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Anyone watching the chemical industry over the decades notices certain substances quietly shape how things get done behind the scenes. Polyphosphoric acid, often overshadowed by its better-known cousin orthophosphoric acid, actually carries an interesting history. In the late nineteenth century, curiosity about condensed forms of phosphoric acids led chemists to tinker with heat and mixtures, hunting for agents with stronger dehydrating power. By the 1940s, serious attention landed on PPA as researchers developed industrial methods for phosphate manipulation and found situations where simple acids could not do the job. Major breakthroughs came when it served as a critical intermediary in manufacturing, especially as the postwar boom demanded more flexible tools for the synthetic organic chemistry industry. You see, PPA made possible what regular phosphoric acid could not—carrying out high-temperature, high-acidity reactions needed for more complex products. This story tracks not only industrial chemistry’s evolution but also how scientific curiosity about molecular structure, bonding, and function delivers real-world results.
Anyone who’s experimented with acid catalysts in a lab knows that PPA doesn’t behave like its simpler relatives. This acid doesn’t just refer to a single molecule, but rather a viscous mixture where phosphoric acid molecules link together in chains, long and short, thickening up the liquid. You won’t find single, sharp melting or boiling points because it acts like a polydisperse soup, with its properties shifting depending on how many phosphate units are hooked up at the moment. Most chemical catalogs classify it by its equivalent content, usually upwards of 115% compared to the neat orthophosphoric acid standard. Handling PPA feels distinct; there’s no mistaking its oily, almost syrupy consistency, which turns out quite useful for chemists aiming to avoid the splashing and volatility of many mineral acids.
Getting to grips with PPA’s physical and chemical quirks helps understand why it stands apart from regular acids. At room temperature, it shows up thick, nearly honey-like, colorless to pale yellow, hygroscopic, and almost odorless. Try pouring it, and it reluctantly leaves the bottle in a slow, gloppy ribbon. Its density overshoots water by a fair margin. This viscosity, much higher than purified phosphoric acid, relates closely to its structure—a tangled network of polyphosphate chains that trap water and limit flow. What really stands out is its powerful dehydrating ability. Regular acids pull out water from some compounds, but PPA earns a spot on the roster of top chemical water scavengers, rivaled mainly by acids like sulfuric or chlorosulfonic. When it comes into contact with organic matter, it strips out water, nudging molecules into new arrangements, especially where simple acid action falls short.
On chemical labels at supply houses, polyphosphoric acid goes beyond a simple percentage claim. Most labels specify content by “% as H3PO4,” since the actual mixture contains chains of various lengths and only loosely matches actual orthophosphoric acid. The labels spell out risks and handling procedures, warning against moisture exposure due to the vigorous exothermic reaction. Concentrations go up to around 120-125%, distinguishing the product from less-condensed forms. Safety classification leans on hazard pictograms—corrosive, health hazard, environmental warnings—and thorough detail about proper storage, such as ventilation and compatible materials, especially plastics and glass that survive the acid’s appetite for organics.
Driving the creation of PPA typically begins with orthophosphoric acid, the product most often derived from phosphate rock digestion via wet or thermal processes. Heating regular phosphoric acid under controlled, water-excluding conditions, chemists provoke condensation, where molecules eliminate water and link up to form longer polyphosphate chains. The key is balancing temperature and evaporation—the aim being to pull off as much water as possible without charring or breaking down the chains, which turns an elegant process into a burned mess. Larger facilities often use thin-film evaporators or special dehydration setups that let heat drive off water efficiently, yielding a product thick enough for industrial use. Any contamination or exposure to humid air can upset the process, shifting the balance back toward shorter chains or lower concentrations, so the whole operation happens under tightly regulated conditions.
In the chemistry lab, PPA doesn’t just sit still—it aggressively pushes molecules into new forms. Chemists reach for it when facing dehydration reactions, such as shifting amides into nitriles, or cyclizations for ring-forming reactions—tasks that would often stall in the presence of too much water or milder acid. The acid’s ability to act as both a proton donor and a water scavenger lets reaction mixtures drive forward, where other acids’ equilibrium would bog down. Engineers sometimes tweak its chain length distribution for specialized tasks, altering temperature profiles or feeding in pre-condensed phosphate mixtures. The result: targeted catalysts tailored to speed up manufacturing steps with higher yields and less byproduct formation. In strong acid conditions, PPA introduces a new landscape of reactivity and opens doors to transformations fundamental to pharmaceutical, dye, and agrochemical synthesis.
