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Potassium Thioglycolate is the monopotassium salt of thioglycolic acid and a sulfur-containing reducing agent used primarily in cosmetic hair-treatment formulations.
Potassium Thioglycolate reduces disulfide bonds in keratin, allowing hair fibers to be removed, waved, straightened, or reshaped under controlled formulation conditions.
Potassium Thioglycolate is highly compatible with aqueous systems and is commonly supplied as a concentrated water-based solution for cosmetic and industrial processing.
CAS Number: 34452-51-2
EC Number: 252-038-4
Molecular Formula: C₂H₃KO₂S
Molecular Weight: 130.21 g/mol
SYNONYMS
Potassium Thioglycolate, Potassium Thioglycollate, Potassium 2-Mercaptoacetate, Potassium Mercaptoacetate, Potassium 2-Sulfanylacetate, Potassium Sulfanylacetate, Thioglycolic Acid Potassium Salt, Thioglycolic Acid Monopotassium Salt, Mercaptoacetic Acid Potassium Salt, Mercaptoacetic Acid Monopotassium Salt, 2-Mercaptoacetic Acid Potassium Salt, Potassium Salt of Thioglycolic Acid, Potassium Salt of Mercaptoacetic Acid, Acetic Acid, Mercapto-, Monopotassium Salt, Acetic Acid, 2-Mercapto-, Potassium Salt, Acetic Acid, 2-Mercapto-, Potassium Salt (1:1), Potassium Hydrogen Thioglycolate, Monopotassium Thioglycolate, Potassium Alpha-Mercaptoacetate, Potassium α-Mercaptoacetate, Potassium Thioglycolate Solution, Aqueous Potassium Thioglycolate, Potassium Thioglycolate 42% Solution, Potassium Thioglycolate 40–44% Solution, Potassium Mercaptoacetate Solution, Potassium Thioglycolate Cosmetic Grade, Potassium Thioglycolate Technical Grade, Potassium Thioglycolate Reducing Agent, Potassium Thioglycolate Depilatory Active, Potassium Thioglycolate Permanent-Wave Active, Potassium Thioglycolate Hair-Straightening Active, Thioglycolate Keratin Reductant, Potassium Keratin-Reducing Salt, Potassium; 2-Sulfanylacetate, C₂H₃KO₂S, C2H3KO2S, CAS 34452-51-2, EC 252-038-4, EINECS 252-038-4, UNII XP5WZO5W6H, DTXSID30885589, HYTYHTSMCRDHIM-UHFFFAOYSA-M
APPLICATIONS
Potassium Thioglycolate serves as an active reducing ingredient in depilatory creams formulated to remove unwanted body hair.
Potassium Thioglycolate weakens the disulfide bonds that provide mechanical strength to hair keratin, allowing treated hair to be removed from or near the skin surface.
Potassium Thioglycolate supports the preparation of rinse-off hair-removal creams intended for approved external body areas.
Potassium Thioglycolate enables depilatory creams to combine keratin-reducing performance with suitable viscosity, spreading behavior, and contact time.
Potassium Thioglycolate functions as a depilatory active in hair-removal gels designed for controlled and uniform application.
Potassium Thioglycolate promotes effective contact between the reducing system and the exposed hair shaft when suitable thickening agents maintain the formulation in position.
Potassium Thioglycolate contributes to depilatory lotions requiring a balance of reducing activity, emulsion stability, and skin application properties.
Potassium Thioglycolate allows formulators to adjust hair-removal performance through careful control of concentration, alkalinity, temperature, and exposure time.
Potassium Thioglycolate facilitates hair removal by reducing cystine linkages within keratin rather than mechanically cutting the hair.
Potassium Thioglycolate helps treated hair become sufficiently soft and fragile for removal through gentle wiping, scraping, or rinsing.
Potassium Thioglycolate acts as a reducing active in permanent-wave formulations intended to create durable curls or waves.
Potassium Thioglycolate softens the internal keratin structure so that hair can assume the shape established by rods, rollers, or other waving tools.
Potassium Thioglycolate promotes disulfide-bond reduction during the first stage of a permanent-waving process.
Potassium Thioglycolate enables the reduced keratin structure to be reorganized before an oxidizing neutralizer reforms disulfide bonds in the new configuration.
