Trade name and systematic chemical name
Phosphotungstic acid hydrate; Tungstophosphoric acid; CAS 12067-99-1
EC number
234-713-5
Molecular formula
H₃PW₁₂O₄₀ · xH₂O (x ≈ 24)
Supplier identification
Manufactured to reagent grade; distributed under ISO 9001:2015 quality management by major laboratory chemical suppliers; typical purity ≥ 99.0%

What hazards are assigned to this acidic heteropoly compound?

Classification according to Regulation (EC) No 1272/2008 [CLP]
Skin corrosion/irritation, Category 1B (H314); Serious eye damage/eye irritation, Category 1 (H318); Specific target organ toxicity – single exposure, Category 3, respiratory tract irritation (H335)
Label elements
Signal word: Danger. Pictograms: GHS05 (Corrosion), GHS07 (Exclamation mark)
Hazard statements
H314: Causes severe skin burns and eye damage. H335: May cause respiratory irritation.
Precautionary statements
P260: Do not breathe dust. P280: Wear protective gloves/protective clothing/eye protection/face protection. P303+P361+P353: IF ON SKIN (or hair): Take off immediately all contaminated clothing. Rinse skin with water/shower. P305+P351+P338: IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing. P310: Immediately call a POISON CENTER/doctor.

Compositional Breakdown and Impurity Profile

Primary component
Phosphotungstic acid hydrate, weight fraction ≥ 99.0% (hydrate basis)
Water of crystallization
Variable, typically 24 H₂O per Keggin unit; anhydrous loss on ignition approx. 5–8%
Trace impurities (typical analysis)
Heavy metals (as Pb) ≤ 0.005%, chloride (Cl) ≤ 0.01%, sulfate (SO₄²⁻) ≤ 0.02%, iron (Fe) ≤ 0.002%
When exposure occurs, the following measures derive from emergency response guides for corrosive solids.
After inhalation
Move victim to fresh air; keep at rest. If breathing is difficult, administer oxygen by trained personnel. Obtain medical attention if symptoms persist.
After skin contact
Immediately remove contaminated clothing and footwear. Rinse with copious amounts of water for at least 15 minutes. Do not apply neutralizing agents. Seek immediate medical evaluation for chemical burns.
After eye contact
Rinse cautiously with water for 20–30 minutes, holding eyelids open. Remove contact lenses, if present. Continue rinsing. Transport to an ophthalmologist without delay.
After ingestion
Rinse mouth with water; do NOT induce vomiting. Give 200–300 mL of water to dilute, if conscious. Never give anything by mouth to an unconscious person. Immediate hospital treatment is mandatory.

Extinguishing media and fire-derived hazards

Suitable extinguishing agents
Water spray, alcohol-resistant foam, dry chemical, carbon dioxide. Select medium based on surrounding materials.
Unsuitable agents
Do not use solid water jet; may spread burning material.
Specific hazards during fire
Thermal decomposition (> 400 °C) releases toxic and corrosive fumes of phosphorus oxides (P₂O₅) and tungsten oxides. Acidic mist may form in the presence of moisture.
Protective equipment for firefighters
Self-contained breathing apparatus (SCBA), EN 137 compliant, and full chemical protective suit (EN 943-1). Contaminated fire water must be contained; do not allow entry into drains or waterways.
For unintentional release, containment and clean-up proceed without generating airborne dust.
Personal precautions
Use full protective equipment as detailed in exposure controls. Prevent personnel from entering spill area without PPE. Avoid dust generation.
Environmental precautions
Do not flush into surface water or sanitary sewer. Dike spill area to prevent runoff. Inform authorities if product reaches aquatic environments.
Methods for containment and cleaning
Sweep or vacuum spillage using equipment with HEPA filtration (EN 1822-1). Place in clean, dry, chemically compatible container (polyethylene or stainless steel). Neutralize residues with dilute sodium bicarbonate solution, then absorb onto inert material (vermiculite, dry sand). Dispose as hazardous waste.

When storing this Keggin-type acid, moisture exclusion is critical

Storage conditions
Keep containers tightly closed in a cool, dry, well-ventilated area. Store at +15 °C to +25 °C. Protect from moisture and incompatible substances. Containers: polyethylene or borosilicate glass with PTFE-lined caps; avoid metal containers.
Handling precautions
Use local exhaust ventilation at powder transfer points. Avoid formation and inhalation of dust. Maintain good housekeeping to prevent accumulation on surfaces. Do not eat, drink or smoke in work areas. Wash hands and face thoroughly after handling.
Incompatible materials
Strong bases, amines, alkali metals, reducing agents, cyanides, sulfides. Contact with water may generate heat (exothermic hydration).
Occupational exposure limits
No specific OEL for phosphotungstic acid. General limits: inhalable dust fraction 10 mg/m³ (ACGIH TLV-TWA for particles not otherwise specified); respirable fraction 3 mg/m³.
Engineering controls
Use enclosed transfer systems or dust collection at point source (capture velocity 0.5–1.0 m/s). Ensure emergency eye-wash stations and safety showers are accessible.
Personal protective equipment
Respiratory: EN 149 FFP2 half-mask when dust exceeds OEL. Hand: EN 374 chemical-resistant gloves (butyl rubber, nitrile), breakthrough time > 480 min. Eye: EN 166 tight-fitting goggles. Body: EN 13034 Type 6 chemical protective clothing.

