# Quick Questions — What is FeCl3? Which parameters should be checked on a FeCl3 COA?

Quick Questions — What is FeCl3? Which parameters should be checked on a FeCl3 COA?

FeCl3 (Ferric(III) chloride, CAS 7705-08-0) is a reddish-brown liquid or yellowish-brown crystalline coagulant widely used in industrial wastewater treatment, drinking water treatment, color removal, and phosphorus removal. A FeCl3 COA is a batch-specific test certificate recording 5 key parameters: FeCl3 content (≥38–42% for liquid, ≥96% for solid), free FeCl2 content (impurity, ≤0.5%), insoluble matter in water, specific gravity at 20°C (1.42–1.45 g/ml for 40% solution), and pH of the original solution (<1.0). Loc Thien directly manufactures and supplies FeCl3 with a COA per batch from the factory.

5 Key Points — What You Need to Know Before Buying FeCl3

1. COA is mandatory — each FeCl3 batch must have its own COA listing all 5 parameters. No COA means no quality control.
2. FeCl3 content is the most important parameter — liquid 40% has a tolerance of ±1%; solid 96% has a tolerance of ±1.5%. If the content is lower, coagulation efficiency drops proportionally.
3. Clearly distinguish solid vs. liquid — solid 96% FeCl3 (flakes or granules) is for plants with mixing tanks; liquid 40% FeCl3 is for direct metering pump systems.
4. Specific gravity at 20°C is a quick field check — a 40% FeCl3 solution has a specific gravity of 1.42–1.45 g/ml. If below 1.40, dilution is suspected.
5. FeCl3·6H2O is the hexahydrate crystalline form — equivalent FeCl3 content is ~60%, typically used in laboratories or small-scale production.

What is a FeCl3 COA? 5 Key Parameters to Check

A COA (Certificate of Analysis) is a document issued by the manufacturer’s QC laboratory for each production batch. Each FeCl3 batch is a separate production run and may have slight variations in technical parameters. The COA records the actual test results for that batch.

For FeCl3, a valid COA must include the following 5 parameters:

1. FeCl3 Content

This is the most important parameter, determining the product’s value and price.

Content below these thresholds means you are paying for water or impurities instead of active ingredient.

2. Free FeCl2 Content

FeCl2 (Ferrous(II) chloride) is an impurity formed during FeCl3 production. The allowable free FeCl2 content is ≤0.5%. If exceeded, the product becomes less stable, coagulation efficiency decreases, and equipment corrosion accelerates.

3. Insoluble Matter

This parameter measures mechanical impurities (sand, dust, sediment) remaining after production. The standard allows ≤0.5% for liquid and ≤1.0% for solid. High insoluble matter causes clogging in metering pumps, storage tanks, and pipelines.

4. Specific Gravity at 20°C

A 40% FeCl3 solution has a specific gravity of 1.42–1.45 g/ml. This is a quick field check — using a hydrometer can immediately detect diluted product.

5. pH of Original Solution

FeCl3 is strongly acidic; the pH of a 40% solution is <1.0. If the measured pH is >1.5, the product may have been partially neutralized due to improper storage or adulteration.

Risks of Buying FeCl3 Without a COA — 3 Real Cases

Case 1: 30% Drop in Coagulation Efficiency Due to Low Content

A paper mill in Binh Duong purchased cheap liquid FeCl3 (15% below market price) without requesting a COA. During operation, the coagulant dosage increased from 250 ppm to 350 ppm, yet the treated water remained turbid. Independent testing revealed the actual FeCl3 content was only 31% instead of the promised 40%. Chemical costs rose 30% over three months before the cause was identified.

Case 2: Factory Audit Rejected — COA Mandatory for Chemical Suppliers

An industrial park wastewater treatment plant received a non-conformance during an ISO 14001 audit because it lacked COAs for the FeCl3 and PAC in use. The audit required traceability for every chemical batch over the past six months. The previous supplier had not retained COAs, forcing the plant to switch suppliers and spend two weeks completing traceability documentation.

Case 3: Metering Pump Clogged Due to Mechanical Impurities

A textile dyeing factory in Dong Nai used 40% FeCl3 from a source without a COA. After two weeks, the diaphragm pump clogged, and the metering pump rotor wore abnormally fast. Inspection of sediment at the tank bottom revealed a 5 cm layer of sand. The insoluble matter content in that batch was 3.2% — six times the allowable limit. Pump repair and spare part replacement costs exceeded 12 million VND.

How to Read a FeCl3 COA Line by Line — Detailed Guide

A standard FeCl3 COA consists of the following sections. Here is how to read each line:

Header: Identification Information

• Product Name / Trade Name: FeCl3 40% Solution or Ferric Chloride Solution
• Batch / Lot Number: Production batch code — each batch has a unique code
• Date of Manufacture (DOM): Production date
• Date of Expiry / Retest Date: Expiry date or retest date
• Quantity: Batch production quantity (in kg or tons)

Body: Test Results

Quick Reading Tips:

• The Result must fall within the Specification range.
• If any parameter is outside the specification, the batch fails.
• Note the Test Method — standard methods are titration, not estimation.