Potassium Thioglycolate supports cold-wave systems designed to produce permanent curls without requiring high processing temperatures.
Potassium Thioglycolate provides controllable reducing performance when concentration, formulation pH, hair porosity, and application time are properly selected.
Potassium Thioglycolate contributes to professional permanent-wave lotions containing compatible alkalizers, conditioning agents, surfactants, and sequestrants.
Potassium Thioglycolate helps achieve more uniform curl formation when the hair is evenly saturated and carefully processed.
Potassium Thioglycolate enables permanent-wave manufacturers to prepare different active strengths for normal, resistant, porous, colored, or previously treated hair.
Potassium Thioglycolate allows the reducing phase to be adapted to the condition and processing tolerance of the intended hair type.
Potassium Thioglycolate serves as a keratin-modifying active in professional hair-straightening formulations.
Potassium Thioglycolate reduces selected disulfide bonds so that curly or wavy hair fibers can be mechanically repositioned into a straighter arrangement.
Potassium Thioglycolate supports thioglycolate-based straightening systems used as alternatives to strongly caustic hydroxide relaxers.
Potassium Thioglycolate enables controlled reshaping when the reducing stage is followed by thorough rinsing and an appropriate neutralizing treatment.
Potassium Thioglycolate facilitates uniform application in cream-based straighteners formulated to remain on selected hair sections.
Potassium Thioglycolate contributes to consistent processing along the hair shaft when application quantity, section size, timing, and hair condition are carefully controlled.
Potassium Thioglycolate allows professional formulators to balance straightening performance with manageable application viscosity.
Potassium Thioglycolate helps minimize uncontrolled movement of the formulation toward the scalp when suitable rheology modifiers are employed.
Potassium Thioglycolate functions as an active ingredient in professional eyelash-waving and lash-lifting systems where regional regulations permit thioglycolate use.
Potassium Thioglycolate softens eyelash keratin so that the lashes can be repositioned over a lifting shield or curling form.
Potassium Thioglycolate supports the reducing stage of two-step professional lash treatments followed by a separate fixing formulation.
Potassium Thioglycolate requires strict control of concentration, finished-product pH, application technique, and contact time because of the proximity of the treatment area to the eyes.
Potassium Thioglycolate contributes reducing activity to other rinse-off hair products designed to modify the shape or structure of keratin fibers.
Potassium Thioglycolate may be incorporated into specialized salon systems when the intended use complies with regional cosmetic restrictions.
Potassium Thioglycolate functions effectively in aqueous formulations because the potassium salt has high water compatibility.
Potassium Thioglycolate allows concentrated liquid grades to be pumped, measured, diluted, and blended with greater ease than many isolated dry reducing agents.
Potassium Thioglycolate supports cream emulsions containing fatty alcohols, emollients, and structuring ingredients that improve application control.
Potassium Thioglycolate can be combined with compatible conditioning polymers to improve combability and reduce roughness after chemical treatment.
Potassium Thioglycolate facilitates accurate industrial dosing when Potassium Thioglycolate is supplied at a standardized active concentration.
Potassium Thioglycolate enables manufacturers to calculate finished-product concentration on a thioglycolic-acid-equivalent basis.
Potassium Thioglycolate supports quality-control procedures involving active-content determination, density testing, pH measurement, color evaluation, and reducing-capacity analysis.
Potassium Thioglycolate allows manufacturers to monitor oxidation and concentration changes before Potassium Thioglycolate is incorporated into finished formulations.
Potassium Thioglycolate functions as a sulfur-containing reducing reagent in selected laboratory and specialty chemical applications.
Potassium Thioglycolate participates in oxidation-reduction reactions through the reactive sulfhydryl functionality of the thioglycolate ion.
Potassium Thioglycolate provides thioglycolate ions for chemical research involving sulfur-containing carboxylates.
Potassium Thioglycolate supports analytical studies in which water-compatible mercapto functionality is required.
Potassium Thioglycolate contributes to coordination and complexation studies involving selected metal ions.
Potassium Thioglycolate can interact with metals through sulfur-containing and carboxylate functionality under suitable experimental conditions.
