Section
| HS Code | 810427 |
| Product Name | Rhodamine B Extra |
| Chemical Name | Rhodamine B chloride |
| Synonyms | Basic Violet 10; C.I. 45170; Tetraethylrhodamine |
| Cas Number | 81-88-9 |
| Ec Number | 201-383-9 |
| Molecular Formula | C28H31ClN2O3 |
| Molecular Weight | 479.02 g/mol |
| Color Index | C.I. 45170 |
| Color Index Name | Basic Violet 10 |
| Dye Class | Cationic xanthene dye |
| Appearance | Dark green to reddish-violet powder or crystals |
| Solubility | Soluble in water and ethanol |
| Absorption Maximum | approx. 553 nm in ethanol |
| Emission Maximum | approx. 627 nm in ethanol |
| Fluorescence | Strong red-orange fluorescence |
| Odor | Odorless |
| Grade | Extra |
| Storage | Store tightly sealed, protected from light, in a cool dry place |
As an accredited Rhodamine B Extra factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Rhodamine B Extra is supplied in a sealed, light-resistant 100 g container with clear chemical labeling and safety warnings. |
| Container Loading (20′ FCL) | Rhodamine B Extra chemical is palletized, secured, and loaded into a 20-foot FCL container for safe ocean freight transport. |
| Shipping | Rhodamine B Extra is usually shipped as a non-regulated solid at ambient temperature in sealed, light-resistant containers. Confirm the current SDS and carrier rules; if it meets environmentally hazardous criteria, ship as UN 3077, Class 9, PG III, proper shipping name Environmentally hazardous substance, solid, n.o.s. (Rhodamine B Extra). |
| Storage | Store Rhodamine B Extra in a cool, dry, well-ventilated area protected from direct sunlight and moisture. Keep containers tightly closed, clearly labeled, and upright. Separate from strong oxidizers, acids, and incompatible materials. Prevent dust generation and avoid inhalation or skin/eye contact. Use secondary containment where appropriate, and follow the SDS and local regulations. Do not store near food or drink. |
| Shelf Life | Typically 2–5 years when stored dry, tightly sealed, protected from light and moisture at ambient temperature; confirm with supplier’s certificate. |
Rhodamine B Extra (C.I. Basic Violet 10, CAS 81-88-9, CI 45170) is a cationic xanthene dye whose acrylic fibre exhaustion follows an ion-exchange mechanism rather than a simple solution-diffusion path. The fibre’s sulfonate and carboxylate groups supply anionic dye sites, and the dye bath must be buffered to pH 4.5–5.5 with acetic acid and sodium acetate. Below this window, the ionic attraction is strong enough to cause rapid unlevelled strike; above it, the electronegative fibre charge is insufficient for reproducible exhaustion. Commercial stock dyeing machines such as Obermaier package units run at a liquor ratio of 1:10 to 1:15 with reversible circulation through tow packages. Dye additions are normally between 0.1% and 1.2% on weight of fibre (owf). The upper limit is not set by dye-site saturation but by loss of wet fastness in deep shades.
The bath is started at 40°C and raised at 1°C/min to 98–100°C. A cationic retarder at 0.5–1.5% owf is required when the shade depth exceeds 0.5% owf. Exhaustion above 95% is normally reached within 45–60 min. The material is then cooled to 70°C and rinsed. Residual unfixed dye is removed with a nonionic scour at 0.5 g/L and 50°C. The final shade is controlled by UV-Vis absorbance of the spent bath at 555 nm; a difference of 0.02 absorbance units between packages indicates incomplete levelling.
| Standard / Method | Parameter | Indoor Textile Acceptance Criterion |
|---|---|---|
| ISO 105-B02:2014 | Light fastness | ≥ grade 4 on blue wool scale |
| ISO 105-C10:2006 | Washing fastness | ≥ grade 4 shade change, ≥ grade 3-4 staining |
| ISO 105-X12:2016 | Dry/wet rubbing | ≥ grade 3-4 dry, ≥ grade 3 wet at pale depths |
| Oeko-Tex Standard 100 Annex 4 | Extractable heavy metals | Limits by product class |
| REACH Regulation 1907/2006 | SVHC and Annex XVII restrictions | No prohibited substance above threshold |
Finished acrylic products include brushed knitwear, faux fur, carpet yarn, and accent upholstery fibre. The dye gives a cold, blue-shifted pink with high tinctorial strength, but light fastness below grade 4 on the blue wool scale limits outdoor use unless UV absorbers are integrated into the fibre finish.
