2B Acid
2B Acid is a pigment-grade aminosulfonic acid used as a diazo component in Red 2B / Red Lake C-type pigment manufacture — a name we want to flag carries genuine ambiguity in parts of the dye trade, which is why we state our exact identification plainly before anything else.
What 2B Acid is, and why buyers source it
A working overview of the compound's chemistry, its place in the aniline-derivative family, and the grades Chelora Chemicals keeps in regular supply.
We need to be direct about something before describing this product: "2B Acid" is not a universally single, unambiguous name across the global dye and pigment trade. The identification we supply under this name — 2-amino-4-chloro-5-methylbenzenesulfonic acid, CAS 88-51-7 — is well corroborated: it appears as a named synonym on independent chemical databases and is carried under this exact trade name by established pigment-intermediate manufacturers. We flag this ambiguity openly rather than let a buyer assume the name alone guarantees an identical product from every supplier — always confirm CAS number 88-51-7 on your purchase order and certificate of analysis.
Chemically, this is an aromatic aminosulfonic acid: an amino group available for diazotisation, a sulfonic acid group that confers water solubility (particularly as its sodium salt) and that becomes part of the finished pigment structure, and a chlorine and methyl group that fix its substitution pattern. Diazotised and coupled onto an appropriate naphthol-type coupling component, it builds the azo chromophore behind Red 2B and related Red Lake C-type pigment chemistry — a well-established, long-standing pigment family distinct from the Naphthol-AS azoic dyeing process used directly on cotton fibre.
Where it fits in the synthesis chain
We supply the free sulfonic acid itself, ready for diazotisation at the pigment manufacturer's own facility. We do not manufacture or supply the finished Red 2B / Red Lake C pigment.
Grades we supply
95% and 98% grades are both seen across the trade; pigment manufacturers specifying consistent shade typically require the higher grade to limit isomeric and inorganic-salt carryover.
How 2B Acid is made
An overview of the production route for orientation purposes. Our manufacturing partners' own process parameters and in-process controls are proprietary and are not disclosed beyond what is needed to interpret the certificate of analysis.
2B Acid is made by sulfonation of a suitably chlorinated toluidine, or alternatively by a nitration-reduction-sulfonation sequence on a chlorotoluene starting material, giving the amino, sulfonic acid, chlorine and methyl substitution pattern in one molecule.
The sulfonation step is run under controlled conditions to achieve the correct ring position for the sulfonic acid group, since the final pigment's shade and fastness properties depend on getting this substitution pattern right, not just on overall purity.
The crude product is purified by crystallisation, taking advantage of its very high decomposition/melting point to separate it cleanly from unreacted starting material and inorganic sulfonation by-products before drying to the free acid powder traded commercially.
Confirm the CAS number, not just the trade name
Because the dye trade's naming conventions for intermediates like this one developed historically and regionally, rather than through a single global standard, the same two or three letters and a colour reference can mean different things depending on which supplier or which decade's catalogue you're reading. We'd rather state plainly that we identify "2B Acid" as CAS 88-51-7, consistent with the strongest and most consistent sourcing we could find, and ask that buyers confirm this matches their own specification before placing a large order under this name alone.
Industries and processes that use it
2B Acid is consumed almost entirely as a synthesis intermediate. The four fields below account for most of the demand we see through our export desk.
Red 2B / Red Lake C Pigment Manufacture
Diazotised and coupled onto an appropriate naphthol-type component to build the azo chromophore behind this established pigment family.
Azo Pigment Intermediate Chemistry
Used more broadly wherever this specific aminosulfonic acid substitution pattern is the required diazo component.
Pigment Lake Manufacturing
Feeds pigment-lake manufacturing processes where an aminosulfonic acid diazo component, rather than a Naphthol AS azoic base, is the correct chemistry for the target product.
How the molecule is typically carried forward
2B Acid's reaction chemistry centres on its amino group, diazotised and coupled to build the azo chromophore, while its sulfonic acid group carries through into the finished pigment structure rather than reacting further itself.
Diazotisation
Standard cold nitrous-acid diazotisation converts the amino group to a diazonium salt, the entry point to azo pigment coupling chemistry.
