You can expect to hear from a technical specialist within 1 business hour. Get medical attention. Eng. Eng. n3kGz=[==B0FX'+tG,}/Hh8mW2p[AiAN#8$X?AKHI{!7. Hydroquinone (C 6 H 4 (OH) 2), also known as benzene-1,4-diol or quinol, is an aromatic organic compound, with a variety of uses in chemistry. Calorim. Reddit and its partners use cookies and similar technologies to provide you with a better experience. Thermodyn. This compound is gathered from the beaver's castor sacs.[35]. Antioxidants, preferably sulfites, including but not limited to sulfites, bisulfites, metabisulfites, their salts, and their derivatives, most preferably sodium metabisulfite, have been used to stabilize certain compositions, which have included hydroquinone. 57, 295300 (2013), R. F. Pires, M. R. Franco Jr, Fluid Phase Equilib. [17], An important reaction is the conversion of hydroquinone to the mono- and diamine derivatives. Thus, while cationic salts of acidic ascorbyl esters, preferably magnesium ascorbyl phosphate and aminopropyl ascorbyl phosphate, have beneficial antioxidant effects on the skin, the combination with hydroquinone in the invention results in a compatible and stable composition. Except where otherwise noted, data are given for materials in their, Hydroquinone oxidation with V2O5/NaClO3/H2SO4, http://www.sciencemadness.org/smwiki/index.php?title=Hydroquinone&oldid=11523, Articles containing unverified chemical infoboxes, GNU Free Documentation License 1.3 or later. uuid:a150f3fd-7f22-4439-aa26-6f445f4017e5 M1 and M2 microemulsions contain ethanol as co-surfactant. All information collection is solely used to support ChemPoint customers service communications. 322, 4855 (2012), K. Tamura, T. Kasuga, T. Nakagawa, Fluid Phase Equilib. In 1-octanol, the decreasing order of the solubility of these compounds is as follows: resorcinol>benzoic acid>salicylic acid>hydroquinone. The solubilities of benzoic acid, salicylic acid, resorcinol and hydroquinone in water and in 1-octanol were measured by the dynamic method which is also called the synthetic method from 297.25 K to 334.45 K. Using differential scanning calorimetry (DSC Q2000 and SDT Q600), the melting temperature and the enthalpy of fusion of these solutes were determined. Eastman Hydroquinone, USP Grade is for skin-lightening products to address hyperpigmentation. The solubility in water is 6.72g/L. 58 / Monday, March 26, 2012 / Rules and Regulations 10/31/2017 EN (English US) 6/8 12.3. 29(3): 283-330, 1999. [Na+].OC(=O)CC(O)(CC([O-])=O)C(O)=O.OC(=O)CC(O)(CC([O-])=O)C(O)=O, SPECIFIC USE OF COSMETICS OR SIMILAR TOILET PREPARATIONS, Preparations for care of the skin for chemically bleaching or whitening the skin, PREPARATIONS FOR MEDICAL, DENTAL, OR TOILET PURPOSES, Medicinal preparations containing organic active ingredients, Acids; Anhydrides, halides or salts thereof, e.g. 43, 13111316 (2007), J. Qing-Zhu, M. Pei-Sheng, Z. Huan, X. Shu-Qian, W. Qiang, Q. Yan, Fluid Phase Equilib. As a polymerisation inhibitor, exploiting its antioxidant properties, hydroquinone prevents polymerization of acrylic acid, methyl methacrylate, cyanoacrylate, and other monomers that are susceptible to radical-initiated polymerization. Have an order or account question? Hope it helps 6 yrs later. The protective system can be an entrapment system, a single or multi-laminar system, such as by formation of vesicle, such as a liposome, or by utilizing wax, paraffin, silicone, polyethylene or any material or system which protects the retinoid from oxidation. English, J.C. and Deisinger, P.J. [27] Several such agents are already available or under research,[28] including azelaic acid,[29] kojic acid, retinoids, cysteamine,[30] topical steroids, glycolic acid, and other substances. ORIGINAL CODE: 0009013, Ref document number: Human exposure to hydroquinone can occur by dietary, occupational, and environmental sources. AT BE CH CY DE DK ES FI FR GB GR IE IT LI LU MC NL PT SE TR, Kind code of ref document: 0000004197 00000 n Some documentation and label information may refer to the legacy brand. uv curable cellulose estersuv curable cellulose esters . . Hydroquinone is extensively used as a photographic developer, an antioxidant, and a stabilizing agent for readily oxidizable polymers. : Metabolism and disposition of hydroquinone in Fischer 344 rats after oral or dermal administration. Hydroquinone is sold by chemical suppliers. Hydroquinone is a major benzene metabolite, which is a well-known haematotoxic and carcinogenic agent associated with malignancy in occupational environments. 