Chemistry is full of compounds that quietly shape modern industries, and benzenesulfonic acid monohydrate belongs in that group. The roots of this compound stretch back to the late 19th century, when sulfonation of benzene paved the way for detergents, dyes, and pharmaceuticals. Chemists needed simple ways to convert aromatic rings into more reactive species, and sulfonic acids offered both solubility and functionality. Companies like BASF and Dow scaled up production in the early 20th century, making these compounds a staple for industrial synthesis, long before the era of green chemistry or environmental regulation intensified. These early developments didn’t get flashy headlines, but without them, the creation of colorfast dyes or stable drug precursors would’ve stalled, impacting everything from healthcare to textiles.
Benzenesulfonic acid monohydrate appears in white to pale crystalline or solid forms, usually with a sharp, almost medicinal odor. Its structure—where a sulfonic acid group attaches directly to a benzene ring, paired with a single molecule of water—gives it both strength and flexibility. Chemical manufacturers value it as both a reagent and intermediate in sectors ranging from cleaning agents to agrochemicals. The compound’s stability, paired with high acidity, allows it to act as a catalyst and precursor, changing up production lines for detergents and dyes. It’s not glamorous, but anyone who’s worked in synthesis knows the value of having a reliable, easy-to-handle acid at hand.
On the bench, benzenesulfonic acid monohydrate melts around 50°C, dissolves easily in water, and flows like a syrup at room temperature. That single molecule of water might sound trivial, but it makes handling and storage a bit smoother by keeping the acid from solidifying in pipes or tanks. Chemically, you’re dealing with a strongly acidic group, with a pKa low enough to protonate most bases and a sulfonate backbone that resists oxidation and many types of chemical attack. It’s stable, doesn’t evaporate, and doesn’t ignite unless mistreated—qualities that matter in large-scale processing and minimize headaches for technicians.
Manufacturers list benzenesulfonic acid monohydrate under technical grades based on purity, water content, and color metrics measured by standardized tests like APHA. Labels might read “Benzenesulfonic acid monohydrate, min. 98% purity, APHA color <50,” with clear hazard pictograms signaling its corrosive nature. Compliance with GHS, REACH, and local transport codes stays mandatory. Every lot must come with an updated Safety Data Sheet (SDS), showing not just regulatory identifiers but specific handling, storage, and spill measures. Even small labs value these straightforward details—clean labeling saves time and supports worker safety.
The classic synthesis involves direct sulfonation of benzene with concentrated sulfuric acid, often under controlled heating. This approach generates benzenesulfonic acid as the hydrate without extra purification steps, saving resources in bulk operations. Automation of this process in chemical plants brings about fewer emissions and lower risks of side reactions. Years of fine-tuning—like optimizing reaction temperature, acid concentration, and mixing rates—mean modern facilities consistently crank out high-purity product with minimal waste. It’s not a process that excites most outsiders, but students in organic chemistry will nod at the straightforward elegance of this transformation.
Benzenesulfonic acid monohydrate stands out for its adaptability. It undergoes sulfonation, sulfoxidation, and neutralization, readily converting to sulfonate salts—important in detergents and dyeing. Reacting it with bases forms sodium or potassium benzenesulfonates, which dissolve neatly in water and foam well, making them a cornerstone in cleaning products. It also helps introduce sulfonate groups onto other aromatic rings, used in making more complex molecules such as certain herbicides and pharmaceuticals. In the lab, reactions with chlorinating agents can swap out the sulfonic acid for sulfonyl chlorides, intermediates for more elaborate syntheses. Flexibility in reactivity often translates to shorter, more economical production routes.
Markets and catalogs list benzenesulfonic acid monohydrate under a slew of names, including “Phenylsulfonic acid monohydrate,” “BSAM,” and “C6H5SO3H·H2O.” Some regional suppliers market it simply as “Sulfonic Acid (benzene type),” which simplifies ordering in high-volume purchases but can trip up researchers cross-referencing literature. CAS number 81-11-8 remains the global reference, supporting traceability for both supply-chain managers and regulatory inspectors. Having dealt with chemicals that go by a dozen interchangeable names, I’ve learned to double-check labels and specs before swapping one batch for another—consistency matters for both safety and results.