Footer: Certification

• Tested by: Name and signature of QC technician
• Approved by: Name and signature of QC manager
• QC Stamp: QC department stamp — this is the legal element of the COA

FeCl3 TDS — Full Technical Data Sheet

A TDS (Technical Data Sheet) is a document summarizing fixed technical parameters of the product, which do not change batch to batch. Below is a reference TDS for Loc Thien’s FeCl3:

Packaging Specifications

Applications

• Wastewater treatment: coagulation for color removal, phosphorus removal, H2S removal
• Drinking water treatment: coagulation for surface water, turbidity and organic matter removal
• PCB etching: FeCl3 is the standard copper etchant
• Pigment production: iron oxide-based pigments
• Sludge treatment: improves dewatering

Solid FeCl3 96% vs. Liquid 40% — Differences & When to Use Which

Detailed Comparison

When to Use Solid FeCl3 96%

• Plant has a dissolving tank with mixing system
• Limited storage space (solid takes less volume than liquid)
• Large volume purchases, long-distance transport (saves freight)
• Has manpower for mixing

When to Use Liquid FeCl3 40%

• Direct metering pump system — no mixing needed
• Plant lacks mixing tank or manpower
• Steady, regular consumption — periodic tanker deliveries
• Requires precise, stable concentration control

FeCl3·6H2O — Hydrated Crystalline Form

FeCl3·6H2O is ferric(III) chloride hexahydrate — yellowish-brown crystals that are highly hygroscopic. Its molecular weight is 270.30 g/mol, with FeCl3 accounting for ~60% and 6H2O for ~40%.

Characteristics

• Large yellowish-brown crystals, easily deliquescent in humid air
• Melting point 37°C — at room temperature (30–35°C), crystals begin to self-dissolve in their own water of crystallization
• Completely soluble in water, strongly exothermic
• CAS 10025-77-1 (hydrated form) — different from CAS 7705-08-0 (anhydrous)

Applications

• Laboratories: analytical chemicals, organic synthesis
• Pilot scale: coagulation trials before scaling up to industrial
• Small production: workshops without large storage tanks
• Small to medium water treatment: manual batch preparation

Buying Notes for FeCl3·6H2O

• Equivalent FeCl3 content (~60%) is lower than anhydrous 96% — recalculate dosage
• Price per kg of pure FeCl3 is usually higher than anhydrous due to crystallization costs
• Shorter shelf life — easily absorbs moisture and deliquesces
• Check COA: parameter should be FeCl3·6H2O content or equivalent FeCl3 content

Frequently Asked Questions (FAQ)

What is the CAS number for FeCl3?

Anhydrous FeCl3 has CAS 7705-08-0. The hexahydrate form FeCl3·6H2O has CAS 10025-77-1. These are two different CAS numbers; distinguish them when ordering and consulting MSDS.

How to quickly check if liquid FeCl3 has been diluted?

Use a hydrometer at 20°C. A standard 40% FeCl3 solution has a specific gravity of 1.42–1.45 g/ml. If the specific gravity is below 1.40, the product is likely diluted. Cross-check with the batch COA.

How long can liquid FeCl3 be stored?

A 40% FeCl3 solution stored in a sealed tank, away from direct sunlight, remains stable for at least 6 months. After this period, recheck specific gravity and content. Avoid open tanks because acid fumes and water evaporation can alter concentration.

What is the difference between FeCl3 and PAC?

Both FeCl3 and PAC are coagulants, but they work differently. FeCl3 forms heavy, fast-settling flocs and is effective at low pH (5.0–8.0). PAC forms lighter flocs, works over a wider pH range (5.0–9.0), and causes less pH drop. FeCl3 has a lower cost per kg of active ingredient but is more corrosive. Many treatment plants use a combination of both.

Does solid FeCl3 96% dissolve completely in water?

Yes, anhydrous solid FeCl3 dissolves completely in water, releasing strong heat. When mixing, slowly add solid FeCl3 to water (never the reverse) while stirring. Typical mixing concentration is 30–40% w/w. The resulting solution is dark brown with pH <1.0.

What documents are needed when buying FeCl3?

When purchasing FeCl3 from a supplier, request the full set: COA (Certificate of Analysis) per batch, TDS (Technical Data Sheet), MSDS (Material Safety Data Sheet), and CO/CQ (Certificate of Origin/Quality) for imported goods. Loc Thien is a direct manufacturer and supplier of FeCl3, providing all these documents for each batch.

Download a Sample FeCl3 COA — Check Quality Before Buying

You can request a sample FeCl3 COA from Loc Thien to review before placing an order. The COA is issued by the factory QC department, listing all 5 parameters: FeCl3 content, free FeCl2, insoluble matter, specific gravity, and pH — matching the actual batch delivered to customers.

Call our technical hotline now — get 15 minutes of consultation on COA parameters, dosage, and delivery options tailored to your plant’s scale.

📞 Hotline: 0979 891 929
📧 Email: [email protected]
🌐 Website: https://locthien.vn

Loc Thien — direct manufacturer and supplier of FeCl3, FeCl2, PAC, NaOH, HCl, H2SO4. 6 warehouses across 3 regions. Nationwide delivery by 5–30 ton tank trucks.