0000008435 00000 n Anal. The protective system can be an entrapment system, a single or multi- laminar system, such as by the formation of vesicles such as a liposome or by utilizing wax, paraffin, silicone, polyethylene, or any material or system which protects the retinoid from oxidation. This invention addresses the problem of formulating a pigmentation disorder treatment composition with hydroquinone without an excessive discoloration of the composition in the pH range of about 7.0. The most preferred example of such an antioxidant is sodium metabisulfite. Eastman Hydroquinone, USP, meets or exceeds the requirements of the United States Pharmacopoeia and is produced under conditions of current good manufacturing practices (cGMP). 20, 14331442 (1986), G. Wienke, J. Gmehling, Toxicol. Hydroquinone occurs as fine, white needles. Cite this article. 65, 5786 (1998), Y.-H. Zhang, Trends Analyt. 0000004433 00000 n These reactions release free oxygen and generate enough heat to bring the mixture to the boiling point and vaporize about a fifth of it, producing a hot spray from the beetle's abdomen. ~lgM~Gc{1S_1Q/_/v">S 9 Hydroquinone is a white, odorless, crystalline solid with an extremely low vapor pressure. For more information, please see our Other aspects, advantages, and modifications are evident from a review of the following claims. HYdroquinone can be found in various skin care products. Thus, merely adding one retinoid to a hydroquinone composition would result in instability and/or discoloration, and adding hydroquinone to a retinoid product would have a similar result. Chem. Additionally, the hydroquinone compositions frequently discolor over time and turn from a whitish color to a brown or even black. This saturated dicarboxylic acid exists as a white powder. 0000003660 00000 n Hydroquinone undergoes oxidation under mild conditions to give benzoquinone, process which is reversible. NR 1L~tyj|ZZ3]jFlszH#bd]="nVj =rBF-=Y?Pe 3(\[3;wR-+7Fn ~pSQ(Rpiw^zYr''t@\vobE]u'C}io0q;^k5C@|zZNNA>,XOrztV;qO*w:MC$OI\_$Io 'v [ Also in this embodiment is a cationic salt of acidic ascorbyl esters, which further helps to maintain the acceptable color desired in the hydroquinone composition. Methods and products for nucleic acid production and delivery, Nucleic acid product and its administration method, Nucleic acid product and method of administration thereof, Compositions and systems for the treatment of hyperpigmentation, Methods for prevention of post-inflammatory hyperpigmentation, Skin care compositions containing retinoids, Improved method for stability of ageing comprising thirosinase inhibitor activity, Use of ascorbic acid to reduce irritation of topically applied active ingredients, COSMETIC COMPOSITIONS WITH ANTIMICOTIC PROPERTIES, EFFECTIVE AGAINST PSORIASIS AND HAIR LOSS AND COSMETIC METHOD FOR, Treatment or prevention of undesired skin pigmentation, Skin care compositions and method of improving skin appearance, Ultrasound enhancement of percutaneous drug absorption, Skin whiteners containing hydroxytetronic acid, Stabilized retinoid-containing skin care compositions, Retinoid compositions containing a water soluble antioxidant and a chelator, Composition and method for treating rosacea and sensitive skin with free radical scavengers, Skin care compositions containing imidazoles and retinoids, Stable compositions containing a retinoid and an enzyme based antioxidant system, Self-tanning compositions containing dha and propolis extract, Composition and process for stabilizing oxygen-unstable species, Bleaching preparation and cosmetic for preventing and improving aging of skin, Composition and method for the treatment of pigmentation disorders, Composition for cosmetic or pharmaceutical use, Remedies for pigmentation and melanocyte proliferation inhibitors, Public reference made under article 153(3) epc to a published international application that has entered the european phase, Divisional application: reference to earlier application, Information on the status of an ep patent application or granted ep patent. The obtained results show that the . Part of Springer Nature. The