Long familiarity means chemists call polyphosphoric acid by a range of names, sometimes confusing for newcomers. Commonly, you’ll see it as “PPA” or “superphosphoric acid.” Other references, especially in older texts, call it “condensed phosphoric acid.” Even within regulatory circles, names oscillate between descriptors like “polyphosphoric acids” or “polyphosphate acid mixtures.” This subtle variety reflects the material’s mixed character, as each batch carries a slightly different chain-length profile, depending on preparation and intended use. Regardless of the naming convention, those working with it recognize its unique properties.
In the world of industrial chemicals, stories of acid burns and runaway dehydration reactions prompt strict safety rules, and PPA ranks as one needing special respect. Splash on the skin and the damage comes quick; fumes or splatters to eyes require immediate flushing and medical attention. Chemical-resistant gloves, goggles, and robust ventilation prove essential. Storage means keeping it away from water sources—including humid air—not just to preserve the acid but to prevent violent heat release. Handling spillages often proves tougher than with other acids, as thick, syrupy puddles resist simple dilution and require neutralization with great care. On a day-to-day level, supervisors insist on regular training, updated safety data sheets, and spill protocols, not just because of regulatory standards but from real-world experience of accidents that leave lasting damage. Waste handling affects environmental planning, as improper disposal can ravage aquatic systems and corrode pipes. Following government and international guidelines, such as those from OSHA or the European Chemicals Agency, drives safer workplaces and keeps the acid’s benefits available without injury or environmental cost.
The list of uses for polyphosphoric acid stretches across manufacturing disciplines, chemistry labs, and specialty industries. In organic synthesis, it repeatedly offers solutions that make complex transformations reliable, whether helping form aromatic anhydrides, aiding in acylation, or catalyzing cyclization. Its water-removing strength finds a place in resin modification, plasticizer production, herbicide formulation, and even specialty battery and glass manufacturing. Pharmaceutical developers look to it for rapid, clean conversions into intermediates critical for next-generation drugs. Some segments, like the production of high-value specialty chemicals, simply couldn’t do without it, given its role in intricate, multi-step synthetic routes. Even in the food world, derivatives of the phosphate group, not necessarily PPA itself, rest on the foundational chemistry explored in polyphosphoric systems.
Recently, curiosity has shifted to modifying PPA’s profile toward greener processes and better recyclability. New research dives into how tailoring chain lengths, or pairing PPA with other catalysts or co-solvents, leads to higher selectivity or milder operating conditions. Academia and industry collaborate to probe safer handling approaches and closed-system processing, aiming to shrink environmental footprints. Specialists in green chemistry now investigate how small tweaks to PPA could replace more hazardous or less efficient acids in fine chemical synthesis. Novel applications appear on the horizon, with scientists experimenting outside traditional organic synthesis—think advanced material fabrication, custom-tuning of polymers, and even specialized coatings for heat- and corrosion-resistance.
One reality keeps recurring: PPA is no benign household acid. Straightforward exposure, even to dilute vapors, irritates skin, eyes, and mucous membranes, with risk increasing for concentrated forms. Long-term exposure, especially to workers dealing with routine handling, demands careful monitoring and routine medical oversight. Animal studies show significant adverse effects at high doses, including gastrointestinal upset and deep tissue necrosis, underscoring its corrosive character. Current research doesn’t tie PPA to chronic systemic toxicity like some heavy metals or solvents, but lack of direct data encourages caution. My own contact with chemists who suffered burns from brief, gloveless exposure reminds me—the safety protocols aren't just red tape; they prevent lifelong scars and loss of dexterity. Environmentally, phosphate runoff linked to improper disposal spurs concern over eutrophication in water bodies, stressing the importance of strict waste management. Safety remains a top concern and research continues to refine safer formulations and user guidance.
