4-Phenolsulfonic acid stands out as a product born from decades of applied chemistry. Its history stretches back to early investigations into aromatic sulfonation, a critical step for the dye industry in the late nineteenth century. Industrial expansion through the 20th century pushed chemists to optimize methods for installing sulfonic groups onto phenolic rings, aiming to improve solubility in water and compatibility with diverse media. This effort paid dividends in the textile and paper industries, establishing the compound as a cornerstone of chemical manufacturing. As technologies advanced, refinements in purification and safety controls further secured its role in laboratories and plants worldwide.
4-Phenolsulfonic acid blends usefulness with versatility. Produced in crystalline or syrup forms, the compound easily dissolves in water, giving a clear to straw-colored solution. It features prominently as a starting point or additive in manufacturing resins, dyes, pharmaceuticals, and as a robust catalyst for condensation reactions. Its pronounced acidity makes it valuable where control over pH and reactivity is essential, whether in resinification or in fine chemical synthesis. Production volumes continue to grow, reflecting its deeply rooted value to several industries—especially those focused on specialty chemicals and intermediates.
As a white to slightly yellow crystalline solid, 4-phenolsulfonic acid brings strong acidity, with a pKa around -2 (sulfonic group), ensuring full dissociation in solution. It melts at roughly 108°C, decomposing upon further heating. Its structure combines a hydroxyl group at the para position on a benzene ring and a sulfonic acid group, resulting in marked hydrophilicity and high water solubility. The molecule is non-volatile at ambient conditions, sparing workers from inhalation hazards common with many lower-weight acids. In typical storage, the compound’s deliquescent nature means it absorbs moisture from air, so sealed containers are not just preferred—they really matter for preserving quality and safety.
Manufacturers specify 4-phenolsulfonic acid’s purity, sulfated ash content, water content, and sometimes heavy metal traces. Typical purity exceeds 98%. Labels carry standard hazard pictograms, noting corrosive properties—skin, eye, and respiratory irritation or burns can result from contact. Container labeling regularly lists the UN number (UN3261: Corrosive solid, acidic, organic, n.o.s.) and clear batch traceability measures. Some suppliers offer granular forms to cut back on dusting and spillage, broadening safe handling options in a range of plant environments. Those in regulated spaces need up-to-date Safety Data Sheets and conformity to local chemical laws.
Most commercial output flows from direct sulfonation of phenol with concentrated sulfuric acid or fuming sulfuric acid (oleum). The process relies on precise temperature control, typically holding reaction mixtures well below 130°C to avoid charring and over-sulfonation. The exothermic character of sulfonation demands robust reactor design, with acid-resistant materials and controlled addition rates to forestall runaway conditions. Following reaction, dilution with water, multiple washes, and filtration or crystallization steps strip away unused acid, byproducts, and color bodies, yielding a product that matches industry standards for purity and performance.
4-Phenolsulfonic acid thrives in chemical transformations, acting as a substrate in azocoupling (for dyes), serving as a sulfonating or activating agent, and taking part in condensation reactions. Its sulfonic acid group gives it resilience in acidic media and compatibility with transition-metal catalysis. Nitration under controlled conditions—though challenging—yields nitro derivatives used in pharmaceutical and pigment industries. Both the phenolic and sulfonic acid groups can be targeted: with alkylation or esterification (phenolic OH), or neutralization to form sodium/potassium salts (sulfonate form). This structural flexibility meets the demands of chemists looking for customizable reactivity, especially when bridging between polar and nonpolar systems in synthesis.
The chemical enjoys widespread recognition under several names, including para-phenolsulfonic acid and p-hydroxybenzenesulfonic acid. Some catalogues reference its sodium salt, sodium p-phenolsulfonate, especially in detergency and dyeing uses. Legacy nomenclature from early German and French treatises, such as "p-Phenolsulfonsäure," still appears in historical records and specialty European formulations. Commercial product codes might cite abbreviated formats like "PPSA" or even internal batch numbers, underscoring the importance of cross-referencing for buyers juggling multiple suppliers or country-specific inventories.
