4-B Acid, also known as P-Toluidine O-Sulphonic Acid, 6 Amino Meta Toluene Sulphonic Acid, or 2-Amino 5-Methyl Benzene Sulfonic Acid, has carved its mark in the colorants sector since the late nineteenth century. Chemists in Europe began experimenting with aromatic amines and sulfonic acids as demand for synthetic dyes overtook natural sources. German chemical laboratories paved the way, with firms like BASF and Bayer laying early patents that shaped the bedrock of today’s dye chemistry. As manufacturing practices matured, this compound moved from small-batch artisanal labs to highly organized industrial output, driven by the needs of textile factories during the industrial revolution. Over the decades, blueprint changes—driven by process safety and environmental regulation—shifted the focus toward higher purity and lower toxicity. Today, the substance connects the roots of classic organic chemistry with innovations in sustainability and industrial safety.
Aromatic compounds always hold a particular fascination for chemical engineers, and 4-B Acid lands in that camp. This compound serves as a vital intermediate—think of it like a missing puzzle piece that ties tracts of synthetic dye chemistry together. Its structure, consisting of an amino group, a methyl group, and a sulfonic acid moiety on a benzene ring, gives it a perfect profile for downstream chemical transformations. The demand through the years speaks to just how much modern society leans on these building blocks—be it vibrant reds for textiles, advanced dyes in inkjet formulation, or new aromatics in research labs. Customers look for consistency, and reputable suppliers work exhaustively to meet strict standards, knowing the impact of even slight variations on end-use performance.
Solid at room temperature, 4-B Acid usually appears as a white to off-white powder, sometimes tinged with gray. The presence of both electron-withdrawing (sulfonic) and electron-donating (amino, methyl) groups on the benzene ring affects reactivity. The compound dissolves in water quite easily, a feature that influences not only manufacturing but environmental management downstream. Heat stability generally checks out up to moderate temperatures, though decomposition can release hazardous fumes, pushing operators to treat storage protocols as non-negotiable. Moisture from humid environments typically remains manageable if sealed, but a leaky drum in a warehouse can spell trouble—especially in terms of material handling and product integrity.
Manufacturers often guarantee a minimum assay value—say, at least 98% purity after drying, excluding inorganic salts. Ash content and iron traces draw attention, since low levels matter for the most exacting dye syntheses. Product gets bagged in polyethylene-lined fiber drums or HDPE containers, barcoded and stamped with lot number, batch date, and hazard warnings that meet international shipping criteria. Labels carry the right GHS pictograms and emergency response codes, reflecting lessons learned from decades of industry incidents. Technical data sheets go out with every shipment, detailing melting point, moisture content, and permitted impurity levels—criteria that chemists like me scrutinize before pulling anything from storage.
Manufacturing 4-B Acid tends to start with p-toluidine, a fairly routine aromatic amine, which undergoes sulfonation using fuming sulfuric acid or concentrated sulfuric acid with an SO3 donor. The trick lies in directing that sulfonic group to the right position—temperature, acidity, and reaction time each get optimized for yield and purity. The reaction mixture cools and then gets poured into water to precipitate the acid, which operators then filter, wash, and dry under controlled conditions. Process know-how separates commodity suppliers from the reliable producers: keeping downstream contaminants low can mean re-purifying batches several times or running quality checks at every step.
4-B Acid sports an amino group highly amenable to diazotization, which lets chemists generate diazo dyes by coupling with phenols, naphthols, and other aromatic partners. Methyl and sulfonic groups increase its selectivity—making mono- or polyazo dyes possible, depending on what gets tossed into the flask next. Derivatives find uses in optical brighteners and specialty pigments. Over the years, modifications have included sulfonation at other positions or converting the free acid to salt forms for enhanced water solubility. The trick for every lab technician—never let your guard down with strong acids or nitrosating reagents; a moment’s carelessness can ruin both the reaction and your safety record.
Chemistry is full of names—sometimes confusing, sometimes telling. This compound goes by 4-B Acid, P-Toluidine O-Sulphonic Acid, 6 Amino Meta Toluene Sulphonic Acid, and 2-Amino 5-Methyl Benzene Sulfonic Acid. CAS numbers help sort out the confusion: 88-44-8 is a key identifier that suppliers and customs officials rely on. Other trade names pop up in industry literature, sometimes referencing a proprietary grade or a dye-line formulation. Whoever’s buying, getting the name and grade right on the purchase order avoids ruined batches and finger-pointing at the plant gate.
