MERCAPTOACETIC ACID

CAS Number: 68-11-1
EC Number: 200-677-4
Molecular Formula: C2H4O2S
Molecular Weight: Approximately 92.12 g/mol.
INCI Name: THIOGLYCOLIC ACID.
Boiling Point: Representative 96 °C at 5 mmHg, approximately 6.7 hPa; this is a reduced-pressure value, not a normal atmospheric boiling point.
Melting Point: Approximately −16 °C for concentrated material; solution freezing behavior depends on composition.
Viscosity: Representative dynamic viscosity 6.55 mPa·s at 20 °C in a reviewed concentrated-product SDS.
Density: Representative 1.326 g/mL at 20 °C for concentrated material; a separately documented approximately 70% aqueous solution has a density of 1.25 g/mL at 25 °C.

COMMON PRODUCT AND CHEMICAL NAMES

Mercaptoacetic Acid
Thioglycolic acid
Thioglycollic acid
2-Mercaptoacetic acid
Mercaptoethanoic acid
2-Mercaptoethanoic acid
Sulfanylacetic acid
2-Sulfanylacetic acid
Acetic acid, mercapto-
TGA

DESCRIPTION AND CHEMICAL IDENTITY

Mercaptoacetic Acid is a small bifunctional molecule containing one thiol, or mercapto, group and one carboxylic acid group. Thioglycolic acid is its widely used commercial synonym, and both names identify CAS 68-11-1.
The structure HS–CH2–COOH places the sulfur-containing group next to the carboxyl group through a methylene carbon. This arrangement supports reactions and interactions that are different from those of an ordinary carboxylic acid without sulfur functionality.
The name Mercaptoacetic Acid does not specify concentration. Industrial literature identifies both distilled high-concentration products and aqueous solutions, while laboratory catalogues offer other defined concentrations and assay levels.

The molecular formula and molar mass identify the Mercaptoacetic Acid molecule. An aqueous commercial solution also contains water and may have specified impurities, so its density, freezing point and handling requirements belong to that solution rather than to an imagined pure compound.
Thioglycolate salts and esters are related derivatives, not interchangeable synonyms for the free acid. Sodium, ammonium, calcium and potassium thioglycolate have different counterions or compositions, while esterification modifies the carboxyl functionality.
Mercaptoacetic Acid must also be distinguished from glycolic acid and from thioacetic acid. Similar names do not establish the same structure, reactivity or application.

MOLECULAR STRUCTURE AND CHEMICAL FUNCTION

The thiol group of Mercaptoacetic Acid provides sulfur-centered reactivity. It participates in oxidation to disulfide structures, radical chain-transfer chemistry and interactions with suitable metal centers or surfaces.
The carboxyl group of Mercaptoacetic Acid provides acid functionality and a site for salt or ester formation. Its ionization changes the molecule's charge and contributes to the behavior of thioglycolates in aqueous formulations.
The two functional groups must be considered together. Depending on the medium and pH, Mercaptoacetic Acid can act as a reducing agent, a ligand, a nucleophilic reagent or a starting material for a more specialized derivative.
Increasing pH changes the distribution of protonated and deprotonated species, including the more reactive sulfur-containing species under sufficiently alkaline conditions. A change in pH can therefore alter reactivity as well as simple acidity.

Oxidation of the thiol can form dithiodiglycolic acid, which contains a disulfide connection between two mercaptoacetic-acid-derived units. The oxidized material is chemically different from the free-thiol reagent, even though carboxyl groups remain present.
Formation of thioglycolides during storage of concentrated products is a separate issue from oxidation to the disulfide. Product assessment should distinguish these pathways instead of describing every storage-related change as a loss caused solely by air exposure.
The molecular structure explains the breadth of application, but it does not make Mercaptoacetic Acid universally compatible. Strong oxidants, strong alkalis and certain metals require particular attention in storage, transfer and formulation work.

COMMERCIAL CONCENTRATIONS AND PRODUCT FORMS

Published industrial information includes distilled thioglycolic acid with a minimum purity of 99% and an aqueous 80% product. These examples demonstrate common supply forms rather than a declaration that every supplier offers identical grades.
A separate laboratory product is supplied at approximately 70% by mass in water. Its concentration and physical data should not be substituted for an 80% solution or a concentrated acid grade.
Dilution changes the amount of active acid delivered per unit mass and also changes the physical behavior of the liquid. A formulation requirement expressed as active TGA is therefore different from an addition expressed as the mass of an unspecified commercial solution.

The use of a thioglycolate salt introduces another distinction. Neutralizing the carboxyl group produces a material with a different ionic form and a formulation-dependent pH; it is not simply a lower concentration of the free acid.
An ester retains a sulfur-containing functional group while modifying the acid end of the molecule. Its solubility, volatility and compatibility can differ substantially from those of TGA.
For a purchase or technical enquiry about Mercaptoacetic Acid, identify the required concentration, intended use and chemical form. These details are more informative than a request for mercaptoacetic acid without further specification.

