| HS Code | 985311 |
| Product Name | Ammonium Citrate Salts |
| Chemical Formula | (NH4)3C6H5O7 |
| Cas Number | 3458-72-4 |
| Molecular Weight | 243.21 g/mol |
| Appearance | White crystalline powder or granules |
| Odor | Slight ammoniacal odor |
| Solubility | Freely soluble in water; slightly soluble in ethanol |
| Melting Point | Decomposes at 185°C |
| Boiling Point | Decomposes before boiling |
| Density | 1.5 g/cm³ at 20°C |
| Ph | 7.0 to 9.0 (5% aqueous solution) |
| Hygroscopicity | Slightly hygroscopic |
| Stability | Stable under normal storage conditions; incompatible with strong acids and oxidizing agents |
| Flash Point | Non-flammable |
| Storage | Keep in a cool, dry, well-ventilated place; store in a tightly closed container |
As an accredited Ammonium Citrate Salts factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 25 kg net in sealed double polyethylene-lined kraft paper bags, with clear hazard labeling and moisture-protective packaging. |
| Container Loading (20′ FCL) | Ammonium citrate salts loaded in 20′ FCL, palletized, secured, with moisture protection and ventilation to prevent clumping. |
| Shipping | Ammonium citrate salts are generally non-hazardous for transport and not regulated as dangerous goods. Pack in sturdy, sealed, moisture-resistant containers, protected from strong acids and oxidizers. No UN number required. Clearly label with the proper chemical name and include a safety data sheet for documentation and handling reference. |
| Storage | Store in a cool, dry, well-ventilated area away from direct sunlight and heat sources. Keep the container tightly sealed to prevent moisture absorption and contamination. Segregate from strong oxidizers, acids, and alkalis. Ensure proper labeling, secondary containment, and access to eyewash/safety shower. Use appropriate PPE when handling. |
| Shelf Life | Store in a cool, dry, airtight container. Shelf life is typically 2–5 years when unopened and protected from moisture and heat. |
In sodium-sensitive autocatalytic nickel-phosphorus deposition, diammonium hydrogen citrate is introduced as the primary complexing ligand and pH-8 buffer in the operating bath. The bath is constructed from Type 316L passivated stainless steel with a polypropylene overflow weir, a 50 µm bag filter followed by a 10 µm polypropylene cartridge filter, and a horizontal centrifugal pump delivering 8–12 tank volumes/h through a fluoropolymer heat exchanger. Alkali-metal contamination is restricted in semiconductor-grade metal deposition and certain MEMS wafer-backside metallization processes; ammonium citrate salts replace sodium citrate in reduced-sodium or ammonium hypophosphite-based electroless nickel formulations. The citrate ligand lowers free nickel ion activity, suppresses homogeneous nucleation, and stabilizes the bath against spontaneous plate-out on heater surfaces and tank walls. The terminal medium-phosphorus and high-phosphorus baths are specified under ASTM B733-04(2020) and ISO 4527:2003.
| Parameter | Medium-P bath, 6–9 wt% P | High-P bath, 10–13 wt% P |
|---|---|---|
| NiSO₄·6H₂O | 21–30 g/L | 15–22 g/L |
| NaH₂PO₂·H₂O or NH₄H₂PO₂ | 22–30 g/L | 30–45 g/L |
| Diammonium hydrogen citrate | 25–35 g/L | 40–60 g/L |
| pH | 8.6–9.0 at 86–89°C | 8.8–9.5 at 87–91°C |
| Deposition rate | 10–16 µm/h | 8–12 µm/h |
| Bath loading | 0.6–1.2 dm²/L | |
Make-up and replenishment are controlled by wet-chemical nickel and hypophosphite titration rather than by fixed volume top-up alone. Diammonium citrate is metered at 0.5–1.0 g/L·h during steady-state production and adjusted to maintain the ranges shown above. On a 4,000 L production line with a 12 kW electric immersion heater, spontaneous plate-out is first observed on the heater sheath when free citrate falls below 18 g/L during a 4 MTO maintenance window. Bath life extends to 8–10 MTO when pH is held within ±0.1 units and citrate depletion is corrected continuously. Local exhaust ventilation is required because free ammonia evolves at the 86–91°C operating range and increases pH drift if not removed. Finished components include hydraulic valve bodies, pump housings, electronic connector shells, and vacuum chamber fittings. EU REACH industrial-use exposure scenarios apply to the metal-treatment preparation; the citrate salt itself introduces no RoHS-restricted substances to the bath.