Anyone who’s handled aromatic amines knows the risks: skin and respiratory irritation, sensitization, and chronic toxicity. Good industrial hygiene starts with closed system transfers, HEPA-filtered hoods, and spill protocols. Employees wear gloves, goggles, and face shields; engineering controls keep airborne dust below allowable exposure limits. MSDS recommendations push for careful segregation of incompatible chemicals, emphasizing avoidance of oxidizers and nitric acid. Fire drills and emergency showers get regular checks, because a hurried cleanup of a minor spill can turn into a bigger problem without quick access to decontamination. Safe disposal requires partnering with licensed waste handlers, since improper releases court both stiff fines and community backlash.
One walk through a dye works or pigment mill and it quickly becomes clear how vital 4-B Acid proves to the entire operation. Its main use centers around azo dye production, especially those bright reds, oranges, and deep maroons that carry so much cultural and commercial value worldwide. Textile dyers lean on these intermediates to bring colorfastness to wool, silk, and cotton. Printing ink formulators benefit from its reliable performance in water-based inks for packaging and publications. Leather finishers, paper makers, and even research chemists tap into its chemistry for both traditional and emerging applications, including reactive dyes and new colorant solutions for electronics or medical diagnostics.
Academic interest in these aromatic sulfonic acids has not faded—if anything, it has grown with advances in catalysis and green chemistry. Research groups investigate new coupling partners to expand available dye colors without increased ecological burden. Others tackle the challenge of improving solubility and processability to fit next-generation manufacturing requirements, like those for inkjet or textile digital printing. Partnerships between producers and academic labs lead to new protocols for minimizing byproducts and increasing atom economy, with growing interest in biotechnological routes for aromatic amine synthesis. The constant push for innovation holds out hope for both efficiency and sustainability, as competition moves away from cost alone toward reduced environmental and worker impact.
Despite offering immense value, aromatic amines can present health risks. Chronic exposure links to skin sensitization and potential carcinogenic effects if workplace hygiene fails. Regulatory agencies keep a close watch; REACH and OSHA requirements set permissible limits for workplace exposure. Test data—spanning acute and chronic toxicity, environmental fate, and potential for bioaccumulation—shape how chemists and regulators manage this class of compounds. Ingested or inhaled dust can irritate mucus membranes and, in high doses, disrupt liver and kidney function. Community health studies around manufacturing clusters in Asia and Europe have driven big improvements in emissions control, worker monitoring, and green disposal. Science tackles the hard questions, but the industry changes when producers buy into better protection and regular updating of safety data.
4-B Acid may hail from a bygone era of dye chemistry, but it holds a strong position as the industry modernizes for new challenges. Continual tweaks to synthesis reduce waste and save energy. Environmental mandates press factories to recycle wash water, reclaim solvents, and lower greenhouse gas emissions. Researchers explore renewable starting materials, aiming to untangle the dependence on oil-based aromatics. Market growth in Asia, especially for textiles, keeps global supply chains on edge for stable prices and high-grade material. Digital textile printing, emerging diagnostic colorants, and specialty pigments point to new avenues that will likely need tailored intermediates built on this trusted backbone. The work ahead involves fusing a century of chemical know-how with a stubborn commitment to safer, cleaner, and more resource-efficient production.
4-B Acid shows up again and again in discussions about dyes and pigments, especially in industries that need colorants for textiles, leather, and plastics. The official name, 1-Amino-4-bromoanthraquinone-2-sulfonic acid, doesn’t exactly roll off the tongue, but chemists tend to know it for its structure and how it opens doors for chemical reactions. I’ve seen it described as a building block—a starting point for making all sorts of bright, long-lasting colors we see on everything from sports shirts to children’s toys.