method of item 1 07 wherein the hydroquinone is present in about 4%. AzA inhibits tyrosinase. Hydroquinone[1] Idrochinone Quinol 1,4-Dihydroxybenzene p-dihydroxybenzene p-hydroxyphenol 1,4-Hydroxy benzene Identifiers CAS Number 123-31-9 Y 3D model (JSmol) Interactive image Beilstein Reference 605970 ChEBI CHEBI:17594 Y ChEMBL ChEMBL537 Y ChemSpider 764 Y DrugBank DB09526 ECHA InfoCard 100.004.199 EC Number 204-617-8 Gmelin Reference 2742 This is a prescription-only ingredient in some countries, including the member states of the European Union under Directives 76/768/EEC:1976. Tests, which results are detailed in the following two tables, are performed to show how well sodium metabisulfite ("SMBS") stabilizes color at each pH at 5C and 40C in 4% hydroquinone ("HQ") compositions. 2008-2023 ChemPoint. 230, 176183 (2005), A. Apelblat, E. Manzurola, N. A. Balal, J. Chem. Antioxidants in the hydroquinone phase are instrumental in stabilizing the color of the hydroquinone composition. x- [ 0}y)7ta>jT7@t`q2&6ZL?_yxg)zLU*uSkSeO4?c. R -25 S>Vd`rn~Y&+`;A4 A9 =-tl`;~p Gp| [`L` "AYA+Cb(R, *T2B- Retinoid compositions, in particular retinoic acid, retinal, and their derivatives, isomers and analogs (such as adapalene, tazarotene and isotretoin) are known to be effective in improving rough skin texture, mottled pigmentation, sallow complexion, lines and wrinkles. It is a reducing agent that is reversibly oxidized to semiquinone and quinone. 0000005306 00000 n Other solubilities: soluble in alcohol and ether,slightly soluble in benzene,readily soluble in ethanol,acetone and methanol, Needle-like Crystals or Crystalline Powder. I can only tell you how to mix the powder solution to the liquid solvent. How do I dissolve hydroquinone powder to make a 20% and 10% concentration? Approved only for prescription use in the U.S. market.Ideal for creams, lotions, and gels for personal care ingredients, pharmaceutical chemical, pharmaceutical excipients, and skin care ingredients. 0000002379 00000 n A common route involves hydroxylation of phenol. The information given is designed only as a guide for safe handling and use. 420, 2429 (2016), W. E. Acree Jr, Thermochim Acta 189, 3756 (1991), F. L. Nordstrm, . C. Rasmuson, J. Chem. A2, Designated state(s): endstream endobj 277 0 obj <>stream Please sign in to view account pricing and product availability. Cookie Notice Hydroquinone is highly susceptible to ring substitution by Friedel-Crafts reactions such as alkylation. . N')].uJr Heat Mass Transf. Variations in pH have proven to result in excessive discoloration ranging from brownish to black. antiphlogistics and cardiaca, Cosmetics or similar toilet preparations characterised by the composition, Cosmetics or similar toilet preparations characterised by the composition containing inorganic ingredients, Sulfur; Selenium; Tellurium; Compounds thereof, Cosmetics or similar toilet preparations characterised by the composition containing organic compounds, Cosmetics or similar toilet preparations characterised by the composition containing organic compounds containing oxygen, . 0000002585 00000 n Hydroquinone is a white crystalline solid, poorly soluble in water, but more soluble in organic solvents. If you are already a ChemPoint customer then sign up for access to our online ordering website. Eye Contact Rinse immediately with plenty of water, also under the eyelids, for at least 15 minutes. Water Solubility 73000 mg/L at 25C 2.6B pH pKa 4.0 - 4.7 pK1 = 9.9 2.12 Oxidation:Reduction Potential +286 mV at 25C and pH 7 ENVIRONMENTAL FATE/BIODEGRADATION J. Chem. LSPS, Laboratoire de Spectrochimie Et Pharmacologie Structurale, University of Tlemcen, BP 119, 13000, Tlemcen, Algeria, Department of Biology, University of Ghardaia, BP 455, 47000, Ghardaia, Algeria, You can also search for this author in Toughness of the polymer increases due to the presence of flexible units in the backbone such as long chain diols (e.g., diethylene glycol, dipropylene glycol, triethylene glycol) or long chain saturated acids (e.g., adipic . It is also used to prepare 2% bleaching creams and certain intermediates for the synthesis of dyes, and it has some activity as an antitumoragent. Lastly, I'd like to add benzoic acid for preservation purposes. The present invention addresses the problem of excessive discoloration in hydroquinone compositions