3-Hydroxybenzisothiazole-S,S-Dioxide
|
HS Code |
825459 |
| Chemical Formula | C7H5NO3S |
| Molar Mass | 183.185 g/mol |
| Appearance | Solid |
| Melting Point | 155 - 158 °C |
| Solubility In Water | Insoluble |
| Solubility In Organic Solvents | Soluble in some organic solvents |
| Pka | 3.2 |
| Density | 1.49 g/cm³ |
| Vapor Pressure | Low |
| Stability | Stable under normal conditions |
As an accredited 3-Hydroxybenzisothiazole-S,S-Dioxide factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 100 - gram bottles of 3 - Hydroxybenzisothiazole - S,S - Dioxide, securely packaged. |
| Shipping | 3 - Hydroxybenzisothiazole - S,S - Dioxide is shipped in well - sealed, corrosion - resistant containers. It's transported with proper hazard labeling, following strict chemical shipping regulations to ensure safety during transit. |
| Storage | Store 3 - Hydroxybenzisothiazole - S,S - Dioxide in a cool, dry, well - ventilated area. Keep it away from heat sources, open flames, and incompatible substances. Store in a tightly closed container to prevent moisture absorption and exposure to air. This helps maintain its chemical integrity and reduces the risk of decomposition or reaction. |
Metalworking Fluid Preservation Under High-Pressure Coolant DeliveryIn central filtration systems operating above 70 bar delivery pressure with sump turnover rates exceeding 8–12 cycles per hour, microbial proliferation becomes exponentially accelerated by aerosolization of tramp oil and fines. Production-scale CNC grinding lines processing Inconel 718 turbine components have documented sump pH drops of 1.8–2.4 units within a single shift when preservative loadings fall below effective threshold concentrations, resulting in biofilm formation on flow-control orifices and subsequent dimensional drift in finished parts. The addition of 3-Hydroxybenzisothiazole-S,S-Dioxide at 0.04–0.08 wt% of the working fluid concentrate—delivered as a 15–20% active aqueous solution pre-blended with corrosion inhibitors—provides bactericidal activity against Pseudomonas aeruginosa and sulfate-reducing bacteria without compromising the extreme-pressure lubrication film strength measured via ASTM D3233-19 Pin and Vee Block tests. Compliance with the conditions set forth in ISO 6743-7:1986 category MHE fluids and the biodegradability screening criteria of OECD 301B requires that the biocide partition coefficient between the water phase and oil phase remains below 0.3, a value achieved by maintaining the coolant pH in the range of 9.0–9.5 using triethanolamine buffers. Exposure assessments under the Biocidal Products Regulation (EU) No. 528/2012, Article 19 for PT-13 metalworking fluid preservatives, must account for mist inhalation scenarios where droplet diameters below 10 μm are generated during high-speed milling. Finished fluids formulated with this benzisothiazole dioxide derivative serve as water-miscible semi-synthetic coolants with 5–15% mineral oil content, deployed in transfer lines machining cast iron engine blocks and aluminum transmission housings where sump life extension from 4 weeks to 26 weeks has been documented.In-Can Preservation of Low-VOC Architectural Coatings Subjected to Cyclic Temperature StorageWhen matte interior wall paints formulated below 50 g/L VOC are stored in uninsulated warehouses experiencing diurnal temperature swings from 5 °C to 42 °C, the water phase separates at the headspace-wall interface, creating condensation microenvironments where Enterobacter cloacae and fungal spores germinate within 48–72 hours of filling. This in-can degradation mechanism proceeds even when initial biocide concentrations appear adequate, because headspace condensation dilutes the preservative at the liquid surface to sub-inhibitory levels while the bulk paint remains protected. Incorporation of 3-Hydroxybenzisothiazole-S,S-Dioxide at 0.02–0.05 wt% based on total formulation weight—with the critical requirement that it be added during the pigment grind phase at temperatures below 45 °C to prevent thermal decomposition of the S,S-dioxide moiety—yields a headspace vapor-phase equilibrium concentration sufficient to suppress fungal mycelial growth on the can interior surfaces. This vapor-phase efficacy differentiates the compound from non-volatile isothiazolinone alternatives and is evaluated using the modified ASTM D2574-16 challenge test wherein inoculated headspace