Potassium Metabisulfite
molecular structure · PubChem
AKA: 16731-55-8, Potassium disulfite, Dipotassium pyrosulfite, Dipotassium disulfite, Sobisu, Dipotassium metabisulfite, Potassium metabisulphite, Potassium disulfite (K2S2O5), Potassium pentaoxodisulfate
Synthetic
Preservative
Medicated Active
Not Clean
Potassium metabisulfite appears as a white granular or powdery solid with a sharp odor of sulfur dioxide. Decomposes at 150 to 190 °C. Density 2.3 g / cm3. Contact severely irritates skin, eyes, and mucous membranes. Low toxicity. Used as a food preservative and an antioxidant.
Solubility Freely soluble in water; insoluble in alcohol
Formula
K2O5S2
Mol. Weight
222.33
CAS #
16731-55-8, 4429-42-9
Form
Powder
State
Potassium metabisulfite appears as a white granular or powdery solid with a sharp odor of sulfur dioxide. Decomposes at 150 to 190 °C. Density 2.3 g / cm3. Contact severely irritates skin, eyes, and m
Functions
Hair Waving Or Straightening
Preservative
Keeps your product from growing bacteria, mold, or yeast. Without these, that jar of cream becomes a petri dish in about a week.
Reducing
Neutralizes Free Radicals
Traditional Use
Developed as a chemical preservative and antioxidant in the 19th century, widely adopted in cosmetics and food preservation to prevent oxidation and microbial growth.
EWG
4
CIR
Safe as used
Pregnancy
Caution
CIR Safety Findings
Not an Irritant
medical-approval
all-shades-safe
Concentration Guide
0.2%
0%0%
Reg. Limit
EU regulatory limit: 0.2%. SO2) Source: EU Cosmetics Regulation (EC) 1223/2009, Annex V (Preservatives), Entry 9.
Regulatory Agencies
Skin Types
●all-skin-types
Best For
General
Pregnancy & Breastfeeding Safe
Caution
The paper trail
🔬Peer-reviewed1 paper →
⚖️Regulatory1 listing →
🛡️Safety-assessed2 reviews →
Counts, not a verdict. A listing isn't a study. The trail, you decide.
Verified Jun 2026
Data: PubChem · CosIng · EWG · CIR