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{{short description|Reducing aromatic compound used as developing agent in black and white photography}} |
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{{refimprove|date=December 2010}} |
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{{Use dmy dates|date=July 2020}} |
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{{chembox |
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{{chembox |
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| verifiedrevid = 444013999 |
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| verifiedrevid = 444014995 |
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| Name = Metol |
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| Name = Metol |
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| ImageFile = P-(methylamino)phenol_sulfate.PNG |
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| ImageFile = Metol Structural Formula V2.svg |
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| ImageName = |
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| IUPACName = 4-(methylamino)phenol sulfate |
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| ImageName = |
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| OtherNames = ''N''-methyl-p-aminophenol sulfate, Pictol, p-(methylamino)phenol sulfate, monomethyl-p-aminophenol hemisulfate, Metol, Elon, Rhodol, Enel, Viterol, Scalol, Genol, Satrapol, Photol. |
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| IUPACName = 4-(methylamino)phenol sulfate |
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|Section1={{Chembox Identifiers |
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| OtherNames = N-methyl-p-aminophenol sulfate, p-(methylamino)phenol sulfate, monomethyl-p-aminophenol hemisulfate, Metol, Elon, Rhodol, Enel, Viterol, Scalol, Genol, Satrapol. |
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| UNII_Ref = {{fdacite|correct|FDA}} |
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| Section1 = {{Chembox Identifiers |
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| UNII_Ref = {{fdacite|correct|FDA}} |
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| UNII = D3W0VWG12M |
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| UNII = D3W0VWG12M |
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| ChEBI_Ref = {{ebicite|correct|EBI}} |
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| ChEBI_Ref = {{ebicite|correct|EBI}} |
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| ChEBI = 55413 |
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| ChEBI = 55413 |
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| SMILES = O=S(=O)(O)O.Oc1ccc(NC)cc1.Oc1ccc(NC)cc1 |
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| SMILES = O=S(=O)(O)O.Oc1ccc(NC)cc1.Oc1ccc(NC)cc1 |
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| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} |
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| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} |
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| ChemSpiderID = 5717 |
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| ChemSpiderID = 5717 |
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| PubChem = 5930 |
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| PubChem = 5930 |
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| CASNo_Ref = {{cascite|correct|CAS}} |
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| CASNo_Ref = {{cascite|correct|CAS}} |
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| CASNo = 55-55-0 |
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| CASNo = 55-55-0 |
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| RTECS = |
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| Section2 = {{Chembox Properties |
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|Section2={{Chembox Properties |
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| Formula = (C<sub>7</sub>H<sub>10</sub>NO)<sub>2</sub>SO<sub>4</sub> |
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| Formula = (C<sub>7</sub>H<sub>10</sub>NO)<sub>2</sub>SO<sub>4</sub> |
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| MolarMass = 344.38 g/mol |
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| MolarMass = 344.38 g/mol |
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| Appearance = |
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| Density = |
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| Solubility = |
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| Solubility = |
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| MeltingPtC = 260 |
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| MeltingPtC = 260 |
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| BoilingPt = |
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| Section7 = {{Chembox Hazards |
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|Section7={{Chembox Hazards |
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| ExternalMSDS = |
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| ExternalSDS = |
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| MainHazards = |
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| EUClass = {{Hazchem T}}<br>{{Hazchem N}} |
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| GHSPictograms = {{GHS08}}{{GHS07}}{{GHS09}} |
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| MainHazards = |
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| GHSSignalWord = warning |
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| FlashPt = |
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| HPhrases = {{HPhrases|H302|H317|H373|H410}} |
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| RPhrases = |
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| PPhrases = {{PPhrases|P260|P280|P301+P312+P330}} |
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| GHS_ref = <ref>GHS: </ref> |
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| FlashPt = |
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| Section8 = {{Chembox Related |
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| OtherAnions = |
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|Section8={{Chembox Related |
