© 2026 Sinochem Nanjing Corporation,
All Right Reserved
Acid Yellow 99 traces its early beginnings to the expansion of synthetic dye chemistry in the late 19th and early 20th centuries. During this era, color chemists focused on creating affordable, bright dyes to meet the rising demand from growing textile industries across Europe and Asia. Over decades, the improvements to synthetic routes for azo dyes opened new paths for dyes like Acid Yellow 99, which brought a distinct bright shade and practical application when compared to natural colorants. Textile and dyeing hubs like Germany and the UK, with their academic and industrial collaboration, drove robust research, leading to more efficient production and refinement of such chemicals. Makers standardized processes by the late 20th century, which pushed Acid Yellow 99 from local specialty labs to large-scale manufacturing plants, making the color available worldwide and compatible with various technical needs.
Dyestuff experts classify Acid Yellow 99 as an azo dye, known for its deep, vivid yellow hue, intended mainly for protein fibers and certain polyamide fibers. Within industrial dye classifications, it stands out because of strong color yield and the reliability of the shade, handling both minor and large-batch textile jobs with consistency. Users have relied on it not just for the tone but also because it registers well under colorimetric standards, which is vital for manufacturers who create regulated goods. Its trade names range across regional markets, with product labels adapting to meet both legislative and commercial demands, which can often lead to an array of entries in dye registries and technical sheets.
Chemically, Acid Yellow 99 falls under the monoazo dye category, meaning its key chromophore contains a single azo group (-N=N-). In appearance, it usually exists as a fine yellow powder or, less commonly, in granules. This dye dissolves well in water, especially under slightly acidic pH, which makes it a mainstay in traditional wool and silk dyeing. Its molecular formula, C18H14N4Na2O7S2, gives it a substantial molecular weight, and it often displays strong solubility in boiling water, producing a transparent, richly colored solution. The dye decomposes at high heat, which is critical to note in thermal processing. Its color strength remains steady up to the moderate acid concentrations typically found in textile work, and its lightfastness, while not as high as some anthraquinone-based dyes, works acceptably for many medium-duty applications.
Textile plants require clear, detailed technical documentation for Acid Yellow 99, especially when meeting international safety or environmental regulations. Quality parameters include purity (measured by HPLC or TLC), shade index, water and salt content, insoluble matter, and pH range for proper dyeing. Common technical sheets outline not only these features, but also specific absorption wavelengths used in color matching; around 410 nm remains common for verifying main color strength. Containers highlight hazard warnings due to the presence of aromatic amines or azo compounds, especially relating to storage and accidental spillage, with hazard pictograms mandated by updated GHS labeling rules.
Synthesis of Acid Yellow 99 centers on diazotization and coupling processes, standard for monoazo dyes. Technicians treat an aromatic amine, often derived from aniline sources, with sodium nitrite in acidic solution to form the diazonium salt. This intermediate couples with a suitable aromatic substrate containing sulfonic acid groups, increasing water solubility and fabric affinity. The dye solution gets neutralized, filtered, and concentrated, then dried into a powder. Production sites maintain strict control of reaction temperature, pH, and reactant ratios because minor variations can shift hues or introduce side products, which hurt both color reliability and regulatory acceptability.
From a chemist’s point of view, the backbone of Acid Yellow 99 allows for limited modification because extensive alteration risks losing the intended chromophore. Salts or metal complexes can adjust the application profile modestly—especially for improving tinctorial value on certain fiber types. High-purity grades depend on subsequent washing steps and filtering to remove excess salts or secondary reaction products, which otherwise muddle the optical properties. On rare occasions, dye houses may blend or over-dye Acid Yellow 99 with other azo or anthraquinone colors for specialized fashion lines, but the core structure remains vital for the signature color performance in acidic baths.
Like many commodity dyes, Acid Yellow 99 goes by different aliases depending on supplier, manufacturer, and country. Major registry numbers include C.I. 13065 and CAS 10343-58-5, while commercial names feature trade monikers preferred by leading dye houses, sometimes combined with suffixes indicating grain size or purification method. Old catalogues occasionally list obsolete synonyms that today serve more as reference for regulatory cross-checks or historical tracing than daily work, but they crop up in older compliance lists or niche publications.
