| HS Code | |
| Productname | Citric Acid (CA) |
| Chemicalformula | C6H8O7 |
| Molecularweight | 192.12 g/mol |
| Casnumber | 77-92-9 |
| Einumber | E330 |
| Appearance | White crystalline powder |
| Odor | Odorless |
| Taste | Sour, acidic |
| Density | 1.665 g/cm³ |
| Meltingpoint | 153 °C |
| Boilingpoint | Decomposes at 175 °C |
| Solubility | Soluble in water and ethanol |
| Ph | 1.8 (0.1 M aqueous solution) |
| Pka | 3.13, 4.76, 6.40 |
| Purity | 99.5–100.5% |
| Grade | Food, pharmaceutical, and technical grades |
| Storage | Cool, dry, well-ventilated area |
| Hs Code | 2918140000 |
As an accredited Citric Acid CA factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Citric Acid CA is supplied in 25 kg multi-wall paper bags with polyethylene liners, palletized and shrink-wrapped for industrial shipping. |
| Container Loading (20′ FCL) | 20′ FCL loading for Citric Acid CA: palletized bags, dry container, secured stowage, even weight distribution, clean, compliant commodity labeling. |
| Shipping | Citric Acid (CA) is generally non-hazardous for transport and not classified as dangerous goods under DOT/IMDG/IATA. Ship in clean, dry, sealed, compatible containers labeled with the product name. Protect from moisture, heat, and contamination. No special UN number or hazard class required; follow local regulations. |
| Storage | Store citric acid (CA) in a cool, dry, well-ventilated area away from direct sunlight, heat, and moisture. Keep containers tightly closed, clearly labeled, and upright. Separate from strong oxidizers, bases, and incompatible materials. Prevent dust generation and avoid contact with eyes, skin, and respiratory tract. Maintain good housekeeping; do not store near food, drink, or animal feed. |
| Shelf Life | Citric acid (CA) shelf life: about 2–3 years when stored cool, dry, tightly sealed, away from moisture, heat, and contaminants. |
In carbonated beverage manufacturing, citric acid anhydrous is received as a crystalline solid with a mean particle size commonly specified between 100 µm and 1,000 µm and dissolved into demineralized water to form a 50% w/w stock solution at 20–25°C in a 316L stainless steel mixing tank equipped with a side-entry high-shear mixer operating at 1,200–1,500 rpm for 15–20 min. The applicable compliance boundary for beverage-grade citric acid includes FDA 21 CFR 184.1033 GRAS status, EU Regulation (EC) No 1333/2008 Annex II for additive E330, the current Food Chemicals Codex monograph, and identity specifications aligned with JECFA; heavy metal and arsenic limits are tested per the cited compendial methods. Finished beverage addition rates for citric acid anhydrous generally fall between 0.10% and 0.40% w/w, producing a process liquid pH of 2.7–3.5; the exact dose is set by total titratable acidity, target acid-to-sugar ratio, and the buffer capacity of any juice or botanical extract in the formulation. In downstream production, the 50% w/w stock solution is dosed into the syrup batch through an electromagnetic flowmeter and servo-driven diaphragm pump after the syrup has passed through a plate heat exchanger; the syrup is then deaerated, mixed with treated water, and carbonated at 0–5°C to a carbon dioxide content of 3.0–4.0 g/L before counter-pressure filling. Citric acid additionally chelates trace iron and copper at 0.05–0.15% w/w, limiting oxidative off-taste formation during shelf life, with retained-pack testing by inductively coupled plasma mass spectrometry used to confirm metal ion control. Terminal product types treated by this route include carbonated soft drinks, fruit-flavored beverages, sports and electrolyte drinks, and dilutable syrup concentrates.
