| HS Code | 700974 |
| Productname | Sodium Thiocyanate |
| Chemicalformula | NaSCN |
| Casnumber | 540-72-7 |
| Molarmass | 81.07 g/mol |
| Appearance | White crystalline solid |
| Odor | Odorless |
| Density | 1.735 g/cm3 at 20 °C |
| Meltingpoint | 287 °C |
| Boilingpoint | 368 °C |
| Watersolubility | Soluble; 139 g/100 mL at 20 °C |
| Ethanolsolubility | Soluble |
| Acetonesolubility | Soluble |
| Hygroscopicity | Hygroscopic |
| Crystalstructure | Orthorhombic |
| Toxicity | Oral LD50 (rat) 764 mg/kg |
As an accredited Sodium Thiocyanate factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Sodium Thiocyanate is supplied in 25 kg moisture-resistant, polyethylene-lined fiber drums with sealed inner bags for safe handling. |
| Container Loading (20′ FCL) | Chemical Sodium Thiocyanate loaded into a 20′ FCL container, palletized in drums, evenly distributed, moisture-protected, and securely braced for safe transport. |
| Shipping | Sodium Thiocyanate is generally not regulated as dangerous goods for transport under DOT, IATA, IMDG, or ADR. Ship in sealed, labeled containers, protected from moisture, acids, and oxidizers. Include the SDS and shipping documents. Follow carrier and destination requirements, and clean spills per local regulations. |
| Storage | Store sodium thiocyanate in a cool, dry, well-ventilated area, away from acids, oxidizers, moisture, and direct sunlight. Keep containers tightly closed, clearly labeled, and within secondary containment. Avoid dust generation, heat sources, and incompatible materials. Maintain separation from food, feed, and drinking water. Protect from physical damage, inspect containers regularly, and follow local regulations and the safety data sheet. |
| Shelf Life | Sodium thiocyanate is stable; shelf life generally 2–5 years if sealed, dry, cool, and protected from moisture and oxidizers. |
Where polyacrylonitrile wet spinning requires a solvent that disrupts nitrile–nitrile dipole associations while remaining miscible with water, sodium thiocyanate is maintained as a 48–52 wt% aqueous solution at 70–90 °C. Production lines premix 10–13 wt% polyacrylonitrile powder into the thiocyanate liquor under inert gas, then homogenise the dope in jacketed dissolution vessels equipped with slow-speed ribbon impellers. The target dope viscosity is 20–40 Pa·s at 45 °C, a range that permits pressure filtration through 20 µm stainless-steel media without excessive gel shear. Dissolved dope is deaerated under 5–10 kPa absolute pressure and transferred by gear pump to spinnerets with capillary diameters between 0.05 mm and 0.12 mm.
Coagulation bath composition is controlled at 10–12 wt% sodium thiocyanate and 30–40 °C; residual solvent content influences solvent–non-solvent exchange rate, skin density, and void formation. Tow leaving the bath is drawn 1.5–3.0× in hot water at 80–95 °C, then washed through 4–6 countercurrent stages to remove free solvent. Final wash overflow is monitored continuously by conductivity; residual sodium thiocyanate on dried fibre is held below 0.05 wt%. Spin finish application and crimping follow for staple lines, while tow lines wind undried product for downstream conversion.
Terminal products include acrylic staple, tow, and PAN-based carbon fibre precursors. Fibre tensile acceptance uses ISO 5079:2020 for breaking tenacity and elongation; precursor destined for carbonisation is additionally screened according to ISO 11566:1996 single-filament tensile practice. Solvent recovery returns filtered and concentrated sodium thiocyanate to the 48–52 wt% range through multiple-effect evaporation; recovered solvent is monitored for iron, sulphate, and dissolved polymer because these impurities alter coagulation rate and fibre colour.
| Parameter | Operating window | Monitoring point |
|---|---|---|
| Dope sodium thiocyanate concentration | 48–52 wt% | mixing tank outlet |
| Dope polyacrylonitrile concentration | 10–13 wt% | dissolution vessel |
| Falling-ball viscosity | 20–40 Pa·s at 45 °C | post-filtration |
| Coagulation bath sodium thiocyanate | 10–12 wt% | bath recirculation loop |
| Bath temperature | 30–40 °C | plate heat exchanger |
| Jet stretch ratio | 1.5–3.0× | first draw stand |
| Residual fibre sodium thiocyanate | <0.05 wt% | final wash overflow |
Argentometric back-titration methods use sodium thiocyanate as titrant after acidifying the sample with nitric acid and adding a known excess of silver nitrate. The indicator is ferric ammonium sulphate, which forms a red-brown Fe(SCN)2+ complex when free thiocyanate appears; the endpoint is visually detectable at approximately 10−5 mol/L thiocyanate. Titrant concentration is commonly 0.1 mol/L, standardized against primary silver nitrate under ASTM E200-22 and restandardized every 48 h because thiocyanate degrades by photochemical oxidation and microbial action in laboratory storage.
