Despite the different stoichiometry in these mixtures which varies the concentration of the reagent, they all follow the same idea of adding HgO to distilled water and concentrated sulfuric acid. The Denigés' reagent is ultimately mercury(II) sulfate in an aqueous solution.
*5 grams of mercury(II) oxide (HgO) is dissolved in 40 mL of distilled water. The mixture is slowly stirred, while 20 mL of concentrated sulfuric acid is added. After adding another 40 mL of distilled water, the solution is stirred until the HgO is completely dissolved.
* The Denigés' reagent can also be prepared by dissolving  5 grams of HgO in 20 mL of concentrated sulfuric acid and 100 mL of distilled water.
*The Denigés' reagent can be modified by using nitric acid in place of sulfuric acid