Because anhydrous citric acid begins to absorb atmospheric water above approximately 70% relative humidity, effervescent granulation suites are generally conditioned to 25°C and 25–30% relative humidity, with compressed air dried to a dew point of -20°C or lower and granulation equipment surfaces maintained above the process dew point to prevent surface condensation. The formulation addition ratio for citric acid anhydrous typically ranges from 20% to 45% w/w of the core tablet mass, combined with sodium bicarbonate at 1.00 g of citric acid to 1.25–1.40 g of sodium bicarbonate, reflecting the stoichiometric demand of 1.31 g of sodium bicarbonate per gram of anhydrous citric acid for complete neutralization of the three carboxyl groups. The applicable compliance boundary includes the Ph. Eur. monograph 0455 for citric acid monohydrate and the corresponding USP-NF monograph for citric acid, with elemental impurities controlled under ICH Q3D because effervescent products are oral dosage forms; residual solvent and water content are managed through granule drying and in-process loss-on-drying checks. Production is conducted by wet granulation in a fluid-bed granulator with dehumidified inlet air at 30–40°C, using anhydrous ethanol or isopropanol as the binder rather than water; granules are dried to a loss-on-drying below 0.2%, screened to 0.150–0.500 mm, and lubricated with sodium benzoate and polyethylene glycol before compression. On a rotary tablet press operating at 20–60 rpm, compression force is held at 15–25 kN to yield tablet hardness of 50–90 N, with disintegration time in 200 mL water at 20°C below 3 min when tested according to Ph. Eur. 2.9.1. Process failure modes include capping and surface pitting when granule moisture exceeds 0.5%; calcium carbonate is excluded from these systems because calcium citrate precipitates on the tablet surface and prolongs disintegration. Terminal product types include effervescent analgesic tablets, vitamin C tablets, electrolyte replacement tablets, and denture-cleaning tablets.
At cold-process cosmetic manufacturing temperatures, citric acid monohydrate is pre-dissolved in the water phase at 0.5–2.0% w/w before pH adjustment, while the final concentration in rinse-off systems is typically 0.1–0.5% w/w, reducing pH from 6.8–7.2 to 4.5–5.5 and chelating residual iron and copper at 0.05–0.2% w/w. The regulatory frame for cosmetic use falls under EC 1223/2009, where citric acid functions as a permitted pH adjuster and chelating agent, while preservation efficacy of the finished formulation is evaluated according to ISO 11930:2019 challenge testing and batch release includes pH, heavy metal, and microbial limits. In a vacuum emulsifier with counter-rotating anchor and disperser blades, the citric acid solution is added to the water phase at 25–35°C after carbomer dispersion but before neutralization; pH is monitored with a calibrated electrode using pH 4.00 and 7.00 buffer solutions. When citric acid is dosed before high-molecular-weight carbomer hydration is complete, final viscosity at 20°C measured by a Brookfield RV spindle at 20 rpm can drop by 10–20%, so addition sequencing is fixed as a production control point. The chelating function is particularly relevant in surfactant systems sensitive to iron-catalyzed oxidation, where citric acid binds transition metals and stabilizes color and fragrance over storage at 45°C for 12 weeks. Terminal product types include sulfate-free shampoos, body washes, skin lotions, and alpha-hydroxy acid toners, where citric acid also stabilizes ascorbic acid and related acid systems.
Circulation loops used for descaling carbon steel heat exchangers are charged with a 6–10% w/w citric acid solution prepared in demineralized water and adjusted to pH 2.0–2.5; the working temperature is held at 60–80°C and circulation velocity is maintained at 1.5–2.4 m/s through a 316L stainless steel positive displacement pump. Corrosion inhibition is required for carbon steel substrates and is evaluated by immersion of pre-weighed coupons according to ASTM G31-21, with corrosion rates compared against an uninhibited citric acid baseline before field cleaning; acceptable corrosion loss is site-specific and depends on acid concentration, temperature, and inhibitor type. The industrial cleaning step is governed by site discharge permits and REACH registration for citric acid as an industrial chelating agent; cleaning performance is monitored through dissolved iron and calcium measurements by spectrophotometry, and spent acid is neutralized to pH 6.0–9.0 before release. Scale composition is analyzed by X-ray diffraction before selecting citric acid, because calcium carbonate and iron oxide scales respond to citrate chelation, whereas sulfate and silicate scales may require mechanical removal or alternative chemistries. After the acid circulation interval, the system is flushed with 0.5% w/w sodium bicarbonate solution until pH exceeds 8.5, followed by passivation with 0.1–0.5% w/w sodium nitrite or an approved passivator for 30–60 min at 40–50°C. Aluminium, zinc, and galvanized steel are incompatible with this method due to rapid citrate attack; the upper temperature limit is 80°C to prevent excessive inhibitor decomposition and to avoid stress corrosion cracking in chloride-contaminated stainless steel equipment. Terminal product types treated on this basis include shell-and-tube heat exchangers, boiler tube circuits, evaporators, and cooling tower heat exchange surfaces.