Corrosive properties mean 4-phenolsulfonic acid commands respect in all handling environments. Acid-resistant gloves, protective goggles, and face shields form the basic gear for plant operators and lab staff. Fume hoods must control even mild heating to prevent inhalation of acidic vapors or decomposition products. Spills, when they occur, can eat through common floor coatings and must be neutralized with sodium bicarbonate before cleanup. Emergency showers and eyewash stations should remain within direct reach. Disposal aligns with local hazardous waste regulations, avoiding ordinary drains, with neutralization and controlled dilution as standard steps for waste acid streams. Safety culture won’t let up, given that tissue damage, burns, and environmental harm can follow misuse or neglect.
4-Phenolsulfonic acid roots itself in a host of applications, extending from resin production to water treatment. In the resin business, it finds favor as a catalyst for making phenol-formaldehyde and other thermosetting resins—speeding up cure times and improving the network polymer structure. Dye and pigment manufacturers appreciate its role in forming water-soluble azo dyes, brightening and stabilizing final colors. The compound supports pharmaceutical synthesis for sulfa drugs and intermediates. Paper and pulp operators sometimes use it as a dispersant or in deinking agents. It figures in electroplating baths, boosting conductivity and deposit quality. Even specialty detergents and disinfectants carry traces, where its biocidal and pH-regulating persona helps key actives achieve top performance.
Work in R&D doesn’t slow because industries demand more environmentally sensitive routes and better catalytic activity. In recent years, laboratories have staked out green chemistry initiatives that limit waste acids and process water. Novel solid-acid versions or immobilized catalysts based on 4-phenolsulfonic acid now appear in patent notes, helping companies shrink carbon footprints and win sustainable credentials. Life science researchers probe its modified forms as building blocks for advanced pharmaceuticals or imaging agents. Some polymer labs use it to fine-tune microstructures, seeking materials that balance flexibility with chemical resistance. As regulatory pressures rise, the quest for safer, more efficient production and end-use keeps the compound at the leading edge of applied chemistry research.
Toxicity studies on 4-phenolsulfonic acid underscore the need for diligent handling. Acute exposure results in severe burns to skin, eyes, and mucous membranes. In animal models, oral or dermal contact typically triggers local tissue damage without significant systemic absorption unless large doses come into play. Chronic exposure scenarios remain less studied, but the compound breaks down in water, and its metabolites usually exit quickly from most biological systems. Regulatory reviews by agencies such as the EPA or ECHA detail disposal, labeling, and maximum workplace exposure limits. Environmental agencies rate it as hazardous for aquatic life if concentrated solutions hit waterways, so containment and neutralization before disposal carry legal and ethical weight.
Looking forward, the chemical’s future lines up with rising needs for specialty intermediates, high-performance polymers, and greener syntheses. Market analysts track growing demand across Asia and the Americas, especially where fine chemical and electronics industries are booming. Greater regulatory focus drives innovation in waste minimization and alternative production methods, with companies investing in closed-loop systems and recyclable catalysts based on phenolsulfonic derivatives. Research continues on less toxic analogs or process aids that match or exceed the acid’s performance, but 4-phenolsulfonic acid’s tenacity, reliability, and adaptability help secure its place for years to come, especially as sustainability goals push all players to imagine safer, stronger, more efficient ways of working with legacy chemicals.
You probably don’t spot 4-Phenolsulfonic Acid on a grocery store shelf or hear about it in casual conversation, but this compound pulls a lot more weight in industry and research than most realize. Drawing from time spent working alongside chemists, I’ve seen how a well-chosen reagent changes the game — and 4-Phenolsulfonic Acid fits squarely into that category.
Anyone who has ever worked around textile or ink factories gets quickly familiar with a swirl of vivid colors and strong chemical scents. Many of those colors start out from reactions involving aromatic compounds, and 4-Phenolsulfonic Acid acts as a building block for some of the brightest and most durable dyes. Because of its sulfonic acid group, the compound adds both water solubility and strong affinity for synthetic or natural fibers, providing a more robust end product compared with standard phenol-based dyes. This chemical helps to fix color, support resistance to washing, and enable precise shade control — a step that carries big commercial implications for textiles and plastics.
