| HS Code | 950774 |
| Product Name | Formaldehyde Solution (Formalin) Veterinary Grade API |
| Chemical Name | Formaldehyde |
| Cas Number | 50-00-0 |
| Molecular Formula | CH2O |
| Molecular Weight | 30.03 g/mol |
| Appearance | Clear, colorless, mobile liquid with a pungent characteristic odor |
| Odor | Pungent and suffocating |
| Solubility | Miscible with water, ethanol, and isopropanol |
| Ph | 2.8 to 4.0 for a 37% aqueous solution |
| Density | Approximately 1.08 to 1.09 g/cm³ at 20°C |
| Specific Gravity | About 1.081 to 1.085 at 25°C |
| Boiling Point | Approximately 96°C for a 37% aqueous solution |
| Freezing Point | Approximately -15°C for a 37% aqueous solution |
| Vapor Pressure | About 0.46 kPa at 20°C |
| Storage Conditions | Store in tightly closed, light-resistant containers at 15-30°C; protect from freezing |
| Stability | Stable when stored under recommended conditions; low temperatures may cause paraformaldehyde precipitation |
| Therapeutic Category | Antiseptic, disinfectant, antimicrobial, and preservative |
| Veterinary Indications | Used as an active ingredient in formulations for disinfection and antimicrobial veterinary medicinal applications |
| Dosage Form Compatibility | Suitable for use in solutions; also applicable as an active or preservative component in tablets, injections, capsules, powders, granules, and premixes |
| Target Species | Cattle, sheep, pigs, poultry, and other animals |
| Incompatibilities | Incompatible with strong oxidizers, strong acids, strong alkalis, gelatin, tannic acid, and heavy metal salts |
| Safety Precautions | Irritating to eyes, skin, and respiratory tract; handle with adequate ventilation and protective equipment |
| Regulatory Status | Veterinary grade active pharmaceutical ingredient for veterinary medicinal product manufacture |
As an accredited Formaldehyde Solution (Formalin) Veterinary Grade API for Tablets / Injections / Capsules / Powders / Granules / Premix / Solutions factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Packaged in 25 kg net HDPE drums with tamper-evident seals, hazard labeling, and safety documentation for veterinary-grade formaldehyde solution. |
| Container Loading (20′ FCL) | 20′ FCL loading of Formaldehyde Solution (Formalin), veterinary grade API, using sealed drums, secured with dunnage, labeled, and segregated safely. |
| Shipping | Shipped as hazardous material UN 1198 (Formaldehyde solution, flammable, toxic). Supplied in sealed, UN-certified HDPE drums/containers with proper hazard labeling and SDS documentation. Transported by ground or freight per IATA/IMDG/ADR regulations. Protect from freezing and excessive heat; keep upright in ventilated area to maintain product integrity. |
| Storage | Store Formaldehyde Solution (Formalin) at 15–30°C in tightly closed, light-resistant containers. Protect from freezing and excess heat, as both promote polymerization and precipitation. Store in a cool, well-ventilated area away from ignition sources, acids, alkalis, oxidizing agents, and incompatible materials. Keep container sealed when not in use, and strictly follow veterinary Good Manufacturing Practices. |
| Shelf Life | Shelf life: 24 months when stored in airtight containers, protected from light, at controlled room temperature. |
In salmonid and cyprinid hatcheries, formaldehyde solution (formalin) veterinary grade is received as an aqueous stock at 36.5–37.5% w/w CH2O with methanol stabilisation typically 6–12% w/w to suppress paraformaldehyde precipitation when stored below 15°C. The stock is not dispensed undiluted; immersion bath preparation occurs in a separate mixing tank constructed of high-density polyethylene or 316L stainless steel, where the stock is metered to 0.15–0.25 mL/L, yielding 60–100 mg/L free formaldehyde. This concentration range is used for external protozoal and monogenean infestations in freshwater finfish when water temperature is maintained above 10°C and below 25°C; above 25°C the risk of gill epithelial necrosis increases sharply. Dissolved oxygen is held at or above 6 mg/L by battery-backed aeration because formaldehyde exerts a measurable chemical oxygen demand, and unionised ammonia is corrected to below 0.02 mg/L NH3 before the bath is started. The exposure window is usually 1–4 h, with the shorter end applied at higher water temperatures or when the batch includes fish showing pre-existing gill lesions. Biological filtration is bypassed for the entire contact period to protect nitrifying biofilm, and the spent bath is neutralised with sodium bisulfite at a molar ratio of approximately 1.1:1 to free formaldehyde before discharge to the site wastewater system. Continuous flow-through raceway application requires a diaphragm metering pump with PTFE and Kalrez seals, coupled to a formaldehyde-specific analyser or redox feedback, because fluctuations in organic matter consume the active molecule and produce poor bath-to-bath reproducibility. Batch-to-batch variance is documented by colorimetric acetylacetone assay or a calibrated formaldehyde-specific electrode before the stock is released for dilution. The veterinary API monograph for the incoming stock must include assay of CH2O content, methanol content, formic acid acidity, and heavy metals before release for dilution; each lot is weighed and the dilution factor recorded so that the final bath concentration can be traced to the batch of origin. Where receiving waters are subject to environmental permits, the discharge limit must be verified case by case, and residual formaldehyde is usually required to be below 1 mg/L after neutralisation.