Handling benzenesulfonic acid monohydrate requires common sense and good practice. Its strong acidity and corrosive effects on skin and eyes mean that splash goggles, gloves, and lab coats stay mandatory. Fume hoods or exhaust systems help manage vapors, especially during heating and neutralization. Spill kits with neutralizing agents like sodium bicarbonate or lime come in handy on production floors. Regulatory frameworks like OSHA and the EU CLP classify and manage the compound under hazardous material guidelines, with environmental discharge limits for sulfonated matter. Strong documentation for storage temperature, secondary containment, and first-aid measures makes sure that even newcomers in a plant know how to stay safe.
You find benzenesulfonic acid monohydrate across a strange mix of industries. In detergents and surfactants, it serves as a raw material for sulfonate builders, lending cleaning power to laundry soaps and industrial degreasers. Dye and pigment synthesis also rely on it, both to introduce sulfonate groups for water solubility and boost dye uptake on fibers. Pharma companies use sulfonic acids to prepare drug intermediates, unlocking pathways for antihypertensives, antivirals, and APIs where a stable, strong acid makes a difference. Water treatment chemicals, electroplating baths, and resins all tap into its reactivity. Colleagues in chemical engineering regularly tell stories about how switching batch acids cuts production costs for everything from weed killers to specialty polymers.
Research on benzenesulfonic acid monohydrate keeps evolving. Newer innovations look for greener preparation methods, replacing concentrated sulfuric acid with solid acid catalysts or reusable sulfonating agents. These approaches works towards less hazardous waste and energy savings. Green chemists in both academia and start-ups look for ways to use benzenesulfonic acid as a recyclable acid in multi-step syntheses, trying to minimize purification steps and solvent loads. Analytical chemists use the compound as a reference material for titrations and calibration standards, supporting both industrial quality control and regulatory compliance. The main push—how to make high-purity product from cheaper, renewable feedstocks—shapes a lot of patents and research grants now.
Toxicologists test benzenesulfonic acid monohydrate for both acute and chronic effects. It’s caustic at high concentrations, damaging to skin and mucous membranes on contact. In water systems, it breaks down into benign sulfate and carbon dioxide, but only after treatment—so process water must be managed with care. Animal studies report low systemic toxicity when exposure is kept below occupational limits, but high doses drive inflammation or tissue burns. Regulatory bodies set workplace exposure thresholds, and batch testing on effluent discharge limits helps keep the environmental impact under control. I’ve seen cases where improper dilution led to worker injury, making robust training important for both lab and factory settings.
The next decade could change the landscape for benzenesulfonic acid monohydrate. Sustainability drives much of the change—companies want bio-based benzene or smarter recovery systems to limit waste and cut costs. Advances in continuous-flow reactors mean precise temperature and pressure control, lessening side-product build-up and enabling smaller, safer plants. Digital process control and machine learning help predict outcomes across different feedstocks, helping both large and small operators save on energy and raw materials. Researchers keep hunting for new catalysts that allow sulfonation under milder, cleaner conditions. Demand for higher-purity grades will only grow as pharma and electronics sectors need lower contaminants and more certification for end-users. Benzenesulfonic acid monohydrate won’t snag headlines, but it will quietly anchor production in sectors the world relies on every day.
Benzenesulfonic acid monohydrate may sound like something tucked away in a lab, but it earns its place in plenty of day-to-day processes. Unlike some hard-to-pronounce chemicals, it brings a clear set of strengths: it stays stable, acts as a strong acid, and dissolves in water with no complaint. I’ve seen examples where a simple bottle of this compound on a shelf speaks for how essential solid acids have become for industry, even for folks who never set foot in a chemistry class.
Anyone who’s run a dishwasher or scrubbed a dirty floor has a brush with the bigger world of sulfonic acids. Companies draw on the powerful cleaning properties of benzenesulfonic acid monohydrate when they create detergents. The acid breaks up grease and dirt by helping water grab hold of grime in a way soap struggles to match. Laundry formulations, dishwashing liquid, and some heavy-duty janitorial cleaners wouldn’t have the same punch without this chemical in the toolkit. Old-timers might remember the first time they switched from soap flakes to detergent, and the difference stuck.