Resins show up everywhere from car parts to furniture finishes and electrical components. 4-Phenolsulfonic Acid comes into play as a catalyst that speeds up condensation reactions, especially in phenol-formaldehyde resin production. These resins stay relevant in circuit boards and insulation. From what I’ve seen in production settings, tweaking catalyst strength means shorter curing times and lower energy costs. Without reliable acid catalysts, resin quality tends to slip, and production lines don’t hit their targets. It’s not just about the science; it impacts real jobs, downtime, and cost control.
The pharmaceutical world leans heavily on sulfonic acids when designing molecules that can dissolve in bodily fluids or act selectively. I remember a case where the synthesis route for a cardiovascular drug required activating an aromatic ring using 4-Phenolsulfonic Acid. The result delivered cleaner reactions and simplified purifications. It’s not just small-scale research labs: large companies use this compound to produce antimicrobial agents and intermediates for active drug substances. In this sector, keeping processes robust means more predictable medicine supply and improved patient outcomes.
Move into electroplating shops, and you’ll see tanks where industrial parts get their finishing layers. Manufacturers use 4-Phenolsulfonic Acid to prep metal surfaces for consistent coatings — especially chrome and nickel. The acid’s ability to condition and clean metal goes a long way toward stronger metal adhesion. From experience, getting electrolytic solutions just right lowers defect rates and boosts product reliability: motorcycles, kitchen fixtures, tools — every one of those benefits from these prep steps.
No chemical comes without risks. 4-Phenolsulfonic Acid brings up handling hazards; its strong acidity and reactivity require safety protocols. Leaks or spills threaten both workers and the environment. Training, proper PPE, sealed transfer systems, and strong regulatory oversight all go together here. There’s interest in green chemistry, so researchers keep looking for safer alternatives and cleaner ways to synthesize sulfonic acids. Industry partnerships and academic labs can drive new solutions by sharing data on both safety and performance.
From dye vats to drug factories, 4-Phenolsulfonic Acid keeps showing up in places that matter to everyday life. Scientists and process engineers keep pushing for ways to harness its benefits without losing sight of worker and environmental protection. As demand for smarter, safer chemistry grows, the knowledge base around compounds like this one deserves just as much attention as the bright colors it helps create.
4-Phenolsulfonic acid, with a chemical formula of C6H6O4S, strikes a balance between simple composition and fascinating function. This molecule forms when a phenol ring, which already holds a reputation for versatility, picks up a sulfonic acid group right at the para or “4” position. Chemists love this sort of substitution. Imagine the classic benzene ring: one hydrogen gets swapped out for a hydroxyl group (making it phenol), then another at the opposite side takes on a -SO3H group. That’s what sets 4-phenolsulfonic acid apart from its chemical cousins.
Structure gets attention not just for knowing what bonds sit where, but also for guiding how this acid behaves in real reactions. Place the sulfonic acid group four carbons away from the hydroxyl group, and it pushes the molecule in specific directions when it reacts with other chemicals. Engineers and scientists see value in this setup because it affects water solubility, acidity, and how well the molecule can serve as a building block for dyes, resins, and medicines.
Draw it out on paper: a six-carbon benzene ring, the -OH group at carbon 1, the -SO3H group at carbon 4. It looks simple, but this orientation changes everything compared to its meta or ortho isomers. Teachers and researchers lean into this detail to show students how minor tweaks shift properties in big ways.
Having spent years around chemical plants and labs, I’ve watched this molecule slip into various processes almost unnoticed. Its high solubility gives companies an edge in formulating water-based adhesives or specialty cleaners. The sulfonic group isn’t just acidic—it’s strong enough to catalyze organic transformations that other acids might botch or slow down. This makes it popular for making resins more flexible or for boosting dye uptake onto wool or silk.
Curiously, the strong electron-withdrawing power of the sulfonic acid group also tames the reactivity of the phenol part. This helps control unwanted side reactions, an asset in pharmaceutical chemistry, where predictability saves both time and money. This molecule shines in its reliability compared to some other aromatic acids that can run wild in multistep syntheses.