Fumigating settable eggs in a sealed cabinet with direct air extraction to a wet scrubber begins with a deep enamel or stainless steel reaction vessel charged with 45 mL formalin (37% w/w) and 30 g potassium permanganate per cubic metre of cabinet volume. The oxidation reaction is delayed for 30–60 s and then releases gaseous formaldehyde rapidly, with peak cabinet concentrations typically in the range of 15–25 ppm; the operator must leave the room before the charge is poured. Cabinet relative humidity is held at 60–70% and air temperature at 20–25°C, because lower relative humidity slows eggshell penetration and higher humidity promotes condensation that can kill blastoderm cells. The exposure cap is 20 min, after which forced extraction reduces airborne formaldehyde to 0.75 ppm before re-entry. In the United States, the permissible exposure limit under 29 CFR 1910.1048 is 0.75 ppm as an 8-h time-weighted average, with a short-term exposure limit of 2 ppm over 15 min; monitoring with a calibrated electrochemical sensor or DNPH derivatisation tube is required when the cabinet is located in an occupied hatchery area. The wet scrubber is charged with sodium sulfite solution at pH 8–9 to capture exhausted formaldehyde, and the scrubber liquid is renewed after each fumigation cycle. Embryo toxicity is not a linear function of concentration; a drop in hatchability can occur when condensate forms on the cuticle, therefore the fumigation chamber is operated with positive pressure at the transfer hatch and negative pressure inside the fumigation envelope. Spent potassium permanganate solids are collected and treated as oxidising waste, not mixed with organic debris. If formalin fogging is used instead of potassium permanganate oxidation, the diluted solution is 0.5–1.0% v/v and applied by cold fogger at 10 mL/m³, but this method is not equivalent to gas fumigation for deep-clean disinfection of stacked setters and must be validated against actual egg surface microbial counts.
Because methenamine tablets depend on hydrolysis in acidic urine to release formaldehyde at the site of action, formalin serves as the starting aldehyde for hexamethylenetetramine synthesis. The condensation reaction uses 6 mol formaldehyde per 4 mol ammonia; ammonia gas is sparged into formalin under controlled temperature 30–50°C and pH 7.0–8.0, and the resulting methenamine is crystallised from methanol after vacuum evaporation. The reactor is glass-lined because the condensation is exothermic, and cooling is supplied by circulating brine to hold the reaction mass inside the specified temperature window. Residual free formaldehyde in the dried methenamine intermediate is controlled below 0.1% w/w, and residual ammonium ion is limited because both alter tablet colour and physical stability. The methenamine hippurate or methenamine mandelate is then milled to ≤100 µm and direct-compressed into 500 mg or 1 g tablets using microcrystalline cellulose and sodium starch glycolate. Tablet hardness is normally set between 8–14 kp; disintegration is tested in 0.1 N HCl at 37°C and must occur within 30 min. Hard gelatin capsules may be filled with the same milled powder at 500 mg for veterinary compounding, and oral granules or sachets are blended with lactose monohydrate and colloidal silicon dioxide to improve flow. The active entity only releases formaldehyde when the dosage form encounters urine at pH below 5.5; the hydrolysis follows first-order kinetics, and the antibacterial effect is determined by the free formaldehyde concentration in urine rather than plasma exposure. For this reason, some protocols co-administer ammonium chloride or methionine to acidify the urine and prevent premature degradation in the proximal gastrointestinal tract. Feline patients are not suitable candidates for this mechanism at canine-equivalent doses because of the risk of chemically induced cystitis, and the prescribing veterinarian must verify urine pH before dose escalation. For direct incorporation of formalin into animal feed premixes, published data for this specific configuration is limited, and regulatory acceptance varies by jurisdiction; formalin-sourced methenamine is the more established oral route where urinary antisepsis is indicated.