Textile plants and dye factories lean on benzenesulfonic acid derivatives. It acts as both a catalyst and a starting point for making dyes stick to fabric. In practice, it helps bring out brighter, deeper colors in everything from t-shirts to upholstery. Without it, many fabrics would quickly lose their luster. Chemists figured out decades ago that adding sulfonic acid groups to dye molecules let them cling to fibers even after repeated washings.
Medicine manufacturing often traces back its ingredients to a handful of reliable chemicals. Benzenesulfonic acid monohydrate carves out a spot in the synthesis of active pharmaceutical ingredients. Some drugs build off the acid’s sulfonate group. Its stability means the reaction takes place with less risk, which matters when safety stakes are high. It keeps reactions moving in the right direction and trims unwanted byproducts, offering a smoother road from raw material to finished medicine.
It’s impossible to ignore the environmental impact, especially with increasing calls for safer chemistry. Benzenesulfonic acid scores an edge over harsher mineral acids. It delivers its acidifying muscle without producing clouds of fumes. Still, strong acids present a set of safety questions. I’ve seen spills—even diluted ones—eat through protective gloves or mar a countertop. Safety gear and good ventilation stay part of the story.
Wastewater treatment plants face challenges breaking down such stable compounds. Manufacturers continue searching for ways to recover and recycle spent acid. Solutions include continuous monitoring, process redesign, and switching to greener feedstocks where possible. Tracking how much chemical gets used, and where it ends up, forms the backbone of responsible handling.
Benzenesulfonic acid monohydrate doesn’t make headlines, but you’ll spot its fingerprints on cleaner laundry, vibrant clothing, and affordable medicine. The challenge isn’t just about making it work for industry, but making it a part of smarter, safer chemistry for the long haul. If companies tackle process safety and tackle waste at the source, then the benefits show up not only on the factory floor but in cleaner waterways and healthier communities. Drawing from both research and lessons learned through years of hands-on work, continuing to update handling and minimizing environmental load gives this workhorse chemical a place in a changing world.
Benzenesulfonic acid monohydrate doesn’t get much attention outside chemistry discussions, but in research circles, it plays more roles than people might think. The chemical formula—C6H6O3S·H2O—wraps together a benzene ring, a sulfonic acid group, and a water molecule. For someone holding a pipette in a lab, getting that formula right means getting the reaction right. Laboratory mistakes rarely make the headline, though they can cost entire afternoons and thousands in lost materials. I’ve seen early-career scientists scramble to catch errors caused by skipping over simple water of hydration.
Book smarts will say C6H6O3S·H2O blends one primary functional group—the sulfonic—onto a stable benzene base, capped by water. From a practical view, this formula sets the tone for how the compound acts in solution, how it stores, and which reactions actually proceed. Forgetting the mono-hydrate water can throw off stoichiometry, bring unwanted variability, and change melting points. More than once, someone has ordered the anhydrous version but worked up their plans based on the monohydrate. I’ve seen reactions fail or produce unhelpful byproducts just because of that invisible H2O.
Factories and research labs use benzenesulfonic acid to drive sulfonation, organic synthesis, and even cleaning formulations. Scale-up work requires consistency. Projects I've followed in industrial scale development run into headaches when suppliers change the hydrate content unannounced. Inconsistent hydrates throw off batch sizes and introduce uncertainty. I appreciate manufacturers that specify the formula fully so operators don’t have to play guessing games with outcomes. The burden lands on every technician in settings from school chemistry to heavy manufacturing. Whether making dyes, pharmaceuticals, or specialized polymers, suppliers and users both need to speak the same formula language—and stick to it.
Many compounds in this class demand a careful approach. Benzenesulfonic acid doesn’t qualify as the world’s most hazardous chemical, but handling still needs competent people on the job. That hydrate molecule affects its reactivity, solubility, and how it interacts with other substances. If someone treats it as dry material by mistake, safety gear gets mismatched, neutralization steps mistimed, and storage guidelines missed. In my own lab, we’ve worked out checklists partly because one missed detail in the formula meant a safety report the next morning.