Potassium Thioglycolate serves as a starting reagent for the preparation of selected thioglycolate derivatives.
Potassium Thioglycolate enables controlled synthesis, precipitation, ion-exchange, and complexation reactions in compatible laboratory systems.
Potassium Thioglycolate provides a standardized source of mercaptoacetate functionality for cosmetic research and formulation development.
Potassium Thioglycolate requires application-specific compatibility, stability, safety, and regulatory assessment before use in any new formulation.
Thioglycolic acid salts, particularly Potassium Thioglycolate and Ammonium Thioglycolate, are commercially associated with permanent-wave and depilatory formulations.
DESCRIPTION
Potassium Thioglycolate is an ionic organic salt produced by neutralizing thioglycolic acid with a suitable potassium base.
Potassium Thioglycolate contains a potassium cation and a thioglycolate anion with both sulfhydryl and carboxylate functionality.
Potassium Thioglycolate has the molecular formula C₂H₃KO₂S and a molecular weight of 130.21 g/mol.
Potassium Thioglycolate is identified by CAS Number 34452-51-2 and EC Number 252-038-4.
Potassium Thioglycolate contains a reactive sulfhydryl group that provides reducing and nucleophilic activity.
Potassium Thioglycolate contains an ionic potassium carboxylate group that provides high compatibility with water-based formulations.
Potassium Thioglycolate dissociates into potassium ions and thioglycolate ions when introduced into sufficient water.
Potassium Thioglycolate consequently provides reducing functionality throughout the aqueous phase rather than remaining confined to an oil phase.
Potassium Thioglycolate is generally manufactured by reacting thioglycolic acid with potassium hydroxide or another suitable potassium-containing neutralizing agent.
Potassium Thioglycolate production requires controlled neutralization, temperature management, concentration adjustment, and protection against excessive oxidation.
Potassium Thioglycolate is commonly supplied as a concentrated aqueous solution containing approximately 40–44% Potassium Thioglycolate.
Potassium Thioglycolate solutions at approximately 42% active content may correspond to about 30% thioglycolic acid equivalent.
Potassium Thioglycolate solution is generally clear to pale in color, although appearance depends on concentration, purity, oxidation level, and storage history.
Potassium Thioglycolate solution normally has a characteristic sulfurous or mercaptan-like odor associated with thioglycolate chemistry.
Potassium Thioglycolate solution supplied by Merck at approximately 42% concentration has a reported density of about 1.25 g/cm³ at 20°C.
Potassium Thioglycolate solution supplied in the same commercial grade has a reported pH range of 6.5–7.5 at 20°C.
Potassium Thioglycolate reduces disulfide bonds present in cystine units within keratin. Potassium Thioglycolate converts part of the crosslinked keratin structure into reduced sulfhydryl-containing structures that can be mechanically reshaped or weakened.
Potassium Thioglycolate causes controlled keratin softening in permanent-wave and hair-straightening applications.
Potassium Thioglycolate causes more extensive keratin weakening in depilatory formulations designed to remove treated hair.
Potassium Thioglycolate becomes more effective under alkaline conditions because increasing pH promotes hair swelling and increases the proportion of reactive thiolate species.
Potassium Thioglycolate may also produce faster irritation or hair damage when alkalinity, active concentration, or processing time becomes excessive.
Potassium Thioglycolate performance therefore depends on finished-product pH, active concentration, application temperature, treatment duration, hair condition, and formulation composition.
Potassium Thioglycolate performance must be validated on the intended hair or skin application rather than predicted solely from raw-material concentration.
Potassium Thioglycolate is highly soluble or dispersible in water-based systems.
Potassium Thioglycolate has very limited compatibility with non-polar oils unless Potassium Thioglycolate is distributed through an emulsion or another multiphase formulation.
Potassium Thioglycolate can be incorporated into creams, lotions, gels, and aqueous solutions when suitable emulsifiers, stabilizers, thickeners, and alkalizers are selected. Potassium Thioglycolate compatibility must be tested because surfactants, fragrances, polymers, metal ions, and botanical ingredients may alter stability or reducing performance.
Potassium Thioglycolate is sensitive to atmospheric oxidation because the sulfhydryl functionality can gradually form disulfide oxidation products.
