Trudging through the early days of organic chemistry, a few compounds always found special attention, and Phenol-4-sulfonic acid sits right among them. Back in the 19th century, chemists scoured coal tar for new molecules and saw how adding sulfonic groups to phenols could push both dye chemistry and analytical techniques forward. The discovery wasn’t a flash-in-the-pan moment, but more a slow burn, as improvements rolled out across years. Synthetic dyes exploded on the market once these kinds of molecules made water-soluble colors more stable. Lab chemists pushed the boundaries using this acid in both classical research and industrial scale jobs, showing how a single sulfur group could redirect the future of multiple fields.
Ask around research labs and chemical factories, and it’s clear why Phenol-4-sulfonic acid turns up everywhere from quality control to polymer synthesis. Sold as a white or light tan crystalline powder, with a heavy punch of acidity, this molecule helps drive oxidation reactions and catalyze resin formation. Its structure—phenol’s well-known ring, now packing a sulfonic acid group at the para spot—offers both reactivity and a boost in solubility that straight phenol or benzenesulfonic acid can’t always match. Chemical distributors often supply forms ranging from pure powder to concentrated aqueous solutions. Each form finds its own niche, dictated by ease of handling and reaction efficiency needs.
With a melting point just north of 108°C and solid-state stability under ordinary storage, the material earns credit for shelf life. Phenol-4-sulfonic acid dissolves easily in water, forming strong acidic solutions that even break up in polar solvents like ethanol and methanol. It’s this mix of organic and ionic character that lets the compound slip into roles usually out of reach for unsubstituted phenol. The molecule draws moisture from the air, so testing always shows a slight weight uptick unless containers close tightly. Crystal structure studies reveal fairly simple hydrogen bonding, helping explain its speed in aqueous reactions. Don’t forget its strong sour smell: by the time you open a bottle, the lab alerts your nose.
Proper labeling states purity—commonly at or above 98%—with details on water content and any trace metals that might sneak in during synthesis. Major suppliers stamp every drum or bottle with batch number, hazard indicators, and expiration date. A full certificate of analysis follows every shipment, including titration data for acid strength and spectroscopic confirmation by IR or NMR. Labels carry the UN code for corrosive substances, hazard pictograms for skin and eye irritation, and storage temperature guidelines to keep the material from caking or picking up water. Logistics teams track every box, since lost containers trigger extensive safety reports.
Industry standard production takes phenol and sulfonates it using concentrated sulfuric acid at controlled temperatures, usually around 100 to 120°C. Engineers carefully moderate both temperature and acid strength, since runaway reactions churn out tars and by-products. Process reactors use corrosion-resistant alloys and vacuum lines to vent sulfonic acid fumes. Bench chemists whip up small batches the same way, but the trick stays the same: pour sulfuric acid slowly into phenol with agitation, then keep stirring until the mixture cools. Isolate the acid by neutralization, precipitation, filtration, and—when purity matters—minimum twice recrystallization.
This molecule transforms in the hands of industrial chemists and researchers alike. It forms salts with sodium, potassium, or calcium by direct neutralization, spinning out reagents useful in dyes and synthetic resins. The phenolic ring stays reactive, ready to receive electrophiles for further substitutions, or to lose the sulfonic acid in desulfonation protocols, steering synthetic pathways toward more complex aromatic structures. The sulfonic group also pairs with amines, linking to produce zwitterionic surfactants used in dispersants and cleaner formulations. Oxidizing agents latch onto the ring more easily after sulfonation, changing reactivity and enabling multi-step schemes that other phenol derivatives don’t tolerate.
Chemical catalogues list this item as 4-hydroxybenzenesulfonic acid and para-sulfonic acid phenol almost interchangeably. Product numbers change depending on supplier, but international trade sticks to a core set of names to prevent mishaps. Engineers working across nations reference CAS registry numbers to eliminate confusion or mislabeling. Synonyms pop up in patents and research articles, so technical teams double-check chemical identity, especially when dealing with isomer mixture risks.