Education addresses part of the challenge. Schools and universities could stress hydration states much more in courses, instead of just repeating the base structure. I’ve seen improved lab handling and reporting in facilities where chemical labels clearly display the full formula, including hydrate content, every single time. Digitized inventory systems help track what comes through the door—but only if the formulas get entered correctly to start. Guiding young researchers to pause and check those values forms good habits. Small prints and abbreviations still trip up the best of us.
Clear labeling, strong documentation, and honest supplier communication make the most difference. A well-stocked lab with laminated safety sheets that spell out the entire formula, not just the main molecule, avoids more headaches than almost any expensive gadget. Sharing good habits across teams keeps everyone safer and protects results. I’ve learned to ask suppliers three times about hydrate forms, and that simple act saves time and resources year after year.
Storing and handling a product the right way sounds obvious, but anyone who’s unpacked a container and found a sticky mess knows it’s not always straightforward. Labels often provide a few lines of instructions before asking us to refer to a data sheet buried on a website. In my years working in various facilities—food processing plants, chemical warehouses, even a local hardware store—seeing things go sideways usually starts with ignoring the basics of temperature, moisture, or contact with other substances. These slip-ups do more than waste material; they ripple out, causing safety hazards, insurance headaches, and loss for everyone involved.
A dry, cool place isn’t just a phrase on every bag or bottle. Heat speeds up chemical reactions inside packaging; cold can thicken liquids or make bags brittle. For food-grade supplies, dairy especially, a rise of even five degrees above safe storage turns a high-quality product into a risky guess. OSHA has documented that spoilage jumps up in facilities without reliable temperature controls. I once worked in a space with inconsistent cooling. One summer, an entire palette of adhesive cured inside the buckets, turning it into expensive trash. Getting storage temp right doesn’t only save money—it keeps customers safe.
Moisture is the silent saboteur for everything from cement to dry pasta. Any seal that’s loose or a lid left open brings in humidity, which can lead to caking, corrosion, or actual microbial growth. Food and pharmaceutical items are particularly sensitive; cross-contamination from airborne particles can sink a company’s reputation overnight. In my first warehouse job, ignoring this meant tossing hundreds of pounds of cake mix after one humid week. Lined bins, tight seals, and regular visual checks protect inventory; it’s worth the extra minute.
Putting reactive chemicals in the same cabinet is asking for trouble. Paint thinner and bleach don’t belong near each other; even household cleaners can cause toxic fumes if they share airspace. I’ve watched safety drills turn real because someone stacked oxidizers and flammables together, thinking “just for a day” wouldn’t matter. The EPA’s guidance on segregation isn’t busywork; it keeps real people from landing in the emergency room.
The oldest product in the back tends to get overlooked for newer, shinier shipments. Every industry talks about FIFO—first in, first out—but pallets get shifted, and a few dusty boxes escape notice. In retail and manufacturing, expired goods work their way to shelves and end up with customers. The routine of checking dates and moving old stock up to the front helps avoid embarrassing phone calls, lost trust, and sometimes even recalls.
No system works without buy-in from the people handling goods day after day. Training goes further than posting a sign; leadership should run hands-on walkthroughs. I’ve seen quality improve overnight after brief, clear reminders about securing lids and wiping spills. It’s not complex, but it matters. Clean, organized spaces also make it easier to spot a problem before it spreads. Companies serious about storage and handling back it up with both clear procedures and visible support from managers.
My memory goes back to crowded undergraduate labs, where bottles labeled “Benzenesulfonic Acid Monohydrate” lined the storage shelves. White crystals, strong odors, and a stern warning on every label. The chemical world is packed with substances that demand careful handling, and this one always grabs attention for a reason. If you’ve ever dripped a little on your glove, you know how that sting lingers. The label warnings are real: this acid doesn’t play nice with unprotected skin, eyes, or airways.
Benzenesulfonic acid monohydrate sits firmly in the “corrosive” camp. Skin contact can burn. Splashes in the eyes will cause pain and damage. Inhaling the dust or vapors brings irritation to the nose and throat, and even low-level exposure can still be uncomfortable. OSHA and other safety agencies classify it as hazardous, not due to some obscure technicality, but because its effects show up quickly and can escalate fast without the right protection.