of a neutral pH. Antioxidants in the hydroquinone phase and inorganic or amino acyl cationic salts of acidic ascorbyl esters, preferably sodium metabisulfite and magnesium ascorbyl phosphate respectively, are effective in stabilizing such hydroquinone compositions, which are used in treatment of pigmentation disorders. Data 53, 12781282 (2008), A. They may also include ingredients with other therapeutic actions, such as anti-inflammatories, antibiotics, exfoliants and peels. Solute (1 g) Water Boiling Water Alcohol Chloroform Ether Other Acenocoumarol 67,000 280 130 1800 Acetaminophen 20 10 1 N sodium hydroxide, 15 Acetohexamide 230 210 Acetylcysteine 5 4 Acetyldigitoxin 6100 62.5 12 >10,000 Ammonium Alum 7 0.5 Aluminum Chloride 0.9 4 Aluminum Sulfate 1 Amantadine Hydrochloride 2.5 5.1 18 polyethylene glycol 400, 70 G(DC:!c?5w [QDP, f\01j&8ea]Ke~z d _5H^j0M.|Y^bYb[Rm~-[ImSv. ;4kNNw?r yn^EOwCDyd>_?TU^vyss*|g9A1 avr 2o~molpb|CZTu(70 CKRu)(5O_^6|Qta', uG70]'vt|n3Xh[vMTc.{o0Y#(O5\/mGfI+L0~1E1~hi:ZY_W6n*EaSn*R+I)Pw|y\^/te;yO. Dietland Muller-Schwarze, 2003, page 43 (, National Institute for Occupational Safety and Health, Additive manufacturing of ceramics from preceramic polymers, http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:31976L0768:EN:HTML, "Clear N Smooth Skin Toning Cream recalled", Skin Bleaching Drug Products for Over-the-Counter Product Use; Proposed Rule, "About the Center for Drug Evaluation and Research - Hydroquinone Studies Under The National Toxicology Program (NTP)", Campaign For Safe Cosmetics - Hydroquinone, "Skin lightening preparations and the hydroquinone controversy", https://en.wikipedia.org/w/index.php?title=Hydroquinone&oldid=1136453324, Wikipedia articles needing page number citations from October 2016, Pages using collapsible list with both background and text-align in titlestyle, Articles containing unverified chemical infoboxes, Creative Commons Attribution-ShareAlike License 3.0, The most widely used route is similar to the, A potentially significant synthesis of hydroquinone from, Hydroquinone was first obtained in 1820 by the French chemists, Pelletier and Caventou (1820) "Recherches chimiques sur les quinquinas" (Chemical investigations of quinquinas [i.e., the bark of various, This page was last edited on 30 January 2023, at 11:09. nQt}MA0alSx k&^>0|>_',G! isosorbide, Ascorbic acid, i.e. "F$H:R!zFQd?r9\A&GrQhE]a4zBgE#H *B=0HIpp0MxJ$D1D, VKYdE"EI2EBGt4MzNr!YK ?%_&#(0J:EAiQ(()WT6U@P+!~mDe!hh/']B/?a0nhF!X8kc&5S6lIa2cKMA!E#dV(kel }}Cq9 Since hydroquinone has a tendency to discolor through oxidation, these antioxidants are used because they have greater tendencies to oxidize than hydroquinone. Chem. SAS Anti-ox booster 1% 0.3g. If youd like my help or recipes for this bleaching cream please contact me on Instagram @kaylinell and @kay.linell or Facebook at kay linell. So, does anybody know of another solvent I could use that has a higher . It is found in wheat, rye, and barley.It is a precursor to diverse industrial products including polymers and plasticizers, as well as being a component of a number of hair and skin conditioners. The amount of crosslinking was controlled by the reaction conditions, including temperature, reaction time, and . Table II shows that at 5C, 4% hydroquinone compositions maintain their white or light straw color with the addition of at least about 0.5% magnesium ascorbyl phosphate at the low pH ranges (from about 3.50 to about 5.50) and when about 1.0 to about 2.0% magnesium ascorbyl phosphate is used in the pH range of about 7.0. Color stability improvement is evident at all levels. Other antioxidants, for example cationic salts of acidic ascorbyl esters, most preferably magnesium ascorbyl phosphate, aminopropyl ascorbyl phosphate, and sodium ascorbyl phosphate, have not been utilized in combination with hydroquinone in view of the acidic pH, generally from about 3.4 to about 3.5, and the recommended pH range for magnesium ascorbyl phosphate is about 7.0 to 8.5. 