Orange G (C.I. 16230) is a certified anionic azo dye used as a biological stain in histology and cytology. Also known as Acid Orange 10, it is commonly used in Mallory’s connective tissue staining method and in procedures requiring orange cytoplasmic or background contrast.
Orange G is used in staining protocols for collagen-containing connective tissue, keratinized cytoplasm, granules, elastic fibers, mast cells, selected pituitary cell populations, and pollen tubes. Staining intensity and selectivity depend on dye concentration, solution pH, fixation, specimen preparation, staining time, and the other reagents used in the method.
Synonyms: Acid Orange 10; Xylene Fast Orange G; Wool Orange 2G; 7-hydroxy-8-(phenylazo)-1,3-naphthalenedisulfonic acid disodium salt.
Key Properties
- Certified biological stain for histology and cytology
- Anionic azo dye
- Color Index number: C.I. 16230
- CAS number: 1936-15-8
- Molecular formula: C16H10N2Na2O7S2
- Molecular weight: 452.37 g/mol
- Appearance: orange powder
- Absorption maximum: approximately 475 nm
- Polysciences catalog number: 00968
Applications
Mallory’s Connective Tissue Staining
Orange G is used as a component of Mallory’s staining method for differentiating collagen and other structures in connective tissue sections. Final color balance depends on the complete stain formulation, fixation method, section preparation, staining sequence, and differentiation steps.
Histology & Cytology Counterstaining
The dye is used as a counterstain in histological and cytological procedures where orange contrast is required in the cytoplasm or surrounding tissue. Concentration and staining time should be selected according to the validated laboratory method.
Papanicolaou-Type Cytology Staining
Orange G is used in Papanicolaou-type staining formulations to produce orangeophilic staining of keratinized cytoplasm under acidic conditions. Laboratories should follow their established formulation, staining sequence, and quality-control procedure.
Specialized Histological Staining
Orange G is also used in methods for staining granules, elastic fibers, mast cells, keratin, mucus, pituitary acidophils, and pollen tubes. Suitability depends on the complete protocol and specimen type.
Staining & Protocol Considerations
- Use the dye concentration specified by the validated staining method
- Control solution pH because staining behavior is pH-dependent
- Account for fixation, tissue processing, section thickness, and specimen type
- Standardize staining and differentiation times across runs
- Use appropriate control slides to confirm staining performance
- Do not substitute another orange dye without verifying the protocol
Staining performance depends on the complete reagent system rather than the dye alone. Changes in solvent composition, pH, dye concentration, staining sequence, or differentiation conditions can alter color intensity and tissue selectivity.
Preparation Tips
- Prepare the staining solution according to the selected histology or cytology protocol
- Use clean glassware and the specified grade of water, alcohol, or other solvent
- Mix until the dye is completely and uniformly dissolved
- Filter the prepared solution when required by the protocol
- Label prepared reagents with concentration, preparation date, and expiration or review date
- Verify performance with an appropriate control specimen before routine use
Handling & Storage
- Store at room temperature in a cool, dry, well-ventilated location
- Keep the container tightly closed when not in use
- Protect the powder from moisture and contamination
- Wear protective gloves and safety glasses during handling
- Avoid generating or inhaling dye dust
- Follow the product Safety Data Sheet for complete handling, storage, and disposal guidance
Why Choose Polysciences?
Trusted by 6,000+ Researchers Worldwide
Cited in Thousands of Peer-Reviewed Studies
U.S. Manufacturing & Global Distribution
Reliable Delivery to 40+ Countries
FAQ
Click a question to expand.
1. What is Orange G stain used for?
Orange G is used in histology and cytology as a component of Mallory’s connective tissue stain, as a counterstain, and in methods for staining selected cytoplasmic and tissue structures.
2. Is Orange G the same as Acid Orange 10?
Yes. Orange G, Acid Orange 10, and C.I. 16230 refer to the same dye. Additional synonyms include Xylene Fast Orange G and Wool Orange 2G.
3. What does certified Orange G mean?
Certified Orange G has been evaluated for biological staining performance under applicable certification requirements. Review the lot-specific Certificate of Analysis for the reported quality-control results.
4. Is Orange G used in Mallory’s stain?
Yes. Orange G is a component of Mallory’s connective tissue staining method. It is used with the other reagents in the protocol to produce differential coloration of tissue structures.
5. Can Orange G be used in Papanicolaou staining?
Orange G is used in Papanicolaou-type cytology formulations to stain keratinized cytoplasm. Preparation and use should follow the laboratory’s validated staining procedure.
6. What is the absorption maximum of Orange G?
Orange G has a listed absorption maximum of approximately 475 nm. The measured value may vary with solvent composition, pH, concentration, and instrument conditions.
Safety & Documentation
Use Orange G with appropriate laboratory ventilation, protective gloves, safety glasses, and standard chemical handling practices. Avoid generating or inhaling dye dust, and wash thoroughly after handling. Refer to the product Safety Data Sheet, product specification, and lot-specific Certificate of Analysis for complete safety and quality information.
