What Is Ammonium Thioglycolate?
Ammonium thioglycolate is an organic compound, a salt of thioglycolic acid.
Its chemical formula is C2H7NO2S. As an ammonium salt of thioglycolate, it contains one mercapto group and one carboxyl group in its molecule. Commonly known as ammonium mercaptoacetate, ammonium thioglycolate, or ATG, its CAS number is 5421-46-5.
This compound has a molecular weight of 109.15 and is typically sold as an aqueous solution. It appears as a clear, colorless liquid at room temperature, with a characteristic sulfur or ammonia-like odor. Its density is 1.190 g/cm3.
For storage, it should be kept away from direct sunlight and high temperatures, and not mixed with strong oxidizers. Due to its potential to corrode metal, metal containers should be avoided. Under normal storage conditions, it is stable.
Ammonium thioglycolate is toxic if ingested and can cause allergic reactions upon skin contact. Handling should be done with care to avoid skin and eye exposure.
Uses of Ammonium Thioglycolate
This compound is widely used for breaking down proteins and as a reducing agent. Its applications include serving as a permanent wave agent, wool dyeing and straightening agent, PVC stabilizer, rust inhibitor, and metal surface treatment agent.
With a neutral pH (6.8 – 7.4), ammonium thioglycolate is safer than other organic solvents. It’s also less toxic compared to hydrochloric acid or sulfuric acid, common ingredients in rust removers. It is user-friendly as a rust remover, turning purple when reacting with red rust, which serves as a cleaning guide.
Principle of Ammonium Thioglycolate
As a reducing agent, ammonium thioglycolate is less hazardous than thioglycolic acid and is widely used.
In hair perming, it breaks down proteins by reducing disulfide bonds in keratin to mercapto groups. As a rust remover, it reduces iron rust to water-soluble iron thioglycolate, facilitating rust removal.
Its reducing action is also applied in synthetic chemistry, where it’s used to synthesize:
- Thiol-functionalized eggshell membranes for removing heavy metals from water.
- Cellulose-rhodamine B-methacrylamide (cellulose-RhBMA).
Types of Ammonium Thioglycolate
Ammonium thioglycolate is available as a chemical reagent in aqueous solutions of various concentrations, such as 45.0~55.0%, 50%, and 60%. It is packaged in volumes like 500mL, 1L, 25g, and 500g, typically in glass bottles, and can be stored at room temperature.
In industrial settings, it is also sold as a rust remover raw material in poly-drum packages of 24 kg or 250 kg. Additionally, it is a key ingredient in neutral rust remover detergents and perm solutions, with various products available from different manufacturers.