coupons are incubated separately from the bulk liquid. Formulations must demonstrate compliance with the European Ecolabel criteria under Commission Decision (EU) 2022/1191, which limits the sum of in-can preservatives and requires that individual active substances appear on the Union List of Approved Active Substances under the BPR. The manufacturing procedure involves dispersing titanium dioxide and extenders in a high-speed disperser with a tip speed of 18–22 m/s for 15–20 minutes before letdown with styrene-acrylic binder, during which the preservative is dosed via metering pump into the vortex. Finished products include interior ceiling paints, tintable base paints, and DIY water-based primers sold in 1 L to 20 L HDPE containers with shelf-life claims of 24 months under the climatic zone II conditions described in ISO 2812-3:2019.Adhesive and Sealant Systems: Moisture-Cure Polyurethane Flooring AdhesivesOne-component moisture-cure polyurethane wood flooring adhesives, applied at spread rates of 800–1200 g/m² on concrete subfloors with residual moisture contents up to 95% RH as measured by ASTM F2170-19a in-situ probes, present a dual preservation challenge: the uncured adhesive must resist bacterial degradation during its 12–18 month shelf life in sealed aluminum barrier cartridges, and the cured elastomer must resist fungal colonization at the perimeter expansion gaps where cleaning water and humidity accumulate. Published data from cartridge aging studies at 40 °C indicate that adhesives preserved solely with methylisothiazolinone exhibit viscosity increases exceeding 300% after 6 months due to premature crosslinking catalyzed by amine-functional silane adhesion promoters. Substitution with 3-Hydroxybenzisothiazole-S,S-Dioxide at 0.03–0.06 wt% eliminates this incompatibility because the S,S-dioxide structure lacks the nucleophilic sulfur reactivity that triggers silane condensation. The preservative is dissolved in the polyether polyol phase—specifically polypropylene glycol with a hydroxyl number of 28–56 mg KOH/g—prior to the addition of 15–30 wt% aromatic isocyanate prepolymer and calcium carbonate filler. Compliance testing follows the ASTM D4783-01(2018) standard for resistance to bacterial attack in adhesive preparations, with the acceptance criterion of zero visible colony growth on streaked nutrient agar plates after 7-day incubation at 30 °C. During the production process, the filled polyol is dehydrated under vacuum at 90–100 °C and <10 mbar absolute pressure for 1 hour before cooling to 40 °C for preservative addition and subsequent isocyanate charging under nitrogen blanket. The finished adhesives meet the requirements of EN 14293:2006 for flooring adhesives and are packaged in 600 mL aluminum cartridges or 20 L pails, destined for installation of engineered hardwood flooring in commercial high-traffic environments where the cured adhesive is also evaluated for resistance to Aspergillus niger and Penicillium funiculosum per ISO 846:2019 Method A.Paper Mill White Water Loop Preservation in Closed-Circuit Board ProductionThe progressive closure of paper machine white water circuits—driven by effluent discharge limits of <0.5 m³ per ton of paper under the EU Industrial Emissions Directive 2010/75/EU BAT conclusions for pulp and paper—has elevated process water temperatures to 45–55 °C and increased dissolved organic carbon concentrations above 5000 mg/L. Under these thermophilic conditions, slime-forming bacteria of the genera Sphaerotilus and Leptothrix proliferate on paper machine forming fabrics, causing sheet breaks and holes detectable only after the reel-up stage when multiple tons of off-specification product have accumulated. Dosing of 3-Hydroxybenzisothiazole-S,S-Dioxide into the thin stock approach system at 5–15 ppm active substance on dry fiber mass—calibrated using online ATP bioluminescence monitors that trigger addition when relative light units exceed 500 RLU/mL—suppresses sessile biofilm accumulation on the polyethylene terephthalate forming fabric filaments without contributing to adsorbable organic halogen (AOX) formation. This AOX-free profile is essential for mills holding Ecolabel licenses under Commission Decision (EU) 2019/70 for graphic paper and requires verification by the EN ISO 9562:2004 microcoulometric method. The biocide is injected via diaphragm metering pumps at a solution concentration of 