In aniline leather drum dyeing, penetration is controlled by the balance between the cationic dye and the anionic leather surface; Rhodamine B Extra exhausts rapidly onto wet blue if the float pH is not buffered. The dye is premixed at 80°C in a 1:10 dye-to-water ratio before addition to a drum float of 200–400% on shaved weight. Bath pH is maintained at 5.0–5.5 with dilute formic acid or an amphoteric buffer. At higher pH the dye penetrates deeper but loses surface intensity; at lower pH it binds superficially and may emphasise loose grain. Drum rotation of 16–20 rpm is typical for garment and shoe upper leathers.
Addition levels vary from 0.05% to 1.5% by shaved wet weight. For aniline leather, a pre-retan with a dispersing synthetic tanning agent opens grain and reduces surface charge. Anionic fatliquors should be added only after dye exhaustion, because Rhodamine B Extra precipitates with sulphated oils. Fixation is completed with formic acid at 0.5–1.0% over 20–30 min; residual float concentration below 0.02 g/L at 555 nm is a practical exhaustion target. Published data for split leather penetration with this specific dye is limited, so mill trials at 0.2% and 0.5% are recommended.
Finished leather is tested under ISO 11640:2018 for rubbing fastness and ISO 11642:2012 for water spotting. The xanthene structure is outside the azo colorant family, but incoming leather chemical lots are normally screened under EN ISO 17234-1 to satisfy the wider buyer audit. EU imports require compliance with REACH Regulation 1907/2006, and finished fashion leather may additionally be tested for extractable heavy metals under Oeko-Tex Standard 100. End products are bookbinding leather, burnished shoe upper, and high-chroma fashion articles, normally protected with a nitrocellulose lacquer topcoat to level out the natural belly-to-shoulder shade differential.
Rhodamine B Extra enters water-based flexographic ink concentrates as a dissolved cationic chromophore that competes with anionic acrylic solution resins. The concentrate is manufactured by dissolving the dye at 5–15 wt% in a solvent blend of deionised water, propylene glycol monopropyl ether, and ethanol. The letdown resin is an ammonia-neutralised acrylic solution with acid number 200–240 mg KOH/g and solids of 25–30%. Final pH must remain below 8.5. Above this threshold the xanthene chromophore shifts toward the colourless lactone form and the visible absorbance at 555 nm collapses, reducing both colour strength and fluorescence. A defoamer and a polyethylene wax emulsion are added after dye dissolution. High-shear mixing with a Cowles dissolver at 5 m/s blade speed is sufficient; grinding is unnecessary unless the formula contains a co-milled pigment.
At press, the concentrate is reduced with water or water/glycol ether to 18–25 s on a Zahn cup 2. Final dye content in the ink ranges from 1 wt% to 5 wt%. Anilox specification depends on coverage: 800–1200 LPI for line work and 500–700 LPI for solids. Drying at 50–70°C with air impingement prevents frost or mottle on coated paper. These inks are intended for non-food-contact paper packaging and display printing. Compliance references EU Directive 94/62/EC for packaging heavy metals, Swiss Ordinance SR 817.023.21 for printing inks, and REACH Regulation 1907/2006. If the printed article is later converted into food packaging, the full migration protocol of Commission Regulation (EU) No 10/2011 must be run; the dye is not presumed to be food-contact compliant. Terminal products include gift wrap, shopping bags, corrugated preprint, and synthetic paper labels.