I’ve seen what happens if you treat this stuff lightly. Phenol-4-sulfonic acid eats through most organic matter on skin and can raise painful blisters. Splash goggles and full nitrile gloves stay non-negotiable across most chemical handling operations. Eye wash stations and polymer aprons line every bench where this acid sits in use. Engineer controls such as fume hoods and vented storage cabinets slow down airborne exposure and curb trace vapors. Emergency response plans require neutralizing spills with sodium bicarbonate before tackling cleanup. Any deviation from best practices brings risk of burns, inhalation irritation, and environmental leaks, so safety training always stays current before new hires start work.
It gets hard to pin the acid on a single use, because demand shows up in so many unexpected places. Water treatment plants depend on the compound as both a disinfectant aid and an analytical standard for phenol index tests. Epoxy and phenolic resin makers use it as a catalyst and hardener, tuning set times and cross-linking strength. Dyers and textile finishers apply sodium salts of the acid in complexation reactions, shifting color tone and fastness in processed fabrics. Biology labs depend on the acidity in protein precipitation or to clean glassware from tough organic stains. Even electronics see it as a dopant in printed circuit board etching baths.
Academic labs chase curious leads in using the acid for organic synthesis routes, especially targeting selective sulfonation or ring activation for further functionalization. Green chemistry folks dig deep into process optimization, cutting down energy inputs and acidic waste generation during synthesis. Pharmaceutical groups test derivatives for antimicrobial and enzyme inhibition properties, hoping for tweaks that push drug development. Analytical chemists publish new protocols for quantifying trace organics in environmental samples, often using phenol-4-sulfonic acid as a marker or reactant. Graduate students track reaction kinetics and mechanistic details using isotopic labeling, feeding fundamental knowledge back into industrial design.
Toxicologists and regulatory agencies log the corrosiveness of phenol-4-sulfonic acid with caution. Direct contact causes rapid skin and tissue destruction. Inhalation of fine dust or concentrated aerosols irritates airways, sometimes leading to pulmonary edema. Experiments in aquatic systems reveal high toxicity to fish and bioindicator species, meaning strict wastewater handling rules apply at both lab and factory scale. Animal toxicity studies report behavioral effects at lower doses, but chronic exposure trials remain limited for human risk. Detailed safety sheets encourage double-layer PPE and limit the acid only to areas with continuous monitoring. Ongoing work tests if certain by-products or degradation fragments cross-react with biological systems, hinting at long-term hazard concerns.
Horizon scanning for phenol-4-sulfonic acid walks a fine line between expanding use and tightening controls. Circular economy chemistry tempts engineers to recycle sulfonic acids from spent dyes and industrial effluents, so research into safe recovery and reuse technologies wins funding. Green manufacturing methods look at solid-acid catalysts or ionic liquids to replace bulk sulfuric acid, chasing lower carbon footprints and less toxic waste. Water treatment faces the biggest changes, with new regulations pushing for less persistent by-products and stricter emission control, so next-generation processes for managing sulfonic acid standards draw heavy attention. Environmental chemists keep watching toxicity profiles as application areas widen, spurring innovation in safer packaging and more biodegradable forms. I’ve met teams that keep an eye out for bio-based alternatives, yet none so far deliver the same punch in reactivity and reliability, meaning phenol-4-sulfonic acid keeps its place as a tough yet essential chemical for the foreseeable future.
Phenol-4-sulfonic acid stands out in the world of chemicals due to its sharp ability to react and break things down. In my early lab days, the sharp, almost biting smell always meant a day of serious focus ahead. It acts as a powerful sulfonating agent, playing a critical role in making dyes, medicines, and even some detergents stronger and more effective. The acid’s structure lets it throw itself into reactions and shift molecules into useful forms fast. Not every acid has this kind of backbone.
Color matters, whether it’s school uniforms or a bold city billboard. Dyes made from phenol-4-sulfonic acid bring brightness and staying power. Textile manufacturers rely on it to create colors that survive dozens of cycles through washing machines. The acid roots itself into dye molecules, locking colors deep into the fabric. Denim mills and T-shirt factories benefit from this up and down the supply chain, and so do you and I every time we pull our favorite shirt from the dryer and see it hasn't faded away.