PHYSICAL AND CHEMICAL PROPERTIES

The following entries combine representative concentrated-material data, a separately identified aqueous-solution example and explicitly labeled calculations. They are not a unified release specification for every product supplied by Ataman Chemicals.
Physical State: Liquid at 20 °C for concentrated commercial material.
Appearance: Clear, colorless to almost colorless in a representative reagent specification; permissible color depends on grade.
Odor: Strong, disagreeable mercaptan-type odor. Odor cannot be relied upon to determine a safe exposure condition.
Molecular Formula: C2H4O2S.
Structural Formula: HSCH2COOH, also written HSCH2CO2H.
Molar Mass: Approximately 92.12 g/mol.
Thiol Functionality: One –SH group per molecule.
Carboxylic Acid Functionality: One –COOH group per molecule.
Representative Melting or Freezing Point: Approximately −16 °C for concentrated material.
Representative Reduced-Pressure Boiling Point: 96 °C at 5 mmHg; a reviewed SDS gives approximately the same temperature at 7 hPa.
Representative Concentrated-Liquid Density: 1.326 g/mL at 20 °C.
Representative Relative Density: 1.33 at 20/20 °C in another reagent reference; this is dimensionless rather than an absolute density in g/mL.
Representative Dynamic Viscosity: 6.55 mPa·s at 20 °C in a concentrated-product SDS revised in September 2024.
Refractive Index: Representative nD20 of 1.505 in concentrated-material reference data.
Water Compatibility: Completely miscible.
Representative Aqueous pH: 1.5 at 10 g/L and 20 °C in the reviewed SDS; the result belongs to that stated test concentration.
Representative Vapor Pressure: 0.5 hPa at 25 °C in the reviewed SDS; another concentrated-product reference gives 0.4 mmHg at 25 °C.
Representative Relative Vapor Density: Approximately 3.2 compared with air equal to 1.
Representative Flash Point: 130 °C by a closed-cup method in reviewed concentrated-product information. Other published figures should retain their method and product basis when compared.
Representative Autoignition Entry: 315 °C at 1,020 hPa by ASTM E659 in the reviewed SDS; this is a test result, not an allowable operating temperature.
Approximately 70% Aqueous-Solution Density: 1.25 g/mL at 25 °C for a separately documented commercial solution.
Theoretical Sulfur Content: Approximately 34.80% by mass for pure TGA, calculated from its formula.
Theoretical Thiol Equivalent Weight: Approximately 92.12 g per mole of thiol groups for pure material.
Theoretical Carboxyl Equivalent Weight: Approximately 92.12 g per carboxyl equivalent, considering one –COOH group per molecule separately from thiol ionization.
Theoretical Carboxyl-Based Acid Number: Approximately 609 mg KOH/g for pure TGA, calculated from one carboxyl equivalent; an actual analytical endpoint and sample composition must be specified.
One mPa·s equals one cP, so the representative dynamic viscosity is also 6.55 cP. Dynamic viscosity should not be confused with kinematic viscosity, which uses different units and requires density for conversion.
The two vapor-pressure entries are approximately consistent after unit conversion: 0.4 mmHg is about 0.53 hPa. They remain separate reference measurements rather than a newly established precision specification.
The boiling-pressure condition is particularly important. Quoting 96 °C without its low-pressure basis would misrepresent the thermal data and could lead to incorrect process assumptions.
Concentration also matters when evaluating physical properties. The density of the documented 70% solution is a solution property, while the molecule's molar mass remains 92.12 g/mol regardless of whether it is supplied neat or dissolved in water.

REACTIVITY, OXIDATION AND STORAGE-RELATED CHANGE

The free thiol gives Mercaptoacetic Acid reducing activity and makes it susceptible to chemical change. Air oxidation is relevant, but the rate and significance depend on the product and its conditions.
An iodometric assay can assess thiol-related reducing content in an appropriate validated method. An acid-base titration answers a different question, so equal total acidity does not establish equal free-thiol content.
The disulfide oxidation product retains carboxyl functionality. A sample can therefore continue to behave as an acid while no longer supplying the same quantity of the intended reducing reagent.
Concentrated Mercaptoacetic Acid can also form thioglycolides during storage. Published supplier guidance for defined laboratory products identifies this concentration-related behavior and notes that controlling air exposure alone does not resolve every stability issue.

This makes storage history relevant to performance-critical uses. Appearance, concentration and chemical assay should be considered together rather than assuming that a clear liquid is unchanged.
Analytical methods that distinguish TGA and dithiodiglycolic acid have been published for formulated products. Such separation can be useful when the application depends on the balance between reducing species and oxidized material.
Storage requirements remain grade specific. A grade of Mercaptoacetic Acid may have particular temperature, headspace or packaging instructions, and laboratory guidance must not be extended automatically to a differently formulated industrial solution.

APPLICATIONS OF MERCAPTOACETIC ACID

The application of Mercaptoacetic Acid follows from its combination of water compatibility, thiol chemistry and carboxylic acid functionality. Some uses involve the free acid, while others depend on conversion to a defined salt, ester or metal-containing derivative.
The distinction is important when preparing a product specification. A raw material used to manufacture an active ingredient is not necessarily suitable for direct use in the same way as the finished formulation.

CHAIN TRANSFER IN AQUEOUS POLYMERIZATION

Mercaptoacetic Acid is documented as a chain-transfer agent in aqueous polymerization, including systems involving acrylic acid and acrylates. Complete miscibility with water is useful when the reaction medium is predominantly aqueous.
In radical chain transfer, the thiol group of Mercaptoacetic Acid can terminate the growth of one radical chain while generating a sulfur-centered species capable of participating in further reaction. The practical result can be control of molecular weight and modification of the resulting polymer architecture or end-group population.
The effect depends on the monomer, initiator system, pH, temperature and relative reactivities. A single chain-transfer constant or addition level should not be assumed applicable to all acrylate and acrylic-acid systems.