Synthesizing 4-phenolsulfonic acid with high selectivity calls for precise control over temperature, concentration, and the type of sulfonating agent used. Factories face risks if venting acids or dealing with by-products isn’t tightly managed—handling such potent acids has real impacts on worker safety and the environment. Fumes linger, spills corrode equipment, and waste disposal costs add up quickly.
Safer and greener production methods have started to catch up. Companies developing solid acid catalysts or using continuous-flow reactors have shown promise in cutting waste and preventing emissions without slowing output. Long-term investments in closed-loop manufacturing, where every drop is recycled, could eventually close the gap between large-scale need and responsible stewardship.
Overall, the chemical formula and structure do more than sit in textbooks—they set the stage for real-world applications, carve out risks, and inspire improvements. Each time I see a bottle labeled “4-phenolsulfonic acid,” I think of the process innovations, the environmental upgrades, and the young chemists learning the difference between a good structure and a great one.
4-Phenolsulfonic acid gets plenty of use in chemical labs and manufacturing, but its hazards should never be underestimated. Direct skin and eye contact burn badly, and inhaling the dust or fumes irritates the lungs fast. Having worked near this material, I've seen how even a quick splash can send someone to urgent care. The right precautions always make the difference between a smooth shift and a safety incident.
You can’t just grab any pair of gloves or safety glasses for this job. Chemical-resistant gloves like nitrile or neoprene shield hands thoroughly; ordinary latex can melt away after a splash. Splash goggles and a sturdy face shield give eyes and face reliable protection. A lab coat or disposable apron saves your clothes and your skin. In a well-fitted respirator, you breathe easy, knowing you’re not pulling in dangerous mist.
Storage space says plenty about how seriously a place takes chemical safety. 4-Phenolsulfonic acid likes a cool, dry, ventilated area, far from direct sunlight. Dampness in the air leads to clumping and corrosion; storing it up high or above eye level raises the risk of spills. Solid shelving with clear labeling helps prevent mix-ups. My practice involves a dedicated chemical storage cabinet, away from acids or strong oxidizers. This minimizes risky reactions with incompatible substances.
After an incident at a warehouse I know, I always check for tightly closed containers, using screw caps. Any cracked or warped container heads to hazardous waste right away. No point in risking fumes escaping or accidental leaks.
Pouring or transferring should happen on a chemical-resistant tray, with spill kits ready. Even a teaspoon on the floor creates a slipping hazard and a risk to anyone nearby. I always make sure a fume hood’s running before opening the container. In my workspace, running water and an emergency eyewash station sit within arm’s reach. Accidents will happen — being able to flush a splash instantly can save vision or skin.
A well-trained crew looks out for each other. Before anyone handles 4-phenolsulfonic acid, proper training covers more than a dry rundown of regulations. Teams go over symptoms of overexposure, clean-up methods, and emergency phone numbers. I print labels big and clear, and post Material Safety Data Sheets nearby.
Small spills need to be neutralized and wiped up using absorbent materials designed for acid work. Used cleanup gear goes in labeled hazardous waste drums. For large spills, I don’t try to handle it alone — alerting an emergency response team makes a big difference. Any leftover or expired substance gets logged and disposed of by licensed waste contractors, no exceptions.
Paying attention to these steps sends a clear message: safety counts at every level. I encourage reporting near-misses; learning from “almost incidents” builds trust and improves procedures. As research and industry standards change, labs and factories must stay up to date with the latest storage protocols. Inspections and safety drills, done regularly, help keep complacency at bay. Long experience has taught me: Respect the risks, support the team, and safe handling always pays off.
For anyone in a lab or chemical plant, 4-Phenolsulfonic Acid stands out for its sharp, biting nature. This compound, typically a crystalline solid or thick liquid, tends to pack a punch: strong acidity, corrosive bite, and a nasty reputation for causing skin and eye burns. Skin contact leads to fast irritation, blistering, or even deeper chemical burns. When this acid touches the eyes, the risk of long-lasting damage or blindness climbs quickly. The fumes sting the nose and throat, making you cough or feel short of breath. Swallowing even a small amount, by accident or mistake, causes severe mouth and throat pain, burns, and stomach upset.