The world’s medicine cabinets have roots in tough, old chemistry tricks, and phenol-4-sulfonic acid helped build a few. Think about drugs for fighting infections or lowering fevers. Pharmaceutical labs use this acid while crafting sulfa drugs. These medicines shut down bacteria by blocking critical pathways, something that simple soap never managed to do. The acid’s reactivity lets scientists bolt on sulfur groups where they need them, shaping potent molecules that save lives in just about every corner of the globe.
Pipes and waterways never stay clean by magic. Municipal plants and industrial cleanup teams turn to this acid’s sulfonation power. Phenol-4-sulfonic acid helps developers create specialized ion-exchange resins. These sticky beads grab heavy metals and nasty organic pollutants, holding them tight until safe disposal. I have seen firsthand how the treated water flows clear on the other end, protecting communities and fish alike from harm. Sure, it’s not glamorous work, but the results are obvious each time a pond or river bounces back from years of abuse.
Phenol-4-sulfonic acid also holds value in analytical chemistry. Labs chasing traces of nitrogen use it as a key reactant for the Kjeldahl method—a famous process for figuring out protein content in food and soil. Farmers rely on that accurate measure to grow better crops, and food producers lean on it to ensure what’s on the grocery shelf matches the label outside. In all these places, the acid keeps the tests sharp and accurate, avoiding slip-ups that could cost money, crops, and consumer trust.
Handling strong acids always brings up concerns for safety and the environment. Gloves, eye shields, and strong ventilation aren’t suggestions; they’re mandatory, as is tight storage and careful disposal. Teaching the next generation about these risks matters as much as discussing the acid’s chemistry. Many regulators and companies have started tracking their usage better, hoping to cut down on spills and missteps that once marked the chemical industry’s early days. Upgrading facilities, training, and reporting on incidents have begun driving thoughtful chemical stewardship in both industry and universities.
Phenol-4-sulfonic acid doesn’t come up in everyday conversation, but it matters a lot in industries that depend on strong, versatile chemistry. Its formula, C6H6O4S, points to a ring of six carbon atoms with a sulfonic acid group attached at the fourth position. For folks interested in how chemicals shape our world, this small detail makes a difference. Many users call this compound p-hydroxybenzenesulfonic acid or 4-hydroxybenzenesulfonic acid, though the ‘phenol-4-sulfonic acid’ label sticks in most lab catalogs.
It’s not just a string of numbers—174.18 grams per mole tells you what a chemist needs to know about quantities. This figure comes from adding up the atomic weights: carbon, hydrogen, oxygen, and sulfur. Precision here matters for anyone mixing reagents or running reactions. Do the math wrong and quality drops instantly. In my own experience setting up a colorimetric test, using the right amount of phenol-4-sulfonic acid turned risky guessing into confident results.
This isn’t a household substance sitting on the shelf. Factories and labs reach for phenol-4-sulfonic acid because it works as a starting point for dyes, drugs, and even resins. Ask a water treatment technician—they’ll say this compound helps them catch ammonia through reliable testing protocols. The chemical structure makes it react in ways that a plain phenol just can’t. Anyone tinkering in analytical labs soon learns how crucial one well-placed sulfonic acid group can be.
I remember my first experience handling strong sulfonic acids. Spill a drop and you feel the sting—this isn’t gentle stuff. I’ve seen seasoned technicians treat it with the same respect reserved for concentrated sulfuric acid. Proper gloves, eye protection, and working in a ventilated area set the stage for safe usage. In communal labs, sharing safety know-how keeps everyone from running into costly or painful accidents. This hands-on approach to safety reflects a culture where protecting people and data always comes first.
Phenol-4-sulfonic acid’s advantages bring questions about environmental impact. The sulfonic group tends to stick around in water systems if waste isn’t treated carefully. I’ve watched strict disposal protocols in action and get why compliance isn’t just red tape—improper dumping can harm plants and aquatic life. Solutions begin with better training for all chemical handlers and extending guidelines directly to the point of use. Interested leaders in industry push for green chemistry options, including recycled feedstocks and upgraded waste treatments to reduce footprint and costs.