Looking ahead, the future for polyphosphoric acid isn’t about more of the same; it’s about smarter, safer, and more responsible technology. As environmental and consumer safety pressures intensify, chemists keep searching for ways to capture PPA’s potent qualities while reducing hazards, cutting waste, and boosting overall sustainability. Some hope lies in recycling and regenerating spent acid where industrial chemistry creates heavier waste now. Others see promise in custom blends or derivatives with selective reactivity, extending applications to energy storage, nanomaterials, and biotechnology. Real progress will follow when technical advance meets real-world responsibility—protecting workers and water sources, reducing waste, and using chemistry as a force for better, not just more.
Polyphosphoric acid makes its mark in the asphalt industry. People rarely think about what holds a busy freeway together during baking summers or winter freezes. Most of us just hope our drive won’t get interrupted by potholes. Road crews turn to PPA because it tweaks the “recipe” of paving asphalt, giving it more strength and flexibility under harsh weather swings and endless truckloads of freight.
Over decades of development, highway engineers noticed that asphalt alone doesn’t always deliver. Polyphosphoric acid brings more elasticity and allows the asphalt to recover its shape after heavy loads. Fewer cracks show up, and road repairs stretch farther between cycles. The U.S. market shows growing use; it’s not just a trend overseas. Data from the Federal Highway Administration highlights a steady shift to modified asphalt to get more value out of each constructed mile.
On farms, production relies on a steady feed of nutrients. PPA works as a source of phosphate for liquid fertilizers. These fertilizers carry roots through the season and help raise strong crops, especially corn in the Midwest or rice across Asia. Farmers want quick-absorbing options; polyphosphoric acid makes this possible by dissolving easily in water and spreading evenly in the field. According to USDA reports and crop science studies, soil nutrition and harvests rise when phosphate levels stay balanced. My own background in small community farming taught me that balanced inputs mean better outcomes year after year, and PPA-based blends handle that job well.
People often ignore the science behind a bumper harvest. That green color in healthy plants usually points to a strong backbone of phosphorus, and polyphosphoric acid delivers a steady supply. The fact that it’s used to manufacture the most common liquid fertilizers in the world reflects the scale of its reach.
Factories use polyphosphoric acid for more than farming or pavement. It’s a workhorse in the production of resins, plastics, and flame retardants. In my experience with small chemical labs, PPA helped fine-tune reactions when making specialty products like pharmaceuticals or dyes. Chemical plants depend on its ability to control moisture and acidity during complicated steps, improving both purity and yield.
Companies value PPA’s stability and strength, helping to streamline production. More products reach shelves thanks to chemical shortcuts provided by polyphosphoric acid, from safer cables in new homes to the preservation of flavor in food manufacturing.
Using PPA isn’t risk-free. Its strong acidity means strict safeguards in transport and handling. Environmental rules exist for a reason; spills can damage waterways and soils if mismanaged, so training and preparedness make all the difference. I recall friends who worked in emergency response—one admitted that working with acids demands extra vigilance on top of usual protocols.
One path forward: invest in safer handling systems and push for recycling processes to capture and reuse phosphorus. Innovation in packaging and delivery would also cut costs and prevent accidents, which ultimately helps protect workers and natural resources alike.
Understanding the concentration or grade of a PPA product isn’t just for scientists and quality control managers. Years ago, I found myself standing in a fertilizer plant, watching as thousands of tons of phosphate-based material poured into hoppers, wondering why this industry obsesses over numbers like “85%” or “75%.” Turns out, concentration shapes performance as much as it affects safety, cost, and even the environment.
Concentration measures the amount of active phosphoric acid in a batch of polyphosphoric acid (PPA). You’ll often spot figures like 105%, 115%, or even 118%. These aren’t just fancy numbers. They hint at how much water the product holds and what level of reactivity or potency you get from every drop. For folks in fields like asphalt modification or flame retardants, this matters. Low-concentration means your product runs weaker or forces you to use more, sometimes at a higher handling cost. That’s why engineers and buyers take concentration grades seriously — not just for the final product, but for the whole supply chain.
Let me give you an everyday analogy. Buying orange juice concentrate instead of ready-to-drink juice gives more flexibility. You decide the strength, the sweetness, and even the amount of water to add. The higher the concentration, the easier it is to tailor the product to your needs. Same goes for PPA — customers expect the batch will deliver exactly what’s promised. A misstep can lead to substandard performance, lost money, and even fines for environmental compliance failures.