Tin-silver-copper solder paste reflow leaves a mixed oxide residue containing SnO₂, Ag₃Sn, and Cu₆Sn₅ particles embedded in spent no-clean flux. In aqueous defluxing, ammonium citrate salts function as an ammoniated chelating cleaner: the citrate binder sequesters Sn(II)/(IV) and Cu(I)/(II) ions while the ammonium counterion holds the wash bath in the range pH 7.2–7.8 and avoids sodium or potassium residues that degrade electrochemical migration resistance. A working concentration of 8–12 wt% diammonium citrate concentrate in deionized water at 55–60°C is used in the first wash section of a 12-stage conveyorized spray-in-air cleaner. Bath pH is maintained with 10 wt% ammonium hydroxide or dilute citric acid additions. The wash sequence includes three wash sumps, four conductivity-controlled DI rinse stages, two air-knife stations, and an infrared drying tunnel at 85°C for 25–30 min.
Final rinse water must maintain 10 MΩ·cm minimum resistivity at 25°C, with overflow set at 2–3 L/min per 100 m² of processed board area. Cleanliness is verified by IPC-TM-650 Method 2.3.25 ROSE testing using a 75% isopropanol/25% deionized water extraction solution, with a release criterion below 1.56 µg NaCl/cm². Surface insulation resistance is measured under 85°C/85% RH and 50 V DC bias according to IPC-TM-650 Method 2.6.3.3, with resistance above 100 MΩ commonly used as the production acceptance limit. Terminal assemblies include automotive engine control units, high-density interconnect flex circuits, 5G transceiver modules, and medical diagnostic cartridges. Operational boundaries are narrow: immersion of bare aluminum bond pads in ammonium citrate above pH 9.0 causes localized etching, and insufficient final rinsing leaves amine residues that can fail ROSE limits even when bulk ionic contamination appears acceptable. The process itself does not add restricted substances under RoHS Directive 2011/65/EU to the finished board.
Rouge, an iron-oxide-rich contaminant layer on electropolished Type 316L surfaces, is removed by a recirculated solution of 8–12 wt% diammonium citrate with 0.5–1.0 wt% hydrogen peroxide at 65–75°C and pH 3.8–4.2. The ammonium citrate salt acts as a ferric ion chelating agent, driving dissolution of FeO(OH) and Fe₂O₃ without the chloride pitting risk associated with hydrochloric acid-based derouging solutions. The CIP skid for this process uses a 15 m³/h centrifugal pump, 316L static spray balls operating at 1.5–2.0 bar, and a 5 µm polypropylene bag filter. Recirculation time is 45–90 min depending on vessel diameter and internal geometry.
After the citrate step, passivation is performed with 0.5 wt% citric acid at 60°C for 30 min in accordance with ASTM A967/A967M-17 or a validated equivalent; pre-cleaning and descaling practices are aligned with ASTM A380/A380M-17. The citrate-chelated effluent is neutralized to pH 6.0–8.0 prior to discharge and monitored for iron content by atomic absorption or ICP-OES. Terminal product types include bioreactors, buffer hold tanks, WFI storage tanks, sanitary transfer manifolds, and tablet coating pans. This method is not suitable for titanium heat exchangers or aluminum valve components; ammonium citrate does not by itself establish a passive chromium oxide film, so an oxidizer or a separate passivation step is required. The process chemical falls under the professional-use exposure scenario of the EU REACH registration for ammonium citrate and introduces no halogenated acid storage hazard.
