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Acid and mordant dyes

Chromotrope 2B

Also known as Chromotrope Red 4B, Khromotrop 2B, Naphtocard Fast Red 3B

CAS 548-80-1Formula C16H9N3Na2O10S2Molar mass 513.37 g/molEC 208-959-9
GHS signal word: Warning. Pictograms: Harmful or irritant 7 suppliers listed
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Chromotrope 2B chemical structure, C16H9N3Na2O10S2, CAS 548-80-1
2D chemical structure

Key facts

What buyers check first

All properties
CAS number
548-80-1
Formula
C16H9N3Na2O10S2
Molar mass
513.37 g/mol
EC number
208-959-9
HS code
320412
Category
Acid and mordant dyes

What is Chromotrope 2B?

Plain description, key identifiers and synonyms

Chromotrope 2B is a chemical substance with the molecular formula C16H9N3Na2O10S2 and a molar mass of 513.37 g/mol. Its CAS registry number is 548-80-1. The IUPAC name is disodium, 4,5-dihydroxy-3-[(4-nitrophenyl)diazenyl]naphthalene-2,7-disulfonate.

Identifiers

Registry numbers, names and line notations, tap to copy

IUPAC name
disodium, 4,5-dihydroxy-3-[(4-nitrophenyl)diazenyl]naphthalene-2,7-disulfonate
CAS number
548-80-1 CAS number cross-checked
EC number
208-959-9
Molecular formula
C16H9N3Na2O10S2
UNII
81Y8BW5764
MDL number
MFCD00003951
InChIKey
AXUUHWJXDWBCSG-UHFFFAOYSA-L
InChI
InChI=1S/C16H11N3O10S2.2Na/c20-12-7-11(30(24,25)26)5-8-6-13(31(27,28)29)15(16(21)14(8)12)18-17-9-1-3-10(4-2-9)19(22)23;;/h1-7,20-21H,(H,24,25,26)(H,27,28,29);;/q;2*+1/p-2
SMILES (canonical and isomeric)
C1=CC(=CC=C1N=NC2=C(C3=C(C=C(C=C3C=C2S(=O)(=O)[O-])S(=O)(=O)[O-])O)O)[N+](=O)[O-].[Na+].[Na+]

Synonyms

  • Chromotrope Red 4B
  • Khromotrop 2B
  • Naphtocard Fast Red 3B
  • C.I. Acid Red 176
  • C.I. Acid Red 176 (VAN)
  • C.I. 16575
  • p-Nitrobenzeneazochromotropic acid sodium salt
  • 2,7-Naphthalenedisulfonic acid, 4,5-dihydroxy-3-((4-nitrophenyl)azo)-, disodium salt
  • C.I. Acid Red 176, disodium salt
  • PCR 2B
  • 4,5-Dihydroxynaphthalene-3-(4-nitrophenylazo)-2,7-disulfonic acid disodium salt
  • C.i. mordant black 93
  • Disodium 4,5-dihydroxy-3-(p-nitrophenylazo)naphthalene-2,7-disulphonate
  • 2,7-Naphthalenedisulfonic acid, 4,5-dihydroxy-3-[(4-nitrophenyl)azo]-, disodium salt
  • 2,7-Naphthalenedisulfonic acid, 4,5-dihydroxy-3-(2-(4-nitrophenyl)diazenyl)-, sodium salt (1:2)
  • 2,7-Naphthalenedisulfonic acid, 4,5-dihydroxy-3-(P-nitrophenylazo)-, disodium salt
  • 2,7-Naphthalenedisulfonic acid, 4,5-dihydroxy-3-[2-(4-nitrophenyl)diazenyl]-, sodium salt (1:2)
  • 4,5-Dihydroxy-3-(2-(4-nitrophenyl)diazenyl)-2,7-naphthalenedisulfonic acid sodium salt (1:2)
  • C.I. Acid Red 176, disodium salt (8CI)
  • Chromatrope 2B
  • Acid Red 176
  • Sodium 4,5-dihydroxy-3-((4-nitrophenyl)diazenyl)naphthalene-2,7-disulfonate
  • 2-(4-Nitrophenylazo)chromotropic acid disodium salt
  • Chromotrope 2B, for microscopy
  • disodium,(3E)-5-hydroxy-3-[(4-nitrophenyl)hydrazinylidene]-4-oxonaphthalene-2,7-disulfonate
Show all 29 synonyms
  • CI 16575
  • 4,5-Dihydroxy-3-(p-nitrophenylazo)-2,7-naphthalenedisulfonic Acid Disodium Salt
  • Disodium 4,5-dihydroxy-3-[(4-nitrophenyl)diazenyl]naphthalene-2,7-disulfonate
  • disodium, 4,5-dihydroxy-3-[(4-nitrophenyl)diazenyl]naphthalene-2,7-disulfonate

Physical and chemical properties

Measured values and descriptors computed from the structure

Physical and chemical properties

Measured values, check the supplier specification for your grade

No measured properties are recorded for this substance yet. Ask suppliers for a technical data sheet.

Values vary by grade. Ask suppliers for the COA or TDS of the batch you buy.

Computed descriptors

Calculated from the structure, useful for screening and formulation

Molecular weight
513.37 g/molcalc.
Exact mass
512.9525 Dacalc.
LogP (octanol/water)
-3.61calc.
Topological polar surface area
222.7 Ųcalc.
Hydrogen bond donors
2calc.
Hydrogen bond acceptors
12calc.
Rotatable bonds
5calc.
Heavy atoms
33calc.
Rings
3calc.
Aromatic rings
3calc.
Fraction sp3 carbons
0calc.
Formal charge
0calc.
Stereocentres
0calc.
Components
3calc.
Lipinski rule of five
Fails (2 violations)calc.

