer wavelength (i.e. through green to orange and red) as the ratio of C, H, N to the other groups in the molecule rises.

Recipes:
 * 10 mL 37% formaldehyde in 90 mL H2SO4 (conc.)
 * 2 mL 37% formaldehyde in 75 mL H2SO4 (conc.)
 * 1 mL 40% formaldehyde in 100 mL of concentrated sulfuric acid
 * 0.2 - 1.0 mL 37% formaldehyde in 10 mL concentrated sulfuric acid