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I’ve been doing experiments these days and needed a reagent called 3-mercaptoacetic acid. Our laboratory has two types of this reagent: one bottle is domestically produced, while the other is imported from Alfa Aesar. The purity of the domestically produced reagent is not sufficient; I have been using imported reagents. It was fine when the weather was cold recently, as the reagent is in solid crystal form. But as the weather has warmed up these past few days, I noticed that the surface layer of the imported reagent has turned into a paste-like substance, while the domestically produced reagent remains liquid. I checked the manual – the melting point of thioacetic acid is -16.8 degrees Celsius; logically, it should remain liquid regardless of the weather conditions. I would like to ask everyone: is there a problem with the reagent (perhaps it has absorbed moisture from the air), or is there some other reason? Thank you! ! Physical and chemical properties are attached below. 1. Physical and chemical constants of the substance: National standard code: 81611; CAS number: 68-11-1; Chinese name: Thioglycolic acid; English names: thioglycolic acid; mercaptoacetic acid; Alternative name: Hydrogen sulfide ethanoate ； Thioethanoic acid Molecular formula C2H4O2S ； HSCH2COOH: Appearance and properties – Colorless transparent liquid with a strong, unpleasant odor. Molecular weight: 92.12. Vapor pressure: 1.33 kPa at 18°C. Flash point: >110°C. Melting point: -16.5°C. Boiling point: 123°C at 3.86 kPa. Solubility: Miscible with water; also soluble in ethanol and ether, as well as in various other solvents. Density: Relative density (water=1): 1.33. Stability: Stable. Hazard symbol: 20 (Acidic corrosive substance). Main uses: Used as a reagent for determining iron levels and as a stabilizer; utilized in the production of potions and hair perming agents