The National Institute for Occupational Safety and Health (NIOSH) and the U.S. Environmental Protection Agency flag this material as a corrosive substance. It breaks down protective barriers in seconds. Based on my own years running a university chemistry prep room, I learned to respect these warnings: I once watched a drop eat a patchy hole right through a new lab coat sleeve within five minutes. No exaggeration—there’s nothing theoretical about burns that bad.
Poorly ventilated rooms make a bad situation worse. Breathing in airborne droplets or vapors can trigger severe coughing, chest pain, or—in workers with asthma—real trouble breathing. Experienced chemists and techs swap stories about shifts ruined by even a single careless spill. Regular, repeated exposure, even in diluted form, leaves hands rough, red, and cracked, not just annoyed. Some evidence, although not as robust as with other acids, ties long-term exposure to lasting dermatitis and possibly increased risk of respiratory problems.
OSHA requires chemical splash goggles, face shields, acid-resistant gloves, and lab coats for a reason. People sometimes cut corners. Every shortcut with corrosives leads, sooner or later, to a moment of regret.
After a direct splash or contact, speed and thoroughness push outcomes in the right direction. If 4-Phenolsulfonic Acid touches the skin, the best plan is to rip off contaminated clothing fast and wash the area with water—lots of it—for at least 15 minutes. Soap helps, but don’t waste time searching for it. Eyes demand real emergency response: Hold the eyelids open under a running eyewash for at least 15 minutes and get medical care immediately.
Swallowing this acid calls for quick action, but not improvisation. Never try to induce vomiting. Drink water or milk if the person is conscious, but call poison control or emergency services right away. For inhalation, move outside into fresh air fast, and offer oxygen if shortness of breath develops, but let medical staff take the lead on anything beyond that.
Acids reveal weaknesses in safety culture fast. Getting teams to respect labels, keep splash shields up, and run regular safety drills cuts injury rates more than the latest fancy gloves. The most reliable labs I’ve worked in always set up clear spill response kits and label every bottle. Emergency showers aren't decorative. Practicing response—over and over—helps new workers shake off panic and act. Reliable incident reporting, linking actual health records to accident logs, guides real change.
Using 4-Phenolsulfonic Acid in any setting calls for respect rooted in direct experience, clear science, and support from all levels. Safety isn’t just paperwork. It’s everything you do before and after the spill.
Any chemist who has spent time in a lab knows the value of understanding how chemicals interact with solvents. 4-Phenolsulfonic acid often lands on reagent shelves and pops up in sulfonation reactions, dye manufacture, and even some pharmaceuticals. One question comes up frequently — will it dissolve in water or other common solvents?
Anyone who’s mixed 4-Phenolsulfonic acid with water notices it vanishes smoothly. This compound carries both a sulfonic acid group and a hydroxyl group. Both groups form hydrogen bonds, which lets the acid slide into solution without a fuss. I remember preparing dye intermediates: throwing 4-Phenolsulfonic acid in water, swirling a beaker, and seeing nothing left behind every time. It stands out compared to hydrophobic chemicals that stubbornly float or sink, refusing to engage.
This acid doesn’t just get along with water — it usually dissolves in polar organic solvents too. A typical choice is ethanol. I’ve used ethanol in pilot reactions where water wasn’t ideal, and 4-Phenolsulfonic acid gave little resistance. Methanol works fine as well. On the other hand, mix the acid with something like hexane or chloroform, and you end up disappointed. No matter how much you stir or heat, little changes. The acid prefers polar company.
Let’s look at hard evidence. Published references say 4-Phenolsulfonic acid’s solubility in water climbs above 100 grams per 100 milliliters at room temperature. That kind of number is rare — most organic compounds don’t come close. Ethanol and methanol also take up a lot, though rates drop off as the carbon chain in the alcohol gets longer. Besides these, solvents like acetone only do a mediocre job.