Published work on low-molar-mass poly(acrylic acid) has investigated TGA alongside other transfer agents. Research on acrylic-acid copolymers also demonstrates its use to obtain polymers with different molecular weights.
For a technical enquiry, identify the monomer system, polymerization medium and required molecular-weight range. Product selection should also consider residual TGA and the effect of sulfur-containing species on the final polymer's specification.
Mercaptoacetic Acid is not the polymerization initiator merely because it participates in the reaction. Chain transfer, initiation and inhibition are different functions that should remain distinct in technical communication.

SPECIALTY ACRYLIC POLYMERS AND RESEARCH IONOMERS

Published research has used thioglycolic acid to control molecular weight during aqueous synthesis of acrylic acid–itaconic acid copolymers. The resulting polymers were investigated as components of experimental glass-ionomer systems.
This is evidence of TGA's role in polymer synthesis, not an approval for industrial TGA to be used directly in a dental or medical product. The purified polymer, residual substances and finished material require their own assessment.
The example also illustrates why molecular-weight control is an application objective rather than a property of the transfer agent alone. The same reagent can produce different polymer outcomes when the reaction system changes.
For commercial polymer development, qualification should connect the raw-material grade with the required final polymer characteristics. A successful literature experiment does not establish an interchangeable production specification.

IRON CONTROL IN OILFIELD FORMULATIONS

Mercaptoacetic Acid is documented in oilfield formulations as both a reducing and metal-complexing component. These functions can help manage iron species whose precipitation would otherwise interfere with a treatment fluid or formation.
Ferric and ferrous iron behave differently in solution. A formulation that combines reduction of ferric species with suitable complexation can address a different problem from a chelant that binds metal without changing its oxidation state.
Published industrial literature identifies well drilling and stimulation among the relevant application contexts. The actual choice depends on fluid composition, acidity, temperature, iron concentration and the other components in the formulation.
Iron control should be assessed with the intended fluid and its anticipated changes during use. A result obtained in one acid system does not establish compatibility or precipitation control in every brine, spent fluid or mixed-metal environment.
The appropriate TGA concentration is a formulation decision based on the required chemistry. This profile does not provide a field-treatment dosage, injection plan or universal iron-control capacity.

CORROSION-INHIBITOR FORMULATIONS

Mercaptoacetic Acid is also documented as a component of selected corrosion-inhibitor formulations, including oil and gas applications. The interactions of Mercaptoacetic Acid with metals and surfaces contribute to the reason it is considered for these systems.
Corrosion inhibition depends on the whole environment. Fluid chemistry, metal composition, temperature and the rest of the inhibitor package determine whether the intended protective effect is obtained.
The role of TGA in a validated inhibitor formulation does not mean that concentrated free acid is non-corrosive to equipment. Raw-material storage compatibility and in-service corrosion performance are separate questions.
For formulation work, state the metal or alloy and the intended fluid conditions. Assessing the complete inhibitor package under representative conditions is more informative than assigning a general corrosion-protection claim to the acid.

METAL-RELATED CLEANING AND AUTOMOTIVE FORMULATIONS

Thioglycolic acid and thioglycolate salts are documented ingredients in selected cleaning systems, including automotive wheel-cleaning applications. Their ability to interact with metal species provides a different function from ordinary surfactant detergency.
The finished cleaner's pH and thioglycolate form matter. A formulated salt-based product cannot be described as chemically equivalent to applying concentrated Mercaptoacetic Acid to the same surface.
Surface compatibility should be evaluated on the intended metal, coating and adjacent materials. An ingredient's ability to bind iron does not establish that every wheel finish, protective layer or decorative metal will tolerate the formulation.
Useful development criteria include the required cleaning performance, material compatibility and stability of the complete product. Odor and exposure control also remain relevant because the sulfur-containing chemistry is not eliminated merely by describing the product as an iron remover.

MINERAL PROCESSING AND SELECTIVE FLOTATION

Mercaptoacetic Acid and related thioglycolates are documented in mineral-processing chemistry. Research has examined TGA as a depressant during separation of molybdenite from copper and iron sulfide minerals.
In one experimental study, the effect on chalcopyrite and pyrite depended on the collector used in the preceding flotation stage. This demonstrates that the reagent operates within an existing surface-chemistry system rather than providing a fixed selectivity independent of other chemicals.
The role of a depressant is different from that of a collector. The behavior of Mercaptoacetic Acid in a particular separation should not be generalized to every thioglycolate derivative, because structural changes can produce a different function.
Ore mineralogy, process water and the complete reagent scheme should guide selection. Laboratory or plant qualification needs to address the actual separation objective rather than simply the presence of a target metal in the feed.

PERMANENT WAVING AND HAIR-RESTRUCTURING SYSTEMS

Thioglycolate chemistry is established in permanent waving and selected hair-straightening systems. The reducing stage acts on disulfide connections within keratin, allowing changes in the fiber's structure under the conditions of a formulated treatment.
Published hair-fiber studies have investigated the relationship between thioglycolic-acid treatment, disulfide changes and mechanical response. They support the chemical role but also show why the effect cannot be described simply as a stronger acid producing a better result.
Commercial formulations commonly use appropriate thioglycolate salts, and some systems use thioglycolate esters. The identity of the active form and the formulation pH are integral to the application.

Reduction and subsequent oxidation have different roles in the overall treatment. A product's final performance depends on the complete process and formulation rather than on free TGA content alone.
The INCI name THIOGLYCOLIC ACID identifies the cosmetic ingredient name; it is not a declaration that an industrial grade is suitable for direct cosmetic use. Finished-product safety and the applicable restrictions must be assessed for the intended use and market.
This application discussion describes raw-material chemistry and does not provide a do-it-yourself hair-treatment procedure. Concentrated acid is toxic and corrosive, and its industrial handling requirements remain separate from those of an assessed finished product.