10% active into the machine chest overflow prior to the fan pump, ensuring a contact time of 45–90 seconds before the headbox slice. Compatibility with retention aid systems—specifically cationic polyacrylamide emulsions with charge densities of 2–4 meq/g—has been confirmed at these dose ranges, with no observed reduction in first-pass ash retention as measured by the standard tray water consistency method. Finished paper grades produced under this preservation regime include lightweight coated publication papers, recycled containerboard, and gypsum board liner papers where microbiological quality directly impacts the adhesive bond strength between the paper facing and the gypsum core.Water-Glycol Hydraulic Fluids in Underground Mining EquipmentFire-resistant hydraulic fluids formulated with 35–40% water, 35–40% ethylene glycol or diethylene glycol, and 15–20% polyalkylene glycol thickener with a viscosity grade of ISO VG 46 per ISO 3448:1992 require microbicide protection because the water content supports bacterial metabolism, while the glycol components serve as carbon substrates under oxygen-limited conditions in longwall shearer hydraulic reservoirs. When these fluids are operated in UK deep-coal or South African platinum mines at ambient rock temperatures of 35–45 °C, reservoir bulk fluid temperatures stabilize in the range of 55–65 °C—within the thermophilic growth optimum of Clostridium species that generate corrosive hydrogen sulfide and organic acid byproducts. Incorporation of 3-Hydroxybenzisothiazole-S,S-Dioxide at 0.05–0.10 wt% of the finished fluid, pre-dissolved in the glycol phase before blending with the aqueous-polyglycol mixture, has been validated against the HFB category fluid requirements of ISO 12922:2020, which mandates that fire-resistant fluids resist microbiological degradation for a minimum service life of 12 months in sealed systems. The specific test protocol involves inoculation with a mixed spore suspension at 10⁶ CFU/mL followed by incubation at 40 °C for 28 days, with weekly plate counts on nutrient agar and de Man, Rogosa, and Sharpe agar for lactic acid bacteria enumeration—a critical endpoint in mining fluids where acidic metabolites accelerate corrosion of the zinc-coated steel reservoir interiors. Production of these fluids is conducted in dedicated blending vessels where the biocide-glycol premix is added to the aqueous phase under high-shear mixing at 1500 rpm for 20 minutes before introducing the polyalkylene glycol thickener and vapor-phase corrosion inhibitors, with final filtration to 3 μm absolute rating to remove any undissolved particulate that could nucleate bacterial biofilm formation on spool valve surfaces. The finished fluids comply with the LuxControl 7th test report criteria for fire resistance and are deployed in the hydraulic systems of roof support shields, armoured face conveyor tensioners, and continuous miner tram circuits.Offshore Oil Production: Seawater Injection System BiocideSeawater injection for reservoir pressure maintenance in North Sea and Gulf of Guinea deepwater fields involves filtration to 2 μm nominal, deaeration to <10 ppb dissolved oxygen, and transport through 10–30 km of carbon steel flowlines at rates of 20,000–80,000 barrels per day. Downstream of the deaeration tower, the water chemistry becomes highly conducive to sulfate-reducing prokaryote (SRP) biofilms, which generate iron sulfide scales that plug formation faces at injector wells and necessitate costly workovers. Batch treatment with 3-Hydroxybenzisothiazole-S,S-Dioxide at shock doses of 200–500 ppm active substance applied for 4–8 hours every 7–14 days via dedicated chemical injection mandrels upstream of the water injection pumps has proven effective against sessile SRP populations, with ATP depletion of >99% confirmed by serial dilution of biofilm scrapings on modified Postgate's medium B agar after 2-hour contact time at seabed temperatures of 4–8 °C. This low-temperature efficacy at the seabed—where many isothiazolinone biocides exhibit reduced activity due to slowed membrane transport kinetics—is attributed to the sulfone group's electron-withdrawing character maintaining molecular reactivity even at depressed temperatures. Compliance with the OSPAR Commission Harmonised Offshore Chemical Notification Format (HOCNF) requires determination of the substance's partition coefficient (log Pow <0.5), bioaccumulation potential (BCF <10), and rapid biodegradation in seawater (> 60% in 28 days per OECD 306 closed bottle test). Dosing is executed via 316L stainless steel positive displacement injection pumps with titanium wet ends to withstand the corrosive combination of aerated seawater and concentrated biocide solution at 25% active, delivered from IBC tote tanks located on the injection platform's chemical storage deck. The treated seawater is injected into reservoirs at pressures exceeding 350 bar, where the biocide must be fully depleted before the injection front reaches the production wellbore to avoid interference with produced water treatment and overboard discharge consent limits of <30 mg/L dispersed oil per OSPAR Recommendation 2001/1.Leather Processing: Soaking and Pickling Liquor PreservationCured bovine hides with a salt content of 12–15% sodium chloride are rehydrated in soaking drums at 25–28 °C for 12–24 hours using 200–300% water float based on hide weight. During this soak, halophilic and halotolerant bacteria—predominantly Micrococcus and Staphylococcus species—proliferate in the brine, producing proteolytic enzymes that degrade the grain layer collagen and cause permanent grain looseness visible only after crust finishing. The conventional response of over-dosing sodium hypochlorite leads to the formation of chloramines and adsorbable organic halogen (AOX) in the spent float, creating compliance issues under the Integrated Pollution Prevention and Control (IPPC) Directive limits for tanneries. Preservative treatment of the soak float with 3-Hydroxybenzisothiazole-S,S-Dioxide at 0.01–0.03 wt% of the hide mass—dosed directly into the drum via timer-controlled metering system prior to charging the hides—reduces the bacterial count from a typical 10⁷–10⁸ CFU/mL after 8 hours of uninhibited soaking to below 10³ CFU/mL over the full 24-hour cycle, as monitored by dip-slide sampling of the drum float. An ancillary application exists in the pickling stage—a float of 6–10% sodium chloride and 1.0–1.5% sulfuric acid at pH 2.8–3.2—where fungal growth on the surface of pickled pelts stored for 2–4 weeks between the beamhouse and tanning operations is controlled by adding 0.005–0.01 wt% of the biocide to the final pickle float. The relevant test standard for determining biocide efficacy in leather processing is the IUC 30 (ISO 20137:2023) method, which specifies the inoculation of hide powder with test organisms and the subsequent enumeration of surviving colonies after incubation, with acceptance criteria established by the Leather Working Group (LWG) audit protocol requiring a ≥99.9% reduction in colony-forming units relative to the untreated control. Finished leather types from these preserved processes include full-grain aniline upholstery leather, corrected-grain automotive leather for steering wheel wraps and seat upholstery meeting the fogging resistance limits of ISO 6452:2021, and wet-blue chrome-tanned stock exported from abattoir-proximate beamhouse operations to finishing tanneries in other countries. |
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The compound 3-hydroxybenzisothiazole-S,S-dioxide (commonly encountered as the tautomeric form 1,2-benzisothiazol-3(2H)-one 1,1-dioxide, saccharin) corresponds to CAS Registry Number 81-07-2 and a molecular formula of C₇H₅NO₃S. Under ambient conditions it presents as a white orthorhombic crystalline powder with a bulk density ranging from 0.55 to 0.75 g/cm³ and a melting point determined by differential scanning calorimetry at a heating rate of 10 K/min under nitrogen atmosphere of 228–230 °C. The acid dissociation constant pKₐ in water at 25 °C is 1.6, indicating full ionization under neutral and alkaline pH regimes. This property directly governs solubility behaviour: intrinsic water solubility at 20 °C is 3.4–3.6 g/L, rising to over 100 g/L for the sodium salt form. Industrial grades are typically supplied with a purity specification ≥98.0 % (anhydrous basis, determined by non-aqueous titration per USP-NF monograph method) and are accompanied by certificates of analysis covering loss on drying (≤0.5 % after 4 h at 105 °C), residue on ignition (≤0.1 %), and heavy metals as Pb (≤10 ppm). The material is listed under FEMA GRAS 4710 for food use and is manufactured under ISO 22000:2018 food safety management systems when destined for food or pharmaceutical applications.