High-methoxy pectin gel networks require a final mass pH below 3.6 to develop a firm, elastic gel, but rapid acidification at the end of the cooking stage can cause local pH collapse and premature pectin chain hydrolysis. Triammonium citrate, permitted as E 380 under Annex II of Regulation (EC) No 1333/2008 and specified under Commission Regulation (EU) No 231/2012, is dissolved in batch water at 0.2–0.5 wt% of finished product weight before pectin hydration. In US practice, ammonium citrate is listed as GRAS under 21 CFR 184.1140. The buffered system controls the transition from the vacuum concentrator at 95–100°C and 78–82°Brix to the starch moulding station, allowing citric acid addition to achieve a final pH 3.3–3.4 without a steep pH trough.
The production process uses a pectin-sugar premix hydrated at 75°C, followed by batch cooking at 108–114°C and vacuum concentration. The buffer is added with the final acid and flavour at 95°C, and the mass is deposited into starch moguls at 60–70°C. Drying proceeds for 12–24 h at 30–40°C and 30–40% RH. Terminal product types include pectin jelly candy, fruit snack pieces, and glazed fruit fillings. Because ammonium salts release free ammonia above 100°C, formulation tolerance is narrow: high-heat long-hold processes develop ammoniacal off-notes, and the salt is generally unsuitable for dairy protein gels or low-acid food systems requiring stronger buffering capacity.
Ceria-zirconia mixed-oxide oxygen storage powders for automotive three-way catalyst washcoat layers have been prepared at production scale by a citrate complexation auto-combustion route in which ammonium citrate salts are generated in situ from citric acid and aqueous ammonia. In a 500 L glass-lined reactor, cerium and zirconium nitrates are dissolved in deionized water, citric acid is added at a citric acid-to-metal molar ratio of 1.2–1.5, and the pH is adjusted to 6.8–7.2 with 25% ammonium hydroxide. The resulting ammonium citrate concentration is 35–55 wt% of the dry precursor mass; citrate ions coordinate Ce³⁺ and Zr⁴⁺ to suppress premature nitrate precipitation during evaporative concentration at 80°C under 60 rpm anchor agitation.
The viscous gel foams at 110–130°C and then self-ignites at 240–270°C when the nitrate-citrate fuel reaction initiates. The resulting porous oxide is calcined at 550°C for 3 h, with specific surface area determined by ISO 9277:2010 and particle size by ISO 13320:2020. The ammonium-based route leaves no alkali metal residue, which is essential where sodium or potassium in the washcoat poisons oxygen storage activity. Terminal product types include three-way catalyst washcoat powders, diesel oxidation catalyst mixed oxides, and solid oxide fuel cell cathode interlayers. Published data for this specific configuration is limited; batch-to-batch surface area variation and exothermic peak intensity are highly sensitive to residual nitrate content and ambient humidity, and scale-up beyond 500 L requires thermal management not fully addressed by current public data.
In commercial high-rise chilled-water loops, iron oxide and calcium carbonate scale deposited on chiller evaporator tubes is removed with a circulated solution of 6–10 wt% diammonium citrate at pH 5.5–6.0 and 40–50°C. The process is implemented with a side-stream descaling pump skid using a 1.0–1.5 m/s line velocity, a 10 µm cartridge filter, and coupon racks holding prepared copper and mild steel specimens. Coupon corrosion is evaluated in accordance with ASTM G31-72(2012) or ASTM G1-03(2017)e1, and dilution water meets ASTM D1193-06 Type II.
The recirculation period is 4–6 h, after which the spent citrate solution is neutralized to pH 6.5–8.0 and discharged. A 0.5 wt% sodium molybdate or proprietary copper corrosion inhibitor is often included to prevent copper citrate complex formation, particularly on copper-tube chillers and brass pump components. Terminal product types include chiller evaporator bundles, condenser water loops, plate heat exchanger circuits, and glycol loop expansion tanks. Operating limits are defined by pH: below pH 5.0, copper dissolution increases and the solution turns blue-green from soluble copper complexes; above pH 6.5, iron sequestration capacity drops and scale removal rate falls below the target for a single-shift cleaning window.