Ready-mix concrete plants in hot-weather operations commonly dose citric acid monohydrate as a 10–30% w/w aqueous solution into the batch water, at an addition of 0.1–0.3% by weight of cement (bwoc); this retards initial setting by 2–5 h at 25–35°C when measured according to ASTM C191. The retardation mechanism is dominated by citrate adsorption onto calcium-silicate-hydrate nuclei and chelation of calcium ions in the pore solution, which suppresses early hydration kinetics without eliminating final strength development when the dosage remains inside the specified band. For concrete admixtures, the performance envelope is verified against ASTM C494/C494M Type B or Type D criteria; for oil-well cementing, thickening-time measurements follow API RP 10B-2 or the relevant API Recommended Practice for the specific slurry class. The solution is introduced through the plant’s automated dosing skid and mixed in a twin-shaft compulsory mixer for 60–120 s; slump is checked to ASTM C143/C143M, and compressive strength cylinders are cast and cured for 1, 7, and 28 days under ASTM C39/C39M. Dosages above 0.5% bwoc can extend final set beyond 24 h and reduce early-age compressive strength; calcium chloride accelerators are avoided in the same mixture because calcium citrate precipitation may generate uncontrolled setting behaviour and diminish water-reducing effectiveness. Published data for the precise retardation response with supplementary cementitious materials at varying water-to-cement ratios is limited, so plant trials are required before full-scale production. Terminal product types include ready-mix concrete for hot-weather placements, oil-well cement slurries, and grouts requiring extended pumpability.
Polyamide thin-film composite reverse osmosis elements are cleaned with a 2% w/w citric acid solution adjusted to pH 2.3–2.8; the cleaning skid maintains a low pressure of 0.4–0.6 MPa, a crossflow velocity of 2–3 m/s, and a temperature of 25–35°C for 30–60 min per stage. Citric acid is effective for removal of iron oxide and calcium carbonate scale but is not effective for silica, barium sulfate, or organic biofilm; published data for specific membrane fouling configurations is limited, and cleaning protocols are therefore validated on pulled elements or side-stream modules before train-wide application. The acid-cleaning step is followed by a high-pH cleaning step if organic fouling or biological activity is present. For potable water systems, the chemical used in this service must comply with NSF/ANSI/CAN 60; membrane performance before and after cleaning is tracked using normalized permeate flow, salt passage, and differential pressure according to ASTM D4194. During circulation, pH is continuously monitored and adjusted with ammonia or additional citric acid to maintain the target band; spent cleaner is neutralized to pH 6.0–9.0 before disposal, and the train is flushed with permeate at 0.2–0.3 MPa for 15–30 min until conductivity returns to baseline. Cellulose acetate membranes are not exposed to citric acid below pH 4.5 because hydrolysis of the polymer backbone accelerates; the cleaning skid uses 316L stainless steel components to tolerate the acidic environment and chloride content of the source water. Terminal product types treated by this procedure are spiral-wound polyamide reverse osmosis elements in desalination, boiler feedwater, and industrial water reuse trains.
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Citric Acid CA is an anhydrous citric acid grade supplied as white crystalline powder or granular solid. The CA designation is a supplier-specific identifier for the anhydrous form, corresponding to compendial monographs for Citric Acid Anhydrous USP, FCC, BP, and Ph. Eur. The molecular formula is C6H8O7, with CAS 77-92-9, EINECS 201-069-1, and molar mass 192.12 g/mol. The FCC monograph establishes assay at 99.5–100.5% on the anhydrous basis and water at ≤0.5%. Sulfate is limited to ≤150 ppm, oxalate to ≤0.036%, lead to ≤1 mg/kg, arsenic to ≤1 mg/kg, and residue on ignition to ≤0.05%. The product is listed as generally recognized as safe under 21 CFR 184.1033 and as E330 in Regulation (EC) No 1333/2008. A 1% aqueous solution exhibits a pH of approximately 2.2; pKa values in dilute aqueous solution at 25°C are 3.13, 4.76, and 6.40.
The anhydrous specification is selected when low moisture contribution or dry blending is critical. Manufacturer technical bulletins commonly report loose bulk density in the range 0.80–1.00 g/cm³ and tapped density up to 1.10 g/cm³. Sieve distribution differs by granulation; fine powder grades are used for dry mixes, while granular grades reduce dusting in conveying. Published data for this specific configuration is limited and should be confirmed against the supplier certificate of analysis.
Storage stability is dominated by hygroscopicity and caking rather than chemical decomposition. The anhydrous crystal lattice absorbs moisture from air; exposure to relative humidity above 60% for extended periods produces surface caking and flow interruptions in rotary valves and screw feeders. Production-scale dry handling with dilute-phase pneumatic conveying often generates fines below 100 µm; when conveying air humidity exceeds 60% RH, filter bags and receiver walls accumulate tenacious residue. Equipment suppliers specify dried air purge with dew point below -20°C for closed-loop conveying. Silos and hoppers constructed from 316L stainless steel or epoxy-lined carbon steel are used; unlined carbon steel is not recommended because acidic dust with condensed moisture can initiate pitting corrosion.