Chloride determination by Volhard chemistry requires precipitation of silver chloride, filtration or nitrobenzene addition, and back-titration of unreacted silver. Method protocols such as AOAC 971.27 specify acidification, silver nitrate excess, and thiocyanate back-titration for saline foods; routine chloride working range after dilution is 0.1–2.0 g/L. The precision of the method is limited by silver chloride exchange when precipitate is not removed; filtered procedures show better repeatability than direct nitrobenzene procedures.
Silver assay in ores and alloys follows the same sequence: nitric acid digestion, silver nitrate addition when chloride is absent, and thiocyanate titration to a persistent 30 s endpoint. Ferric indicator solution is prepared at 10% w/v in dilute nitric acid, and the titration is performed under diffuse laboratory lighting to reduce photodecomposition of silver chloride. Reporting to 4 significant figures is achievable only after titrant restandardization on the day of use.
When cyanide use is restricted by permitting or tailings liability, sodium thiocyanate can be combined with ferric sulphate at pH 1.5–2.5 to form the Au(SCN)2− complex. The ferric/ferrous couple maintains solution potential above 700 mV vs SHE; typical bench-scale leach conditions include 0.1–0.5 M thiocyanate and 0.01–0.1 M ferric ion. Published column studies report oxide ore gold extraction in the range of 80–95% over 24–72 h at 25–35 °C, although published data for specific ore mineralogy and particle size distributions is limited.
Process control requires ferric ion addition in molar excess over gold but below concentrations that precipitate jarosite. A practical Fe3+:Au molar ratio in bench tests is 3–5:1, and dissolved oxygen is maintained below 2 mg/L to slow thiocyanate oxidation. Pregnant solution recovery by activated carbon is weaker for Au(SCN)2− than Au(CN)2−; weak-base resins are evaluated when thiocyanate concentrations exceed 0.2 M to avoid carbon fouling and iron precipitation.
Operational boundaries are narrow. Below pH 1.5, thiocyanate decomposes and may release hydrogen cyanide in the presence of oxidising agents; above pH 3.0, ferric hydrolysis forms solids that blind heap leach columns and pipework. Acid consumption is higher than cyanide leaching because ferric sulphate solutions are acidic, and stainless-steel contact requires hydrogen cyanide monitoring and forced ventilation.
In batch alkylation, sodium thiocyanate is charged with a polar aprotic solvent into a glass-lined reactor, and an alkyl chloride or alkyl bromide is added at a NaSCN:alkyl halide molar ratio of 1.1–1.5:1. The stirred suspension is held at 60–100 °C for 4–12 h; conversion of activated primary alkyl halides to alkyl thiocyanates typically exceeds 90%. Sodium chloride precipitates and is removed by centrifuge or pressure filter before solvent is recovered under vacuum at 40–60 °C.
Alkyl thiocyanates isomerize to isothiocyanates when heated above 100 °C or when a Lewis acid catalyst is present. The isomer ratio is monitored by gas chromatography with flame ionisation detection; residence time is limited at temperatures above 120 °C because polymeric by-product formation increases. The crude product is washed with water to remove residual sodium thiocyanate, then dried over molecular sieve and distilled under reduced pressure.
Downstream products include pharmaceutical intermediates, crop protection agents, and specialty thio compounds. Material specifications for sodium thiocyanate used in these alkylations commonly require ≥98.0% NaSCN, ≤0.5% chloride, and ≤0.2% sulphate. The reaction exotherm is controlled by staged addition of the alkyl halide; the reactor jacket temperature is held below 90 °C during the first 30 min, and the vent line is routed to a dilute caustic scrubber.
