Barium sulfite (7787-39-5) Physical and Chemical Properties
Barium sulfite
Inorganic barium sulfite supplied as a slightly water‑soluble, odorless solid for industrial and specialty chemical applications.
| CAS Number | 7787-39-5 |
| Family | Sulfites (inorganic salt) |
| Typical Form | Powder or crystalline solid |
| Common Grades | EP |
Barium sulfite is an inorganic ionic salt belonging to the sulfite class; it can be formulated as \(\ce{BaO3S}\) and consists of the alkaline earth cation \(\ce{Ba^2+}\) paired with the sulfite anion \(\ce{SO3^2-}\). Structurally it is an extended ionic lattice in the solid state rather than a discrete covalent molecule; the computed descriptors reflect a two-component, non‑covalent unit (covalently-bonded unit count = 2) and a net formal neutral charge. The sulfite anion is the conjugate base of sulfurous acid and features a trigonal‑pyramidal oxo‑anionic structure with lone pairs and delocalized negative charge over the three oxygen atoms, while the barium center provides charge balancing and a high lattice energy that limits aqueous solubility relative to alkali metal sulfites.
Chemically, barium sulfite displays the class‑typical acid–base and redox tendencies of sulfites: limited dissolution releases \(\ce{SO3^2-}\) which is protonated under acidic conditions to \(\ce{HSO3-}\) and \(\ce{H2SO3}\)/\(\ce{SO2}\); sulfite anions are moderately reducing and are gradually oxidized by molecular oxygen to sulfate, ultimately forming the very insoluble sulfate salt \(\ce{BaSO4}\). The substance is an odorless solid with low polarity in the solid lattice but potential for alkaline behavior in sufficiently concentrated aqueous solutions of dissolved anion. Where solubility is limited, practical aqueous behavior is governed by the balance between the small dissolved fraction and solid‑phase equilibria.
Common commercial grades reported for this substance include: EP.
Basic Physical Properties
Density
No experimentally established value for this property is available in the current data context.
Melting or Decomposition Point
No experimentally established value for this property is available in the current data context.
Solubility in Water
Barium sulfite is reported as an odorless solid that is slightly soluble in water. Solubility is limited by the strong lattice interactions between \(\ce{Ba^2+}\) and \(\ce{SO3^2-}\); when dissolution occurs the anion may equilibrate with protonated forms in solution. In practical aqueous systems the dissolved concentration will be low and equilibrium with a solid phase will control dissolved sulfite activity. In oxidizing, aerated aqueous environments the sulfite anion is susceptible to gradual oxidation to sulfate, which can drive precipitation of \(\ce{BaSO4}\) and further reduce soluble barium concentrations.
Solution pH (Qualitative Behavior)
No single numerical \(\mathrm{pH}\) value is applicable because solubility is low and aqueous \(\mathrm{pH}\) depends on dissolution extent and solution buffering. Where appreciable \(\ce{SO3^2-}\) is present in solution, the anion is the conjugate base of sulfurous acid; solutions tend to be neutral to mildly alkaline unless acidified. Acidification shifts speciation toward \(\ce{HSO3-}\)/\(\ce{H2SO3}\) and can liberate \(\ce{SO2}\) gas.
Chemical Properties
Acid–Base Behavior
Barium sulfite functions as a source of the sulfite anion \(\ce{SO3^2-}\). In aqueous media \(\ce{SO3^2-}\) undergoes protonation equilibria to form \(\ce{HSO3-}\) and ultimately \(\ce{H2SO3}\)/\(\ce{SO2}\) under strongly acidic conditions. Because \(\ce{SO3^2-}\) is a relatively strong base among oxyanions of sulfur, its presence raises solution basicity when dissolution is significant. Conversely, exposure to acids converts the solid to more soluble barium salts and can result in release of sulfur dioxide; such acid–driven transformations are of practical importance for processing and safety.
Reactivity and Stability
Barium sulfite is gradually oxidized by atmospheric oxygen to sulfate, with the net conversion of \(\ce{SO3^2-}\) to \(\ce{SO4^2-}\); this transformation can lead to formation of the highly insoluble solid \(\ce{BaSO4}\). The solid is generally stable under dry, neutral conditions but will react with strong acids to produce soluble barium species and sulfur dioxide. Thermal decomposition behavior and specific decomposition temperatures are not provided in the available data. Because sulfite anions are reducing relative to sulfate, care is required with oxidizing agents; contact with strong oxidizers can lead to exothermic oxidation.
