3,3'-Dichlorobenzidine Dihydrochloride
A biphenyl diamine salt, supplied as 3,3'-dichlorobenzidine dihydrochloride (33DCBH), used as the central precursor in diarylide yellow and orange pigment manufacture.
What is 3,3'-Dichlorobenzidine Dihydrochloride?
3,3'-Dichlorobenzidine dihydrochloride, abbreviated 33DCBH, is a gray to light tan crystalline powder built on a biphenyl backbone: two benzene rings joined by a single C–C bond, each carrying an amino group and a chlorine atom, supplied as the dihydrochloride salt of the diamine.
Both amino groups are tetrazotized together to form a bis-diazonium salt, which is then double-coupled to two molecules of a coupling component such as acetoacetanilide. That double coupling across the biphenyl core is what defines the diarylide pigment family — the well-known benzidine yellows and oranges used across printing inks, plastics and coatings.
At Chelora Dyes, 33DCBH is crystallised and dried to a controlled particle profile and consistent salt form, so tetrazotization and double-coupling reactions downstream run cleanly and give a reproducible shade batch to batch.
- Appearance
- Gray / light tan
- Odour
- Faint, characteristic
- Solubility
- Water (as salt), dilute acid
- Function
- Diarylide precursor
- Grade
- Technical / pigment
Biphenyl core with two amino (salt) and two chloro substituents
- Molecular formulaC12H12Cl4N2
- Molecular weight326.05 g/mol
- IUPAC name3,3'-Dichlorobenzidine dihydrochloride
- Functional groupsDiamine (as HCl salt), halide (x2), biaryl
- CAS number612-83-9
Technical product information
Standard specification for Chelora Dyes' technical grade 3,3'-Dichlorobenzidine dihydrochloride. Custom-grade and bulk specifications are available on request.
| Chemical name | 3,3'-Dichlorobenzidine dihydrochloride |
|---|---|
| Synonyms | 33DCBH, o-Dianisidine analogue (dichloro series), DCB·2HCl |
| CAS number | 612-83-9 |
| Molecular formula | C12H12Cl4N2 |
| Molecular weight | 326.05 g/mol |
| Assay (purity) | ≥ 98.0% |
| Appearance | Gray to light tan crystalline powder |
| Free base melting point | 132–133°C (free base, for reference) |
| Moisture content | ≤ 1.0% |
| Insoluble matter | ≤ 0.3% |
| Solubility | Soluble in water and dilute hydrochloric acid; limited solubility as free base |
| Packaging | 25 kg / 50 kg bags, 500–1000 kg jumbo bags |
| Shelf life | 24 months in sealed original packaging |
Applications of 3,3'-Dichlorobenzidine Dihydrochloride
Diarylide yellow pigments
Tetrazotized and double-coupled to build diarylide yellow pigments used in printing inks, plastics and coatings.
Diarylide orange pigments
Used as the biphenyl core in diarylide orange pigment synthesis for high-strength process inks.
Pigment dispersions
Feeds into pigment intermediates used in masterbatch, coatings and printing ink formulation.
Fine chemical intermediates
Supplies a chlorinated biphenyl-diamine core for further condensation and specialty chemical synthesis.
Textile printing pigments
Applied in pigment preparations formulated for textile printing pastes.
Analytical reagents
Used as a reference and tetrazotization reagent in analytical and research-scale pigment chemistry.
Why choose Chelora Dyes
Consistent purity
Assay controlled at ≥98% with moisture and appearance verified before dispatch.
Full documentation
COA, SDS, and regulatory data supplied with every shipment.
Flexible volumes
From 25 kg bags to jumbo-bag bulk quantities.
Technical support
Process, tetrazotization, and compliance guidance from our chemistry team.
Storage and guidelines
- Store in tightly sealed original packaging in a dry environment.
- Keep in a cool, dry, well-ventilated area, ideally in a dedicated, access-controlled store.
- Protect from moisture pickup and avoid unnecessary transfer between containers.
- Segregate from strong oxidising agents.
- Use compatible containers: lined HDPE bags or drums, clearly labelled.
- Re-seal bags promptly after use and log handling in line with site exposure-control procedures.
Handling precautions
3,3'-Dichlorobenzidine and its salts are listed by IARC and regulated in many jurisdictions (including OSHA specific-substance and REACH SVHC listings) as substances with carcinogenic potential, based on animal and occupational data.
Handling should be carried out in closed or well-contained systems wherever possible, with dedicated PPE, respiratory protection where dust control cannot be guaranteed, and adherence to site occupational exposure limits.
Avoid skin contact and inhalation of dust; provide local exhaust ventilation and dedicated laundering for contaminated clothing.
Consult the full Safety Data Sheet and applicable local regulations for exposure limits, monitoring requirements, spill containment, disposal, and first-aid measures before any handling operation.
Frequently asked questions
What is 3,3'-Dichlorobenzidine dihydrochloride used for?
It is tetrazotized and used as the central diarylide precursor in the manufacture of diarylide (benzidine) yellow and orange pigments, which are widely used in printing inks, plastics and coatings.
Why is the biphenyl and dichloro structure significant?
The biaryl backbone carries two amino groups, one on each ring, which are tetrazotized together and double-coupled to two molecules of a coupling component. The chlorine atoms adjacent to each amino group influence the resulting shade and crystal structure of the finished diarylide pigment.
Is 3,3'-Dichlorobenzidine dihydrochloride soluble in water?
The dihydrochloride salt form is more water-soluble than the free base, which is why it is supplied and handled in this form for tetrazotization under acidic aqueous conditions.
What purity do you supply?
Standard technical grade is supplied at a minimum assay of 98%, with moisture and insoluble matter held within tight limits. Higher assay grades can be manufactured to order for sensitive pigment applications.
What packaging sizes are available?
25 kg and 50 kg multiwall paper or HDPE-lined bags, with bulk supply available in 500 kg and 1000 kg jumbo bags.
How should it be stored, and for how long?
In sealed original packaging in a cool, dry, ventilated store away from strong oxidisers and moisture. Shelf life is 24 months from manufacture when storage conditions are maintained.
Is it hazardous to handle?
3,3'-Dichlorobenzidine and its salts are classified and regulated as substances with carcinogenic potential in most jurisdictions, so handling requires closed or contained systems, dedicated PPE, dust control and adherence to site occupational exposure limits. Review the Safety Data Sheet and local regulatory requirements before any handling operation.
Do you provide a Certificate of Analysis?
Yes. Each batch ships with a Certificate of Analysis and Safety Data Sheet covering assay, moisture, appearance and relevant regulatory documentation.