From my work in materials procurement, surprises in chemical strength almost always meant expensive adjustments down the line. Customers want to trust that today’s PPA matches last month’s. The more variable the concentration, the more unpredictable the batch results. For manufacturers, that’s a headache. Unexpected changes mess up batch records, regulatory reporting, and product recipes. Regulators do random spot checks, and discrepancies invite penalties.
Reliable grades reflect solid quality control. Working with certified suppliers — those who provide batch-by-batch assay data — makes a difference. I’ve seen companies choose a slightly costlier partner just for this confidence boost, sidestepping hidden costs associated with mixing errors or regulatory headaches.
Not all concentration mistakes show up immediately. Sometimes a blend “passes” early tests but causes issues months later in storage or use. Lower grades may bring more impurities, which can catalyze unwanted side reactions or harm equipment over time. A cheap deal on a low-grade PPA turns sour if equipment corrodes, leading to downtime or dangerous leaks. Environmental authorities also place stricter emissions and waste regulations on sites handling more water or impurities in chemical inputs.
In practice, responsible manufacturers share detailed technical data and train staff to interpret it. They make adjustments early in procurement, setting clear grade expectations backed by buyer-supplier contracts. Automatic monitoring and mixing systems help track outputs minute by minute — another layer of protection against costly mistakes. These habits build trust across the value chain.
If you’re buying PPA, don’t just take what’s on paper at face value. Ask suppliers for recent concentration assay results. Challenge them on how they verify every batch. Look beyond price, weighing the tradeoff between grade, stability, and quality. If you can, visit a supplier’s facility to see their process firsthand. Only then can buyers operate with confidence — protecting not just their bottom line, but safety and compliance, too.
Polyphosphoric acid, commonly used in asphalt, chemical manufacturing, and pharmaceuticals, carries serious hazards if not respected. My time around chemical plants has shown me that a label reading “corrosive” warns of more than just a mild skin irritation. A small splash can burn a hole through sleeves, and fumes will attack the nose without hesitation. These qualities demand careful handling—not only for personal safety but for the sake of everyone in the building.
Keeping this acid safe begins with the container. Stainless steel tanks and drums resist attack that would easily eat through mild steel or aluminum. Over the years, I’ve seen workers try storing acids in plastics to save money; it might last for a month, then a leak appears. Polyethylene tanks work for limited concentrations, but anything stronger needs steel. Never stack these containers where they could fall. One bump from a forklift, and the cleanup turns into a nightmare.
Temperature control matters just as much. Polyphosphoric acid thickens or breaks down in the wrong conditions. Think of it like honey: left out in the cold, it sets like a rock, but in the heat, it runs everywhere. Strong sunlight will warp plastic tanks and stress seals. I’ve watched summer heat push pressure inside barrels high enough to pop a cap. So, ventilation and shade aren’t negotiable—they keep vapors low and tanks stable.
In a lab or on a production line, splash goggles and acid-resistant gloves give the first line of defense. Years of chemical work made this a habit, not just a rule from a safety poster. A cotton shirt won’t cut it; a lab coat or chemical apron takes more abuse. I’ve witnessed a glove catch a drip, neutralized quickly with running water—without it, a scar would have told a different story.
Good ventilation pulls acid vapors away from faces and lungs. A single whiff burns deep enough to remind anyone to check the fume hood before pouring. Respirators come out when large quantities move, but it’s clear that local exhaust fans stop most problems before they spread.
Spills happen, no matter how careful people act. Early in my career, a barrel valve failed on a loading dock. Fast reaction—throwing on a face shield, laying down acid-neutralizing powder, and cordoning off the area—kept harm minimal. Sand and sodium carbonate work best for mopping up. Never try to flush a spill straight down the drain; this only pushes the problem further.
For those working regularly with polyphosphoric acid, training should go beyond a checklist. Drills, videos, and open discussions about “near misses” help everyone stay alert. Eye-wash stations and emergency showers must stay clear and get regular checks. After seeing a colleague freeze up during a real incident, I respect the benefit of rehearsals—muscle memory can save the day.
Rules and procedures protect people, but workplace culture makes them endure. Workers speak up if something feels off. Supervisors listen, and nobody skips a glove or takes shortcuts for speed. I’ve watched labs with a strong safety culture promote internal trainers and conduct regular review sessions to keep procedures sharp. In these places, recordable injuries plummet, and everyone—regardless of experience—remains careful with polyphosphoric acid.