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Ammonium citrate salts are supplied as dibasic ammonium citrate, C6H14N2O7, CAS 3012-65-5, and triammonium citrate, C6H17N3O7, CAS 3458-72-8, with the less common monobasic ammonium citrate, C6H11NO7, CAS 1185-57-5, available for lower-pH formulation work. Commercial grades are differentiated by residual sodium, potassium, chloride, sulfate, and iron limits, by hydration state, and by particle-size distribution; low-iron electronic-grade powders and granular low-sodium grades are the predominant forms used in wet-chemical surface preparation. The citrate anion functions as a tridentate sequestrant through its central hydroxyl and terminal carboxylate groups, forming water-soluble complexes with Fe(III), Ni(II), Zn(II), Cu(II), and Ca(II). The ammonium counterion volatilizes as ammonia during high-temperature processing, leaving lower non-volatile ash than alkali-metal citrates. In the European Union, triammonium citrate is designated E 380, with permitted quantum satis use in specified food categories and speccriteria published in Commission Regulation (EU) No 231/2012.
Buffering and chelation strength depend on citrate speciation. Citric acid pKa values of 3.13, 4.76, and 6.40 position dibasic ammonium citrate as an effective buffer in the pH 4.8–5.5 window; triammonium citrate shifts the dominant species toward the fully deprotonated citrate trianion at pH above 6.8. This speciation difference determines formulation selection: dibasic ammonium citrate is preferred where acidic metal-oxide dissolution and nickel-ion complexation coexist, while triammonium citrate is selected for near-neutral cleaning and pH-buffered passivation solutions. Dilute solutions of dibasic ammonium citrate at 5% w/v exhibit pH 5.0–5.5 at 25 °C when measured by glass electrode according to ASTM E70-19. In electroless nickel bath make-up, the protonated citrate species also influences hypophosphite reduction kinetics; bath suppliers therefore specify both assay and pH band rather than total citrate content alone.
Replacement of sodium citrate with ammonium citrate dibasic in hypophosphite-reduced electroless nickel baths addresses a specific contamination path: the sodium ion remains soluble through bath life, raises ionic strength, and is adsorbed or incorporated at the deposit surface, where it affects solderability and corrosion resistance after thermal excursion. At a make-up charge of 15 g/L of chelant, sodium citrate dihydrate contributes approximately 3.5 g/L of sodium, whereas low-sodium ammonium citrate dibasic with sodium ≤0.005% contributes ≤0.75 mg/L under the same charge. Production-scale baths of 200 L to 500 L operating at pH 4.5–5.5 and 85 °C–90 °C require continuous pH adjustment with aqueous ammonia; the ammonium citrate system tracks buffering demand without introducing a non-volatile cation. Bath monitoring protocols from industrial suppliers commonly maintain free nickel concentration through complexometric titration, while sodium residual is separately controlled by ICP-OES using a method comparable to ASTM E1479. In semiconductor packaging and connector metallization, sodium limits in the bath are supplier-specific but commonly fall between 10 mg/L and 50 mg/L; published data for specific high-phosphorus bath configurations is limited.
In immersion cleaning and pre-paint conversion-coating operations, ammonium citrate salts are blended at 3 wt%–5 wt% with nonionic surfactants and dispensed through ultrasonic tanks operating at 25 kHz to 40 kHz. The ammonium form prevents silicate and carbonate scale formation in hard water where sodium-free rinsing is required. Cleaning temperature is normally held at 50 °C–65 °C; above 65 °C ammonia loss increases and pH drifts downward, requiring exhaust ventilation and caustic scrubbing of ammonia vapour. For ferrous substrates, citrate-based ammonium salts remove Fe(III) oxides through chelating dissolution, but the bath has a finite iron-loading capacity; process control by redox titration or UV-Vis at 420 nm is used to avoid precipitation of iron citrate sludge. Published data for specific production-scale ultrasonic bath configurations is limited; supplier formulations are validated on substrate coupons before line conversion.