DEPILATORY FORMULATIONS

Selected thioglycolate salts are used in depilatory formulations because of their action on hair keratin. Calcium, potassium and other defined salts appear in the established technical literature, depending on the formulation.
Depilation and permanent restructuring are different objectives. Their finished products should not be treated as interchangeable merely because both use thioglycolate chemistry.
The chemical form, alkalinity and other formulation components influence the response of the hair and surrounding tissue. A raw-acid specification cannot by itself establish the behavior or suitability of the finished preparation.
Cosmetic requirements distinguish product types and conditions of use. A concentration limit or safety conclusion applicable to one category should not be transferred automatically to another or presented as a universal TGA allowance.

LEATHER BEAMHOUSE PROCESSING

Alkaline sodium thioglycolate is documented for hair removal during the beamhouse stage of leather manufacture. Mercaptoacetic Acid is relevant as the chemical basis for this thioglycolate technology rather than as a blanket recommendation to use raw acid directly on hides.
The process objective differs from cosmetic depilation even though both relate to keratin chemistry. Hide condition, process chemistry and the requirements of subsequent leather operations determine the useful treatment system.
Technical selection should consider the complete beamhouse process, waste streams and compatibility with other reagents. Claims of reduced environmental burden require evidence for the actual operating system rather than an assumption based solely on substituting one sulfur-containing material.
Where thioglycolate is compared with sulfide-based chemistry, handling and effluent assessment remain necessary. The change in reagent does not remove the need to evaluate sulfur-containing residues and interactions elsewhere in the process.

FINE-CHEMICAL AND DERIVATIVE MANUFACTURE

The combination of a thiol and a carboxylic acid makes TGA a useful synthetic starting material. Industrial literature identifies uses in preparation of selected agrochemical intermediates, polythiols, thioesters and other specialty chemicals.
The intended transformation determines which functionality is used or modified. Esterification at the carboxyl group, for example, produces a thioglycolate ester whose properties differ from those of the starting acid.
Derivative manufacture can require particular control of water, free-thiol content, oxidation products and trace contaminants. A grade acceptable for one formulation may therefore be unsuitable for a more sensitive synthesis.
The fact that TGA is a precursor does not transfer the properties, safety classification or end-use approvals of the derivative to the acid. Product descriptions should name the material actually used at each stage.

THIOGLYCOLATE ESTERS AND PVC-STABILIZER CHEMISTRY

Selected thioglycolate esters are used as intermediates in stabilizer chemistry, including organotin mercaptide technologies associated with PVC. This is a derivative application rather than a general direct use of free Mercaptoacetic Acid as a finished PVC stabilizer.
Ester structure and subsequent metal-containing chemistry determine the characteristics of the stabilizer. The final stabilizer package must be assessed for processing, compatibility and its intended polymer use.
When this application is relevant to a purchase, specify whether the requirement is free acid for ester manufacture or a particular downstream thioglycolate. A shared thioglycolic-acid origin does not make these materials interchangeable.

PETROLEUM CATALYST AND METAL-PASSIVATION TECHNOLOGIES

Industrial literature identifies thioglycolic-acid-derived mercaptides in selected catalyst metal-passivation applications. These derivatives are used to address unwanted effects associated with contaminating metals in refinery catalyst systems.
This application should remain distinct from oilfield iron control in an aqueous treatment fluid. The chemical form, equipment and performance objective are different.
The relevant derivative and application approval must be identified before a raw-material grade is selected. A general statement that TGA binds metals does not establish a universal catalyst-treatment method or suitability for every refining process.

IRON ANALYSIS AND LABORATORY REAGENT USE

Thioglycolic acid is an established reagent in selected spectrophotometric iron methods. Formation of a colored iron-containing system under defined analytical conditions allows measurement against an appropriate calibration.
Published methods report absorption measurements around 530–535 nm, depending on the method. These wavelengths belong to specific analytical systems and are not a universal optical constant of pure Mercaptoacetic Acid.
The reducing and complexing behavior of Mercaptoacetic Acid can both be relevant. Sample preparation, pH and coexisting substances must be addressed by the validated method rather than assumed from the reagent name.
Analytical-grade specifications may therefore include a suitability test in addition to chemical assay. For accurate work, reagent quality, blanks, standards and method controls should match the intended determination.

NANOMATERIAL LIGANDS AND SURFACE RESEARCH

TGA is documented as a capping ligand in aqueous preparation of selected semiconductor quantum dots, including CdTe and CdSe research systems. The sulfur-containing group interacts with the particle surface while the carboxyl functionality contributes to the behavior of the capped material in the surrounding medium.
Published studies have examined TGA alongside other ligands and shown that ligand choice affects the resulting colloid and optical properties. A reagent's presence in a synthesis does not establish one fixed quantum yield or particle size.
The ligand and nanocrystal must also be distinguished. Statements about the optical or electrical behavior of a TGA-capped particle are properties of that prepared material, not intrinsic properties of the neat acid.
This is a research application and does not imply an established medical use or unrestricted suitability for biological exposure. The complete nanomaterial, including its inorganic core and residual reagents, requires its own assessment.