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You take the cream, put it in a container, take the powder measurement and add it. 1 Solubility data for compounds that ordinarily are liquids at 25 are expressed in terms of the ratio of the volume of solute to the volume of solvent; i.e., 1 mL dissolved in mL of solvent. Inhalation Remove to fresh air. 0000000731 00000 n 88, 161164 (2010), J. Delgado, Int. It would be desirable to combine the pigmentation disorder treatment with this skin benefit ingredient in one composition. Chem. Free format text: One of these, 4-butylresorcinol, has been proven to be more effective at treating melanin-related skin disorders by a wide margin, as well as safe enough to be made available over the counter. [34], It is also one of the chemical compounds found in castoreum. ORIGINAL CODE: 0009012, Free format text: volume42, Articlenumber:1 (2021) Then add it to the ingredients. Hydroquinone Safety Data Sheet according to Federal Register / Vol. Hydroquinone can be made through several routes. Acta 423, 137144 (2000), S.-T. Lin, S. I. Sandler, Ind. J. Pharm. [33], Hydroquinone has been shown to be one of the chemical constituents of the natural product propolis. Classical photo shops . Thermodyn. Phase A: Dissolve L-Ascorbic Acid in distilled water via agitation and gentle heating (warm, never hot or you will denature the ascorbic acid). It has a white-solid appearance. D-170D Solubility of EASTMAN Hydroquinone and Derivatives Subject: Hydroquinone and hydroquinone derivatives listed in this publication are used as intermediates for manufacturing a variety of products and as polymerization inhibitors for vinyl monomers and unsaturated polyester resins. Solubility: Moderately soluble in water, glycerin, propylene glycol, and highly soluble in ethanol Features & Benefits Can work in conjunction with glycolic acid to help reduce pigment in melasma Non-GMO Extremely low vapor pressure USP Grade European Pharma Grade Drug master file available upon request Applications A preferred embodiment utilizes encapsulation. Some hydroquinone compositions include antioxidants, such as ascorbyl palmitate. On this Wikipedia the language links are at the top of the page across from the article title. It can also be found on eBay and Amazon. However, hydroquinone discolors at the pH range of 7.0 to 8.5. A further embodiment of the invention includes a method for stabilizing a hydroquinone composition (with about 1% to about 12% hydroquinone, preferably about 2% to about 10%, more preferably about 2% to about 8%, and most preferably about 3% to about 4%) with a neutral pH of from about 5.5 to about 8.0, more preferably a pH of from about 5.5 to about 7.5, and most preferably at a pH of from about 6.0 to about 7.5, by adding a water-soluble antioxidant, preferably sulfite, including but not limited to sulfites, bisulfites, metabisulfites, their salts and their derivatives, most preferably sodium metabisulfite, and a cationic salt of acidic ascorbyl esters, preferably sodium ascorbyl phosphate, more preferably aminopropyl ascorbyl phosphate, most preferably magnesium ascorbyl phosphate. One embodiment of the invention is a composition which comprises hydroquinone (about 1% to about 12%, preferably about 2% to about 10%, more preferably about 2% to about 8%, more preferably with about 2% to about 4%, and most preferably about 3% to about 4%) and has a neutral pH of from about 5.5 to about 8.0, more preferably a pH of from about 5.5 to about 7.5, and most preferably at a pH of from about 6.0 to about 7.5. The color stability of the hydroquinone composition is promoted by one or more antioxidants in the hydroquinone phase, preferably sulfite, including but not limited to sulfites, bisulfites, metabisulfites, their salts and their derivatives, most preferably sodium metabisulfite, and a cationic salt of acidic ascorbyl esters, most preferably magnesium ascorbyl phosphate. Recent pieces of . S.C. Gad, T. Pham, in Encyclopedia of Toxicology (Third Edition), 2014 Environmental Fate and Behavior. PubMedGoogle Scholar. Eng. C6H4O2) is formed. This invention relates to methods and compositions for the treatment of pigmentation disorders, including hyperpigmentation and vitiligo. HYPERPIGMENTARY STAIN ELIMINATING CREAM FOR FACE SKIN AND ITS USE. Anyone you share the following link with will be able to read this content: Sorry, a shareable link is not currently available for this article. Learn more about Institutional subscriptions, C. M. S. de Mendona, I. P. de Barros Lima, C. F. S. Arago, A. P. B. Gomes, J. Therm. If you have any specific questions, please include them in the comments section. Forms of retinoids have been developed wherein the retinoid is protected by a protective system. Chim. Hydroquinone, like phenols are very weak acids and can be deprotonated. 