Thermal data indicate melting at 153°C and decomposition above approximately 175°C. This limits hot-melt compounding and high-temperature dry blending above the decomposition threshold. The material is not classified as thermally unstable under ambient storage; however, batch-to-batch variance in caking behavior is observed when pallets are stored in non-climate-controlled warehouses in coastal regions. Stability protocols for pharmaceutical applications follow compendial storage conditions, with desiccant-lined packaging and heat-sealed polyethylene liners.
The dissolution of anhydrous citric acid differs from the monohydrate because the anhydrous crystal must first hydrate before full solvation. This additional enthalpy contribution is measurable in large make-up tanks. Aqueous solubility at 20°C is approximately 59.2 g/100 mL, rising steeply with temperature; concentrated stock solutions therefore require heated make-up tanks and jacketed piping. A 30% w/w solution remains stable at 20°C, while higher concentrations may crystallize during line stops if temperature drops.
In beverage syrup rooms, citric acid is frequently predissolved as a 50% w/w solution using hot water and then polished through 20 µm cartridge filters before metering. The acidification curve is a function of the triprotic dissociation sequence; the first two carboxyl groups dominate pH depression in the beverage-relevant range of pH 2.5–3.5. Equipment for dissolution is specified in polypropylene, 316L stainless steel, or fiberglass-reinforced plastic. Avoid contact with mild steel, particularly at temperatures above 40°C.
In acidified vegetable and fruit processing, Citric Acid CA is added as a dry powder or predissolved solution to depress pH below 4.6, which is the critical boundary for inhibiting Clostridium botulinum growth in thermally processed acidified foods. The addition rate is product-dependent and is determined by measuring equilibrium pH after thermal processing, not solely by titration. In high-sugar fruit spreads, citric acid is dosed after cooking as a 50% w/w solution to initiate pectin gelation; direct dry addition into the hot vessel can produce localized gel fractures and uneven acid distribution. Continuous dosing skids use magnetic-flow meters and pH feedback loops.
In dairy protein beverages, the same acidulant is used more cautiously because micellar casein destabilizes at pH 4.6 and below. Citric Acid CA is therefore added at the final batching stage with high-shear dispersion, and the pH is maintained above the isoelectric point unless the formulation is designed as acidified milk. In beverage concentrates, citrate also sequesters trace Fe³⁺ and Cu²⁺, reducing oxidative off-flavor development. The chelation of Fe³⁺ is significant below pH 4.0; above pH 7.0, citrate chelation capacity is reduced.
In cement hydration control, Citric Acid CA is used as a set retarder. In ordinary Portland cement systems, additions of 0.1–0.3% by mass of cement are commonly reported to extend initial set to 4–6 h at 20°C; overdosing above 0.5% can delay final set beyond 24 h and reduce early compressive strength. The mechanism is adsorption onto tricalcium aluminate and calcium silicate hydrate surfaces, suppressing nucleation. The exact threshold is cement-specific and requires calorimetric testing according to ASTM C1702 or equivalent isothermal calorimetry. Published data for this specific configuration is limited; no single dosage can be transferred across cement types without trial mixes.
In oilfield acidizing, Citric Acid CA is added to hydrochloric acid as an iron-control agent at loadings determined by dissolved iron concentration. The citrate chelates Fe³⁺ as the acid spends and pH rises above 2.0, preventing ferric hydroxide precipitation in the formation. In high-temperature wells above 120°C, citric acid may undergo thermal decomposition and its chelation capacity declines; published data for this specific configuration is limited and requires flowback ion analysis.
In effervescent granulation, Citric Acid CA is combined with sodium bicarbonate or sodium carbonate. The anhydrous grade is preferred because the monohydrate can initiate premature reaction during storage and wet granulation. Granulation is carried out in fluid-bed equipment or high-shear mixers with low moisture content; relative humidity in the granulation suite is maintained below 30%. The effervescent reaction produces trisodium citrate, water, and carbon dioxide; the stoichiometric acid-to-carbonate ratio is 1:3 for complete neutralization.
| Parameter | Limit | Reference/Method |
|---|---|---|
| Assay | 99.5–100.5% | FCC / Ph. Eur. |
| Water | ≤0.5% | Karl Fischer titration |
| Sulfate | ≤150 ppm | Compendial method |
| Oxalate | ≤0.036% | Compendial method |
| Lead | ≤1 mg/kg | ICP-MS after digestion |
| Arsenic | ≤1 mg/kg | Hydride AAS |
| Residue on ignition | ≤0.05% | Gravimetric |
| Readily carbonizable substances | Passes | Compendial test |
| Clarity and color of solution | Passes | Compendial test |
Lot release typically includes sieve analysis, bulk density, and residual moisture in addition to compendial purity. Particle size specifications are negotiated by end use; fine powder grades are used in dry beverage mixes, while granular grades are preferred for bulk conveying.