For cast acrylic sheet coloration, Rhodamine B Extra is normally predissolved in methyl methacrylate before being added to the prepolymer syrup. The syrup is carried to 10–20% conversion in the reactor before dye addition, which limits free radical attack on the xanthene chromophore. Loading in transparent pink-red sheet is 0.001–0.05 wt% based on monomer. Fluorescence self-quenching increases above this range, so higher loadings are limited to opaque or edge-lit sheet where surface emission dominates.
Cell casting polymerises in a water bath at 45–60°C, followed by post-cure at 110–120°C. The sheet must not see temperatures above 200°C anywhere in the cycle. Thermogravimetric analysis of Rhodamine B shows onset of mass loss near 210°C, and exposure above that threshold degrades the diethylamino substituents and shifts the shade from red-pink to brown-pink. Injection moulding grades of PMMA processed above 230°C are therefore not suitable without first running a thermal stability trial. Optical control uses ASTM D1003-21 for luminous transmittance and haze, and a fluorescence spectrophotometer with excitation 555 nm and emission 580 nm for intensity.
Outdoor or continuously illuminated sheet needs 0.1–0.3 wt% benzotriazole UV absorber to slow photofading. Electronic display applications in the EU are checked against RoHS Directive 2011/65/EU; lead, cadmium, mercury, and hexavalent chromium must remain below the directive’s maximum concentration values. If the sheet is used in toys, EN 71-3 migration limits apply. End products are edge-lit signage, equipment display windows, safety markers, and decorative furniture panels.
Fluorometric linearity controls non-potable water tracing with Rhodamine B Extra; the product is not approved as a potable water additive and must be restricted to closed loops, waste streams, or non-contact hydrology. An initial stock solution is prepared at 0.1% in deionised water. It is injected with a positive-displacement metering pump to give a downstream concentration of 1–10 ppb. In-situ or flow-through fluorometers with excitation near 555 nm and emission near 580 nm provide a linear response from 0.05 ppb to 10 ppb at a 10 mm optical path. Calibration must be performed with site water because turbidity, dissolved organic carbon, and pH alter the quantum yield. A two-point calibration with a site-water blank and a 5 ppb standard is the minimum; field instruments require temperature compensation of 1–2% per °C.
In cooling circuits the dye is injected upstream of the suspected leak or mixing zone, and detectors are placed at bleed lines, condensate return, or downstream sumps. The observed peak arrival time gives the residence time distribution. Silt, biomass, and corrosion products adsorb the dye; the water should be pre-filtered to 5 µm before the run. Effluent colour permit limits must be checked before discharge because the dye remains visible at low ppb concentrations. End uses include heat-exchanger leak detection, cooling tower basin circulation tests, and wastewater residence time distribution studies.
In coloured smoke compositions, Rhodamine B Extra functions by vaporisation, not by flame emission. The dye must be carried into the smoke cloud before it decomposes; the coolant in the composition is therefore as important as the total dye content. Published data for specific military smoke formulations is limited, but test and training mix designs generally carry 40–50 wt% dye. The fuel/coolant phase is typically lactose or sucrose, and potassium chlorate is the oxidiser. The coolant suppresses flame temperature so that the dye sublimates in the expansion zone rather than carbonising on the pellet surface.
Dry blending is performed in a remotely operated ribbon blender with static grounding and explosion venting. The dye particle size is reduced to 10–25 µm d50 in a pinned-disc mill; a narrow particle size distribution improves vaporisation rate and visual density. Sodium bicarbonate at 1–3 wt% is a suitable auxiliary coolant. Moisture content below 0.5% is mandatory before loading into grenade bodies or canisters. Contact with ammonium salts must be avoided because it accelerates dye decomposition and shade weakening. Storage above 80°C reduces colour intensity over time.
The final article is classified under the UN Transport of Dangerous Goods framework based on construction and explosive content; signal devices are commonly assigned to Class 1.4S, but the exact entry must be confirmed by the national competent authority. The dye’s visible emission is a red-pink cloud; terminal uses are military signalling, fire training simulators, airsoft smoke devices, and film special effects.