Dyestuff manufacturing relies on strong foundations. 4-B Acid helps form the backbone of a variety of synthetic dyes, including acidic and direct dyes. These dyes color natural fibers like wool, silk, and cotton, which means some of the boldest, most wash-resistant colors in a new shirt might trace back to this one ingredient. I recall visiting a textile mill where quality and durability in color ranked as top priorities. 4-B Acid made that possible, giving shirts life for dozens, sometimes hundreds, of washes.
It’s not just fabrics. Some companies use derivatives of 4-B Acid as intermediates in pigment production, especially for plastics and inks. Recycled plastic bottles or toy figurines showing rich, deep hues often get their colors from a process that started with this very molecule. Even the paper in magazines and colorful packaging uses pigments that, at their root, came through 4-B Acid chemistry.
Running a lab or factory introduces a new layer of responsibility. 4-B Acid, like many specialty chemicals, requires glove-and-goggles-level care. Its dust can irritate skin and eyes, and I learned early on not to underestimate hazards from dry powders. Many chemical operators and safety managers drill routines for minimizing airborne particles and making cleanup easier. Leftover solutions go through special treatment steps before they hit wastewater drains. In places with strict environmental laws, each gram receives tracking in disposal logs and safety documentation.
There’s another layer of concern: the long chain of chemical reactions sometimes produces unwanted byproducts. These leftovers, if not managed, may damage local waterways or affect workers who spend years handling them. Regulatory bodies across Europe and North America look at these risks, setting research grants and enforcement priorities. Companies designing new dyes often search for cleaner processes or alternative intermediates that reduce health and environmental impact.
Better technology can cut down hazardous exposure. Engineers work on closed reactor systems, so powders like 4-B Acid never leave their pipes until they have turned into less risky liquids. Some manufacturing plants invest in real-time air monitoring, alerting staff even if minute traces escape. Leadership teams recognize that worker health, environmental licensing, and community trust go together, and investments in safer work practices keep the business viable for the long run.
In my experience, every step—from raw material transport through waste treatment—relies on a mix of chemistry know-how and human oversight. Developing greener dye intermediates or improving old processes takes constant effort, not just because regulators demand it, but because everyone down the chain benefits when workplace air stays clean and rivers run clearer. Keeping track of a single compound like 4-B Acid tells a bigger story about chemical progress and the growing responsibilities that come with it.
4-B Acid pops up quite a bit in dye and pigment chemistry. Known to the experts as 4-Aminobenzenesulfonic acid, it comes with a straightforward chemical formula: C6H7NO3S. This formula’s not just a collection of letters and numbers—it’s a gateway to everything this compound can do in textile, leather, and research labs across the world. Anyone who deals with chemistry in a hands-on way can tell you that clarity about a chemical’s formula helps avoid missteps, wasted time, and costly accidents.
Every letter in C6H7NO3S tells you something. The six carbons, seven hydrogens, one nitrogen, three oxygens, and one sulfur aren’t just random building blocks. In this acid, the para-amino group sits right across from the sulfonic acid group on a benzene ring, which matters a lot because it influences how the molecule reacts with other chemicals and what sort of dyes you end up with at the end of a process. If you’ve tried mixing dyes for textiles, you probably learned the hard way that using the wrong starting compound throws off colors, consistency, and performance. That basic formula tells everyone mixing or reacting chemicals exactly what to expect.
For me, the details behind these formulas started to matter when I worked with a local textile workshop. We kept running into issues with dye batches producing different shades. After weeks of scratching our heads, the culprit turned out to be confusion over what “4-B Acid” actually meant—some shipments were labeled without enough detail. Only after tracing every step and getting our hands on a proper chemical analysis did we land on the right formula and solve the problem. This experience drove home how confusion over something as “small” as a formula can balloon into production headaches, lost money, and a frustrated team.
It’s one thing to have a tough day at the dyeing tank. It’s another thing when safety is on the line. Anyone working with chemicals knows that mixing up compounds based on a guess or flawed label can endanger health. C6H7NO3S isn’t explosive or wildly toxic in the way some industrial chemicals are, but accidents happen. In the wrong hands, hazardous reactions or environmental contamination become real threats if people mix up 4-B Acid with similar-sounding compounds that carry different risks.
