Gallium(III) Sulfate Hydrate: Properties, Handling & Lab Use

Gallium(III) sulfate hydrate is a water-soluble inorganic gallium salt widely used as a gallium ion source in materials science, semiconductor research, catalysis, and biological studies.

Chemical Formula

Ga2(SO4)3·xH2O

CAS Number (anhydrous basis)

13494-91-2

Appearance

White to off-white crystalline powder

Solubility

Soluble in water; forms acidic aqueous solutions due to Ga³⁺ hydrolysis

Molecular Weight (anhydrous)

427.64 g/mol

Storage Condition

Store in a cool, dry, well-ventilated area in a tightly sealed container

SKU

G190759

Chemical Identity and Physical Properties

Gallium(III) sulfate hydrate (Ga₂(SO₄)₃·xH₂O) is the hydrated form of gallium(III) sulfate, an inorganic salt in which gallium exists in its stable +3 oxidation state. The compound appears as a white to off-white crystalline powder and is readily soluble in water. Upon dissolution, Ga³⁺ ions undergo partial hydrolysis, generating mildly acidic solutions; researchers should account for this pH depression when preparing aqueous formulations.

The anhydrous molecular weight is approximately 427.64 g/mol (CAS 13494-91-2). Commercial hydrated grades carry variable degrees of hydration (denoted xH₂O); the precise water content should be confirmed by thermogravimetric analysis or supplier certificate of analysis before use in stoichiometrically sensitive protocols. Gallium(III) sulfate is stable under ambient conditions but is hygroscopic and should be protected from atmospheric moisture to prevent caking and weight gain.

Key Laboratory Applications

Gallium(III) sulfate hydrate serves as a versatile precursor and reagent across several research domains:

• Semiconductor and thin-film research: Ga³⁺ ions derived from this salt are used in the synthesis of gallium oxide (Ga₂O₃) thin films and nanostructures, which are of interest as wide-bandgap semiconductor materials for power electronics and UV photodetectors.
• Catalysis: Gallium-containing catalysts prepared from soluble gallium salts have been investigated for dehydrogenation reactions and zeolite modification, where Ga³⁺ acts as a Lewis acid site.
• Biomaterials and antimicrobial research: Gallium ions are known to disrupt iron-dependent bacterial metabolism. Gallium(III) sulfate provides a readily bioavailable Ga³⁺ source for in vitro studies of antimicrobial activity and cytotoxicity assays.
• Electrochemical and electrodeposition studies: Aqueous gallium sulfate baths are employed in electrochemical investigations and the electrodeposition of gallium-containing alloy films.
• Analytical chemistry standards: The compound can serve as a primary standard or reference material for ICP-OES/ICP-MS gallium calibration when accurately weighed and dissolved.

Safe Handling, Storage, and Waste Disposal

Personal Protective Equipment (PPE): When handling Gallium(III) sulfate hydrate, wear appropriate PPE including nitrile gloves, safety glasses or goggles, and a laboratory coat. If dust generation is likely during weighing or transfer, use a dust/particulate respirator (minimum FFP2/N95 equivalent) and work inside a fume hood or ventilated enclosure.

First Aid Measures: In case of skin or eye contact, flush immediately with copious water for at least 15 minutes and seek medical advice. If ingested, do not induce vomiting; seek medical attention promptly. Inhalation of dust should be managed by moving the affected individual to fresh air.

Storage: Store in a tightly sealed container in a cool (15–25 °C), dry, and well-ventilated area, away from incompatible materials such as strong oxidisers and strong bases. The hygroscopic nature of the salt necessitates desiccant use or storage in a desiccator for long-term preservation of quality.

Waste Disposal: Gallium-containing waste must be disposed of in accordance with applicable local, national, and institutional regulations governing heavy-metal waste. Do not drain aqueous gallium solutions into the sewer without authorisation. Consult your institutional Environmental Health and Safety (EHS) office for approved disposal procedures.

Preparation of Aqueous Gallium(III) Sulfate Solutions

Due to the variable hydration level of commercial Gallium(III) sulfate hydrate, accurate solution preparation requires the following steps:

1. Determine effective Ga content: Consult the certificate of analysis (CoA) for the lot-specific assay value or perform thermogravimetric analysis (TGA) to establish the exact water content and thereby the true Ga₂(SO₄)₃ mass fraction.
2. Weighing: Tare a clean, dry weighing vessel. Quickly transfer the required mass of the hydrated salt and cap or cover promptly to minimise moisture uptake.
3. Dissolution: Add the weighed salt to the required volume of ultrapure water (18.2 MΩ·cm) with gentle stirring or sonication. The compound dissolves readily at room temperature. Note that the resulting solution will be mildly acidic (typically pH 3–5 depending on concentration) due to Ga³⁺ hydrolysis.
4. pH adjustment (if required): Adjust pH using dilute H₂SO₄ (to avoid introducing extraneous anions) or dilute NaOH, noting that excess base will precipitate Ga(OH)₃.
5. Filtration and storage: Filter through a 0.22 µm membrane filter if sterility or particle removal is required. Store solutions in polypropylene or glass containers at 4 °C and use within a validated stability window.