Production-scale handling of 3-hydroxybenzisothiazole-S,S-dioxide in dedicated powder-processing suites reveals a persistent operational bottleneck: electrostatic charging during pneumatic conveying leads to adhesion on stainless-steel contact surfaces, causing batch weight deviations of up to 2.5 % on lines processing fewer than 50 kg per cycle. This is mitigated by controlled humidification of conveying air to 50 ± 5 % RH and by specifying conveying line velocities below 15 m/s. No explosive dust hazard classification is mandatated under ATEX Directive 2014/34/EU for particle size distributions with a median diameter (D₅₀) greater than 100 µm; however, micronized grades with D₅₀ below 40 µm require a St 1 dust explosion class assessment in accordance with EN 14034-1:2004+A1:2011.
In Watts-type nickel electroplating solutions (NiSO₄·6H₂O 240–300 g/L, NiCl₂·6H₂O 30–50 g/L, H₃BO₃ 35–45 g/L), 3-hydroxybenzisothiazole-S,S-dioxide functions as a Class-II brightener, operating in synergistic combination with Class-I carriers (e.g., 1,4-butyne diol or its ethoxylated derivatives). The minimum effective concentration documented on horizontal cathode pilot cells at 3 A/dm² and 55 °C is 0.3 g/L; above 2.5 g/L, a marked deterioration in throwing power occurs, accompanied by a cathodic current efficiency drop of 4–7 % relative to the additive-free baseline. Hull cell panels (JIS H 8615) run for 5 min at 2 A total current show burn-free bright range extension from 1.8–2.5 cm to 7.0–8.5 cm when saccharin concentration is maintained between 0.8 and 1.5 g/L together with a suitable carrier. In-line monitoring via UV absorbance at 268 nm permits automated replenishment at consumption rates averaging 12–18 g per 10,000 ampere-hours on continuous reel-to-reel lines running steel strip at 2–6 m/min.
The primary decomposition pathway of 3-hydroxybenzisothiazole-S,S-dioxide in acidic aqueous media proceeds via ring-opening hydrolysis to ortho-sulfobenzoic acid and ammonium ions. In a pH 4.0 buffer at 60 °C, first-order rate constants determined by ion chromatography indicate a half-life of approximately 420 h. The accumulation of ortho-sulfobenzoic acid above 0.8 g/L in a production bath induces a measurable shift in the pitting potential on mild steel mandrels: stepwise polarization curves in a 0.5 M Na₂SO₄ supporting electrolyte exhibit a 35 mV anodic shift of the breakdown potential. Routine bath maintenance on automotive bumper plating lines therefore integrates activated carbon treatment every 40–60 operating hours and high-performance liquid chromatography analysis with retention time matching against a certified ortho-sulfobenzoic acid reference standard (≥99.0 % purity) to ensure the decomposition product remains below the threshold.
In plastics pretreatment for electroless nickel on ABS, 3-hydroxybenzisothiazole-S,S-dioxide is employed as a stabilizer in colloidal palladium/tin activation systems. The additive suppresses spontaneous tin(II) oxidation in the accelerator bath, extending bath life from 2–3 weeks to more than 12 weeks when dosed at 0.05–0.15 g/L. This practice is documented in process qualifications under IEC 60068-2-58 for plated-through-hole reliability in printed wiring boards.