Solvent-based spirit stains for wood finishing use Rhodamine B Extra as a high-tinctorial-strength shading component; the concentrated stock stain is made at 0.2–2.0 wt% in methanol, ethanol, or isopropanol. For spray application the stain is diluted to 0.05–0.5 wt% active dye with alcohol and glycol ethers. Open-pore hardwoods such as maple, beech, and birch accept the dye as a transparent red-pink base; closed-pore species need a pre-stain conditioner to reduce blotching. The solution is applied by conventional spray at 0.5–1.5 bar atomising air or by flow coating, then flashed at 20–25°C. A seal coat of shellac or nitrocellulose lacquer follows. Because Rhodamine B Extra is cationic, some acidic shellac solutions can precipitate the dye; a compatibility test with 5% stock stain in the selected shellac is required before full batch production.
The dye has limited photostability under direct UV, so decorative millwork requires a topcoat with a UV absorber. VOC content must comply with EU Directive 2004/42/EC for wood coatings or the relevant regional solvent emission regulation. The stain is not intended for food-contact surfaces or toys. End products include musical instrument lacquer undercoats, high-end furniture, interior millwork, and display fixtures.
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Rhodamine B Extra is supplied as the monohydrochloride salt of C.I. Basic Violet 10 (C.I. 45170; CAS 81-88-9; EC 201-383-9), with molecular formula C28H31ClN2O3 and relative molecular mass 479.02 g/mol. The dry product is a dark green to violet crystalline powder; dilute aqueous solutions show an intense pink-to-magenta colour with a visible absorption maximum between 543 nm and 554 nm depending on solvent polarity and pH. The suffix “Extra” in dyehouse nomenclature does not identify a single numerical model but is used by manufacturers to distinguish a grade with controlled spectrophotometric strength, reduced insoluble residue after make-down, and tighter lot-to-lot colour consistency relative to commodity Basic Violet 10 powders. Because no ISO test method is available for colouristic strength of basic dyes, strength is normally expressed as a percentage of a producer-supplied type standard; absolute purity and strength are not interchangeable. Certificates of analysis should be requested for moisture content, ash content, insoluble matter, and heavy metal residues. The product is available in powder, microgranular, and liquid forms, but the Extra designation does not automatically indicate a dust-reduced morphology.
The product designation Rhodamine B Extra covers different manufacturer-specific grades; the user should fix a single supplier lot as the reference before large-scale production. Literature values for molar absorptivity at the absorption maximum in ethanol are on the order of 1.0 × 105 L mol−1 cm−1; this high absorptivity permits low mass addition in transparent colourant systems but also makes stock solution concentration errors visible as large shade deviations. The visible absorption maximum is solvent-sensitive: published maxima for Rhodamine B chloride include 543 nm in ethanol and 554 nm in water. Incoming inspection must use the same solvent system as the producer reference because a solvent mismatch can produce false strength differences even when dye content is identical. Moisture content is determined by drying at 105°C to constant mass; the acceptance limit is producer-specific and should not be taken from generic literature. Insoluble matter is checked by filtration through a 5 µm membrane after standardized make-down; excessive insolubles indicate poor predispersion or upstream contamination.
| Parameter | Identity or control value | Method / limitation |
|---|---|---|
| Colour Index generic name | C.I. Basic Violet 10 | Colour Index International |
| Colour Index constitution number | 45170 | Colour Index International |
| CAS registry number | 81-88-9 | Chemical Abstracts Service |
| EC number | 201-383-9 | EINECS/ELINCS listing |
| Molecular formula | C28H31ClN2O3 | Producer certificate |
| Relative molecular mass | 479.02 g/mol | Producer certificate |
| Visible absorption maximum | 543–554 nm | Solvent- and pH-dependent |
| Colouristic strength | Percent of type standard | Producer-specific spectrophotometric method |
Compared with Rhodamine 6G, the absorption maximum of Rhodamine B Extra is bathochromic by 13 nm to 26 nm depending on solvent system. The product also differs from solvent-soluble reds such as Solvent Red 49 because it is water-soluble and cationic; this restricts direct incorporation into nonpolar polymer matrices but allows strong interaction with anionic substrates. In applications where solvent dyes are used for transparent plastics, Rhodamine B Extra is generally unsuitable at useful colour strengths without polar carriers or specialised masterbatch technology.