After continuous disc-stack centrifugation and depth filtration of bacterial culture harvest, formalin is metered into the inactivation vessel at 0.3–0.5% v/v final concentration for clostridial toxoids, equivalent to 1.1–1.85 g/L free formaldehyde; enveloped viral antigens are treated at 0.05–0.2% v/v, equivalent to 0.185–0.74 g/L. The lower end of the viral range is selected when over-inactivation degrades neutralising epitopes, particularly for paramyxovirus and lentivirus antigens. The vessel is constructed of 316L stainless steel with bottom-mounted magnetic drive agitation, and the jacket maintains 37±1°C throughout the 24–72 h campaign. pH is held at 7.0–7.4 with phosphate buffer, and the reaction is not assumed linear after 24 h because antigen-specific degradation and residual infectivity decline at different rates. Pilot inactivation studies for each antigen lot establish the minimum time for a reproducible 3-log reduction in live titre under worst-case loading. Inactivation kinetics are followed by live-virus titration on cell culture and concurrently by residual formaldehyde measurement using chromotropic acid derivatisation. Residual free formaldehyde is neutralised with sterile sodium metabisulfite solution at 0.1–0.2% w/v, but the neutralising dose must be confirmed by amperometric titration rather than fixed volume because excess metabisulfite can damage toxoid antigenicity. Final vaccine batches are tested against the free-formaldehyde limit in Ph. Eur. 2.4.18, commonly 0.02% w/w unless a higher residue is explicitly justified for the target species and route. Injection products containing formalin-inactivated antigens require a post-neutralisation hold step and sterile filtration through 0.22 µm membrane filters, and the temperature during neutralisation should not fall below 4°C if the antigen is cold-labile. This application is the most restrictive in terms of API purity because formic acid and methanol in the formalin stock can transfer into the injectable product and contribute to visual haze or pyrogen load.
A 2 m long footbath charged with formalin at 2–5% v/v of the 37% w/w stock, equivalent to 0.74–1.85% w/w active formaldehyde, is used in dairy herd digital dermatitis programmes to reduce spirochete transmission on walk-through concrete in milking parlours. The bath volume is approximately 180–200 L at 0.15 m liquid depth and 0.6 m width; the solution is refreshed after 150–200 cow passes or when settled organic solids exceed 5% v/v. Pre-bath hoof washing with plain water reduces slurry loading, but the wash water must drain away from the bath to prevent dilution drift below 2%. Contact time is determined by cow walking speed, usually 10–15 s per pass. Daily use at 5% v/v can produce hoof and pastern irritation, so most protocols alternate formalin with copper sulfate or zinc sulfate on 2–3 days per week. Barn air at operator height remains below 0.3 ppm time-weighted average during the milking shift, which requires mechanical ventilation of 6–10 air changes per hour in the footbath room. Storage of the concentrated formalin stock must be separated from the milking tank and from feed storage to prevent accidental oral exposure.