Good solubility matters. In analytical chemistry, poor dissolving causes headaches — incomplete reactions, messy titrations, and clogs in chromatography columns. In industry, water solubility also means easier clean-up and safer handling, since spills and residues rinse away with water. On the flip side, limited solubility in nonpolar solvents prevents unwanted migration during extractions, which can be a bonus in multistep syntheses. I’ve watched lab mates breathe sighs of relief when an acid stays put in the aqueous layer, away from the organic one they want to keep pure.
One roadblock: not every application tolerates that much water. Sometimes, moisture-sensitive reactions demand an anhydrous environment. In those cases, people add polar aprotic solvents like DMSO or DMF, which improve the outlook but come with their own baggage — think toxicity and disposal nightmares. One possible fix: neutralize 4-Phenolsulfonic acid to its sodium salt. This tweak boosts solubility further and fits better for specific downstream chemistries.
Lab users and industry managers both win by knowing how this acid behaves with solvents. Picking the right partner for 4-Phenolsulfonic acid makes for efficient processes and safer workspaces. Schools that teach hands-on chemistry do students a favor by guiding them through solubility rules. Careful selection, based on data and real-world handling experience, makes chemistry more predictable and productive.
| Names | |
| Preferred IUPAC name | 4-Hydroxybenzenesulfonic acid |
| Other names |
Benzenesulfonic acid, 4-hydroxy- p-Hydroxybenzenesulfonic acid Sulfanilic acid 4-Hydroxybenzenesulfonic acid |
| Pronunciation | /ˈfɛn.ɒl.sʌlˈfɒn.ɪk ˈæs.ɪd/ |
| Identifiers | |
| CAS Number | 98-67-9 |
| Beilstein Reference | 1209226 |
| ChEBI | CHEBI:17586 |
| ChEMBL | CHEMBL28360 |
| ChemSpider | 12375 |
| DrugBank | DB04458 |
| ECHA InfoCard | 100.013.126 |
| EC Number | 3.1.6.20 |
| Gmelin Reference | 84154 |
| KEGG | C01717 |
| MeSH | D010687 |
| PubChem CID | 979 |
| RTECS number | SM8575000 |
| UNII | 1P9D6T86NA |
| UN number | 2585 |
| CompTox Dashboard (EPA) | DTXSID9020660 |
| Properties | |
| Chemical formula | C6H6O4S |
| Molar mass | 192.19 g/mol |
| Appearance | light yellow flake solid |
| Odor | Odorless |
| Density | 1.24 g/cm³ |
| Solubility in water | Very soluble in water |
| log P | -0.38 |
| Acidity (pKa) | -2.8 |
| Basicity (pKb) | 6.92 |
| Magnetic susceptibility (χ) | -9.6e-6 cm³/mol |
| Refractive index (nD) | 1.605 |
| Viscosity | 30~50 mPa.s (25°C) |
| Dipole moment | 8.53 D |
| Thermochemistry | |
| Std molar entropy (S⦵298) | 198 J·mol⁻¹·K⁻¹ |
| Std enthalpy of formation (ΔfH⦵298) | -770.2 kJ/mol |
| Std enthalpy of combustion (ΔcH⦵298) | -1029.7 kJ/mol |
| Hazards | |
| Main hazards | Corrosive, causes severe skin burns and eye damage, harmful if swallowed, causes respiratory irritation. |
| GHS labelling | GHS05, GHS07 |
| Pictograms | GHS05,GHS07 |
| Signal word | Danger |
| Hazard statements | H318, H314 |
| Precautionary statements | Precautionary statements: P280, P305+P351+P338, P310 |
| NFPA 704 (fire diamond) | 3-0-2-Acid |
| Flash point | 230 °C |
| Autoignition temperature | 450 °C |
| Lethal dose or concentration | LD50 (oral, rat): 640 mg/kg |
| LD50 (median dose) | LD50 960 mg/kg (rat, oral) |
| NIOSH | WF8575000 |
| PEL (Permissible) | Not established |
| REL (Recommended) | 0.1-1.0% |
| IDLH (Immediate danger) | Unknown |
| Related compounds | |
| Related compounds |
Phenol Benzenesulfonic acid Sulfanilic acid p-Cresol 2-Phenolsulfonic acid |