Everyday consumers never see phenol-4-sulfonic acid, yet products rely on its chemistry. Accurate formulas and molecular weights let chemists create everything from color change test kits to advanced pharmaceuticals. Cutting corners or ignoring safe practice risks breakdowns both in trust and environmental standards. Knowledge about compounds like this one lifts the quality of science, safety, and sustainability in ways that benefit everyone.
Phenol-4-sulfonic acid belongs to a family of chemical compounds people use in labs and industry. If you read the safety data sheet, one lesson stands out: this stuff isn’t just a mild irritant. Skin contact causes severe burns, and breathing in the dust or vapors can make it hard to breathe. Just last year, I watched colleagues dealing with a tiny spill in a well-ventilated lab, and everyone scrambled for eyewash stations within seconds. Accidents involving strong acids like this don't give second chances; a little carelessness often leaves a mark—literally.
At home, most folks stick cleaning supplies high up or behind locks. With phenol-4-sulfonic acid, the thinking stays the same, but the stakes rise. Store this acid away from sunlight, out of damp basements, and never near organic materials or bases. Temperatures count: it stays stable at room temperature, but not next to a radiator or in a place where bottles might freeze and thaw. Don’t share shelf space with things that react explosively—some oxidizers, stuff containing chlorine, and strong bases are off-limits.
Spill trays under containers often save more than work time—they stop small leaks from ruining floors and getting tracked outside. Heavy-duty shelving that can take a bump matters too, since glass bottles break if someone’s hands slip.
Experience taught me protective gear isn’t a formality. Lab coats, goggles, acid-resistant gloves—sometimes it feels overdone, right up until the moment someone slips up. Direct skin contact burns immediately, and the fumes eat through regular masks. Use a fume hood, not just for show, but because one whiff can sting your nose for hours.
Transporting the acid calls for sealed containers. Don't pour it near crew not wearing protection, and don’t pipette by mouth—stories from older chemists make that plain. Wash up before leaving the lab, and forget pouring this acid into water without double-checking: always add acid slowly to water, never water to acid, since strong reactions spit hot, dangerous mixtures everywhere.
Rules mean little unless everyone buys in. I saw new team members breeze through online safety modules, but scatter in panic during an actual spill. Regular drills changed that. Having spill kits accessible isn’t enough; run real rehearsals so folks know how to use them. Post the nearest eyewash and shower station locations, and remind people to stay calm if the worst happens.
Good labeling makes a real difference, too. Handwritten notes fade, get smudged, or don’t warn about the real hazards. Use labels that stick and can’t be confused, and never reuse bottles from other chemicals.
Control and respect for strong chemicals don’t just protect individual workers. They keep whole buildings safe. Regular inspections catch slow leaks, aging storage bottles, or shelves ready to give out. Sharing photos of past accidents and near-misses does more to teach lessons than stacks of manuals. With so many chemicals in circulation, a practical and no-nonsense approach to storage and handling saves time, money, and sometimes, more than that.
Big improvements often come from small steps. Stock enough gloves, run occasional safety checks, and keep clear written procedures visible. Encourage open talk about mistakes, and reward careful work. Safety with phenol-4-sulfonic acid starts before opening the bottle—and never really ends.
Phenol-4-Sulfonic Acid shows up in plenty of chemical processes and research labs. It does important work in dyes, pharmaceuticals, and even some plastics, but it's not something to take lightly in person. If you've ever worked with strong acids, you know the nervous feeling you get just uncapping a flask. With this material, that feeling is justified.
The hazards tie back to both skin and respiratory exposure. Contact with the skin gives a chemical burn that leaves a red, tender mark. Inhaling the dust or fumes stings your throat and can provoke a cough or shortness of breath. Splash some in your eyes? Get ready for sharp pain and maybe even eye damage. This acid also irritates the lining of your mouth if swallowed. Beyond that, phenol derivatives absorb through the skin, so there’s a genuine risk even if you’re just touching it once in a while. Over time, repeated exposure adds up, possibly affecting your liver and kidneys.