Accurate labeling and records go further than compliance. These practices keep teams safe and save money. Companies sometimes use internal codes for shortcuts, which works until new employees or outside partners get confused. I saw good results by pushing for clear communication—not just chemical formulas, but full names and safety data sheets attached to every storage location. Investing in simple documentation and regular staff training makes a difference that you notice in both productivity and peace of mind.
Sourcing 4-B Acid from reputable suppliers isn’t just about getting the lowest price. The right chemical formula tells buyers and regulators that your process delivers what it promises. Especially with an increased global focus on safety and quality control, sticking to that standard pays off. Customers, partners, and regulators trust clear information—not mystery codes or vague product names. That’s a lesson learned from the ground up, time and again.
| Common Name | 4-B Acid |
|---|---|
| IUPAC Name | 4-Aminobenzenesulfonic acid |
| Chemical Formula | C6H7NO3S |
| Main Uses | Dye and pigment intermediate, chemical research |
4-B Acid, also called p-Aminobenzenesulfonic acid or sulfanilic acid, pops up in the world of dyes, paper brighteners, and even some pharmaceuticals. Most folks never hear about it outside factory walls, but for the people who work with chemicals or for anyone curious about the safety of ingredients, 4-B Acid raises some questions. Nobody wants to discover a hazardous material hiding inside a useful compound.
Research and workplace safety boards offer clear warnings about 4-B Acid. Data from the U.S. National Institutes of Health and the European Chemicals Agency describe it as an irritant. The powder can cause eye and skin irritation on contact. Breathing in dust drags similar risks—burning nose, coughing, even headaches for workers who handle it without protection. Eating it sounds unlikely, but accidental ingestion can irritate the mouth and gut. In rare cases, some people report rashes or allergic skin responses.
The bigger fear with any chemical comes from long-term exposure. There’s not enough evidence to blame 4-B Acid for chronic conditions like cancer or nerve damage, but the irritant effects alone give it a spot on many lists of “handle with care” chemicals. Scientific bodies place 4-B Acid in a lower-risk group compared to chemicals like benzene, lead, or asbestos, but that doesn’t hand out a free pass to ignore safety. Proper storage and protective equipment go a long way.
I’ve spent time talking to technicians and chemists who handle 4-B Acid in dye and pigment manufacturing. Gloves, lab coats, goggles, and dust masks are standard. Factory teams get regular safety briefings; spills and exposure aren’t swept under the rug. Occasionally, a sudden sneeze or skin rash reminds everyone why the protocols exist. As someone who values workplace safety, that kind of respect for the rules is essential. Lax controls never help anybody, whether you’re cleaning up a warehouse or boiling up pigment in a laboratory.
People who don’t spend time in chemical plants might worry about environmental leaks. Luckily, the acid tends to break down in soil and water, but large spills still threaten aquatic life for a short time—something regulatory agencies watch closely.
The discussion about 4-B Acid always comes back to clear information and responsible handling. Regulatory agencies in many countries set exposure limits. The U.S. Occupational Safety and Health Administration, the European Chemicals Agency, and similar groups write the rulebook. Companies must follow strict training and emergency measures. Labels warn about risks, storage containers keep powder under control, and spill plans line the walls. All these steps stop minor exposures from turning into big health problems.
It always pays to read labels, check data sheets, and ask questions. Transparency matters. While 4-B Acid won’t rank among the most dangerous chemicals in the warehouse, its irritant properties keep it under the microscope. If new studies raise additional concerns, strict rules adapt. Until that happens, the best answer comes from knowledge, training, and never taking chemical handling lightly. Every workplace with a chemical stash—no matter the substance—owes its staff dignity and safety. That’s as important as the science itself.
Working with chemicals means owning responsibility, and 4-B Acid is no exception. In labs or manufacturing spaces, this acid plays a role in dyes, pharmaceuticals, and sometimes even research. Its sharp, sometimes pungent odor stays in memory, and skin feels it quickly if splashed. Missteps here don’t just end with minor burns—people and property both sit at risk if care falls short.
I’ve seen storage rooms stacked high and chaotic, but with 4-B Acid, a clean, dry, locked spot matters more than packed shelves. Moisture sneaks in and starts the reaction early, raising pressure inside containers. Good shelving sits far from direct sunlight and away from heat sources. After years in the field, dusty corners cost more than giving the chemical its own labeled space.