Alkaline and near-neutral scale-removal formulations for heat exchangers and boiler sections can be converted from ammonium oxalate to ammonium citrate dibasic where wastewater oxalate limits or calcium oxalate sludge disposal costs are controlling variables. Citrate forms soluble calcium chelates with less persistent solid-volume build-up than calcium oxalate, although iron oxide dissolution kinetics are slower than oxalate at equivalent pH. Clean-in-place skids that recirculate 5 wt% ammonium citrate dibasic at 70 °C–80 °C for 4 h–8 h require post-treatment for chelated iron and copper, usually by pH adjustment to 9.0 with lime or caustic followed by clarification. In comparison, ammonium oxalate circuits must remove precipitated calcium oxalate by filter press; the citrate route can be processed through membrane filtration only when free citrate has been broken by oxidation or biological treatment. At temperatures above 80 °C, thermal decomposition of the ammonium ion accelerates, causing pH drop and ammonia release; closed-loop scrubbers are required. The system is incompatible with strong oxidizers and concentrated nitric acid.
Grades destined for electroless nickel and chemical polishing are controlled by lot-specific certificates of analysis. Representative acceptance limits for a low-iron dibasic ammonium citrate are shown in Table 1; general-purpose technical grades permit higher sodium and iron residuals.
| Parameter | Acceptance limit | Test method |
|---|---|---|
| Assay, anhydrous basis | ≥98.0% | acid-base titration |
| pH, 5% w/v at 25 °C | 5.0–5.5 | ASTM E70-19 |
| Residual sodium | ≤0.005% | ICP-OES, comparable to ASTM E1479 |
| Residual potassium | ≤0.01% | ICP-OES |
| Chloride | ≤0.001% | turbidimetric |
| Sulfate | ≤0.005% | turbidimetric |
| Iron | ≤0.001% | colorimetric |
| Heavy metals, as Pb | ≤0.0005% | sulfide precipitation |
| Moisture, Karl Fischer | ≤0.5% | ISO 15512 |
| Particle size D90 | 100–250 µm | ISO 13320 |
In sol-gel synthesis of multicomponent oxides such as lithium iron phosphate and ceria-doped zirconia, triammonium citrate is added at a citrate-to-metal molar ratio of 1:1 to 2:1. The ammonium ion decomposes under calcination in air, leaving no alkali residue in the calcined oxide; this is the key difference from sodium citrate in cathode precursor manufacture. Spray-dried precursor powders show lower aggregate hardness with ammonium citrate than with citric acid alone because the ammonium salt modifies gel-network structure. Published data for specific cathode precursor formulations is limited; pilot-scale spray-drying trials at inlet/outlet temperatures of 180 °C/85 °C are used to validate flowability and sintering activity.
Compared with sodium citrate, ammonium citrate dibasic lowers non-volatile cation residue; the ammonium ion departs as ammonia and water during thermal processing, while sodium remains as sodium carbonate. This property controls selection in electroless nickel, semiconductor rinsing, and ceramic precursor processing. Compared with ammonium oxalate, ammonium citrate has lower calcium chelation strength per mole but avoids oxalate precipitation and is more readily biodegradable by the standard carbon skeleton pathway; citrate-based salts are generally classified as readily biodegradable under OECD 301B, whereas oxalate destruction may require an additional oxidation step. Compared with disodium EDTA, citrate is biodegradable but has lower thermodynamic stability with heavy metals; citrate should not be used as the sole sequestrant when chelated effluent must be discharged without advanced oxidation or electrochemical treatment.
Operational boundaries are defined by moisture sensitivity and ammonia volatility. Dibasic ammonium citrate is hygroscopic at relative humidity above 60%; pre-drying at 60 °C to constant mass is required for gravimetric dispensing. Batch-to-batch moisture variation is a field failure mode in automated make-up systems because a 0.2% moisture shift on a 500 kg batch changes anhydrous assay by 0.2%, sufficient to shift pH in a 200 L bath by approximately 0.05 pH units if not compensated. Automated systems therefore use Karl Fischer data and lot-specific assay to calculate dry-basis mass. Storage in sealed polyethylene-lined drums below 40 °C is standard. Ammonia release increases above pH 9 and above 65 °C; incompatible process additions include concentrated nitric acid, strong oxidizers, and reactive metals in acidic media. For food-grade E 380 triammonium citrate, production follows HACCP and European Union additive hygiene rules, with maximum residual solvent and heavy-metal limits governed by Commission Regulation (EU) No 231/2012.