Safety Data Sheets (SDS) hit the point again and again: corrosive to skin, eyes, and mucous membranes, especially in larger amounts. Handle it wrong, and you get chemical burns that heal slowly. Spilled material + water = heat and even more irritation. If it gets on clothing, it usually eats right through. Pouring it into a beaker can kick up enough dust to sting your sinuses if your mask sits loose. It’s not about theoretical risk—plenty of seasoned chemists sport little scars from lapses with this acid.
This chemical doesn’t do the environment any favors either. Strong acids like benzenesulfonic acid can lower the pH of water and soil, harming plant and aquatic life. Anyone who’s worked at a wastewater plant knows the tight control needed before disposal. Facilities running dye, detergent, or chemical synthesis processes learn fast that neutralization of acid waste is non-negotiable. A careless rinse down the drain causes more trouble than most realize, and regulations follow strict lines to stop environmental damage.
Companies that work with large volumes see another side: corrosion of equipment. Benzenesulfonic acid chews through untreated steel, soft plastics, and even gloves made for everyday cleaning. Visible pitting, weakened seals, and even sudden pipe failures can result from leaks or long-term vapor exposure, driving up costs for replacements and emergency maintenance. The acid’s power can’t really be downplayed. It forces proper training, special material selection, and a culture of respect from every technician and engineer involved.
Protection starts with common sense and real adherence to lab or plant protocols. Nitrile or neoprene gloves hold up far better than the thin latex most beginners grab. Full-face shields and splash goggles block surprise splashes. Good fume hoods and strong room ventilation clear the air. And, every station needs easy access to eyewash stations and showers. Those who cut corners get bitten eventually—experienced supervisors can spot the fresh burns on newcomers who get complacent.
Knowledge combined with real-world respect changes how people handle hazardous chemicals. Benzenesulfonic acid monohydrate stays hazardous by any sensible definition and earns its corrosive warning. Chemistry and manufacturing fields wouldn’t function without tough substances like this, but that usefulness comes bundled with serious responsibility.
Benzenesulfonic Acid Monohydrate works as a strong sulfonating agent in labs and factories. Its purity matters—mixing a batch with trace metals or moisture out of spec impacts every downstream process. An analyst running titrations for cleaning products needs high purity to avoid unexpected results. Water treatment operators want assurance that the acid won't bring in unwanted contaminants. Pharmacies and research teams rely on paperwork outlining every contaminant, right down to single digits, often below 99%. I’ve seen it in action—using technical grade material in analytical work can spike baseline readings and waste valuable samples. Quality takes on greater weight when you move outside the lab, in manufacturing, where a single variable in the acid’s profile can slow production or throw off yields.
Most reputable suppliers quote at least 98% or 99% purity for Benzenesulfonic Acid Monohydrate. That percentage describes how much of the material is truly benzenesulfonic acid; the remainder could be water, sodium, iron, or dust from old pipelines. Go below 98% and you’re gambling with yield and safety, especially if precision matters. Some applications do fine with lower grades, but that usually comes from experience and a real-world understanding of what’s at stake—like in industrial degreasers, where cost cuts sometimes justify a lower grade, even at the risk of build-up or foaming problems later on.
Suppliers often list “technical grade” for industrial cleaning uses and “reagent grade” for lab or pharma work. Reagent grade typically means a tighter specification, and buyers pay extra to avoid unpleasant surprises. I’ve reviewed data sheets where technical grade shows a wider range for metals and moisture but remains consistent—this level of transparency makes all the difference for end users. It comes down to trust: knowing what’s in your drum or bottle matters more than a marketing pitch. Reagent grade rarely strays from batch-to-batch quality, so research teams stake their reputation on that level of reliability.