Direct substitution of sodium saccharin dihydrate (CAS 6155-57-3) with the free acid form requires accounting for the 14.7 % mass difference attributable to sodium content and hydration water. In a sweetener tablet direct-compression process, switching to the acid form at equivalent sweetness dosage—550 sweetness units relative to sucrose—mandates reformulation of the lubricant system. Blends containing 0.5 wt% magnesium stearate exhibited a 42 % increase in ejection force measured on a rotary tablet press equipped with 10 mm flat-faced tooling and instrumented with 5 kN load cells when the acid replaced the sodium salt, attributed to the absence of the crystalline water that provides die-wall lubrication during compaction. This was confirmed by compaction simulator data at a dwell time of 50 ms: tensile strength determined by diametral compression (ASTM D3967-16) remained within 1.1–1.3 MPa, but residual die-wall stress increased from 2.2 MPa to 3.8 MPa.
The organoleptic threshold for the characteristic bitter-metallic aftertaste of 3-hydroxybenzisothiazole-S,S-dioxide in water is 12–18 mg/L as determined by a trained sensory panel following ISO 13301:2018 triangle test methodology. This aftertaste, arising from the activation of human bitter taste receptors TAS2R43 and TAS2R44, imposes a blending requirement with masking agents—typically acesulfame potassium, cyclamate, or erythritol—at mass ratios varying from 1:0.5 to 1:2 depending on the food matrix. A direct comparison with sodium cyclamate (E952) highlights a critical production planning factor: cyclamate provides a sugar-like temporal profile without the rapid-onset bitterness but requires a bulk density of 0.65–0.85 g/cm³ and a sweetness potency only 30–40 times that of sucrose, versus saccharin’s 300–550 times. The logistical consequence for a 10,000 tonne per annum soft drink line translates to 18–22 fewer pallet deliveries per production campaign when saccharin is formulated in a synergistic cyclamate/saccharin 10:1 blend, a parameter directly influencing warehouse footprint and ISO 14040 life-cycle transport emissions calculations.
| Parameter | Industrial Grade | Food Grade (USP-NF) | Test Method |
|---|---|---|---|
| Purity (anhydrous) | ≥97.0 % | ≥98.0 % | Non-aqueous acid-base titration |
| Loss on drying | ≤1.0 % | ≤0.5 % | USP 〈731〉 |
| Melting point | 226–230 °C | 228–230 °C | USP 〈741〉 Capillary |
| Heavy metals (as Pb) | ≤20 ppm | ≤10 ppm | USP 〈231〉 |
| Arsenic | ≤3 ppm | ≤1 ppm | USP 〈211〉 |
| Particle size (D₉₀) | 200–300 µm | 150–250 µm | Laser diffraction (Malvern) |
In sulfamate nickel electroforming for precision optical tooling, the need for low-stress deposits requires saccharin dosing within a narrow concentration window. Residual stress measured on a spiral contractometer in accordance with ASTM B636-84 shows a transition from compressive −12 MPa to tensile +8 MPa as the saccharin concentration moves from 0.5 g/L to 2.0 g/L in a bath containing nickel sulfamate 400 g/L, nickel chloride 5 g/L, and boric acid 35 g/L operated at 50 °C and pH 4.0. The stress-null point occurs at 0.9 ± 0.05 g/L, a value that must be maintained with a tolerance of ±0.07 g/L over multi-day electroforming runs for x-ray telescope mirror shells where form error must not exceed λ/10 at 632.8 nm.
Published data for the incorporation of 3-hydroxybenzisothiazole-S,S-dioxide as a sulfur-bearing carbonization promoter in acrylic fiber precursors for carbon fiber manufacture is limited. Laboratory-scale thermogravimetric analysis in air at 1 °C/min ramp rate has shown a shift in cyclization exotherm onset from 195 °C to 182 °C when pre-treated with a 0.5 wt% methanolic solution, but replication on a continuous stabilization oven with 12,000 filament tows at production speeds exceeding 3 m/h remains undocumented in peer-reviewed literature.