Quality Considerations and Regulatory Notes

Purity and grade selection: For research applications, select the highest commercially available purity grade consistent with experimental requirements. Trace-metal-grade or ICP-grade Gallium(III) sulfate should be chosen when low metal-ion background is critical (e.g., cell culture, trace analysis). Aladdin Scientific's product G190759 is intended for research use; refer to the current CoA for lot-specific purity, heavy-metal impurity profile, and moisture data.

Regulatory classification: Gallium(III) sulfate hydrate is not currently listed as a controlled substance or REACH substance of very high concern (SVHC) in most jurisdictions; however, users are responsible for verifying current regulatory status in their country of use. The compound is not classified as a dangerous good for transport under standard small-quantity laboratory exemptions in many regions, but consult the applicable SDS and courier regulations before shipment.

Documentation: Retain the CoA, SDS, and batch records in accordance with institutional quality management requirements. For GxP-compliant laboratories, re-test incoming material according to your site's incoming quality control (IQC) procedures.

Frequently asked questions

What is the typical degree of hydration in Gallium(III) sulfate hydrate, and does it affect weighing accuracy?

Commercial Gallium(III) sulfate hydrate is sold with a variable and often unspecified degree of hydration (xH2O). Because the water content directly affects the molar mass used in solution calculations, users should always verify the actual water content via TGA or rely on the lot-specific assay value on the CoA before preparing stoichiometrically defined solutions.

Why does dissolving Gallium(III) sulfate in water produce an acidic solution?

Ga³⁺ is a small, highly charged cation that undergoes significant hydrolysis in water, releasing protons (H⁺) and forming hydroxogallium species such as [Ga(OH)]²⁺. This hydrolysis process lowers the pH of the resulting solution, typically to between pH 3 and 5 depending on concentration. Researchers should be aware of this effect when the pH of their experimental system is critical.

Is Gallium(III) sulfate hydrate suitable for cell culture or biological assays?

Gallium(III) sulfate can be used as a Ga³⁺ source in in vitro biological studies, including antimicrobial and cytotoxicity assays, but it must be of sufficient purity to avoid interference from heavy-metal contaminants. Solutions should be sterilised by 0.22 µm filtration, and pH should be adjusted to physiological range prior to addition to cell culture media, as the inherently acidic solution could otherwise stress cells.

How should Gallium(III) sulfate hydrate be stored to maintain its quality?

Store Gallium(III) sulfate hydrate in a tightly sealed container in a cool (15–25 °C), dry environment away from moisture, strong oxidisers, and strong bases. Because the compound is hygroscopic, it is advisable to use a desiccant or store it in a desiccator. Opened containers should be resealed immediately after use and inspected for caking or colour change before each use.

Can Gallium(III) sulfate hydrate be used as a gallium source for synthesising gallium oxide nanostructures?

Yes, Gallium(III) sulfate hydrate is a practical water-soluble Ga³⁺ precursor for hydrothermal, sol-gel, and co-precipitation syntheses of gallium oxide (Ga2O3) nanostructures. Researchers should consider that sulfate anions remaining in the reaction mixture may incorporate into the product or influence morphology; thorough washing and annealing steps are typically employed to obtain phase-pure Ga2O3.

References

1. Cotton, F. A.; Wilkinson, G.; Murillo, C. A.; Bochmann, M. Advanced Inorganic Chemistry, 6th ed.; Wiley-Interscience: New York, 1999. (General properties of gallium compounds)
2. Bernstein, L. R. Mechanisms of therapeutic activity for gallium. Pharmacol. Rev. 1998, 50(4), 665–682.
3. Minami, T. Transparent conducting oxide semiconductors for transparent electrodes. Semicond. Sci. Technol. 2005, 20(4), S35–S44. (Context: wide-bandgap Ga2O3 semiconductor applications)
4. European Chemicals Agency (ECHA). REACH Regulation – Substances of Very High Concern (SVHC) Candidate List. https://echa.europa.eu/candidate-list-table (accessed 2024).

Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.