No dyestuff conversation escapes the topic of safety, because azo dyes, including Acid Yellow 99, require careful oversight. Manufacturing floors lock down inhalation and skin contact hazards, and processors adopt rigorous ventilation, dust control, and personal protective equipment policies. Disposal and effluent treatment stay top-of-mind, because incomplete reactions or spills can introduce unwanted colorants into groundwater. Textile firms work with updated SDS (Safety Data Sheets), which reflect both acute risks and chronic health studies. Since a handful of azo dyes sparked reform after being linked to aromatic amine release under certain conditions, regulatory agencies in the EU and North America have placed regular controls and checks, so dye plants remain up to date or risk recall and enforcement.
Acid Yellow 99 finds widespread use across the classic wool and silk sectors, which take best to acid-dye processes. The dye absorbs efficiently on animal fibers, and traditional dye vats or jet-dye procedures draw out its full brilliance. Besides the textile market, some sectors use it for coloring leather, paper, and even certain types of food packaging (subject to local regulation). Research stations sometimes deploy it in analytical labs as a colorimetric reagent or pH indicator due to its strong, distinct signal in solution. Small craft industries and hobbyists gravitate to this dye for hand-dyeing, where vibrant results with minimal equipment come with familiarity and easy access to technical support online.
For a dye as established as Acid Yellow 99, research hasn’t slowed—today’s interests trend toward lowering environmental impact, reducing process waste, and substituting safer substitutes where possible. University labs and public-private consortia attempt to modify synthesis routes to trim hazardous byproducts, or use greener solvents and milder reagents. Developers look for better dye fixation and level-dyeing characteristics, which directly influence water and energy consumption for commercial plants. Spectroscopic analysis, including UV-Vis and advanced NMR/LC-MS techniques, now supports rigorous structure confirmation and impurity tracking. On the user end, R&D teams pass design feedback to chemists, suggesting tweaks that can extend colorfastness or sharpen bath exhaustion—areas where even small wins add up to major efficiency gains in large-scale production.
Concern over azo dyes kicked up in the late 20th century, with higher scrutiny after discoveries that certain derivatives could release carcinogenic amines under specific chemical or biological conditions. Although Acid Yellow 99 does not fall under the most strictly banned categories, toxicology studies continue to watch its breakdown products and possible allergenicity. Animal studies, in vitro mutagenicity assays, and long-term eco-toxicity data guide regulatory frameworks across continents. Efforts continue to clarify safe exposure limits and environmental thresholds, and robust monitoring keeps any drift in composition or impurity profile from slipping through the cracks in the supply chain. Workers, communities, and buyers benefit from transparent reporting, and new forms of bioassays and environmental markers give extra confidence to regulatory oversight.
Current industry shifts push Acid Yellow 99 in two directions—sustaining its main role in fiber dyes and phasing out use where alternatives or tighter safety standards demand it. Clean technology, improved waste treatment, and lifecycle analysis measure the real impact of synthetic dyes, and the results drive both legislative action and market demand. New “greener” colorants arrive every year, but cost, reliability, and practical application still keep dyes like Acid Yellow 99 in broad use. Collaborations between manufacturers and sustainable chemistry researchers look promising for updating production, implementing closed-loop processes, and ensuring the chemical’s legacy adapts to stricter environmental guardrails. With the next generation of plant managers, chemists, and lab techs trained on both classic and modern standards, this dye’s story continues, living in balance with changing tastes, technologies, and standards.
Acid Yellow 99 often catches the attention of manufacturers due to its strong, vivid shade and dependable performance. Years ago in a textile factory, I handled fabrics dyed with Acid Yellow 99. That sharp yellow did more than please the eye; it stuck through many washes and kept its bold character where other dyes started to fade. Dye makers in the textile field continue to rely on Acid Yellow 99 because it treats wool, nylon, and some silk with a lightfast, level color that shoppers recognize right away.