In acrylic fibre exhaust dyeing, Rhodamine B Extra is retained by ionic interaction with anionic dye sites rather than by simple partition. The bath is initially adjusted to pH 4.5–5.0 with acetic acid and sodium acetate; this pH window keeps the dye in its cationic form and minimises hydrolysis of the fibre sites. Heating rate is a critical processing parameter: from 75°C to 98°C, a rate of 0.5°C/min to 1.0°C/min is typical for package and beam machines to prevent tippy packages and core-to-surface shade variation. On pressurized package machines, flow reversal and pump pressure must be balanced to avoid fibre packing and preferential liquor channelling. Cationic retarders with defined molecular mass ranges or anionic levelling agents are added in combination depths; excessive anionic agent forms a dye–surfactant complex that blocks screens and deposits on machinery. Dye uptake can be followed by transmission measurement at the 554 nm maximum, but calibration against the specific machine liquor is required because turbidity and residual auxiliaries change the baseline. Fastness evaluation should follow ISO 105-B02:2014 for artificial light and ISO 105-C06:2010 for domestic laundering; no universal fastness rating for Rhodamine B Extra can be assigned without specifying substrate, depth, and aftertreatment.
Alkaline hydrolysis of the carbinol form and complexation with anionic species are the principal sources of shade variation. At pH above 8.0, the coloured cationic form converts to the weakly coloured carbinol base; the shift is reversible upon acidification below pH 5.0, but repeated pH cycling can produce metastable aggregates that lower apparent strength. Hard-water ions such as calcium and magnesium reduce effective dye solubility and can form carbonate deposits on heating; pre-treatment with 1 g/L to 3 g/L of a sequestrant compatible with cationic dyes is required when total hardness exceeds 100 mg/L CaCO3. Residual anionic dispersants from upstream preparation machinery can react with the cationic chromophore at the liquor surface and produce sticky interfacial films; machine cleaning protocols must remove these deposits before dyeing. Shade reproducibility is influenced by ionic strength, pH drift, and dwell time above the glass transition of the fibre. In basic-dyeable polyester, the host fibre has sulphonate groups that interact with the dye; heating rate from 80°C to 120°C under pressure should be controlled to avoid abrupt exhaustion at the available dye sites. Colour difference measurement using ASTM D2244-16 is recommended after drying and conditioning; numerical tolerances must be linked to end-use cutting yields.
Paper machine applications exploit the high directness of Rhodamine B Extra on lignocellulosic furnish. The dye is most often prediluted to a 1 g/L to 5 g/L stock solution in warm water and metered into the thick stock line or white water; alum is added to lower furnish pH below 5.0 and improve retention. Variability in cationic demand of the furnish—from broke, carbonate filler, or recycled fibre—shifts the effective charge balance, causing the dye to bleed into white water or to produce two-sided colour variation. On blade coating or size press, compatibility with starch and polyvinyl alcohol binders is pH-dependent; the low pH required for dye fixation can hydrolyse some ester-based binders. Leather finishing use is restricted to non-food-contact articles, typically in base coats where the dye is blended with anionic acrylic or protein binders. Direct mixing of undiluted Rhodamine B Extra solution with anionic emulsions can produce microscopic coacervates that reduce gloss and crock-fastness; a small-batch compatibility trial under production shear is required before main batch addition.