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'''Metol''' (or '''Elon''') is a trade name for the ] with the formula <sub>2</sub>HSO<sub>4</sub>. It is the ] salt of ''N''-methylaminophenol. This colourless salt is a popular ] used in ].<ref name=Ullmann>Gerd Löbbert "Photography" in Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim. {{doi| 10.1002/14356007.a20_001}}</ref> |
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==Synthesis and degradation== |
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'''Metol''' is the chemical compound with the name '''monomethyl-''p''-aminophenol hemisulfate'''. It is a developing agent used in black & white ]s. In its pure form, it is a ] rather light-sensitive ] which is the half ] (hemisulfate) ] of ''N''-methyl-''p''-aminophenol. |
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Several methods exist for the preparation of ''N''-methylaminophenol. It arises by decarboxylation of ''N''-4-hydroxyphenylglycine (]). It can be obtained by reaction of ] with ].<ref>{{cite journal | doi = 10.1021/ja01459a014 | year = 1919 | author = Harger, Rolla N. | journal = ] | title = Preparation of Metol | volume = 41 | pages = 270–276 | issue = 2| url = https://zenodo.org/record/1428838 }}</ref> |
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Being an electron-rich arene, metol is readily degraded by ].<ref>{{cite journal |doi=10.1016/s0043-1354(99)00339-5 |title=Degradation of Photographic Developers by Fenton's Reagent: Condition Optimization and Kinetics for Metol Oxidation |date=2000 |last1=Lunar |first1=L. |journal=Water Research |volume=34 |issue=6 |pages=1791–1802 }}</ref> |
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==Synthesis== |
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Metol has been prepared by the reaction of ] with ], followed by neutralization with ].<ref>{{cite journal | doi = 10.1021/ja01459a014 | year = 1919 | author = Harger, Rolla N. | journal = ] | title = Preparation of Metol | volume = 41 | pages = 270}}</ref> |
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==Application== |
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==Application== |
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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 ] 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 (]). 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, ] (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. |
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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 ] is called an MQ developer. This combination of agents provides greater developer activity since the rate of development by both agents together is greater than the sum of rates of development by each agent used alone (]). This combination is very versatile; by varying the quantities of Metol, hydroquinone, and restrainer, and adjusting the pH, the entire range of continuous tone developers can be made. Therefore, this form of Metol replaced most other developing agents except for hydroquinone, ] (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. |
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==History== |
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==History== |
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Alfred Bogisch discovered in 1891 that methylated ] has more vigorous developing action than ''p''-aminophenol, and Julius Hauff introduced this compound as a developing agent. (Hauff operated a chemical business for which Bogisch worked.) Exact description of Bogisch and Hauff's early Metol is indefinitive, but it is most likely methylated at the ortho position of the phenol group (''p''-amino-''o''-methylphenol), rather than at the amino group. Some time after, Metol became to mean N-methylated variety and o-methylated variety had fallen out of use. Aktien-Gesellschaft fuer Anilinfabrikation (]) sold this compound under trade name Metol and it became by far the most common name, followed by Eastman Kodak's trade name Elon. |
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Alfred Bogisch, working for a chemical company owned by Julius Hauff, discovered in 1891 that methylated ] has more vigorous developing action than ''p''-aminophenol. Hauff introduced this compound as a developing agent. The exact composition of Bogisch and Hauff's early Metol is unknown, but it was most likely methylated at the ortho position of the benzene ring (''p''-amino-''o''-methylphenol), rather than at the amino group. Some time later, Metol came to mean the ''N''-methylated variety, and the ''o''-methylated variety fell out of use. Aktien-Gesellschaft für Anilinfabrikation (]) sold this compound under the trade name Metol, which became by far the most common name, followed by ]'s trade name Elon. |
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Because it has been in use for this purpose for over 100 years and often by amateur ]s, there is a wide body of evidence about the health problems that contact with Metol can cause. These are principally local ] of the hands and fore-arms as well as some evidence of sensitization dermatitis in which subsequent exposure triggers of a chronic condition that is resistant to medication. The use of Metol in highly ] ]s and the presence of other materials in darkrooms that have been implicated in dermatitis such as ] may exacerbate some health impacts. |
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Because it has been in use for this purpose for over 100 years, and often by amateur photographers, there is a substantial body of evidence regarding the health problems that contact with Metol can cause. These are principally local ] of the hands and forearms. There is also some evidence of sensitization dermatitis.<ref>{{cite journal |doi=10.1021/tx060121y |title=Electrophilic Chemistry Related to Skin Sensitization. Reaction Mechanistic Applicability Domain Classification for a Published Data Set of 106 Chemicals Tested in the Mouse Local Lymph Node Assay |date=2007 |last1=Roberts |first1=David W. |last2=Aptula |first2=Aynur O. |last3=Patlewicz |first3=Grace |journal=Chemical Research in Toxicology |volume=20 |issue=1 |pages=44–60 |pmid=17226926 }}</ref> |
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==References== |
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==References== |
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{{Reflist}} |
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