Textile dyeing stands at the core of Acid Yellow 99’s use. Its color shows best on wool and nylon, where the dye forms sturdy bonds with fibers in an acid bath. Many manufacturers claim Acid Yellow 99 allows designers to meet consistent shade demands. I saw this myself: batches would match day after day. This repeatability makes supply chains smoother and easier to manage. Leather goods also benefit. Tanners use Acid Yellow 99 to create yellow leather belts, shoes, wallets, and bags that won’t bleed color during daily wear or on a rainy walk home. The color feels strong, but also natural enough to pair with other dyes or treatments.
Printers see real value in Acid Yellow 99 for specialty inks. Before synthetic dyes like this came along, natural yellows from plants weren’t as stable. Most printing experts agree that the acidic formulation delivers sharper, longer-lasting prints. Paper mills sometimes turn to Acid Yellow 99 for specialty giftwraps, decorative prints, and colored office sheets. In my time working with school supplies, we used this dye for colored notebooks because the pigment stood out and didn’t stain kids’ backpacks the next year. Companies appreciate that, especially when cheap alternatives don’t last as long or smear too easily.
Regulations limit the dye’s direct use in foods in many countries, but some regions allow Acid Yellow 99 in select foodstuffs or packaging. Its vivid color appeals to candy makers or snack producers looking to catch the eye on crowded store shelves. Cosmetic labs sometimes use the pigment for soaps and bath products, always checking batch safety and rules set by local governments. That attention to safety and sourcing shows how difficult it can be for chemical suppliers to balance creativity and compliance — a story I’ve heard more than once from industry contacts working in regulatory affairs.
Acid Yellow 99’s versatility also brings responsibility. Textile dye factories produce wastewater that may retain leftover dye and chemicals. Poor treatment practices ruin river life; workers in unsafe plants suffer, too. The good news is that several big manufacturers now invest in closed-loop water systems and better filtration. This shift helps protect community health and conserve water for the long haul. Companies choosing acid dyes like Acid Yellow 99 need to source from suppliers who prove their waste is contained and recycled, not dumped. Consumers can make a difference by reading labels, supporting transparent brands, and asking questions about ecological impact — even if all we want is a splash of color on a scarf or a backpack. Acid Yellow 99 proves that even a single dye can spark improvements across health, safety, and the environment, if enough people speak up.
Plenty of bold, bright dyes exist. Acid Yellow 99 stands out because it creates vivid yellow hues that catch the eye. Textile manufacturers love its bright punch, and sometimes nail polish makers and artists reach for it too. The ease of application on wool, silk, and synthetic fibers has fueled its popularity in the fabric world. Still, the real question that deserves attention is about the effect on skin and personal safety.
Everything we put on skin or wear on our bodies deserves scrutiny. Acid Yellow 99 also goes by its chemical name, C.I. 13065. Manufacturers rely on this dye for both color strength and staying power, especially in fashion or home textiles. Scientific research helps us get past marketing: the structure breaks down into aromatic amines, some of which research connects to allergies or, in certain cases, health risks if they build up in the body.
I’ve spent hours searching for clear guidance from health authorities and chemical registries. Regulatory agencies like the European Chemicals Agency (ECHA) flag this yellow dye as an irritant, with warnings about possible allergic skin reactions. The U.S. Environmental Protection Agency and the EU both raise eyebrows at long-term or frequent skin exposure. Dermatologists caution that dyes like this, if not thoroughly tested for consumer products, can sometimes trigger rashes, itching, or more serious consequences in folks with sensitive skin.
Factories treat fabric dyes with a long checklist of safety and environmental controls. When Acid Yellow 99 gets used in industrial settings, handlers wear gloves, work in ventilated spaces, and dispose of waste carefully. Finished products may hold only traces of the original chemical, but the process isn’t foolproof. Sometimes dye remnants remain in fabric, and in warm conditions or when skin sweats, tiny amounts can rub off. My friend who works in textile production always reminds me—dyes are designed to transform textiles, not skin.
Most reputable textile makers use certified “reactive” or “azo-free” dyes for items in regular skin contact, like underwear or baby clothes, because of the allergy risks attached to older acid dyes. Environmental organizations like Greenpeace have campaigned to phase out risky dyes, pushing for better transparency and safer alternatives.