| Application | Formalin stock dilution | Active CH2O | Exposure/contact | Critical limit |
|---|---|---|---|---|
| Salmonid immersion bath | 0.15–0.25 mL/L | 60–100 mg/L | 1–4 h | DO ≥ 6 mg/L; NH3 < 0.02 mg/L |
| Hatching egg fumigation | Undiluted + 30 g KMnO4 per m³ | 15–25 ppm gas | 20 min | RH 60–70%; 20–25°C |
| Dairy footbath | 2–5% v/v | 0.74–1.85% w/w | 10–15 s | Refresh after 150–200 passes |
| Clostridial toxoid inactivation | Metered to reactor | 0.3–0.5% v/v formalin (1.1–1.85 g/L CH2O) | 24–72 h at 37°C | Residual free CH2O ≤ 0.02% w/w |
Maintain dedicated low-pressure spray equipment for 10% v/v formalin surface decontamination in swine and poultry housing after depopulation, when porous concrete and wood require deeper penetration than quaternary ammonium compounds provide. The room is sealed and sprayed at 0.4–0.5 L/m³ using an orchard-type sprayer with a flat-fan nozzle; air temperature is held at 21–25°C and relative humidity at 60–70% for 24 h. Entry is prohibited until airborne formaldehyde falls below 0.75 ppm and the air exchange system has completed at least three room volume replacements. Where virucidal claims are required, test data under EN 14675:2015 should support the 24 h contact time for the target enveloped porcine and avian viruses. Wastewater collected from the decontamination area is oxidised with sodium hypochlorite at a 1.5:1 molar ratio to formaldehyde before release, but the two chemicals must never be mixed in the supply line because the oxidation reaction is strongly exothermic and can generate volatile chlorine species under acidic conditions. Repeated exposure of stainless steel surfaces to formalin vapour can produce weld pitting if the steel is not passivated with nitric acid after each campaign. The decontamination application is physically separated from API storage and pharmaceutical manufacturing to prevent cross-contamination of the veterinary grade stock with environmental residues.
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Formaldehyde Solution (Formalin) Veterinary Grade API for Tablets / Injections / Capsules / Powders / Granules / Premix / Solutions is a stabilized aqueous concentrate in which the active carbonyl species is present at 36.5–37.5% w/w formaldehyde (CH2O), with methanol as a polymerisation inhibitor at 10–15% w/w and the balance being water. The solution is clear, colorless, and pungent, with a density of 1.080–1.090 g/mL at 20°C, a pH between 2.8 and 4.0, and a boiling range beginning near 96°C. The molecular mass of the monomer is 30.03 g/mol, and the CAS number is 50-00-0. The veterinary-grade API is distinguished from industrial 37% formalin by the compendial release controls for formic acid at not more than 0.05% w/w, heavy metals at not more than 5 ppm by Ph. Eur. 2.4.8, sulfated ash at not more than 0.1% w/w, and methanol content retained inside the 10–15% w/w band. Industrial formalin may meet total aldehyde strength but is not released to a pharmacopoeial monograph, making it unsuitable for wet granulation, medicated premix dilution, aqueous oral-solution compounding, and vaccine inactivation where trace aldehyde-related impurities and metal residues are controlled.
Methanol is not an inert diluent in this product. It retards the formation of paraformaldehyde, a low-solubility polyoxymethylene that appears as a white film at the liquid–headspace interface when the solution is stored below 15°C. Within 15–25°C, the 10–15% w/w methanol content keeps the solution pumpable and filterable for process use. Formic acid is generated by slow air oxidation and by the Cannizzaro disproportionation of formaldehyde under alkaline microenvironments. Limiting formic acid to 0.05% w/w prevents a significant downward pH drift and reduces variability when the API is added to buffered vaccine fluids. Methanol is also a Class 2 residual solvent under ICH Q3C, with a permitted daily exposure of 30 mg/day and a concentration limit of 3000 ppm in the finished drug product; the limit applies to the dosage form, not to the concentrate. The formaldehyde assay is commonly performed by sodium sulfite titration, in which one equivalent of sodium hydroxide is released per equivalent of formaldehyde and titrated with 0.5 N sulfuric acid. Methanol content is verified by headspace gas chromatography using Ph. Eur. 2.2.28, while formic acid may be determined by titrimetric or ion-exclusion chromatographic release methods. A supplier certificate of analysis should document batch assay, methanol content, formic acid, heavy metals, sulfated ash, density, and identification.