Metal shelves can corrode, so plastic or coated shelving stands out as more reliable. Container seals need regular checks—just a pinch of acid at the rim signals it’s time to replace the lid. Ventilated storage means any vapors leave instead of pooling, keeping workers out of harm’s way. Placing acid drum near a sink or eyewash station, though tempting, usually brings more trouble if there’s a sudden spill.
No shortcuts make sense with hazardous material. In the lab, lab coats, thick gloves, and shatterproof goggles have served me best. Thin old gloves or open-toed shoes, which show up during rush jobs, land workers in the nurse’s station soon afterward. Double-checking label dates and concentration beats guesswork every time.
Open containers slowly and only in well-ventilated places. Fume hoods aren’t only for exotics—using them with 4-B Acid keeps airways clear and eyes from burning. Pouring should go slow, straight down the sides of beakers or flasks. Splashing means wasted product at minimum and injury at worst.
Cleanup plans—those save the most trouble. A spill kit with neutralizing agents, absorbent pads, and secure disposal bags stays within arm’s reach, not locked away. I always tell new staff: Acid doesn’t wait for a break to spill. Training often sounds repetitive, but quick action in emergencies only comes from regular drills and reminders.
Paperwork turns into protection when tracked right. Clear records—date received, date opened, expiration, and hazard classification—give everyone in the room a fair shot at avoiding accidents. Material Safety Data Sheets ought to be posted near the entrance, not buried in a desk. Risk labels—bold, unambiguous, sticking tight—help visitors as much as long-term staff.
Fire safety gets overlooked, even though 4-B Acid doesn’t catch flames easily on its own. Pair it with incompatible materials—oxidizers, bases, or certain metals—and the risk creeps up. Separating inventory by hazard class, marked shelves, and clear floor space keep accidents from snowballing.
Years of working with acids taught me that compliance isn’t about ticking boxes—it’s about long careers unharmed. Following guidelines from groups like OSHA or the EPA doesn’t just mean avoiding fines; it means fewer medical visits and no headline-making accidents. Peer reviews help, as seasoned workers spot risky habits that newer folks overlook.
Walking through these steps keeps people and investment intact. 4-B Acid’s strengths don’t have to become risks if safety habits take root and everyone feels responsible for the room’s next mistake—or its next uneventful day.
I grew up surrounded by fabric shops along the avenue, watching new shipments of fabric make their way from factory to storefront. In textile manufacturing, 4-B Acid plays a big role in creating dyes that bring color to cloth. You won’t see it mentioned on a tag or in a press release, but this ingredient helps turn bland cotton into shirts with vivid patterns and deep blues. Textile companies rely on it for its ability to help produce colorfast, long-lasting dyes. When the demand for trend-forward colors spikes, so does the demand for dye intermediates like 4-B Acid.
Anyone who has held a glossy magazine, a brochure fresh from the printer, or even a comic book, has come in contact with the result of complex chemistry. Printing ink manufacturers lean on 4-B Acid to make their products more vibrant and long-lasting. This acid helps bind pigments that resist fading. In my own work with small local print shops, I noticed the rush to source high-quality dyes every time customers requested brighter, longer-lasting prints. 4-B Acid stood out as a key ingredient in hitting those marks, especially for jobs that needed to shine under presentation lights or sunlit displays at a trade fair.
I have seen firsthand how chemistry quietly powers the pharmaceutical world. 4-B Acid serves as a stepping stone for some drug molecules. It’s not a treatment itself, but many drug companies include it early in a long chain of chemical transformations. This ingredient helps industrial chemists shape complex compounds from basic starting materials. Sometimes it shows up in drugs used to control infections or manage chronic conditions. In this field, quality standards hit the roof, and that has driven companies to source consistently pure 4-B Acid to keep their reputation — and, more importantly, keep patients safe.
Everyday products, from adhesives to bright plastic parts, can trace some of their toughness and color to 4-B Acid. I’ve toured factories where batches of specialty chemicals hum away in giant kettles, blending the acid with other compounds to create colorants for plastics and coatings for automotive trims. The small tweaks possible with 4-B Acid make a difference for manufacturers who can’t afford faded dashboards or chipping coatings on gadgets. This matters most to teams who have to explain their decisions directly to customers — nobody wants to answer a warranty claim over a flaky surface coating.