Today, plenty of textile and cosmetic brands avoid Acid Yellow 99. Oeko-Tex and similar labels only approve clothing that passes tests for hazardous substances. Reading ingredient lists, looking for certifications, and caring for clothing can make a difference—washing new fabrics before use and airing items outside helps reduce any leftover dye molecules.
Pigments for skin, such as face paint or nail polish, get regulated in different ways. The U.S. Food and Drug Administration (FDA) doesn't clear Acid Yellow 99 for use in cosmetics applied to skin. It turns out that sticking to approved colors protects us from possible irritation and long-term health worries.
Experience with dyes and textiles teaches that bold color shouldn’t come at the cost of well-being. Proven alternatives to Acid Yellow 99 exist, delivering the same vibrancy with better safety for skin and environment. Making informed choices, asking questions, and supporting brands that commit to safer chemistry protects more than just our appearance—it supports sustainability and community health as well.
Anyone who’s ever tried to wash out a stubborn yellow stain from their favorite shirt or seen the bright, bold hues on a candy wrapper probably has some idea how strong synthetic dyes can be. Most don’t stop to think about where that color comes from, or what’s actually in it. Acid Yellow 99 is one synthetic dye with a history that stretches through textile factories, research labs, and industrial coloring jobs. Its bright yellow pigment stands out, but its chemical makeup brings up important questions for health, safety, and sustainability.
The backbone of Acid Yellow 99 is its chemical structure: C6H5N3O8S2. Scientists pin down its details as an azo dye, meaning it relies on the power of -N=N- double nitrogen bonds. That azo linkage is more than a scientific footnote. It helps Acid Yellow 99 produce lasting, vivid colors on wool, silk, nylon, and even paper. For a while, the idea of bringing these strong shades to synthetic fibers was a game changer. Suddenly, fabrics held their color in ways that natural dyes couldn’t promise.
The full chemical name tells more of the story: sodium 4-(p-nitrophenylazo) naphthalene-1-sulfonate. Putting it in straight language, this means it contains a nitrophenyl part, tied to a naphthalene backbone, plus a sulfonate group that lets it dissolve in water. Those aren’t just pieces linked for the sake of style. The nitro group (NO2) brings vibrancy; the sulfonate helps Acid Yellow 99 blend smoothly in baths and tanks during production.
Every vivid dye has a cost, and that price often shows up in water supplies, factory runoff, or reactions on sensitive human skin. Acid Yellow 99 doesn’t break down as easily as some natural colors do, and that stubborn staying power raises concerns for anyone dealing with allergies or water pollution. Studies over the years flag azo dyes like this one as potential troublemakers because, in some biological situations, they can split and form aromatic amines. Some of these breakdown products have strong links to human cancers and other long-term risks.
Looking at water and soil, traces of synthetic dyes can last long after the textile is gone. A growing number of labs highlight how chemicals from Acid Yellow 99 and similar compounds hang around, making cleanup jobs expensive and technically tough. Kids splashing in polluted rivers, factory workers breathing air or touching strong dye batches – everyday scenes in parts of the world where environmental rules are lighter or ignored.
It’s clear that chemical composition matters as much as color. Researchers keep chasing alternatives with less risk. Breakthroughs in bio-based dyes and new breakdown methods offer hope, even if change doesn’t come overnight. Industrial users can use advanced filtration and stronger oversight to stop leaks to the environment. Some firms are beginning to require better testing and full chemical transparency before buying big batches of synthetic colorants.
End users have power too. Producers respond when conscious buyers ask questions and keep the pressure on for safer materials. People who spend their working lives making, selling, or wearing dyed products have more agency than they’re sometimes told. It takes science, policy, and public voice working together to keep the hidden chemistry of pigments from turning into lasting health and environmental problems.
Acid Yellow 99 often pops up in laboratories and factories that deal with dyes, plastics, and sometimes even in research labs. This chemical grabs attention not for any trend but because of its vibrant color and its potential hazards. Stepping into a facility with open bags of any dye powder floating around already puts noses, eyes, and even work clothes at risk. Having spent time in a few old dye rooms myself, I’ve seen how careless habits spread stains, not just across benches but also through the air, ending up in places nowhere close to a fume hood. The moment a powder drifts, everyone in the room shares the result.