Packaging does a lot more than just hold a product. You learn this quickly working in manufacturing. Out on the floor, it’s about keeping the product dry, easy to move, and ready to use when it’s needed, not just about eye-catching design. When someone asks which packaging suits PPA, I think about the variety of customers, storage conditions, and shipping realities we’ve faced over the years. Long experience says: what works in a lab won’t always fly in a warehouse or on a truck in 100-degree heat.
PPA granules often land in thick, multi-layered bags, usually made of polyethylene or kraft paper lined with plastic. These aren’t your grocery store plastic sacks. A 25-kilogram bag can stop moisture, sunlight, and dust from sneaking in. Stacking is sometimes rough, especially when the team rushes through a big order, so bags need to be tough enough not to split if dropped. Most warehouses stack these bags on pallets for quick movement. Folks in food or pharma plants want tear-resistant packaging with seals that don’t pop open, especially with powders or fine grains that tend to leak. Bags work best when customers use up product quickly, before humidity or pests become a problem.
Some businesses think bigger. Fiber drums or plastic drums answer the call when someone orders hundreds of kilograms, plans to store product for months, or moves it across the globe. These drums close tight and stand up well to rough handling. We used plastic liners in drums for extra barrier protection, mostly for fine powders that can clump from even a little humidity. Our logistics staff favored locking ring seals—once the lid’s down, they stay put, so nothing gets in or out accidentally. This option fits big manufacturers who want to minimize handling and exposure at every step.
Big projects or plants with heavy needs go for bulk bags, called FIBCs (Flexible Intermediate Bulk Containers) or “super sacks.” These giants carry up to a metric ton of material, cutting down both handling time and packaging waste. It’s impressive to watch a forklift move one bulk sack that holds as much as forty regular bags. If you handle these, you want dependable loops for lifting and liners if the climate is damp. One drawback: in smaller warehouses, finding room for a one-ton bag can get tricky, and lifting without the right gear risks safety or product spills.
Customers sometimes ask for custom sizes or environmentally friendlier packaging. We’ve had requests for biodegradable liners or bags from recycled materials. It’s not always an easy switch because protection and shelf-life come first, but several suppliers now offer real biodegradable plastics or use less virgin material. Cost goes up with these options, and we've seen long-term tests to make sure no product quality gets lost in the process. Another solution has been reusable returnable drums, mainly where our customers maintain solid supply-chain logistics to make it work. This approach cuts down on plastic and fits companies looking to hit sustainability targets.
Real-life experience shows the "best" packaging answers three questions: How long will this sit before use? How rough is the handling on the way there? Who’s going to open it and how? Teams working on the ground know what lasts and what breaks. It pays to listen to them, not just the specs on paper. From weatherproof drums to bags sealed like vaults, there’s always a tradeoff between cost, protection, ease of use, and environmental footprint. Smart buyers work with their supplier instead of just picking whatever’s at the top of the list. The best packaging isn’t the same for everyone, and it shouldn’t be.
Polyphosphoric acid keeps showing up in the headlines—usually because somebody somewhere finds out that what’s on the spec sheet doesn’t line up with what’s in the drum. I’ve spent my share of years walking through chemical plants, and the feeling in the gut when an inspector raises a red flag is universal. You want your operations tight, your paperwork tighter, and the last thing you need is a cross-examining auditor finding out that your chemical isn’t up to code.
Folks sometimes glance past the paperwork, assuming it’s just a checkbox. Polyphosphoric acid falls under tight regulatory watch for good reason. Environmental Protection Agency rules set strict benchmarks on things like heavy metal traces, while the American Association of State Highway and Transportation Officials (AASHTO) keeps a close eye on materials used in asphalt modification. Nobody wants contaminated runoff or substandard roads that crack open by the next season. If someone skips a detail, the headache doesn’t end with a warning letter—it costs money, reputation, and possibly livelihoods.
Truth is, not every supplier runs the same game. Some importers cut corners, using batches from sources with loose controls. Numbers on the Certificate of Analysis mean very little unless the testing holds up under scrutiny. With the global supply chain, inconsistencies creep in, especially with grades labeled “technical” instead of “reagent” or “food.” Phosphorus content, clarity, free acid, and the presence of impurities carry real consequences on product performance and health safety. Companies get one shot to prove they care about all of this.