Potassium Thioglycolate oxidation can reduce active strength and may increase color, odor variation, or batch inconsistency.
Potassium Thioglycolate oxidation can be accelerated by air exposure, elevated temperature, trace transition metals, and unsuitable storage conditions.
Potassium Thioglycolate stability can be improved through sealed packaging, controlled processing, suitable equipment, and carefully selected chelating systems.
Potassium Thioglycolate reacts rapidly with strong oxidizing agents because oxidation consumes the active sulfhydryl functionality.
Potassium Thioglycolate should therefore remain separated from peroxide neutralizers and other oxidizers until the intended treatment stage.
Potassium Thioglycolate may form increasing amounts of free thioglycolic acid when Potassium Thioglycolate is exposed to strongly acidic conditions.
Potassium Thioglycolate acidification can alter odor, irritation potential, corrosivity, reducing behavior, and formulation stability.
Potassium Thioglycolate solution may interact with or corrode certain metals during storage and processing.
Potassium Thioglycolate should be handled with supplier-approved plastic, lined, or corrosion-resistant equipment.
Potassium Thioglycolate use in cosmetics is regulated according to application category, ready-to-use concentration, finished-product pH, professional-use status, and required warning statements.
Potassium Thioglycolate cosmetic concentration is generally expressed as thioglycolic acid equivalent rather than as the total weight of the potassium salt.
Potassium Thioglycolate remains permitted in the European Union under the restrictions applying to thioglycolic acid and its salts.
Potassium Thioglycolate limits include 8% thioglycolic acid equivalent for general-use waving or straightening products, 11% for professional-use waving or straightening products, 5% for depilatories, 2% for other rinse-off hair products, and 11% for professional eyelash-waving products.
PROPERTIES
Chemical Name: Potassium Thioglycolate
IUPAC Name: Potassium 2-Sulfanylacetate
INCI Name: Potassium Thioglycolate
Chemical Class: Potassium mercapto-carboxylate salt
Substance Type: Sulfur-containing reducing agent
Parent Acid: Thioglycolic Acid
CAS Number: 34452-51-2
EC Number: 252-038-4
PubChem CID: 23688957
UNII: XP5WZO5W6H
DSSTox Substance ID: DTXSID30885589
Molecular Formula: C₂H₃KO₂S
Molecular Weight: 130.21 g/mol
Exact Mass: Approximately 129.949 Da
InChIKey: HYTYHTSMCRDHIM-UHFFFAOYSA-M
SMILES: C(C(=O)[O-])S.[K+]
Functional Groups: Sulfhydryl and carboxylate
Ionic Components: Potassium cation and thioglycolate anion
Primary Function: Reducing agent
Cosmetic Functions: Depilatory, permanent waving, hair straightening, eyelash waving, and keratin modification
Typical Commercial Form: Concentrated aqueous solution
Typical Commercial Concentration: Approximately 40–44% Potassium Thioglycolate
Typical Thioglycolic Acid Equivalent: Approximately 29–31%
Common Commercial Grade: Approximately 42% Potassium Thioglycolate
Physical State of Common Commercial Grade: Liquid
Appearance: Clear to pale-colored aqueous solution, depending on grade and storage history
Odor: Characteristic sulfurous or mercaptan-like odor
Density of Merck 42% Grade: Approximately 1.25 g/cm³ at 20°C
pH of Merck 42% Grade: Approximately 6.5–7.5 at 20°C
Water Solubility: Highly soluble
Oil Solubility: Very limited in non-polar oils
Volatility: Low for the potassium salt
Reducing Activity: High
Keratin Activity: Reduces cystine disulfide bonds
Metal-Binding Ability: Present through sulfur and carboxylate functionality
Oxidation Sensitivity: Gradually oxidized by air
Acid Sensitivity: Strong acidification increases free thioglycolic acid formation
Incompatible Materials: Strong oxidizing agents, strong acids, and incompatible metals
Metal Corrosivity: Concentrated commercial solution may be corrosive to metals
Hazard Classification of Merck 42% Solution: May be corrosive to metals, toxic if swallowed, may cause an allergic skin reaction, and harmful to aquatic life with long-lasting effects
Transport Classification of Merck 42% Solution: UN 2922, Corrosive Liquid, Toxic, N.O.S., Class 8 with subsidiary hazard 6.1, Packing Group II
EU General-Use Hair Waving or Straightening Maximum: 8% calculated as thioglycolic acid, ready-to-use pH 7.0–9.5
EU Professional Hair Waving or Straightening Maximum: 11% calculated as thioglycolic acid, ready-to-use pH 7.0–9.5
EU Depilatory Maximum: 5% calculated as thioglycolic acid, ready-to-use pH 7.0–12.7
EU Other Hair Rinse-Off Product Maximum: 2% calculated as thioglycolic acid, ready-to-use pH 7.0–9.5
EU Professional Eyelash-Waving Maximum: 11% calculated as thioglycolic acid, ready-to-use pH 7.0–9.5
Storage Stability: Protect from air, heat, contamination, oxidizers, acids, and incompatible metals
The molecular identifiers are reported by PubChem, while the commercial solution properties and hazard statements refer specifically to Merck’s approximately 42% Potassium Thioglycolate solution.