Black nickel electrolytes contain nickel sulphate hexahydrate at 75–100 g/L, zinc sulphate heptahydrate at 30–40 g/L, sodium thiocyanate at 10–20 g/L, and boric acid at 20–30 g/L. The bath operates at pH 5.6–6.0 and 20–28 °C; cathode current density is held between 0.5 A/dm² and 2.0 A/dm². Nickel anodes are used, with anode area kept at 1:1 to 2:1 relative to cathode area to limit anode polarisation.
Thiocyanate is consumed at the cathode and must be replenished by amp-hour totaliser or periodic wet analysis. Below 8 g/L NaSCN, deposit colour shifts from black to grey-brown; above 25 g/L, internal stress increases and adhesion to copper or nickel undercoats is reduced. Bath pH is adjusted with dilute sulphuric acid or nickel carbonate; pH above 6.2 precipitates zinc hydroxide, while pH below 5.6 lowers throwing power and can destabilise the thiocyanate complex.
Because acidic thiocyanate baths can release small amounts of hydrogen cyanide at the cathode, exhaust ventilation and cyanide detection are required. Rinse water discharge is managed under US EPA 40 CFR 413 electroplating categorical standards; spent baths are treated by alkaline chlorination to oxidise thiocyanate before precipitation of nickel and zinc hydroxides.
| Parameter | Low boundary | High boundary | Observed effect outside window |
|---|---|---|---|
| Sodium thiocyanate | 8 g/L | 25 g/L | grey-brown deposit / stress and adhesion loss |
| pH | 5.6 | 6.2 | low throwing power / zinc hydroxide precipitation |
| Bath temperature | 20 °C | 28 °C | dull deposit / increased evaporation |
| Cathode current density | 0.5 A/dm² | 2.0 A/dm² | incomplete coverage / burnt edges |
In photographic fixing operations, sodium thiocyanate accelerates dissolution of silver halides in ammonium thiosulphate fixers. Fixer concentrates may include 5–20 g/L sodium thiocyanate as a silver-solvent adjuvant, reducing clearing time for iodide-rich emulsions. The working bath is held at 20–30 °C, and replenishment is controlled by silver electrode measurement; silver concentration above 5 g/L reduces fixing capacity and increases washwater silver load.
Thiocyanate-containing fixers are maintained above pH 5.0. If acid stop bath carryover drives the fixer below pH 4.5, thiocyanate can decompose and release hydrogen cyanide. Processing lines therefore insert a water rinse or buffered stop bath between the acid stop and the fixer tank; published data for specific archival processing configurations is limited, so bath pH is recorded at the start of each shift.
Terminal use is concentrated in industrial photofinishing and graphic arts films where iodide content is high; digital imaging has reduced volume. Waste fixer is treated by electrolytic silver recovery or steel wool cartridges before thiocyanate-bearing effluent is discharged under municipal pretreatment limits. Residual silver in photoprocessing effluent is often limited to 5 mg/L by local sewer use codes.
Competitive Sodium Thiocyanate prices that fit your budget—flexible terms and customized quotes for every order.
For samples, pricing, or more information, please contact us at +8615380400285 or mail to sales2@ascent-chem.com.
We will respond to you as soon as possible.
Tel: +8615380400285
Email: sales2@ascent-chem.com
Flexible payment, competitive price, premium service - Inquire now!
Sodium thiocyanate (NaSCN, CAS 540-72-7, EC No. 208-754-4, molar mass 81.07 g mol−1) is an inorganic pseudohalide salt supplied as a white crystalline solid, granular crystal, flake, or aqueous solution. Commercial supply is specified by grade rather than by a conventional model number: technical grade, photographic grade, concrete admixture grade, refined grade, and reagent grade are the common procurement descriptors. The anhydrous solid is hygroscopic and becomes deliquescent at elevated relative humidity; closed packaging, dry-air purge, or nitrogen blanketing is therefore required in bulk storage. Aqueous solubility at 20 °C exceeds 100 g per 100 g water, and the resulting solution is dense and corrosive to mild steel unless passivated or coated equipment is used. In production-scale receiving, the material is commonly handled in 25 kg polyethylene-lined bags, 500 kg supersacks, 1000 kg fibc, or as bulk solution in tank trailers. Transfer lines are typically 316L stainless steel or polypropylene, with dust extraction at bag-dump stations to limit respiratory exposure to the fine crystalline fraction.