The comparative profile below separates the veterinary-grade API from industrial formalin and solid paraformaldehyde. Values are representative release targets and do not replace a batch-specific certificate of analysis.
| Parameter | Veterinary-grade formalin API | Industrial 37% formalin | Paraformaldehyde solid |
|---|---|---|---|
| Total HCHO content | 36.5–37.5% w/w | 37–40% w/w | 91–95% w/w as releasable HCHO |
| Methanol stabilizer | 10–15% w/w | 0–15% w/w depending shipping grade | <1% w/w |
| Formic acid | ≤0.05% w/w | often 0.05–0.2% w/w | not routinely controlled |
| Heavy metals | ≤5 ppm by Ph. Eur. 2.4.8 | not routinely controlled | not routinely controlled |
| Physical form | clear liquid | clear liquid | free-flowing flakes or granules |
| Introduction to solid dosage forms | metering pump and spray lance in wet granulation | bulk liquid transfer only; not permitted in registered drug process | screw feeder or dry sift-in |
| Release standard | USP 43–NF 38 / Ph. Eur. monograph | technical grade specification only | technical grade or fumigation grade |
For wet granulation, the solution is introduced by positive-displacement or peristaltic metering pumps with delivery accuracy of ±1.0% into a high-shear granulator or ribbon blender with 316L stainless steel contact surfaces and EPDM or PTFE gaskets. The liquid is sprayed onto a moving powder bed rather than discharged into a static bed; the nozzle should be placed just above the product surface and the vessel should be closed under extraction because formaldehyde is volatile at ambient processing temperature. No universal binder-to-liquid ratio can be stated across all formulations: starch, microcrystalline cellulose, calcium carbonate, and proteinaceous binders respond differently to the solution, and the wet-mass endpoint must be established on the specific granulator model by torque or power-consumption monitoring. After granulation, the wet mass is dried immediately to the loss-on-drying target in the batch master record. For liquid dosage forms, the concentrate is diluted into purified water or buffer at 15–25°C in a closed, stirred vessel with vapor extraction; addition to an open vessel with high-shear agitation can reduce the measured assay through evaporation losses.
Compared with solid paraformaldehyde, the liquid API eliminates solids handling, dust exposure, and the need for depolymerization before active formaldehyde is available. However, the water load of 47.5–53.5% w/w and the methanol content require a drying step after wet granulation, whereas paraformaldehyde can be dry-blended and then depolymerized under heat or alkaline conditions. The choice between the liquid and solid source is therefore a mass-balance and process-drying decision, not simply a substitution by equivalent aldehyde content. Compared with technical disinfectant-grade formalin, the veterinary-grade liquid is the only form appropriate for registered drug manufacturing because the release certificate addresses pharmacopoeial identity, purity, and stabilizer limits. Substitution without qualification violates cGMP under 21 CFR 211 and can introduce uncontrolled residual solvent and impurity profiles.
Cold storage is the primary physical stability boundary for formalin veterinary grade. Although methanol at 10–15% w/w lowers the paraformaldehyde precipitation threshold, it does not eliminate precipitation under cold-chain warehouse excursions. At 2–8°C, drums may form a white interfacial film or a settled deposit of polyoxymethylene oligomers. Light haziness may resolve after warming to 20–25°C with gentle recirculation, but high-molecular-weight material may not and should not be forced through a 0.22 µm filter because the membrane can blind and the filter train can become a localized source of concentrated aldehyde exposure. If a drum has been exposed to cold storage, the contents should be warmed to 20–25°C and assayed before use; visual clarity alone is not a release test. During spray application of the API into a ribbon blender or horizontal mixer, the liquid is delivered through a 0.3–0.5 mm stainless-steel nozzle at the moving powder-bed surface. Published equipment-specific spray-rate data for veterinary premix formulations is limited; the validation variable is not a fixed flow rate but a consistent formaldehyde assay across stratified samples collected at 10 locations after a defined mixing interval. Blend uniformity is confirmed by a validated derivatization or titration method with acceptance criteria established in the analytical method validation, not inferred from the bulk liquid assay alone.
Injection-grade biological use of formaldehyde solution is not the direct injection of the concentrate; the material is diluted into a closed, temperature-controlled inactivation vessel containing buffered aqueous medium. Phosphate-buffered saline or citrate buffers are preferred over Tris because Tris contains primary amines that deplete free formaldehyde and alter reaction kinetics. The reaction of formaldehyde with amino groups on viral or bacterial antigens is pH- and temperature-dependent; at pH 7.0–7.8 and controlled mixing, inactivation rate can be predicted for a given antigen matrix only when free formaldehyde remains in excess throughout the contact period. Medium components such as ammonium salts, amino acids, and sodium sulfite depress free aldehyde availability and invalidate any nominal inactivation cycle. After the fixed inactivation time, free formaldehyde is quenched with sodium metabisulfite or an equivalent aldehyde scavenger, and residual free formaldehyde is measured by derivatization with 2,4-dinitrophenylhydrazine and HPLC. The final bulk must meet the limit set in the marketing authorization; that limit is product-specific and cannot be inferred from the concentrate assay. Aseptic addition of the API through a 0.22 µm PVDF or PTFE filter is used where the downstream biological process requires a low bioburden concentrate, but filtration does not convert technical-grade formalin into pharmacopoeial material.