FORMULATION CHOICES AND PERFORMANCE LIMITATIONS

The best chemical form depends on the required function. Free acid may be selected as a synthetic reagent, while a neutralized salt or ester may be more appropriate in a particular finished formulation.
Water miscibility is useful in aqueous systems, but it does not establish compatibility with every component. Metals, oxidants, alkaline materials and other reactive substances can alter the chemistry as well as the physical appearance.
Comparison with another reducing or complexing agent should reflect the target process. Reducing power, ligand behavior, pH response, sulfur content and downstream requirements can matter differently in polymerization, cleaning and iron control.
A change in Mercaptoacetic Acid concentration also changes water addition and the amount of active reagent delivered. Converting between commercial solutions requires the actual assay and a clearly defined mass basis.
The raw-material specification for Mercaptoacetic Acid should therefore connect to a practical performance test. Molecular-weight control, iron solubility, cleaning response and derivative yield are different endpoints and should not be treated as interchangeable evidence of product quality.

STARTING FORMULATION APPROACHES FOR MERCAPTOACETIC ACID

The following examples illustrate how Mercaptoacetic Acid can be evaluated during formulation and process development. These starting approaches are not validated commercial recipes, production instructions, or final formulations confirmed to comply with applicable regulations.
The suggested levels are illustrative starting points for preliminary laboratory trials. Mercaptoacetic Acid, also known as Thioglycolic Acid or TGA, contains both thiol and carboxylic acid groups. Its assay, reducing capacity, oxidation state, and the other raw materials used can significantly influence performance. Laboratory evaluation, performance testing, occupational safety assessment, and applicable regulatory checks are required for each application.
Unless otherwise stated, percentages refer to weight percentages in the final formulation, expressed as 100% active Mercaptoacetic Acid equivalent. Calculate the quantity of commercial raw material from its actual assay and adjust the water accordingly. For example, a target of 7.0% active acid requires 10.0% of a raw material containing 70.0% Mercaptoacetic Acid. Thioglycolate salts require conversion to the corresponding acid equivalent rather than direct substitution by weight.

EXAMPLE 1: MERCAPTOACETIC ACID CHAIN TRANSFER AGENT SCREENING IN ACRYLIC EMULSION POLYMERIZATION

Objective: To determine how the dosage of Mercaptoacetic Acid affects polymer molecular weight, viscosity, monomer conversion, and application performance in an established acrylic emulsion polymerization system.

Starting components:

Mercaptoacetic Acid: approximately 0.10%, 0.25%, 0.50%, and 1.00% active acid based on total monomer weight, with a separate zero-addition control

Monomer mixture, such as butyl acrylate / methyl methacrylate / acrylic acid: keep constant

Emulsifier system: keep constant

Initiator system and dosage: use an established system and keep constant

Buffering or neutralizing system: keep the defined pH control strategy consistent

Demineralized water: adjust to maintain the same total water content and target solids

Reactor temperature: use the established process setpoint, such as approximately 80 °C for a suitable thermally initiated system

Feed duration, agitation, and post-reaction holding time: keep constant

These levels are proposed screening points, not a universal optimum. Thioglycolic Acid can transfer growing radical chains and thereby influence molecular weight. Its reducing activity can also affect initiator behavior, so molecular weight and reaction rate must be evaluated separately.

Application approach:

Prepare an established control batch using the selected acrylic emulsion process.
Prepare a dilute aqueous Mercaptoacetic Acid feed with a documented active concentration, using compatible equipment.
Introduce the TGA feed through a controlled addition strategy suitable for the selected polymerization system, maintaining the same addition profile across trials.
Keep the initiator feed separate from the Mercaptoacetic Acid feed. Do not premix concentrated TGA with persulfates or other oxidizing initiators.
Maintain the specified temperature, monomer feed profile, and pH control strategy while recording any change in reaction rate or cooling demand.
Complete the established holding and cooling stages, then measure solids, conversion, residual monomer, viscosity, particle size, and coagulum.
Determine molecular weight and molecular weight distribution using a suitable validated analytical method. Compare viscosity at the same solids content, pH, and measurement temperature.
Evaluate relevant film properties, such as adhesion, flexibility, hardness, or water resistance, before selecting the Mercaptoacetic Acid dosage.
Use suitable reactor cooling, venting, local exhaust ventilation, eye and face protection, and chemical-resistant gloves. Mercaptoacetic Acid is corrosive and toxic through several exposure routes; concentrated handling requires controls appropriate to the current safety data sheet.

EXAMPLE 2: MERCAPTOACETIC ACID-BASED IRON CONTAMINATION REMOVER SCREENING

Objective: To examine how the active level of Mercaptoacetic Acid, converted to thioglycolate during pH adjustment, affects iron contamination removal, rinsability, and substrate compatibility.

Starting approach:

Mercaptoacetic Acid: approximately 1.0%, 2.0%, and 3.0% active acid equivalent

Compatible nonionic surfactant: an illustrative fixed level of approximately 0.5–1.0% active surfactant

Diluted sodium hydroxide solution: sufficient to neutralize the carboxylic acid and reach the selected final pH

Demineralized water: sufficient to reach 100%, including the water introduced with other raw materials

Final pH: select a setpoint within approximately 6.5–7.5 and keep it constant across trials

Evaluation temperature: approximately 20–25 °C, kept constant

Contact time, application quantity, and agitation: keep constant

Select one surfactant concentration within the proposed range and use it in every comparison. Near neutral pH, the acid is present predominantly as a thioglycolate salt. The cleaning performance therefore reflects a Mercaptoacetic Acid-derived system rather than an unneutralized acid solution.