77, No. Retinoids, in particular retinoic acid, retinal, and their derivatives, isomers and analogs (such as adapalene, tazarotene and isotretoin), which are protected have been shown to also be color stable in hydroquinone, magnesium ascorbyl phosphate and sodium metabisulfite composition at about a neutral pH, preferably from about 5.5 to about 8.0, more preferably from about 5.5 to about 7.5, and most preferably from about 6.0 to about 7.5. 0 7 r @ &. Unfortunately, retinoids, in particular retinoic acid, retinal, and their derivatives, isomers and analogs (such as adapalene, tazarotene and isotretoin) also have discoloration problems due to oxidation. Availability. Cationic salts of acidic ascorbyl esters, including inorganic salts, preferably magnesium ascorbyl phosphate, and amino acyl derivatives, preferably aminopropyl ascorbyl phosphate, are preferred in this invention. Stir until uniform. Add the hydroquinone to the water. HYdroquinone can be found in various skin care products. [Na+].OC(=O)CN(CC([O-])=O)CCN(CC(O)=O)CC([O-])=O, trimethyl-[phenyl-bis(trimethylsilyloxy)silyl]oxysilane, C[Si](C)(C)O[Si](O[Si](C)(C)C)(O[Si](C)(C)C)C1=CC=CC=C1, C\C(=C/C=O)\C=C\C=C(\C=C\C1=C(CCCC1(C)C)C)/C, 1-hexadecanoyl-2-(9Z,12Z-octadecadienoyl)-sn-glycero-3-phosphocholine, CCCCCCCCCCCCCCCC(=O)OC[C@H](COP([O-])(=O)OCC[N+](C)(C)C)OC(=O)CCCCCCC\C=C/C\C=C/CCCCC, 2-[2-[2-[2-[2-[2-(2-dodecoxyethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethanol, C[Si]1(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O1, O=C1C(=O)C(C2=CNC3=C(C(C(=O)C4=C32)=O)C)=C2C4=CNC2=C1C, [Na+].[Na+].[Na+]. STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN. I'd like the consistency to be thin like a gel so that it absorbs quicker. We have found that a cream containing 5% of hydroquinone and 0.05 % of laevo-ascorbic acid remains white, and the emulsion remains unbroken after many months of storage, The laevo-ascorbic or cevitamic acid is pr'eferably employed in the free condition; but if desired, the salts, and especially the water-soluble salts thereof, may be employed . This chamber is lined with cells that secrete catalases and peroxidases. V)gB0iW8#8w8_QQj@&A)/g>'K t;\ $FZUn(4T%)0C&Zi8bxEB;PAom?W= 2023 Springer Nature Switzerland AG. Hydroquinone is considered to be readily biodegrable and photodegradable. COMMON BRAND NAME (S): Aclaro, Aclaro PD, Alera, Alphaquin HP, Alustra, Claripel, Complex B . The experimental solubilities were correlated using two regression equations. It is understood that while the invention has been described in conjunction with the detailed description thereof, that the foregoing description is intended to illustrate and not limit the scope of the invention, which is defined by the scope of the appended claims. Our team has been notified and we will fix it as soon as possible. Int J Thermophys 42, 1 (2021). Monobenzone occurs as a white, almost tasteless crystalline powder, soluble in alcohol and practically insoluble in water. [23] This conclusion was reached based on the extent of absorption in humans and the incidence of neoplasms in rats in several studies where adult rats were found to have increased rates of tumours, including thyroid follicular cell hyperplasias, anisokaryosis (variation in nuclei sizes), mononuclear cell leukemia, hepatocellular adenomas and renal tubule cell adenomas. The present invention is not to be limited by any mechanism described in the specification, because it is defined by the claims. Treatment with hydroquinone interferes with the action of tyrosinase, which is an enzyme used in the synthesis of melanin, and compositions are sold across the counter at about 2% hydroquinone and by prescription at higher concentrations. Provided by the Springer Nature SharedIt content-sharing initiative, Over 10 million scientific documents at your fingertips, Not logged in vz >I d50dwp?i4,H3. This range of pH has been preferred for hydroquinone compositions, because it has been believed that the hydroquinone is less likely to excessively discolor under acid conditions. https://doi.org/10.1007/s10765-020-02750-4. HlRMo0WB:NnVCnE4(i0 (1* )@NzHR!>i;8XaXnsO0LNT0l$B%"NAb0I9V *6/-\vn0W"fKF:AAgl:psRZ?k`&eB IUQ0ET;W#vL=@XwRG{-LHlTz]^s%OB(GF 11'I