Not every manufacturer upholds the same production standards. Any lapse—be it equipment maintenance or changes in raw sodium benzenesulfonate sources—reflects in batch consistency. I’ve received deliveries with visible haze and had to return them. In regulated settings, a batch report isn’t optional—it’s as vital as the acid itself. Spot checks avoid knock-on costs from contaminated product. In competitive markets, some suppliers push prices by skipping critical purity tests. This creates pressure for buyers who must balance budgets against the cost of failed reactions and wasted man-hours.
Trusted supply chains develop through long relationships and routine testing—third-party audits, batch certificates, and traceability cut down on surprise contaminants. Stores that treat Benzenesulfonic Acid Monohydrate like a bulk commodity set themselves up for problems; buyers should demand full chemical analysis before payments clear. Some industries push for digital tracking of every lot, which reduces disputes and protects users when batches don’t deliver. Transparent access to testing data lets buyers choose purity based on practical needs, not just price or paperwork. Real assurance comes from seeing the numbers yourself and talking directly with production teams, not faceless order forms.
| Names | |
| Preferred IUPAC name | Benzenesulfonic acid monohydrate |
| Other names |
Benzenesulfonic acid hydrate Benzenesulphonic acid monohydrate Benzenesulfonic acid, monohydrate Phenylsulfonic acid monohydrate |
| Pronunciation | /benˈziːn.sʌlˈfɒn.ɪk ˈæs.ɪd ˌmɒn.oʊˈhaɪ.dreɪt/ |
| Identifiers | |
| CAS Number | 10098-19-2 |
| 3D model (JSmol) | `/model=c1ccc(cc1)S(=O)(=O)O.O` |
| Beilstein Reference | 385378 |
| ChEBI | CHEBI:75955 |
| ChEMBL | CHEMBL1232983 |
| ChemSpider | 121352 |
| DrugBank | DB14287 |
| ECHA InfoCard | 100.006.740 |
| EC Number | 246-678-1 |
| Gmelin Reference | 1611596 |
| KEGG | C11445 |
| MeSH | D000595 |
| PubChem CID | 23668504 |
| RTECS number | DB6600000 |
| UNII | 51409S3N7A |
| UN number | UN2584 |
| Properties | |
| Chemical formula | C6H6O4S |
| Molar mass | 224.24 g/mol |
| Appearance | White to off-white crystalline powder |
| Odor | Slight odor of sulfur dioxide |
| Density | 1.37 g/cm³ |
| Solubility in water | Soluble in water |
| log P | -2.3 |
| Vapor pressure | 0.0013 hPa (20 °C) |
| Acidity (pKa) | −2.8 |
| Basicity (pKb) | -6.5 |
| Magnetic susceptibility (χ) | -57.6 x 10^-6 cm³/mol |
| Refractive index (nD) | 1.576 |
| Viscosity | 80 mPa·s (20 °C) |
| Dipole moment | 1.70 D |
| Thermochemistry | |
| Std molar entropy (S⦵298) | 212.2 J/mol·K |
| Std enthalpy of formation (ΔfH⦵298) | -741.6 kJ/mol |
| Std enthalpy of combustion (ΔcH⦵298) | -3569.7 kJ/mol |
| Pharmacology | |
| ATC code | A16AX |
| Hazards | |
| Main hazards | Corrosive, causes severe skin burns and eye damage, harmful if swallowed or inhaled |
| GHS labelling | GHS02, GHS05, GHS07 |
| Pictograms | GHS05,GHS07 |
| Signal word | Warning |
| Hazard statements | H314: Causes severe skin burns and eye damage. |
| Precautionary statements | P264, P280, P301+P330+P331, P305+P351+P338, P310 |
| NFPA 704 (fire diamond) | 3-0-2-Acidos |
| Flash point | > 160°C (320°F) |
| Lethal dose or concentration | LD₅₀ Oral - Rat - 2,426 mg/kg |
| LD50 (median dose) | LD50 (median dose): Oral rat LD50: 500 mg/kg |
| NIOSH | DA6475000 |
| PEL (Permissible) | PEL: 1 ppm |
| REL (Recommended) | 0.93 mg/m3 |
| Related compounds | |
| Related compounds |
Benzenesulfonic acid Benzenesulfonic acid sodium salt p-Toluenesulfonic acid Benzenesulfonyl chloride Benzenesulfonamide |