Workers rely on clearly labeled drums to keep their hands and lungs safe. Overexposure can lead to skin and respiratory issues—nobody forgets an accident in the chemical room. On the customer side, a segment manager at a major roofing company told me about a supplier snafu where mislabeled PPA led to failed adhesion and callbacks on half a dozen new jobs. Consider the knock-on frustration down the line: patch jobs, lost accounts, safety fixes. Good documentation and complete compliance would have made all the difference.
Build relationships with suppliers who document every step, from raw ore to finished acid. Reliable partners use independent labs and share results quickly. Random spot-checks during the year go a long way to build trust—both with regulators and with your end users. If a batch doesn’t match, quarantine it. Don’t wait for a customer to discover the problem. Results from labs with ISO 17025 certification give that extra peace of mind.
The industry doesn’t always make it easy. Costs climb. Regulations change as research uncovers new risks—microcontaminants, production byproducts, and so on. But the alternative never turns out well. Nobody wants shut downs from a failed audit or, worse yet, a news report about health risks tied to your product. Invest in lab tests now, run the extra paperwork, double-check those certificates. Your business sticks around because people trust the results.
| Names | |
| Preferred IUPAC name | oxopolyphosphoric acid |
| Other names |
Polymetaphosphoric acid Superphosphoric acid PPA |
| Pronunciation | /ˌpɒli.fɒsˈfɔːrɪk ˈæsɪd/ |
| Identifiers | |
| CAS Number | 8017-16-1 |
| Beilstein Reference | 3593941 |
| ChEBI | CHEBI:29316 |
| ChEMBL | CHEMBL1201582 |
| ChemSpider | 13438755 |
| DrugBank | DB14583 |
| ECHA InfoCard | 05beea43-6d92-410a-b653-1f0fc11bfa34 |
| EC Number | 236-639-8 |
| Gmelin Reference | 27143 |
| KEGG | C02322 |
| MeSH | D011080 |
| PubChem CID | 10574 |
| RTECS number | TB6125000 |
| UNII | 607T57H1YN |
| UN number | UN3264 |
| Properties | |
| Chemical formula | H₃PO₄₍ₙ₎ |
| Molar mass | 115.94 g/mol |
| Appearance | Clear, viscous liquid |
| Odor | Odorless |
| Density | 2.01 g/cm³ |
| Solubility in water | Miscible |
| log P | -1.4 |
| Vapor pressure | <0.1 hPa (20 °C) |
| Acidity (pKa) | -3 |
| Basicity (pKb) | 1.7 |
| Magnetic susceptibility (χ) | -5.1×10⁻⁶ cm³/mol |
| Refractive index (nD) | 1.438 (20 °C) |
| Viscosity | 200-400 cP (25°C) |
| Dipole moment | 2.15 D |
| Thermochemistry | |
| Std molar entropy (S⦵298) | 266 J·mol⁻¹·K⁻¹ |
| Std enthalpy of formation (ΔfH⦵298) | -1711 kJ/mol |
| Hazards | |
| Main hazards | Corrosive, causes severe skin burns and eye damage, harmful if swallowed or inhaled, reacts violently with water and bases, releases toxic fumes. |
| GHS labelling | GHS05, GHS07 |
| Pictograms | GHS05,GHS07 |
| Signal word | Danger |
| Hazard statements | H314: Causes severe skin burns and eye damage. |
| Precautionary statements | P264, P280, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P321, P363, P405, P501 |
| NFPA 704 (fire diamond) | Health: 3, Flammability: 0, Instability: 2, Special: - |
| Lethal dose or concentration | LD50 (oral, rat): 2600 mg/kg |
| LD50 (median dose) | LD50 (oral, rat): 2,650 mg/kg |
| NIOSH | WXK37000AQ |
| PEL (Permissible) | PEL (Permissible Exposure Limit) for Polyphosphoric Acid (PPA): 1 mg/m³ (as phosphoric acid, OSHA PEL) |
| REL (Recommended) | 0.2 mg/m³ |
| IDLH (Immediate danger) | 1000 mg/m3 |
| Related compounds | |
| Related compounds |
Phosphoric acid Pyrophosphoric acid Metaphosphoric acid Orthophosphoric acid |