Molecular and Ionic Parameters
Formula and Molecular Weight
- Molecular formula: \(\ce{BaO3S}\)
- Molecular weight: 217.39 g·mol−1
Computed molecular descriptors: - Exact mass: 217.862062 - Monoisotopic mass: 217.862062 - Topological polar surface area (TPSA): 82.4 Å^2 - Hydrogen bond donor count: 0 - Hydrogen bond acceptor count: 4 - Rotatable bond count: 0 - Heavy atom count: 5 - Complexity: 18.8
Constituent Ions
- Cation: \(\ce{Ba^2+}\)
- Anion: \(\ce{SO3^2-}\)
The substance exists as an ionic solid (extended lattice) in which the barium cation and sulfite anion interact electrostatically; the ionic character and the large charge on barium contribute to limited aqueous solubility and strong lattice energies relative to alkali metal sulfites.
Identifiers for structural descriptors (provided for technical use): - SMILES: [O-]S(=O)[O-].[Ba+2] - InChI: InChI=1S/Ba.H2O3S/c;1-4(2)3/h;(H2,1,2,3)/q+2;/p-2 - InChIKey: ARSLNKYOPNUFFY-UHFFFAOYSA-L
(Insert SMILES, InChI and InChIKey values exactly as technical identifiers where required in informatics workflows.)
Identifiers and Synonyms
Registry Numbers and Codes
- CAS number: 7787-39-5
- European Community (EC) number: 232-112-2
- UNII: D71W8VF49C
- DSSTox Substance ID: DTXSID00228489
- Nikkaji Number: J43.702F
- Wikidata: Q415543
Synonyms and Common Names
Reported synonyms and alternative names include: - Barium sulfite - Barium sulphite - BARIUM SULFITE [MI] - BARIUM SULFITE (BASO3) - barium(2+);sulfite - Sulfurous acid, barium salt (1:1) - Bariumsulfit
(Additional depositor-supplied identifiers and synonyms exist; the above are representative names used in technical contexts.)
Industrial and Commercial Applications
Functional Roles and Use Sectors
Barium sulfite has documented use in the manufacture of paper and is associated with pulp and paper processing contexts. As a member of the sulfite class, it can function in roles related to sulfite chemistry such as reducing agent behavior, sulfite bleaching processes, or as an intermediate in treatments where sulfite anion activity is required; specific applications depend on formulation, solubility considerations, and downstream processing.
Typical Application Examples
Typical, high‑level application examples include use in pulp and paper processing where sulfite chemistry is applied; limited solubility and the potential for oxidation to sulfate influence how the substance is deployed in industrial process streams. No further detailed, application‑specific performance data are available in the current data context.
Safety and Handling Overview
Health and Environmental Hazards
- Exposure limits reported for particulate or barium‑expressed concentrations (values expressed as barium): maximum allowable concentration (MAK): 0.5 \(\mathrm{mg}\,\mathrm{m}^{-3}\) (inhalable fraction); permissible exposure limit (PEL): 0.5 \(\mathrm{mg}\,\mathrm{m}^{-3}\), as Ba; threshold limit values (TLV): 0.5 \(\mathrm{mg}\,\mathrm{m}^{-3}\), as Ba; IDLH: 50.0 \(\mathrm{mg}\,\mathrm{m}^{-3}\), as Ba.
- Hazard origins: toxicological concerns derive principally from soluble barium species (systemic toxicity following significant absorption) and from sulfite chemistry (e.g., release of \(\ce{SO2}\) on acidification, and potential allergenic or respiratory effects in sulfite‑sensitive individuals). The solid is gradually oxidized by air to sulfate, which may affect long‑term environmental fate and drive formation of insoluble \(\ce{BaSO4}\).
- Control measures: control airborne dust, provide local exhaust ventilation where dust or powders are handled, and use appropriate respiratory, eye and skin protection to limit inhalation and dermal exposure. Avoid conditions that lead to acid release or generation of sulfur dioxide.
For detailed hazard, transport and regulatory information, users should refer to the product‑specific Safety Data Sheet (SDS) and local legislation.
Storage and Handling Considerations
Store the material in a cool, dry, well‑ventilated area in tightly closed containers to minimize moisture uptake and dust generation. Avoid contact with strong acids (to prevent release of \(\ce{SO2}\)) and strong oxidizers that could react with sulfite anions. Minimize prolonged exposure to air in finely divided form if oxidation to sulfate is undesirable for process reasons. Maintain standard good industrial hygiene practices: separate storage from incompatible materials, implement spill control for powders, and provide training and PPE appropriate to barium and sulfite hazards.
For detailed hazard, transport and regulatory information, users should refer to the product‑specific Safety Data Sheet (SDS) and local legislation.
