CAS Number: 55-55-0
Linear Formula: C7H9NO · 1/2H2SO4
Molecular Weight: 172.19
Other Names: N-methyl-p-aminophenol sulfate, p-(methylamino)phenol sulfate, monomethyl-p-aminophenol hemisulfate, Metol, Elon, Rhodol, Enel, Viterol, Scalol, Genol, Satrapol.
Metol is the organic compound with the formula [HOC6H4NH2(CH3)]HSO4. It is the hydrogen sulfate (HSO4−) salt of the protonated derivative of N-methylaminophenol. This colourless salt is a popular photographic developer used in black & white photography. Metol is an excellent developing agent for most continuous tone developer applications, and it has been widely used in published developer formulas as well as commercial products. However, it is difficult to produce highly concentrated developer solutions using Metol, and therefore most Metol developers are supplied in dry chemical mix. A developer containing both Metol and hydroquinone is called an MQ developer. This combination of agents provide greater developer activity since the rate of development by both agents together is greater than the sum of rates of developments by each agent used alone (superadditivity). This combination is very versatile; by varying the quantities of Metol, hydroquinone, restrainer, and adjusting the pH, the entire range of continuous tone developers can be made. Therefore, Metol replaced most other developing agents except for hydroquinone, Phenidone (which is more recent than Metol), and derivatives of Phenidone. Notable formulas include Eastman Kodak D-76 film developer, D-72 print developer, and D-96 motion picture negative developer.
