4B Acid
4B Acid is a pigment-grade aminosulfonic acid, structurally and commercially a close relative of 2B Acid, used as a diazo component in Red/Orange 4B-type lake pigment manufacture — identified unambiguously across every independent source we checked, unlike its "2B" counterpart.
What 4B 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.
4B Acid (2-amino-5-methylbenzenesulfonic acid) is a simpler relative of 2B Acid, lacking the chlorine substituent that distinguishes the latter. Unlike 2B Acid's name, which carries genuine ambiguity across parts of the dye trade, "4B Acid" showed no conflicting identity anywhere in our research — the trade name, CAS number and chemical structure agree consistently across every independent source we checked, including a direct match on a major pigment-intermediate manufacturer's own product catalogue.
Chemically, it carries the same two functional handles as 2B Acid: an amino group for diazotisation, and a sulfonic acid group that confers water solubility and carries through into the finished pigment structure. Diazotised and coupled appropriately, it builds the azo chromophore behind Red/Orange 4B-type lake pigments.
Where it fits in the synthesis chain
We supply the free sulfonic acid itself. We do not manufacture or supply the finished lake pigment made from it.
Grades we supply
95% and 98% grades are both seen across the trade.
How 4B 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.
4B Acid is made by sulfonation of p-toluidine, or alternatively by a nitration-reduction-sulfonation sequence starting from toluene, giving the amino, sulfonic acid and methyl substitution pattern in one molecule.
As with 2B Acid, the sulfonation step is run under controlled conditions to place the sulfonic acid group correctly on the ring, since this governs the shade and fastness properties of the finished pigment downstream.
The crude product is purified by crystallisation and dried to the free acid powder traded commercially, tested for residual starting material and inorganic by-products before release.
A cleaner identity story than its "2B" relative
Where 2B Acid required us to flag a genuine naming ambiguity in the wider trade, 4B Acid did not — every independent source we checked, including a direct manufacturer catalogue listing, agreed exactly on CAS 88-44-8 as the chemical behind this trade name. We note the contrast here because it's a useful, honest signal of how much confidence to place in each identification.
Industries and processes that use it
4B 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/Orange 4B-Type Lake Pigment Manufacture
Diazotised and coupled onto an appropriate component to build the azo chromophore behind this pigment family.
Azo Pigment Intermediate Chemistry
Used more broadly wherever this specific aminosulfonic acid substitution pattern is the required diazo component.
How the molecule is typically carried forward
4B Acid's reaction chemistry mirrors 2B Acid's: the amino group is diazotised and coupled to build the azo chromophore, while the sulfonic acid group carries through into the finished pigment.
Diazotisation
Standard cold nitrous-acid diazotisation converts the amino group to a diazonium salt.
Azo coupling
The diazonium salt couples with an appropriate component to build the azo chromophore that defines the finished Red/Orange 4B-type lake 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.
4B Acid against its near relatives
4B Acid, 2B Acid and Fast Bordeaux GP Base are the three azo/azoic dye-intermediate trade names in this part of our range.
| Product | CAS Number | Typically Used In | Notes |
|---|---|---|---|
| 4B Acid | 88-44-8 | Red/Orange 4B-type lake pigment manufacture | The product on this page. |
| 2B Acid | 88-51-7 | Red 2B / Red Lake C 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 severe skin burns and eye damage (legacy R34/self-classification; see note).
May cause cancer (flagged as an unresolved, possibly erroneous data point — see note).
Danger
No harmonised EU CLP Annex VI entry was located for this substance. We found one self-classification source listing an R45 cancer-risk phrase (equivalent to H350) alongside R34 (causes burns), a combination that is unusual for this simple aminotoluenesulfonic acid structure and may reflect a data carry-over error from a related entry in that source's database — we flag this honestly rather than either repeating it as settled fact or silently dropping a potentially real hazard statement. We recommend treating the H350-equivalent statement as unconfirmed and verifying against the current SDS shipped with your specific lot, which is the governing document regardless of what we display here. IARC has not evaluated this substance.
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 and oxidisers, treating it as a corrosive solid pending confirmation of the exact current hazard classification. Keep containers tightly sealed.
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 4B 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 4B Acid used for?+
02What is the CAS number of 4B Acid?+
03What purity grades does Chelora Chemicals supply?+
04Is 4B Acid hazardous?+
05Why does this page flag an unusual cancer-hazard statement?+
06Is this the same compound as 2B Acid?+
07Do you supply the finished lake pigment?+
08What packing options are available?+
09How long does delivery take?+
10Can I get a sample before placing a bulk order?+
11How is 4B Acid manufactured?+
12What is the shelf life, and how should it be stored?+
Need 4B 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.