A representative incoming-specification profile for technical-grade sodium thiocyanate concentrates on assay, trace iron, sulfate, chloride, water, and water-insoluble matter because these residuals affect later performance in fiber spinning, chemical synthesis, and concrete admixture compounding. The following consolidated acceptance profile is adapted from supplier certificates of analysis and bulk procurement agreements:
| Parameter | Acceptance range | Test method |
|---|---|---|
| Assay as NaSCN, dry basis | 98.0–99.0% | Argentometric titration with silver nitrate |
| Iron as Fe | ≤0.0003% | ICP-OES after closed-vessel digestion |
| Chloride as Cl | ≤0.01% | Ion chromatography or silver titration |
| Sulfate as SO42− | ≤0.02% | Turbidimetry or ion chromatography |
| Water by loss on drying | ≤0.5% | Karl Fischer titration or oven drying at 105 °C |
| pH of 5% aqueous solution | 6.0–8.0 | Calibrated pH electrode |
| Water-insoluble matter | ≤0.005% | Gravimetric after filtration |
| Heavy metals as Pb | ≤0.001% | ICP-MS or colorimetric sulfide |
Sampling and sample preparation are performed under low-humidity conditions because hygroscopic moisture uptake biases both assay and water results. Incoming bulk shipments are sampled with a riffler or thief sampler, and composite samples are split in a dry room before analysis. Reagent-grade material may be tested according to general methods in ISO 6353-1; specific trace limits are set by the seller’s certificate of analysis. For continuous dissolution, a jacketed stainless-steel mix tank with high-shear disperser, eductor funnel, and recirculation loop is preferred. Dissolution is endothermic, so heating to 30 °C to 40 °C is commonly used to maintain feed rate. In open-topped day hoppers above the disperser, anhydrous sodium thiocyanate can pick up more than 0.2% moisture within one shift when ambient relative humidity exceeds 60%, and the resulting mass gain must be subtracted from batch water calculations.
In winter concreting and precast production, sodium thiocyanate is incorporated into non-chloride accelerating admixtures because it accelerates setting and early strength development without adding chloride ions to the pore solution. The dosage, expressed on anhydrous NaSCN by mass of cementitious material, is generally held between 0.4% and 2.0%. The lower end is specified when high-range water-reducing admixtures or supplementary cementitious materials already modify early hydration; the upper end is limited to cold-weather flatwork or precast operations where rapid form turnover is required. Admixtures formulated with NaSCN are evaluated under ASTM C494/C494M as Type C or Type E formulations, using ASTM C403/C403M penetration resistance for setting-time performance and ASTM C39/C39M for compressive strength development. Production trial batching at ready-mix plants checks compatibility with polycarboxylate ether water reducers, air-entraining agents, and lignosulfonates; the addition sequence is fixed to avoid local concentration spikes that can cause flash setting at the point of introduction.
The performance boundary is distinct from calcium chloride acceleration. Sodium thiocyanate produces a less exothermic response than calcium chloride at equivalent setting-time reduction; therefore, in ambient temperatures below −5 °C, the admixture alone is not sufficient and heated mix water, insulation, or supplementary thermal protection is required. Overdose conditions above 2.0% may accelerate early hydration excessively, increase water demand, and reduce later-age compressive strength in high-alkali cements. In mass concrete, the use of NaSCN is constrained by thermal gradient control, and a thermal modeling review is performed before dose selection. Field QC also monitors slump retention and entrained air stability because the thiocyanate anion can alter the adsorption equilibrium of organic admixtures on cement particle surfaces. Quantitative peer-reviewed data for all proprietary NaSCN-containing admixtures are not fully published; industrial selection therefore relies on laboratory validation and plant-scale batching trials against the applicable concrete standard.
In acrylic fiber wet-spinning lines, aqueous sodium thiocyanate is used as the solvent for acrylonitrile copolymers. The spinning dope solvent concentration is generally maintained between 50 wt% and 55 wt% NaSCN, with density and refractive index used as rapid on-line compositional checks. The coagulation bath is a diluted NaSCN solution; bath temperature, immersion length, and circulation rate are controlled by plate heat exchangers and multi-stage filtration to remove gel particles. Spinneret configuration, capillary diameter, and wash-cascade flow are adjusted to control filament cross-section, skin thickness, and residual solvent. After coagulation, hot-water washing removes residual thiocyanate, and the dilute solvent is concentrated by evaporation or membrane recovery before return to dope preparation. The sodium salt is selected in this process because it does not release ammonia during solvent recovery, unlike ammonium thiocyanate, and it provides stable dope viscosity over extended hold times. However, sodium accumulation can occur in the coagulation circuit if make-up water contains high hardness, requiring ion exchange or controlled purge streams to maintain ionic strength.