Formulators replacing Solvent Red 49 or Rhodamine 6G in aqueous ink and paper tinting concentrates must account for the bathochromic hue and higher water solubility of Rhodamine B Extra. The visible absorption maximum shifts from approximately 530 nm for Rhodamine 6G to 543 nm in ethanol and 554 nm in water for Rhodamine B, so shade matching cannot be performed by mass equivalence alone. In water-based inkjet and flexographic ink bases, pH is maintained between 4.0 and 6.5 to prevent carbinol formation; below pH 3.0, fluorescence quenching and dye aggregation may occur without an increase in tinctorial strength. Glycol ethers and alcohol co-solvents increase solubility but can suppress the effective charge interaction with paper sizing agents. Anionic rheology modifiers, dispersed pigments, and many wetting agents are incompatible in concentrated solution because they form insoluble coacervates with the cationic dye. A predispersion test in a 500 mL beaker with a 40 mm diameter Cowles blade can reveal incompatibility before scale-up; mixing time and temperature should be recorded to permit lot-to-lot comparison. Long-term storage stability of liquid concentrates requires biocides compatible with cationic dyes; oxidative biocides can partially degrade the xanthene chromophore and produce a hypsochromic shift in stored batches. Accelerated storage trials at 40°C for 90 days with regular spectrophotometric monitoring are recommended; published data for this specific configuration is limited.
Above pH 8.0, the equilibrium between the coloured cationic form and the weakly fluorescent carbinol form reduces fluorescence quantum yield and absorption. Consequently, aqueous tracer applications using Rhodamine B Extra require buffering at pH 4.0–6.5 and, where fluorescence is used for detection, a fluorimeter calibrated against known concentration standards in the same matrix. The Stokes shift between the absorption maximum and the emission maximum is roughly 20 nm to 25 nm in water, and band-pass settings must be chosen to reject scattered excitation light. In environmental tracer studies, natural organic matter and turbidity cause inner-filter effects that lower apparent concentration; standard addition calibration is necessary when background absorbance is significant. The product should not be used where low acute aquatic toxicity is required without treatment because the dye imparts strong visible colour at concentrations below 1 mg/L. Published data for this specific configuration is limited.
Visible spectrophotometric strength testing is performed by dissolving a known mass of dye in deionized water or ethanol, measuring absorbance at the producer-specified wavelength, and comparing the result to a type standard under identical path length and temperature. The Beer-Lambert linear range must be verified for each spectrophotometer because the high molar absorptivity of Rhodamine B can produce nonlinear detector response at absorbance values above 0.8 AU. For reliable strength calculations, measurements are diluted to maintain absorbance between 0.2 AU and 0.8 AU. Temperature control during measurement is required because the absorption band broadens with increasing temperature, shifting apparent strength by a small but statistically significant amount. Colour difference measurements on dyed substrates are performed with a d/8° integrating sphere spectrophotometer using D65 illumination and 10° observer, followed by ASTM D2244-16 calculations in the CIELAB system. Goniophotometric measurement is not required for routine textile colour assessment, but optically uneven leathers and coated papers require multiple readings to estimate spatial variance. Strength and shade must be separated statistically: a large difference in strength appears as a lightness change, while hue shifts often indicate pH history or contamination rather than poor dye content.
Rhodamine B Extra is not approved for food, pharmaceutical, or cosmetic colouration in the European Union or the United States, and it must not be used in food-contact packaging that shows detectable migration. Under Regulation (EC) No 1907/2006 Annex II, the safety data sheet shall identify the product as a cationic dye with aquatic toxicity concerns. Industrial wastewater containing the dye should be decolourised by adsorption on activated carbon or by oxidative treatment; direct discharge of coloured effluent can exceed visible colour limits. Dust control during handling is critical; the powder form should be added in a ventilated make-down area or purchased as a dust-reduced grade where available. Incompatible materials include concentrated strong oxidising agents, anionic polymer flocculants, and strongly alkaline liquors above pH 8.0. Storage in closed containers between 5°C and 35°C is typical for dry strength retention; bulk liquid versions may require mild agitation and freeze protection below 0°C.
