For example, the C-Clarifying Serum contains 10 percent prescription strength vitamin C and four percent prescription strength hydroquinone to promote a brighter, more even skin tone.
If you want to hasten the process, use over-the-counter skin creams designed to lighten dark spots; many of these contain hydroquinone, a bleaching ingredient.
Over-the-counter skin bleaches don't contain as much of the active ingredient hydroquinone as prescription bleaches and may be used in less severe cases.
Chromium oxychloride reacts violently on phenol, producing hydroquinone ether, O(C 6 H 4 OH)2; chromic acid gives phenoquinone, and potassium permanganate gives paradiphenol, oxalic acid, and some salicylic acid (R.
All four mono-hydroxyxanthones are known, and are prepared by heating salicylic acid with either resorcin, pyrocatechin or hydroquinone; they are yellow crystalline solids, which act as dyestuffs.
7-dihydroxyxanthone, known as euxanthone, is prepared by heating euxanthic acid with hydrochloric acid or by heating hydroquinone carboxylic acid with 3-resorcylic acid and acetic anhydride (S.
7-trihydroxyxanthone, is found in the form of its methyl ether (gentisin) in gentian root; it is obtained synthetically by condensing phloroglucin with hydroquinone carboxylic acid.
It crystallizes in tables which melt at 140° C. and boil at 267° C. When heated with 10% hydrochloric acid to 180 C. it yields hydroquinone (J.
Quinhydrone, C 6 H40 2 -C 6 H 4 (OH) 2, is formed by the direct union of quinone and hydroquinone or by careful oxidation of hydroquinone with ferric chloride solution.
, 27, p. 39 2), crystallizes in colourless prisms which melt at 234° C. When heated in vacuo to 240° C. it yields hydroquinone, quinone and pyrogallol.