For stainless steel passivation, Citric Acid CA is dissolved to 4–10 wt% and maintained at 60–70°C; immersion times of 20–30 min are described in ASTM A967 for citric acid passivation of austenitic stainless steel. The solution pH is typically 1.8–2.5. Passivation tanks and heating coils are specified in 316L stainless steel or polypropylene; carbon steel and copper-bearing alloys are excluded. Unlike nitric acid passivation, citric acid does not generate NOx vapors, but the bath must be filtered and monitored for iron accumulation. Published data for this specific configuration is limited; bath life is determined by ferric citrate buildup and pH rise rather than acid depletion alone.
In descaling of calcium carbonate deposits in plate heat exchangers, 5–10 wt% citric acid solution at 60–80°C is circulated until residual hardness and pH stabilize. Over-dosing above 10 wt% at the upper temperature limit increases the risk of corrosion on gasketed stainless steel surfaces, particularly if chloride contamination exceeds 50 ppm. Rinsing with demineralized water after cleaning is mandatory to prevent acidic residue retention in crevices.
Citrate coordinates metal ions through two carboxylate oxygen atoms and the central hydroxyl oxygen. Reported stability constants at 25°C in 0.1 M ionic strength are log K 11.85 for Fe(III)-citrate, log K 4.7 for Ca-citrate, and log K 6.1 for Cu(II)-citrate. By comparison, Fe(III)-EDTA is log K 25.1 and Ca-EDTA is log K 10.7. The lower stability constants make citrate more biodegradable and less likely to mobilize heavy metals from sediments, but they also reduce performance in highly alkaline cleaning or water treatment where strong chelation is required.
The operational boundary for citrate chelation is pH-dependent. Below pH 3.0, the predominant species is un-ionized citric acid, and metal complexation is weaker. Between pH 4.0 and 7.0, chelation is most effective for Fe(III). Above pH 8.0, hydroxyl competition and citrate ionization reduce calcium chelation; EDTA or gluconate systems are generally selected. In oilfield acidizing, citric acid is used as an iron-sequestering additive in hydrochloric acid treatments to prevent ferric hydroxide precipitation after acid spending. Typical loading is determined by dissolved iron concentration and formation mineralogy; published data for this specific configuration is limited and requires flowback ion analysis.
In replacement assessments for liquid acidulants, Citric Acid CA is compared against acetic, phosphoric, lactic, malic, and tartaric acids, and against EDTA as a chelator. The distinction is based on pKa, physical state, chelation capacity, and regulatory status.
| Attribute | Citric Acid CA | Citric Acid Monohydrate | Acetic Acid | Phosphoric Acid | EDTA |
|---|---|---|---|---|---|
| Physical form | Anhydrous solid | Solid with water of crystallization | Liquid | Liquid | Solid sodium/calcium salts |
| Molar mass | 192.12 g/mol | 210.14 g/mol | 60.05 g/mol | 98.00 g/mol | 292.24 g/mol for disodium salt |
| pKa | 3.13, 4.76, 6.40 | Same as anhydrous | 4.76 | 2.15, 7.20, 12.32 | Varies by salt |
| Fe(III) chelation log K | 11.85 | Same as anhydrous | Not applicable | Not applicable | 25.1 |
| Regulatory status | GRAS 21 CFR 184.1033; E330 | Same as anhydrous | GRAS 21 CFR 184.1005; E260 | GRAS; E338 | Food additive 21 CFR 172.135 |
| Typical use | Dry acidulant, chelator, descaling, passivation | Acidulant when cooling effect is desired | Preservative, pH control, volatile acid | Acidulant, flavor acid, rust inhibitor | Industrial chelation, cleaning, water treatment |
When EDTA replacement is considered, the comparison must account for pH-dependent loading capacity and wastewater biodegradability. Citric acid has no nitrogen and is readily biodegradable under standard aerobic conditions; EDTA is not readily biodegradable in many activated sludge systems. However, citric acid is not a direct substitute in high-pH descaling or electroless copper baths where strong chelation at pH above 9 is required.
Formulators switching from monohydrate to Citric Acid CA should adjust dry-batch water compensation and dissolution tank thermal controls. Published data for this specific configuration is limited; pilot-scale trials with the actual mixer geometry and line temperature profile are required before full qualification.