Application approach:

Charge most of the demineralized water into a compatible vessel and add the surfactant with gentle agitation.
Add Mercaptoacetic Acid slowly to the aqueous mixture while monitoring temperature.
Introduce the diluted sodium hydroxide solution gradually under controlled agitation and cooling. Allow the mixture to equilibrate before making the final pH adjustment.
Add the remaining water, homogenize, and recheck pH at the defined measurement temperature.
Apply a measured quantity to standardized test panels carrying comparable iron contamination.
After the selected contact period, rinse consistently and assess residual contamination using a defined visual rating, image analysis, or another suitable quantitative method.
Record any color development, but do not use color intensity alone as proof of complete iron removal.
Evaluate gloss, staining, discoloration, corrosion, and damage to coatings or adjacent materials. Include untreated panels and an active-free formulation control.
Monitor active thiol content, appearance, pH, and performance during preliminary stability testing before selecting a candidate formula.
Neutralizing Mercaptoacetic Acid releases heat. Avoid uncontrolled alkali addition and contact with bleach, hypochlorites, or other strong oxidizers. Use ventilation, splash protection, and appropriate gloves; collect contaminated rinse water for suitable treatment or disposal.

EXAMPLE 3: MERCAPTOACETIC ACID ACTIVE LEVEL EVALUATION IN A PERMANENT WAVING LOTION

Objective: To compare the effects of Mercaptoacetic Acid equivalent concentration on curl formation, processing response, and hair fiber condition in an ammonium thioglycolate-based laboratory waving lotion.

Starting approach:

Mercaptoacetic Acid: approximately 5.0%, 6.0%, and 7.0% active acid equivalent

Aqueous ammonia of a specified concentration: sufficient for controlled neutralization and adjustment to the selected alkaline pH

Glycerin: an illustrative fixed level of approximately 1.0–2.0%

Compatible nonionic wetting agent: an illustrative fixed level of approximately 0.1–0.3% active material

Demineralized water: sufficient to reach 100%

Final pH: select a setpoint within approximately 8.5–9.0 and keep it constant across trials

Hair tress type, rod diameter, lotion-to-hair ratio, evaluation temperature, and processing schedule: keep constant

Select one glycerin level and one wetting agent level for the complete series. After neutralization with ammonia, Mercaptoacetic Acid is present primarily as ammonium thioglycolate. Report the reducing agent concentration as Thioglycolic Acid equivalent, not as the total weight of the ammonium salt solution.
These trial levels do not establish product safety or regulatory compliance. Use cosmetic-grade materials, assess the complete formula, and verify the requirements for the intended product category and market before further development.

Application approach:

Charge most of the demineralized water and dissolve the glycerin and compatible wetting agent under gentle agitation.
Add Mercaptoacetic Acid slowly to the aqueous phase using suitable ventilation and temperature monitoring.
Add the specified aqueous ammonia gradually under cooling to form the ammonium thioglycolate system and reach the selected pH.
Adjust the final batch weight with water, allow temperature and pH to stabilize, and verify the active reducing agent concentration using a suitable assay.
Prepare standardized hair tresses and apply each candidate lotion at the same lotion-to-hair ratio under a defined laboratory protocol.
Compare the selected exposure periods without changing the other test conditions, then rinse thoroughly.
Where the test protocol requires oxidative fixation, use a separately prepared, compatible fixing product after rinsing. Never mix the waving lotion directly with hydrogen peroxide or another oxidizing fixer.
Assess curl formation, curl retention after washing, wet combing, breakage, and hair fiber strength using consistent methods.
Compare the Mercaptoacetic Acid levels and select a candidate based on both waving performance and fiber condition.
Evaluate pH drift, active thiol retention, packaging compatibility, and microbiological quality during further development. Any preservative system must be assessed for compatibility and demonstrated efficacy.
Conduct initial trials on hair tresses. Mercaptoacetic Acid, alkaline thioglycolate mixtures, and ammonia require effective ventilation, eye protection, and suitable gloves. Product safety assessment, labeling, and applicable restrictions must be addressed before any human-use evaluation.

ASSAY, IMPURITIES AND PRODUCT CONSISTENCY

Useful product parameters include concentration or assay, water content, color and the relevant oxidation or condensation products. Application-specific trace-metal limits may also be important where the chemistry is sensitive to metal contamination.
The assay method deserves explicit attention. An iodometric result, an acid-base titration and a chromatographic determination can describe different aspects of the sample.
Published analytical work distinguishes thioglycolic acid from dithiodiglycolic acid in formulated products. This is valuable where the free-thiol fraction matters more than total carboxylic acidity alone.
A certificate of analysis should identify measured batch results and their methods. Typical catalogue data are useful for comparison but should not be presented as guaranteed release limits unless the supplier's specification says so.
For a new supply, confirm the intended grade, concentration and application with Ataman Chemicals. Current SDS and TDS information, batch traceability and any necessary end-use documentation should refer to the actual proposed product.
Shelf life and packaging must also be confirmed for that grade. A storage period for a defined laboratory solution cannot establish the expiry of every distilled acid or industrial aqueous product.

FIRST AID MEASURES FOR MERCAPTOACETIC ACID

Eye Contact with Mercaptoacetic Acid: Immediately rinse cautiously with plenty of clean water, remove contact lenses if easy to do, and continue rinsing while obtaining urgent medical assistance. Mercaptoacetic Acid can cause severe eye damage; treatment must not wait for symptoms to improve.
Skin Contact with Mercaptoacetic Acid: Immediately remove contaminated clothing and rinse affected skin with plenty of water or a shower. Obtain immediate medical attention because skin exposure can involve both corrosive injury and absorption.
Inhalation of Mercaptoacetic Acid: Move the person to fresh air without exposing the rescuer and obtain immediate medical assistance. Significant exposure can have delayed respiratory effects, so apparent early improvement does not replace medical assessment.
Ingestion of Mercaptoacetic Acid: Rinse the mouth and obtain immediate medical or poison-center assistance. Do not induce vomiting or attempt neutralization, and never give anything by mouth to an unconscious person.
Medical Information for Mercaptoacetic Acid Exposure: Provide the Mercaptoacetic Acid label, concentration and current SDS. Rescuers must avoid contact with contaminated clothing or liquid and use appropriate protection.