Measured physico-chemical parameters (hydrate)

Appearance
White to off-white crystalline powder, occasionally pale yellow upon prolonged storage.
Odor
Odorless.
pH (aqueous solution, 1% w/v)
Approximately 1.0–1.5
Melting point/freezing point
89 °C (hydrate loses water; decomposition sets in above 400 °C)
Bulk density
1.6–2.0 g/cm³
Water solubility
Very soluble, > 500 g/L at 20 °C
Partition coefficient (n-octanol/water)
Log P < 0 (estimated, strong hydrophilicity)

Reactivity boundaries and hazardous decomposition

Thermal stability
Stable under recommended storage conditions. Loss of water of crystallization occurs above 60 °C; Keggin structure remains intact to approximately 400 °C.
Conditions to avoid
Excessive heat, open flames, moisture, incompatible chemicals.
Hazardous decomposition products
When heated to decomposition, emits phosphine (traces), phosphorus oxides, tungsten oxide fumes, and acidic vapors.
Corrosivity to metals
Corrosive to mild steel and galvanized surfaces in the presence of moisture; stainless steel 316L shows resistance only at ambient temperature and low concentrations.
Acute oral toxicity
LD50 rat: 3,300 mg/kg bw (OECD TG 401). Ingestion causes severe mucosal burns.
Acute dermal toxicity
LD50 rabbit > 2,000 mg/kg bw; primary hazard is corrosivity rather than systemic toxicity.
Skin corrosion/irritation
In vitro reconstructed human epidermis assay (OECD 439) indicates full-thickness skin corrosion. Rabbit Draize test confirms irreversible skin damage.
Serious eye damage/irritation
BCOP assay (OECD 437) demonstrates corrosive potential; category 1 for eye effects.
Respiratory or skin sensitization
No sensitization reported in available literature; a weight-of-evidence assessment using guinea pig maximization test (OECD 406) gives negative result.
Mutagenicity/carcinogenicity
In vitro Ames test (OECD 471) negative. No in vivo data indicating carcinogenic potential. Not classified by IARC, NTP, or ACGIH.

Ecotoxicological fate in aquatic compartments

Toxicity to fish
LC50 (Danio rerio, 96 h) = 150 mg/L (nominal); effects attributable to pH shift rather than systemic toxicity.
Toxicity to daphnia
EC50 (Daphnia magna, 48 h) = 110 mg/L under static conditions (OECD 202).
Persistence and degradability
The inorganic heteropolyanion is not readily biodegradable; hydrolysis products (phosphate, tungstate) are naturally occurring. Half-life in water depends on pH.
Bioaccumulation potential
Log P < 0 indicates negligible bioaccumulation (BCF < 10). Tungsten species do not significantly bioconcentrate in aquatic organisms.
Waste treatment methods
Dispose via licensed hazardous waste incinerator (EU waste code 06 04 05*: wastes from inorganic chemical processes, metal-containing). Acidic neutralization with lime before controlled landfilling is an alternative with prior authority approval.
Contaminated packaging
Triple-rinse container and treat rinsate as hazardous waste. Dispose of emptied containers according to national regulations (Directive 94/62/EC on packaging and packaging waste).

Transport classification for corrosive solids

UN number and proper shipping name
UN 3260, Corrosive solid, acidic, inorganic, n.o.s. (Phosphotungstic acid)
Transport hazard class(es)
Class 8 (Corrosive substances), Packing Group III
Environmental hazards
Not environmentally hazardous according to ADR/IMDG/IATA criteria.
Special precautions
Segregate from alkalis, amines, and foodstuffs during carriage. Transport in containers resistant to acid attack (UN 1H2 polyethylene drums).
Current regulatory listings that affect commercial distribution and use.
EU Regulations
REACH (EC) No 1907/2006: Registered; pre-registration completed. Harmonized classification and labeling in Annex VI of CLP: Table 3, index 024-005-00-2. Seveso III Directive 2012/18/EU: not listed as a qualifying quantity substance.
US Federal Regulations
TSCA inventory: listed. SARA Title III Section 302 Extremely Hazardous Substances: not listed. Section 313 (TRI reporting): Tungsten compounds are not listed individually; however, phosphorus is reportable under certain conditions.
International inventories
Included in DSL (Canada), AICS (Australia), IECSC (China), KECI (South Korea), ENCS (Japan), PICCS (Philippines).