Tablet and capsule formulations rarely use formaldehyde solution as a direct-compression ingredient. The liquid is introduced in wet granulation when the formulation requires a reactive processing aid or when the final dosage form must contain a defined residual aldehyde function. Direct addition to a dry blend is unsuitable because the water load and the carbonyl reactivity create localized high-moisture regions and can initiate condensation reactions with hydroxyl, amine, and sulfhydryl excipients. If the finished product is enclosed in gelatin capsules, free formaldehyde becomes a dissolution-risk variable. Gelatin crosslinking by formaldehyde is accelerated at pH above 6.0, at low shell moisture, and at elevated storage temperature; the resulting crosslinked film can slow shell rupture and cause variable release in USP <711> dissolution testing. For this reason, formaldehyde-sensitive capsule products require aldehyde scavengers or alternative shell polymers such as HPMC. The residual free formaldehyde in the final dosage form should be specified and justified by stability, dissolution, and impurity data submitted in the veterinary marketing authorization.
Formaldehyde is incompatible with ammonia, primary and secondary amines, sulfite, bisulfite, sulfide, and hypochlorite. With ammonia, the reaction forms hexamethylenetetramine and consumes the aldehyde; with sulfite or bisulfite, it forms hydroxymethanesulfonate adducts and reduces free formaldehyde before the intended unit operation. These reactions are fast and exothermic at high concentration, so the concentrate should not be premixed with alkaline reagents or reducing agents in a closed drum. In a tablet or premix blend containing amine-functional excipients, the sequence of addition should avoid direct contact between the concentrate and the amine-rich component; the solution is first dispersed onto an inert carrier such as microcrystalline cellulose or starch. If the formulation contains ammonium chloride or other ammonia-generating effervescent couples, the aldehyde should be segregated through process design because hexamethylenetetramine formation can create a crystalline impurity with different solubility and degradation properties. For gelatin-containing systems, added formaldehyde scavengers such as glycine, lysine, or metabisulfite may be used only after confirming that the scavenger does not deplete the intended free-formaldehyde specification in the product; the scavenger level is determined experimentally, not from stoichiometric assumption alone.
For analytical verification of the delivered dosage form, free formaldehyde in premix or granulated matrices is often quantified by derivatization. 2,4-dinitrophenylhydrazine reacts with aldehydes under acidic conditions to form hydrazones that can be separated by reverse-phase HPLC with ultraviolet detection at 360 nm. The method is suitable for aqueous and solid matrices when extraction recovery is validated. Acceptance limits for the final dosage form are set by the registration dossier and are not automatically equal to the assay of the concentrate; loss of volatile aldehyde during drying and reaction with excipients must be characterized in process validation. If published data for a specific veterinary premix is limited, the applicant should generate a mass balance for formaldehyde across blending, drying, and stability storage using the same derivatization method and a validated extraction procedure.
Material handling is governed by an occupational exposure limit of 0.3 ppm as an 8-hour time-weighted average and 0.6 ppm as a short-term limit under Directive (EU) 2019/983, with local exhaust ventilation and drum-level fume extraction. The concentrate should be stored in high-density polyethylene, 316L stainless steel, or glass-lined vessels; unlined carbon steel, copper, and aluminum are incompatible because formic acid and formaldehyde promote corrosion and metal ion release. The product is classified as Carc. 1B and Muta. 2 under CLP; this classification does not prohibit use as a veterinary API, but it imposes closed-system handling, documented exposure controls, and residue management. Substitution of industrial formalin into a registered veterinary process is not acceptable without full change control, because the absence of compendial release limits for formic acid, heavy metals, and stabilizer content can shift degradation behavior and impurity burden. When published data for a specific dosage form is limited, the substitution risk is assessed by forced degradation and use-point assay verification rather than by total aldehyde strength alone.