That’s not all. The substance reacts with water by releasing heat, and it mixes with many common solvents. I learned early on that you can’t treat all acids the same—this one needs respect at every step.
Accidents involving even a small amount can set off a chain reaction. Spills not only contaminate tabletops, but also vaporize, causing headaches and nausea. Runoff into drains threatens to harm aquatic life, because its toxicity doesn’t just stop at the lab door. An NIOSH report points out that both the acid and its phenolic group bring extra dangers for anyone cleaning up.
The EPA has also flagged phenol-based compounds for their risk to waterways and the food chain. So, keeping spills off the floor and out of drains isn’t just good practice—it’s the law in many places. Gloves, safety goggles, and face shields aren’t optional, they’re your basic gear.
I remember my first chemical burn from a strong acid: it wakes you up fast. The first thing to do with a skin splash is take off any contaminated clothing right away. Wash the area under running water for thirty minutes—don’t cut corners, even if it feels better after a few minutes. For eye exposure, rinse gently with clean water for the same amount of time, keeping your eyelid open as best as you can. Medical help isn’t just a suggestion at this stage.
If you breathe in the vapors, get to fresh air immediately and loosen any tight clothing. A cough or burning in your chest is a reason to call for medical backup. Swallowing it brings a whole new set of problems: rinse your mouth, don’t try to vomit, and call a poison center while heading straight to the ER.
Always keep safety showers and eyewash stations easily reachable wherever acids like this get handled. I never work with any strong acid, especially this one, unless I know that escape route by heart. Quick action makes all the difference, both for you and anyone else working nearby.
Structured training, clear protocols, and genuine respect for hazardous chemicals save lives. Double-check labels and storage conditions each shift. Avoid shortcuts and label everything so nobody makes a mistake in a hurry. The goal is simple: use your head, respect the risks, and look out for your co-workers. Mistakes with Phenol-4-Sulfonic Acid don’t give many second chances.
For any workplace that uses this material, regular drills and visible first-aid posters help keep safety top of mind. If in doubt, ask for help, don’t tough it out. Chemical safety never gets old—and neither do the basics.
Phenol-4-sulfonic acid holds a reputation for reliability that chemists, lab techs, and manufacturers count on every day. Most folks see it as a white to off-white powder, sometimes finding it sold as a 65% solution. Different uses demand different specs, and it’s more than a footnote that this chemical appears in multiple grades and forms.
Laboratories experimenting with analytical methods prefer reagents with high purity. These top-quality, “analytical grade” variants cut down on the risk of interference. Impurities can wreck a titration or spoil a calibration curve in ways that will drive any lab analyst up the wall. In my experience, using a lower-purity sample for sensitive reactions means chasing errors and wasting time repeating work.
Industrial settings, especially for dye manufacturing or resin chemistry, tend to chase cost savings without letting go of basic quality. Technical or industrial grades often fit here. These batches typically carry more residual water or leftover inorganic salts, but still do the job.
Here’s the thing: those choices aren’t just about purity. Some processes run smoother with a fixed strength solution or a preferred particle size. Producers may offer it in powder form, as a blend with other sulfonic acids, or as a liquid at specific concentrations (often 20%, 65%, or even higher). Water content matters because moisture swings alter mixing, reactivity, and shelf stability.
Folks sometimes grab whatever’s on the shelf, thinking all phenol-4-sulfonic acid is equal. Choosing an unsuitable grade can mean contaminated end products, regulatory headaches, or safety issues. If you build a polymer batch with impurities, the yield drops or finished material falls out of spec for color or durability. Pharmaceutical manufacturers face even tighter rules – here, trace metals and contaminants can lead to batch rejection and regulatory fines.
Costs ramp up fast if you end up with the wrong grade. A gallon of ultra-pure acid for a production-scale dye operation wastes money, and nobody wants to pay a premium when plain technical grade would have worked.
Over the years, I’ve seen confusion between “grade” and “concentration” trip people up. Each major chemical supplier lists specs for water, iron, chlorides, and more, plus handy certificates of analysis. A vendor willing to explain lot-to-lot shifts or put contaminants in black and white builds trust. It’s worth picking up the phone or firing off an email to ask for these numbers before placing an order, because sticking a scoop in an unlabeled drum just isn’t good enough.