Azo coupling
The diazonium salt couples with an appropriate naphthol-type coupling component to build the azo chromophore that defines the finished Red 2B / Red Lake C-type pigment.
Salt formation (sulfonic acid group)
The sulfonic acid group can be converted to its sodium or other metal salt for solubility or lake-forming purposes, a standard part of pigment-lake manufacture rather than a separate synthetic step on our end.
2B Acid against its near relatives
2B Acid, 4B Acid and Fast Bordeaux GP Base are the three azo/azoic dye-intermediate trade names in this part of our range — related by their shared role as diazo components in colourant manufacture, though they serve different branches of that chemistry.
| Product | CAS Number | Typically Used In | Notes |
|---|---|---|---|
| 2B Acid | 88-51-7 | Red 2B / Red Lake C pigment manufacture | The product on this page. |
| 4B Acid | 88-44-8 | Red/Orange 4B-type lake pigment manufacture | Also supplied — see its product page. |
| Fast Bordeaux GP Base | 96-96-8 | Azoic (ice-colour) diazo base for cotton dyeing | Also supplied — see its product page. |
Exact physical constants and purity specifications are confirmed per batch on the certificate of analysis — treat the notes above as a sourcing guide rather than a specification sheet.
Safety classification at a glance
Based on GHS classification as commonly listed for this substance. This is a summary for orientation only — always work from the current safety data sheet supplied with your specific batch.
Causes skin irritation.
Causes serious eye irritation.
May cause respiratory irritation.
Warning
No harmonised EU CLP Annex VI entry was located for this substance. The classification above reflects self-classification data (irritant to eyes, respiratory tract and skin) consistent across the source we could verify; it is also transport-classified as UN 3261, Class 8, Packing Group III (corrosive solid, acidic), which should be read alongside the GHS statements rather than in place of them. IARC has not evaluated this substance. We recommend checking the SDS shipped with each specific lot given the identity ambiguity flagged elsewhere on this page.
Keeping it on spec between delivery and use
General storage guidance for this grade. Site-specific storage rules, segregation requirements and re-test intervals should follow your own EHS procedures and the MSDS issued with your batch.
Store in a cool, dry area away from strong bases (given its acidic, corrosive character) and oxidisers. Keep containers tightly sealed to prevent moisture pickup.
How it ships from Indonesia
Standard packing and export terms for this product. Confirm exact figures against your order — they vary slightly by destination and quantity.
What travels with every batch
Specification is agreed before the purchase order, not discovered on arrival. Every shipment of 2B Acid leaves with a documented, checkable paper trail.
Certificate of Analysis
Batch-wise assay (by GC), isomer purity, melting point range and moisture, issued against the agreed specification so your QC team can check it, not just file it.
Safety Data Sheet
GHS-format SDS in English covering hazard classification, handling, storage, first-aid and spill response for the exact grade shipped.
Technical Data Sheet
Reference physical and chemical properties, recommended storage and typical applications, for internal circulation to your process or R&D teams.
Certificate of Origin
Confirms Indonesian origin for customs clearance and any preferential-duty claim at your destination port.
Dangerous Goods Declaration
UN packing group, classification and shipper's declaration prepared ahead of loading so documentation never holds up customs.
Third-Party Inspection
Independent pre-shipment inspection and re-sampling can be arranged on request, at your cost, for buyers who require it as a matter of policy.
Frequently asked questions
What buyers most often ask our sales desk about this grade.
01What is 2B Acid used for?+
02What is the CAS number of 2B Acid?+
03What purity grades does Chelora Chemicals supply?+
04Is 2B Acid hazardous?+
05Is "2B Acid" always the same chemical everywhere in the trade?+
06Do you supply the finished Red 2B pigment?+
07Is this the same kind of product as Fast Bordeaux GP Base?+
08What packing options are available?+
09How long does delivery take?+
10Can I get a sample before placing a bulk order?+
11How is 2B Acid manufactured?+
12What is the shelf life, and how should it be stored?+
Need 2B Acid on spec, on time?
Send us your required purity, quantity, packing preference and destination port. Our desk quotes most enquiries within one working day.