The free sulfonamide hydrogen of 3-hydroxybenzisothiazole-S,S-dioxide participates in unwanted acid-base reactions with tertiary amine catalysts such as 1,4-diazabicyclo[2.2.2]octane (DABCO) during polyurethane foam production. When dry-blended into a polyether polyol premix containing 0.3 pph DABCO and stored at 40 °C for 72 h, the mixture exhibits a viscosity increase from 850 mPa·s to 1,220 mPa·s measured on a Brookfield viscometer at 25 °C, spindle 4, 20 rpm, indicating incipient crosslinking. This incompatibility is not observed with the sodium salt form, which remains fully ionized in the polyol medium. Process engineers designing metering systems for flame-retardant flexible foams thus specify that only the pre-neutralized sodium or potassium salts be employed where amine-catalyzed systems are present, or alternatively that the acid form be pre-dissolved in the isocyanate component after verifying absence of residual water that would liberate carbon dioxide.
In silver electroplating baths for semiconductor lead frames, the anion of 3-hydroxybenzisothiazole-S,S-dioxide acts as a grain refiner competing with cyanocomplex decomposition products. Bath analysis by cyclic voltammetric stripping at a rotating disk electrode (2,000 rpm) reveals that saccharin concentrations above 1.0 g/L shift the silver deposition peak cathodically by 15–20 mV, modifying the nucleus density from 2 × 10⁹ cm⁻² to 1.2 × 10¹⁰ cm⁻² as counted by chronoamperometric transient analysis using the Scharifker-Hills model. This directly affects wire bond pull strength after thermal aging at 175 °C for 500 h: deposits formed with 1.0 g/L saccharin retain 87 % of initial pull strength versus 62 % for additive-free deposits.
| Property | 3-Hydroxybenzisothiazole-S,S-dioxide | Sodium saccharin dihydrate |
|---|---|---|
| Molecular weight | 183.18 g/mol | 241.20 g/mol |
| Solubility in water at 20 °C | 3.5 g/L | 1,000 g/L |
| pH of 1% aqueous solution | 2.0–2.5 | 6.0–7.5 |
| Crystal water content | None | ~15 wt% |
| Sweetness potency (vs. sucrose) | 550 | 300–450 |
| Compatibility with amine catalysts | Risk of adduct formation | No adverse reaction |
The monohydrate form of 3-hydroxybenzisothiazole-S,S-dioxide, obtained by recrystallization from water below 35 °C, exhibits a distinct X-ray powder diffraction pattern with characteristic peaks at 12.7°, 16.3°, and 25.8° 2θ (Cu Kα radiation). This phase is metastable above 40 °C and reverts to the anhydrous form over 8–12 h at 50 °C in a fluidized bed dryer. Pharmaceutical tableting operations that require precise dose uniformity necessitate control of this phase transition because the true density shifts from 1.62 g/cm³ (monohydrate) to 1.70 g/cm³ (anhydrous), thereby altering volumetric filling in a dosing disk of a rotary capsule filler.
Under EU Regulation (EC) No 1333/2008, 3-hydroxybenzisothiazole-S,S-dioxide is authorized as food additive E954 with maximum use levels specified in Annex II for categories 05.1 through 16. Export documentation for shipments to EU member states must include a batch-specific migration test report performed under EU 10/2011 simulant conditions when the substance is incorporated into polymeric packaging materials. A typical migration limit for the sum of saccharin and its salts is 15 mg/kg food simulant. Non-compliance with this documentation chain has been the second-most frequent cause of border rejection for synthetic sweetener shipments at Rotterdam port inspection posts, based on aggregated Rapid Alert System for Food and Feed (RASFF) notifications between 2018 and 2023. Therefore, manufacturers maintaining ISO/IEC 17025:2017 accreditation for their in-house HPLC-MS/MS method reduce the probability of rejection to below 0.3 %.