Handling chemicals like 4-B Acid brings up real concerns about safety and the environment. I’ve met operators who wear layers of protective gear just to load a single drum. Chemical companies now invest more in closed systems and air filtration to reduce risks. The industry keeps looking for greener processes: some research teams are finding new ways to synthesize colorants that cut down on waste and energy use. For buyers and product developers, asking tough questions about a chemical’s origins and disposal plan will shape better habits downstream. Everyone involved — from factory workers to brand managers — ends up playing a part in making the use of 4-B Acid safer and more responsible.
| Names | |
| Preferred IUPAC name | 4-amino-3-methylbenzenesulfonic acid |
| Other names |
P-Toluidine O-Sulphonic Acid 6 Amino Meta Toluene Sulphonic Acid 2-Amino 5-Methyl Benzene Sulfonic Acid |
| Pronunciation | /ˈfɔːr-biː ˈæsɪd/ |
| Identifiers | |
| CAS Number | 88-44-8 |
| 3D model (JSmol) | `4BAcid.pdb` |
| Beilstein Reference | 1207935 |
| ChEBI | CHEBI:28424 |
| ChEMBL | CHEMBL3252450 |
| ChemSpider | 27710 |
| DrugBank | DB14005 |
| ECHA InfoCard | 03bbd31f-13f7-4081-94bc-d5a67f5c15fd |
| EC Number | 220-502-8 |
| Gmelin Reference | Gmelin 185992 |
| KEGG | C02448 |
| MeSH | D014055 |
| PubChem CID | 74113 |
| RTECS number | CY8050000 |
| UNII | 6D8QO8YFU9 |
| UN number | 2585 |
| CompTox Dashboard (EPA) | DTXSID5020158 |
| Properties | |
| Chemical formula | C7H9NO3S |
| Molar mass | 201.24 g/mol |
| Appearance | White to off white powder |
| Odor | Odorless |
| Density | 1.38 g/cm3 |
| Solubility in water | Soluble in water |
| log P | -2.1 |
| Acidity (pKa) | Acidity (pKa): 2.2 |
| Basicity (pKb) | 12.1 |
| Magnetic susceptibility (χ) | Magnetic susceptibility (χ) of 4-B Acid (P-Toluidine O-Sulphonic Acid or 6 Amino Meta Toluene Sulphonic Acid or 2-Amino 5-Methyl Benzene Sulfonic Acid): -8.2 × 10⁻⁶ cm³/mol |
| Refractive index (nD) | 1.585 |
| Dipole moment | 3.61 D |
| Thermochemistry | |
| Std molar entropy (S⦵298) | 202.3 J mol⁻¹ K⁻¹ |
| Std enthalpy of formation (ΔfH⦵298) | -663.8 kJ/mol |
| Std enthalpy of combustion (ΔcH⦵298) | -1213 kJ/mol |
| Pharmacology | |
| ATC code | A16AX |
| Hazards | |
| Main hazards | Harmful if swallowed, causes skin and eye irritation, may cause respiratory irritation. |
| GHS labelling | GHS02, GHS07 |
| Pictograms | GHS05,GHS07 |
| Signal word | Warning |
| Hazard statements | Hazard statements: Harmful if swallowed. Causes skin irritation. Causes serious eye irritation. May cause respiratory irritation. |
| Precautionary statements | P264, P280, P301+P312, P305+P351+P338, P337+P313 |
| NFPA 704 (fire diamond) | 2-1-0 |
| Flash point | >100°C |
| Autoignition temperature | Autoignition temperature: 500°C |
| Lethal dose or concentration | LD50 oral rat: 4000 mg/kg |
| LD50 (median dose) | LD50 (median dose): Oral rat LD50: 4000 mg/kg |
| NIOSH | SL8225000 |
| PEL (Permissible) | 15 mg/m3 |
| IDLH (Immediate danger) | Not established |
| Related compounds | |
| Related compounds |
6-Nitro 2-Toluene Sulphonic Acid Meta Toluene Diamine 4-Chloro 2-Amino Toluene 4-Nitro 2-Toluene Sulphonic Acid |