Mistakes often happen because nobody took time to train staff on deciphering labels or understanding supplier blurb. Quality control matters as much in a university lab as it does in a dye vat or pharmaceutical reactor. Documentation, regular checks, and even on-site moisture testing keep projects on the rails. Those steps pay off in time saved, waste avoided, and safer workspaces.
So, phenol-4-sulfonic acid appears in a stack of grades and concentrations, each serving a real-life need. A little attention to detail goes farther than marketing promises or price tags. After all, every successful synthesis or process relies on the right starting materials handled with care and a bit of old-fashioned knowhow.
| Names | |
| Preferred IUPAC name | 4-hydroxybenzenesulfonic acid |
| Other names |
Benzenesulfonic acid Phenolsulfonic acid Phenol-p-sulfonic acid p-Hydroxybenzenesulfonic acid |
| Pronunciation | /ˈfiːnɒl.fɔːl.sʌlˈfɒnɪk.ˈæsɪd/ |
| Identifiers | |
| CAS Number | 98-67-9 |
| 3D model (JSmol) | `3DModel: C1=CC(=CC=C1S(=O)(=O)O)O` |
| Beilstein Reference | 1080996 |
| ChEBI | CHEBI:31243 |
| ChEMBL | CHEMBL271881 |
| ChemSpider | 17719 |
| DrugBank | DB14115 |
| ECHA InfoCard | 100.008.682 |
| EC Number | 2866-76-0 |
| Gmelin Reference | 5811 |
| KEGG | C00864 |
| MeSH | D010645 |
| PubChem CID | 1048 |
| RTECS number | SJ7175000 |
| UNII | FJI4Y2FD3Q |
| UN number | UN2585 |
| CompTox Dashboard (EPA) | DTXSID2020095 |
| Properties | |
| Chemical formula | C6H6O4S |
| Molar mass | 192.19 g/mol |
| Appearance | White to yellowish crystalline powder |
| Odor | Odorless |
| Density | 1.485 g/cm3 |
| Solubility in water | Very soluble |
| log P | -1.56 |
| Vapor pressure | <1 mmHg (20 °C) |
| Acidity (pKa) | -2.8 |
| Basicity (pKb) | 12.0 |
| Magnetic susceptibility (χ) | -34.5e-6 cm³/mol |
| Refractive index (nD) | 1.595 |
| Viscosity | 85 cP (25°C) |
| Dipole moment | 3.45 D |
| Thermochemistry | |
| Std molar entropy (S⦵298) | 163.0 J·mol⁻¹·K⁻¹ |
| Std enthalpy of formation (ΔfH⦵298) | -474.7 kJ·mol⁻¹ |
| Std enthalpy of combustion (ΔcH⦵298) | -1977 kJ·mol⁻¹ |
| Pharmacology | |
| ATC code | N01AX11 |
| Hazards | |
| Main hazards | Corrosive, causes severe skin burns and eye damage, harmful if swallowed, inhaled or in contact with skin. |
| GHS labelling | GHS05, GHS06, GHS08 |
| Pictograms | GHS05,GHS07 |
| Signal word | Danger |
| Hazard statements | H302, H314 |
| Precautionary statements | P260, P264, P270, P271, P280, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P321, P363, P405, P501 |
| NFPA 704 (fire diamond) | 3-2-2-Acid |
| Flash point | > 182 °C |
| Autoignition temperature | 120°C (248°F) |
| Lethal dose or concentration | LD50 oral rat 400 mg/kg |
| LD50 (median dose) | LD50 (oral, rat): 400 mg/kg |
| NIOSH | SD2450000 |
| PEL (Permissible) | No PEL established |
| REL (Recommended) | 0.5 mg/L |
| IDLH (Immediate danger) | 250 ppm |
| Related compounds | |
| Related compounds |
Phenol Sulfanilic acid p-Cresol Benzenesulfonic acid Sodium p-toluenesulfonate |