Dope viscosity is a function of polymer molecular weight, polymer concentration, and NaSCN concentration, and it is measured continuously by rotational or falling-ball viscometry. In batch preparation, the dissolution vessel is jacketed and nitrogen-blanketed because shear heating in high-viscosity dope can raise temperature and initiate gel formation. Filtration of the spinning dope is performed through fine-mesh polymer filters before the spinneret pack to reduce broken filaments and spinneret blockage. Residual thiocyanate in the washed fiber is monitored as a quality parameter because incomplete washing alters downstream drawing behavior and final fiber color. The recovery loop must be designed for the high boiling point and ionic strength of sodium thiocyanate solutions; evaporator fouling and salt crystallization in low-flow zones are operational failure modes observed on production lines. When the solvent is switched from ammonium thiocyanate to sodium thiocyanate, flowmeter calibration, density setpoints, and pH controls require recalibration because the sodium salt changes solution density and eliminates the weak-base buffering effect of the ammonium ion.
Mass-for-mass substitution is inappropriate because the cation identity changes molecular weight, thiocyanate content, solution density, and vapor behavior. Sodium thiocyanate contains 71.6% thiocyanate by mass; ammonium thiocyanate contains 76.3%; potassium thiocyanate contains 59.8%. For a process designed around thiocyanate ligand availability, replacing NaSCN with NH4SCN at the same mass increases the available thiocyanate by approximately 6.6%, while replacing with KSCN decreases it by approximately 16.5% relative to the sodium salt. Cation mass fraction is 28.4% for sodium, 23.7% for ammonium, and 40.2% for potassium. The ammonium salt can release ammonia under alkaline process conditions and may shift pH in electroplating or wet-spinning circuits; the potassium salt increases potassium ion load and can precipitate poorly soluble potassium salts in some formulations. Sodium thiocyanate is therefore not a generic drop-in substitute and must be evaluated through bench-scale compatibility testing before plant trials.
| Comparative parameter | Sodium thiocyanate | Ammonium thiocyanate | Potassium thiocyanate |
|---|---|---|---|
| CAS RN | 540-72-7 | 1762-95-4 | 333-20-0 |
| Molar mass, g mol−1 | 81.07 | 76.12 | 97.18 |
| Thiocyanate content, mass % | 71.6 | 76.3 | 59.8 |
| Cation content, mass % | 28.4 | 23.7 | 40.2 |
| Ammonia release in alkaline process fluid | None | Possible | None |
Sodium thiocyanate is also used in analytical chemistry for the spectrophotometric determination of iron(III) through the formation of red iron-thiocyanate complexes. The reagent blank and chloride content must be controlled because chloride modifies the complex equilibrium and can reduce absorbance. In organic synthesis, sodium thiocyanate is used to convert activated alkyl halides or tosylates to alkyl thiocyanates through nucleophilic substitution. The reaction is conducted under controlled temperature because exothermic rearrangement can generate isothiocyanate by-products. Process-scale reactors for this substitution generally use glass-lined or fluoropolymer-lined equipment and maintain sufficient agitation to avoid localized high SCN⁻ concentration.
Calcium thiocyanate is another alternative in concrete acceleration, but its calcium content and higher cation charge influence aluminate-phase hydration and water-reducer performance differently from the sodium salt. Sodium thiocyanate introduces sodium rather than calcium, which affects alkali-silica reaction risk in aggregate systems with reactive silica. In dry-mix mortar formulations, sodium thiocyanate can be pre-blended into dry mixtures, but storage must avoid moisture; coated or compacted granules are sometimes used to reduce caking in silo storage. Published data comparing all thiocyanate salt forms under identical cement systems are limited; industrial selection is therefore based on plant-scale performance testing rather than universal numerical guidance. Documentation for cross-border shipment includes the safety data sheet, CAS registration, EC number, and REACH registration status where applicable. Standard technical-grade sodium thiocyanate is not intended for direct human ingestion or food-contact use, and pharmaceutical or analytical applications require separate purity verification against the relevant monograph or specification.