FIRST AID
Inhalation: Move the affected person immediately to fresh air and keep the affected person at rest in a position comfortable for breathing. Prevent further exposure to Potassium Thioglycolate mist, vapor, or aerosol and obtain urgent medical attention if coughing, dizziness, respiratory irritation, or breathing difficulty occurs.
Skin Contact: Remove clothing and footwear contaminated with Potassium Thioglycolate without delay. Rinse the affected skin with plenty of water, wash thoroughly with soap, and obtain medical attention if redness, pain, burns, or allergic symptoms develop.
Eye Contact: Immediately rinse eyes exposed to Potassium Thioglycolate with clean running water for at least 15 minutes while holding the eyelids open. Remove contact lenses when present and easy to remove, continue rinsing, and seek immediate medical attention.
Ingestion: Rinse the mouth thoroughly after Potassium Thioglycolate ingestion and do not induce vomiting. Contact a poison information center or physician immediately because concentrated Potassium Thioglycolate solution may be toxic if swallowed.
Note to Physicians: Treat Potassium Thioglycolate exposure symptomatically and provide supportive care. Evaluate Potassium Thioglycolate exposure for corrosive injury, systemic toxicity, allergic skin reaction, and delayed respiratory effects according to the exposure route and concentration.
Merck classifies its approximately 42% Potassium Thioglycolate solution as toxic if swallowed, potentially corrosive to metals, capable of causing an allergic skin reaction, and harmful to aquatic life with long-lasting effects.
HANDLING AND STORAGE
Handling: Handle Potassium Thioglycolate with closed or carefully controlled transfer equipment whenever practical. Avoid inhaling Potassium Thioglycolate mist or aerosol and prevent Potassium Thioglycolate contact with the eyes, skin, clothing, strong acids, oxidizers, and incompatible metals.
Ventilation: Provide effective general ventilation and local exhaust wherever Potassium Thioglycolate is transferred, sampled, mixed, diluted, or filled. Use suitable respiratory protection when ventilation cannot adequately control Potassium Thioglycolate mist or aerosol exposure.
Storage: Store Potassium Thioglycolate in tightly closed, supplier-approved containers within a cool, dry, and well-ventilated area. Protect Potassium Thioglycolate from excessive heat, direct sunlight, unnecessary air exposure, freezing when specified by the supplier, and contamination by incompatible substances.
Spill and Leak Procedures: Restrict access to areas affected by Potassium Thioglycolate releases and provide adequate ventilation before cleanup. Contain Potassium Thioglycolate with inert non-combustible absorbent, prevent Potassium Thioglycolate from entering drains or surface water, and transfer recovered waste into compatible labeled containers.
Handling Precautions: Wear chemical-resistant gloves, tightly fitting safety goggles, protective clothing, and a face shield when Potassium Thioglycolate splash exposure is possible. Keep emergency eyewash and safety-shower facilities accessible, wash thoroughly after handling Potassium Thioglycolate, and consult the current supplier-specific Safety Data Sheet before commercial use.
Potassium Thioglycolate storage, transportation, and workplace controls must follow the concentration-specific Safety Data Sheet because hazard and transport classifications can change between commercial grades.