HANDLING AND STORAGE OF MERCAPTOACETIC ACID

Handling Mercaptoacetic Acid: Restrict handling to trained personnel using the current SDS and an approved procedure. Prevent splashes and avoid skin, eye and inhalation exposure during opening, sampling and transfer.
Ventilation for Mercaptoacetic Acid: Provide appropriate local extraction or enclosed handling where vapors, mist or aerosols may be released. Strong odor is not a substitute for exposure assessment, and loss of odor awareness does not establish that the atmosphere is safe.
Personal Protection for Mercaptoacetic Acid: Use suitable chemical splash goggles, face protection where required, compatible gloves and protective clothing. Glove material and breakthrough information must relate to the actual concentration and task.

Respiratory Protection for Mercaptoacetic Acid: Select any required respiratory equipment through an appropriate workplace program. Ordinary particulate protection must not be assumed suitable for vapor exposure or an unknown emergency atmosphere.
Storage of Mercaptoacetic Acid: Keep Mercaptoacetic Acid closed, correctly labeled and in supplier-approved compatible packaging under the stated temperature conditions. Prevent contamination and separate it from incompatible chemicals.
Temperature Control for Mercaptoacetic Acid: Follow the supplied grade's instructions. Some concentrated laboratory products specify refrigerated storage, but their temperature range should not be copied as a universal instruction for every industrial solution.
Air Exposure and Mercaptoacetic Acid: Follow any specified headspace or inert-gas requirements and minimize unnecessary exposure. Oxygen control addresses oxidation concerns but does not guarantee prevention of every concentration-related storage change.

Equipment Compatibility for Mercaptoacetic Acid: Confirm tanks, pumps, seals and transfer lines for the actual concentration and service conditions. The use of Mercaptoacetic Acid in an inhibitor formulation does not establish compatibility of an unlined metal vessel with concentrated acid.
Spill Response for Mercaptoacetic Acid: Isolate the area and use trained responders with suitable protection and the current SDS. Prevent entry into drains and collect material using compatible equipment and absorbents.
Inventory Control for Mercaptoacetic Acid: Maintain lot identity, concentration and storage records where relevant. Review changes in appearance or analytical performance before releasing suspect material to a critical application.

HEALTH, FIRE AND ENVIRONMENTAL INFORMATION

Reviewed concentrated-product information classifies thioglycolic acid as toxic if swallowed, in contact with skin or inhaled, and as causing severe skin burns and eye damage. Skin sensitization is also identified in the reviewed safety information.
The acute toxicity is important alongside corrosivity. Preventing visible burns alone is not an adequate exposure-control objective because absorption and inhalation also require control.
Occupational guidance notes that odor fatigue can occur. Workplaces should use appropriate ventilation and exposure assessment rather than attempting to judge safety by the strength of the mercaptan smell.
Liquid Mercaptoacetic Acid is combustible, and heating or fire can generate hazardous sulfur-containing fumes and carbon oxides. A closed-cup flash-point reference does not establish that heated process equipment is safe without a separate assessment.

Strong oxidants and strong alkalis can cause hazardous reactions, and certain metals are incompatible. Controlled neutralization within a designed formulation process must not be confused with improvised spill treatment or first aid.
Prevent releases to water, soil and drainage systems. Complete water miscibility does not mean that disposal through a drain is acceptable, and metal-containing process residues may present additional waste-management requirements.
Unused Mercaptoacetic Acid, contaminated cleanup material and formulated waste should be assessed according to their actual composition. An authorized waste route should be used, with relevant product and contamination information available to the contractor.

TRANSPORT INFORMATION

Reviewed concentrated-product transport information identifies UN 1940, THIOGLYCOLIC ACID, class 8, packing group II. The current SDS and shipping requirements must be checked for the supplied concentration and consignment.
The transport description and workplace hazard classification serve different purposes. Class 8 does not replace consideration of the toxic and sensitizing hazards identified in the product's safety information.
Packaging and closures must be suitable for Mercaptoacetic Acid and approved transport arrangement. A container used for another organic acid or a dilute finished cleaner should not be assumed suitable for concentrated Mercaptoacetic Acid.

FREQUENTLY ASKED QUESTIONS

Is Mercaptoacetic Acid the same as thioglycolic acid?
Yes. Both names identify the substance with CAS 68-11-1 and EC 200-677-4.

What is the chemical structure of Mercaptoacetic Acid?
The structure of Mercaptoacetic Acid is HSCH2COOH, with one thiol group and one carboxylic acid group in the same molecule.

Is thioglycolate simply another name for the free acid?
The term can describe its deprotonated form or salts and derivatives in context. A specific salt or ester should not be treated as identical to free Mercaptoacetic Acid.

Is Mercaptoacetic Acid the same as glycolic acid?
No. TGA contains a thiol group, while glycolic acid has different functionality and chemical behavior.

Why is TGA useful in aqueous polymerization?
The water miscibility of Mercaptoacetic Acid and thiol-based chain-transfer behavior make it useful for molecular-weight control in suitable systems.