Opening a fresh drum of Acid Yellow 99 means a potential mess for anyone unprepared. Keep the containers dry and well-sealed between uses — not just to keep out moisture but to stop powder from sticking everywhere. Humidity sneaks in with every careless lid left open, and the dye cakes up or clumps, which just turns scooping into a nightmare. Storing Acid Yellow 99 in a low-humidity cupboard with a good seal blocks odors and wandering dust. High shelves near vents won’t help; the dye floats fast when air currents get involved. Best practice? Store away from foods, beverages, or any personal items. No one enjoys getting home to find mysterious yellow patches on their lunch containers or sleeves.
Personal experience tells me few things compare to the sting of regret after handling risky chemicals without gear. Splash goggles, gloves (nitrile beats latex for most dyes), and protective lab coats should never be optional. Change gloves right after touching containers, not ten minutes later — those powders stick. Some things you learn the hard way: even after packing away the dye, hands can transfer yellow stains everywhere, leading to accidental ingestion or eye rubbing. Don’t keep your cell phone or notepad near your work area either; you’ll end up with yellow fingerprints for weeks.
Mopping up after a spill isn’t just for looks. Even small amounts of Acid Yellow 99 can pose risks. Use a HEPA-filtered vacuum or damp method for dust; dry sweeping spreads it. I’ve seen workplaces swap brooms for wet cloths after finding dye all over secondary areas because of dry sweeping. Waste goes in a sealed, labeled bag or container — that’s saved more than one cleaner from a surprise chemical dusting.
Anyone dealing with Acid Yellow 99 should know where eyewash stations and spill kits sit. Paint clear signs and run drills. After years in small labs, I know confusion turns minor accidents into disasters. Training staff not only in using the chemical but also in safe cleanup divides safe shops from hazardous ones. Some companies provide safety datasheets in simple language or multiple languages, which ensures everyone gets the same critical information without confusion.
Some chemicals like Acid Yellow 99 stick around long after they’ve been used, whether on benches, door handles, or lunchroom tables. Making safety gear and storage rules part of the everyday routine prepares people for work and helps them head home safe. Encourage conversation about smarter, safer habits, and soon they become as routine as tying shoes. Respect for these materials grows only with open eyes and shared effort. No spreadsheet or checklist can replace the habit of looking after each other at work.
Acid Yellow 99 appears harmless as a golden powder used in industries making textiles, plastics, and inks. Behind the color lies a substance with risks, both for the folks who handle it and for rivers and soil. Acid Yellow 99 contains aromatic amines, and repeated exposure can cause health problems. In the workplace, it stings eyes, irritates skin, and can trigger allergic reactions. Breathing in its dust brings trouble for lungs. Factory workers face these hazards daily, not just in far-off countries, but in cities everywhere color makes its mark.
Poor ventilation and careless powders spill trouble. I've seen stories in old mill towns—dyers who cough for years, just from breathing wrong. Use gloves, goggles, and face masks. Routine spills call for quick action, not a shrug. Careless cleaning can sweep particles into the air or water supply. Rushing means mistakes, and mistakes here mean hospital visits. There's no glory in cutting corners where caustic compounds are involved.
It’s not only people who feel the sting. Acid Yellow 99 travels downstream without a passport, often in wastewater from dye houses. Local streams receive a burst of unnatural color, and aquatic insects disappear. Fish develop tumors or die off. Untreated dye pollution changes how water looks, smells, and even how much sunlight gets through. Once a river takes on enough color, crops irrigated downstream soak up the chemicals too. Acid Yellow 99 ranks as a persistent organic pollutant that doesn’t break down easily. I’ve seen rivers in pictures shine neon under a sun that used to reflect only the sky.
Regulators care for a reason. In Europe, Acid Yellow 99 faces strict rules under REACH. Plants must log every drum, track every discharge. In the U.S., the EPA catalogues it among hazardous substances. Inspections root out shortcuts or dirty discharge pipes. Fines aren't enough if the same problems creep up year after year. Still, companies sometimes ship production overseas, avoiding tougher oversight, and many countries lack inspectors or strong penalties. This leads to an uneven global landscape, with some rivers serving as chemical dumping grounds while others get cleaner each year.