Calculated for screening. Confirm critical figures with the supplier.

Murcko scaffold

The ring system that remains when every side chain is removed

Murcko scaffold of this chemical, c1ccc(N=Nc2ccc3ccccc3c2)cc1

c1ccc(N=Nc2ccc3ccccc3c2)cc1

3 rings, 18 atoms, the Diazene, 2-naphthalenylphenyl- ring system.

600 other chemicals share this scaffold

Safety and hazards

GHS classification summary, not a safety data sheet

GHS signal word
Warning
GHS07: Harmful or irritant
Harmful or irritant

Hazard statements

  • H315Causes skin irritation.
  • H319Causes serious eye irritation.
  • H335May cause respiratory irritation.
Precautionary statements (16)
  • P261Avoid breathing dust, fume, gas, mist, vapours or spray.
  • P264Wash skin thoroughly after handling.
  • P264 + P265Wash skin thoroughly after handling. Do not touch eyes.
  • P271Use only outdoors or in a well-ventilated area.
  • P280Wear protective gloves, protective clothing, eye protection and face protection.
  • P302 + P352If on skin: Wash with plenty of water.
  • P304 + P340If inhaled: Remove person to fresh air and keep comfortable for breathing.
  • P305 + P351 + P338If in eyes: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing.
  • P319Get medical help if you feel unwell.
  • P321Specific treatment (see supplemental first aid instructions on the label).
  • P332 + P317If skin irritation occurs: Get medical help.
  • P337 + P317If eye irritation persists: Get medical help.
  • P362 + P364Take off contaminated clothing. And wash it before reuse.
  • P403 + P233Store in a well-ventilated place. Keep container tightly closed.
  • P405Store locked up.
  • P501Dispose of contents and container in accordance with local regulations.

GHS classification summary, not a safety data sheet (SDS). Classifications can differ by supplier, grade and concentration. Always check the supplier's SDS.

Full safety data and first aid

Chromotrope 2B suppliers

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Where suppliers are based

7 suppliers in 2 countries

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Chromotrope 2B price

Indicative price range per kg from live supplier offers

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Uses and applications

What the substance is used for, by industry and function

Regulatory status

Inventories, regulations and trade controls that list this substance

United States

  • TSCA inventory (USA)
    Status: Active in US commerce

HS code and trade data

Customs classification and reported world trade statistics

Global trade

World import and export statistics for the HS code Chromotrope 2B is traded under.

HS 3204.12Indicative HS code

Acid dyes, whether or not premetallised, and preparations based thereon, mordant dyes…

World exports in 2024
$792M
+6.2% vs 2023, imports $791M
2019 to 2024
Top exporters
  1. India * partner reported34.9%
  2. China9.3%
  3. Germany7.4%
Top importers
  1. China15.3%
  2. Italy8.2%
  3. United States7.3%

* Partner reported figures, a lower bound.

Reported customs values in USD, not prices.Full trade data

The HS code shown for Chromotrope 2B is indicative (it was assigned by structure rules). Confirm the classification with your customs broker before shipping.

Frequently asked questions

Quick answers about Chromotrope 2B, based on the data on this page

What is Chromotrope 2B?

Chromotrope 2B is a chemical substance with the molecular formula C16H9N3Na2O10S2 and a molar mass of 513.37 g/mol. Its CAS registry number is 548-80-1. The IUPAC name is disodium, 4,5-dihydroxy-3-[(4-nitrophenyl)diazenyl]naphthalene-2,7-disulfonate.

What is the CAS number of Chromotrope 2B?

The CAS registry number of Chromotrope 2B is 548-80-1.

What is the molecular formula and weight of Chromotrope 2B?

The molecular formula of Chromotrope 2B is C16H9N3Na2O10S2 and its molar mass is 513.37 g/mol.

What is Chromotrope 2B used for?

Known uses and roles of Chromotrope 2B include textile dyes in textiles and leather and mordants and dye fixing agents in textiles and leather.

Is Chromotrope 2B hazardous?

Chromotrope 2B carries the GHS signal word "Warning". Main hazards: causes skin irritation, causes serious eye irritation, may cause respiratory irritation. This summary is not an SDS, always read the supplier safety data sheet.

What is the HS code of Chromotrope 2B?

Chromotrope 2B is usually classified under HS code 320412 (Acid dyes, whether or not premetallised, and preparations based thereon, mordant dyes…). This is indicative, confirm it with your customs broker before shipping.

Where can I buy Chromotrope 2B?

CompoundList lists 7 suppliers of Chromotrope 2B in India and United States. Send one free request to get and compare quotes. Your contact details stay private until you accept a quote.

Where can I buy Chromotrope 2B in India?

5 suppliers in India list Chromotrope 2B on CompoundList. Filter the suppliers list by country and send a request to compare prices, grades and delivery times.

What is the price of Chromotrope 2B?

Suppliers quote Chromotrope 2B on request because prices depend on grade, purity, quantity and destination. A free request on CompoundList gets you several quotes to compare.

Guides for buyers

Practical guides that help when you source, ship or handle Chromotrope 2B

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Data last updated 7 Oct 2026. Details may have changed, please confirm them with the supplier. Report an error on this page
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