Does Mercaptoacetic Acid act as a polymerization initiator?
The documented role of Mercaptoacetic Acid is often chain transfer. Initiation is a separate function determined by the reaction system.

Why is Mercaptoacetic Acid used for iron control?
Mercaptoacetic Acid can combine reducing and complexing behavior, which is useful in appropriately designed formulations that need to manage iron species.

Does corrosion-inhibitor use mean the acid is safe for all metals?
No. The effect of a complete inhibitor formulation is different from the compatibility of concentrated acid with storage or processing equipment.

Can concentrated Mercaptoacetic Acid be used directly as a cosmetic product?
Mercaptoacetic Acid is an industrial raw material, not a ready-to-use treatment. Cosmetic applications require a suitable grade, assessed formulation and compliance with the applicable conditions of use.

What is the INCI name of Mercaptoacetic Acid?
The ingredient name is THIOGLYCOLIC ACID; this name does not independently establish suitability of a particular commercial grade.

Is the 96 °C boiling value an atmospheric boiling point?
No. The representative value is reported at 5 mmHg, approximately 6.7 hPa.

Are the properties of concentrated TGA valid for an aqueous solution?
Not automatically. Density, viscosity, freezing behavior and other physical properties depend on concentration and composition.

Can air exposure affect the quality of Mercaptoacetic Acid?
Yes. Thiol oxidation is relevant, while concentrated products can also undergo other storage-related changes that are not prevented simply by excluding air.

Does total acidity prove that the free-thiol content is unchanged?
No. Acid-base and thiol-related assays measure different aspects of the material, and oxidation products can retain carboxyl groups.

Is the mercaptan odor a reliable exposure warning?
No. Odor fatigue can occur, and the absence of a noticeable smell does not establish safe conditions.

What should be checked before ordering Mercaptoacetic Acid?
Confirm concentration, assay method, relevant impurities, intended application, storage conditions and the current technical, safety and batch documentation.

TECHNICAL SUMMARY

Mercaptoacetic Acid is a bifunctional aqueous-compatible sulfur reagent whose value comes from the combination of thiol and carboxylic acid chemistry. The same molecular structure supports several different functions, but each application emphasizes a different aspect of the chemistry.
The thiol supplies reducing and radical-transfer behavior and can interact with suitable metal centers or surfaces. The carboxyl group supplies acid functionality, supports salt and ester manufacture and influences the aqueous behavior of the molecule and its derivatives.
This dual function explains why Mercaptoacetic Acid should not be characterized merely as an organic acid. It also explains why the free acid, a neutralized thioglycolate and a thioglycolate ester must be identified separately when discussing performance, handling and supply specifications.

In polymerization, the principal objective is often control of molecular weight through chain transfer. The resulting polymer depends on the monomer and reaction system, so TGA does not provide one fixed molecular-weight response or a universal addition level.
In metal-related applications, reduction and coordination can operate together. Oilfield iron control, formulated cleaning and selective flotation nevertheless remain distinct uses because the relevant metal species, surrounding medium and required outcome differ.
Cosmetic and leather applications depend strongly on the active chemical form and formulation conditions. Thioglycolate chemistry can alter keratin-related structures, but the intended result and acceptance requirements differ between permanent restructuring, depilation and industrial hide processing.
Derivative manufacture adds another layer of distinction. A raw acid may be used to make a thioglycolate ester or another specialty intermediate, while the downstream material has different physical properties and a separate end-use assessment.

Physical data for Mercaptoacetic Acid should preserve their conditions. The commonly cited reduced-pressure boiling point must retain its pressure, while density, viscosity and refractive index must retain their temperature and concentration basis.
The same care applies to aqueous solutions. A nominal solution concentration describes delivered active content, and the additional water affects formulation calculations and physical behavior; it does not change the molar mass of the acid molecule itself.
The quality of Mercaptoacetic Acid is more than total acidity. A formulation that depends on free thiol needs an appropriate measure of that functionality, because disulfide formation can reduce the intended reducing content while carboxylic acid groups remain in the sample.
Storage-related change should therefore be considered chemically rather than judged solely by appearance. Oxidation and thioglycolide formation are different issues, and the concentration of Mercaptoacetic Acid, packaging and storage history influence the useful specification.
Analytical control should match the application. A validated iodometric assay, a chromatographic separation and a functional performance test can provide complementary information, while no single measurement proves suitability for every use.

Commercial selection is strongest when the required chemical form, concentration and performance objective are stated together. Current technical and safety documents, batch results and relevant end-use information can then be assessed against a defined need.
The handling implications remain substantial across this technical range. Concentrated Mercaptoacetic Acid is toxic and corrosive, and successful industrial use requires control of contact, inhalation, incompatible reactions and storage conditions alongside the intended process chemistry.
Mercaptoacetic Acid consequently serves as a versatile reagent and precursor when its functional chemistry is matched to the application. Verified concentration, maintained chemical quality and application-specific assessment provide the basis for reliable use without transferring unsupported claims between the acid, its solutions and its derivatives.

CONTACT AND TECHNICAL ENQUIRIES

Ataman Chemicals can be contacted about Mercaptoacetic Acid with the required concentration, intended application and relevant quality parameters. Product availability, grade identity, packaging and current documentation should be confirmed for the proposed supply.
For a technical enquiry, identify whether the requirement concerns free acid, an aqueous solution or manufacture of a derivative. Include the required assay basis and any application-specific impurity or performance criteria so that the proposed material can be reviewed against the actual use.
Ataman Chemicals
Phone: +90 216 577 10 10
Email: info@atamankimya.com