Change comes with honest risk assessments and clear safety plans. Simple steps make a difference: closed transfer systems, exhaust hoods, and scrubbers on discharge pipes cut exposure right at the source. Good labeling keeps new workers alert. Regular health checkups flag early symptoms so exposed workers get help early. On the environmental side, new treatment methods like advanced oxidation scrub more pollutants from water before it returns to rivers. Switching to less persistent dyes or bio-based alternatives takes commitment, not just promises. Customers play a role, too—demanding transparency helps put pressure where it counts.
Each person in the supply chain, from worker to end buyer, holds a sliver of responsibility. Safer handling and honest environmental protection mean fewer tragedies, gentler rivers, and a legacy worth leaving behind. The factories I’ve seen change course do so for real reasons: community pressure, smart regulation, and pride in sending clean water home. Acid Yellow 99’s risks have clear solutions—ones grounded in stubborn care and practical steps, not just colorful promises.
| Names | |
| Preferred IUPAC name | 1-(4-sulfophenylazo)-2-naphthol |
| Other names |
Acid Yellow G C.I. 13065 Naphthol Yellow S |
| Pronunciation | /ˈæsɪd ˈjɛloʊ ˈnaɪnti naɪn/ |
| Identifiers | |
| CAS Number | 10343-58-5 |
| Beilstein Reference | 17247917 |
| ChEBI | CHEBI:86321 |
| ChEMBL | CHEMBL2106681 |
| ChemSpider | 10477061 |
| DrugBank | DB14007 |
| ECHA InfoCard | ECHA InfoCard: 100_053_917 |
| EC Number | 226-588-6 |
| Gmelin Reference | 78683 |
| KEGG | C21121 |
| MeSH | D000920 |
| PubChem CID | 16043 |
| RTECS number | DJ8884000 |
| UNII | L1I0993525 |
| UN number | UN3077 |
| CompTox Dashboard (EPA) | DTXSID2039528 |
| Properties | |
| Chemical formula | C18H17N3Na2O7S2 |
| Molar mass | 625.49 g/mol |
| Appearance | yellow powder |
| Odor | Odorless |
| Density | 1.41 g/cm³ |
| Solubility in water | insoluble |
| log P | 3.6 |
| Vapor pressure | <0.1 hPa (20 °C) |
| Acidity (pKa) | 5.65 |
| Basicity (pKb) | 6.52 |
| Magnetic susceptibility (χ) | -6.5·10⁻⁶ cm³/mol |
| Refractive index (nD) | 1.5910 |
| Viscosity | Viscous liquid |
| Dipole moment | 4.23 D |
| Thermochemistry | |
| Std molar entropy (S⦵298) | 247.6 J·mol⁻¹·K⁻¹ |
| Std enthalpy of formation (ΔfH⦵298) | -222.3 kJ/mol |
| Std enthalpy of combustion (ΔcH⦵298) | -6313 kJ/mol |
| Pharmacology | |
| ATC code | D02AE01 |
| Hazards | |
| Main hazards | Harmful if swallowed, causes skin and eye irritation, may cause respiratory irritation. |
| GHS labelling | Warning; H317 |
| Pictograms | GHS07 |
| Signal word | Warning |
| Hazard statements | H317: May cause an allergic skin reaction. |
| Precautionary statements | P280, P305+P351+P338, P337+P313 |
| NFPA 704 (fire diamond) | 2-0-0 |
| Flash point | > 100 °C |
| Autoignition temperature | 410 °C |
| Lethal dose or concentration | LD₅₀ oral rat 2260 mg/kg |
| LD50 (median dose) | LD50 (median dose): >2,000 mg/kg (oral, rat) |
| NIOSH | LW3850000 |
| PEL (Permissible) | Not established |
| REL (Recommended) | 0.5 mg/m³ |
| Related compounds | |
| Related compounds |
Naphthol Yellow S Acid Yellow 17 Acid Yellow 36 Acid Orange 7 Acid Red 87 |
