What color is FeCl2? Iron(II) chloride solution is usually pale green/light green. The salt itself dissolves well in water so it does not "precipitate FeCl2"; when alkali is added you will see Fe(OH) precipitate.2 White → bluish-gray, then turns brown when oxidized.
Iron II chloride (ferrous chloride)CAS 7758-94-3Using coagulants for water treatment and laboratory applications. Common industrial form: solution. 15-30%, with COA/MSDS included per batch when quoting B2B prices.
- Standard solution color: pale green; yellow/brown is usually an indication of iron.2+ oxidized to Fe3+.
- FeCl2 dissolves in water — the “precipitate” is usually Fe(OH)2/Fe(OH)3 After alkali or oxidation, not chloride salts separate out.
- Quick distinction from FeCl3: FeCl2 is pale green; FeCl3 is yellowish-brown/brown.
Many technicians and buyers asked the same question at the same time: What color is FeCl2?Does the solution precipitate, and how can you identify a sample with an "unusual color"? This article summarizes practical observations in the lab and factory (for reference), helping you interpret color and precipitation correctly according to their chemical nature — it does not replace internal SOPs or batch COA.
What color is FeCl2 in each form?
The color of FeCl2 depends on its state (crystalline/solution) and degree of oxidation. When you open the can or take a sample, observe it under normal light, noting the concentration and pH if available — color alone is not a substitute for quantitative analysis.
- Hydrated crystals/solids: It is usually pale green to light green (the commercially available hydrated form is more common than the anhydrous form).
- Anhydrous form: It can be white/grayish white; it is highly hygroscopic and easily changes state when exposed to humid air.
- Aqueous solution: Pale green / light green — the characteristic color of the Fe ion2+ in an aqueous environment (aqua complex).
- A “yellow” or “brown” solution: often suggests a portion of Fe2+ has been converted to Fe3+ (Oxidation). The extent and rate depend on pH, dissolved oxygen, temperature, and residence time.
For liquid industrial products, the catalog typically shows concentrations around... 15-30%The color may vary slightly between containers but should remain within the light green range if stored in a sealed container, protected from air and accidental alkalization. Upon receiving the product, compare the COA (Fe concentration).2+The presence of impurities, pH (if any) is more important than subjectively determining whether a color is "beautiful".
Does FeCl2 form a precipitate?
The short answer: FeCl2 salt dissolves well in water.Therefore, a clean, mildly acidic solution is usually clear and does not "spontaneous precipitate FeCl2". What you see settling at the bottom is usually a reaction product or impurity/oxidation, not "undissolved FeCl2".
Common scenarios:
- Add alkali (NaOH, KOH, lime, etc.): iron ion2+ Fe(OH) hydroxide precipitate forms.2The initial color is usually white or bluish-white, quickly turning grayish-blue, then brown upon contact with air due to Fe(OH)2 oxidized to Fe(OH)3.
- Slow oxidation in the liver: A film or light brown precipitate (iron(III) hydroxide/oxide) may appear, especially if the cap is open, the pH is increased, or impurities are present.
- Unintentional dilution/neutralization: Local pH increase → Fe(OH) precipitatesx.
Direction equation (lab/reference):
FeCl2 + 2 NaOH → Fe(OH)2↓ + 2 NaCl
4 Fe(OH)2 + O2 + 2 H2O → 4 Fe(OH)3
Therefore, when searching "What color is FeCl2 precipitate?", the practical answer is: White iron(II) hydroxide precipitate → grayish-blue → brown upon oxidation — not the FeCl2 solution itself that "solidifies into a green color".
Color and Precipitation Identification Chart
| Observe | Common meanings | Test suggestion |
|---|---|---|
| The solution is pale green and clear. | FeCl2 in the Fe state2+ relatively stable | Compare with the Certificate of Analysis (COA), store in a sealed container. |
| Yellow/brown solution | It may have been partially oxidized to Fe.3+ | pH check, can open time, oxidation levels. |
| Add NaOH: white precipitate → grayish-blue precipitate | Fe(OH)2 characteristic iron(II) salts | Compared to FeCl3 (which forms a reddish-brown precipitate immediately) |
| The precipitate turns brown in air. | Oxidation of Fe(OH)2 → Fe(OH)3 | Chemically normal; record the time. |
| Add AgNO3: white precipitate | Cl ion- (AgCl) — confirmed chloride | Not enough to distinguish Fe2+/Fe3+ |
The table above is for quick identification. For production batches, the decision to use or not use is still based on the COA, jar test (if using coagulation), and internal procedures — not just on color.
How do FeCl2 and FeCl3 differ in color?
The two iron chloride salts are often confused on shelves and in price quotes. Differentiating them by color helps you avoid using the wrong iron compound when preparing coagulants or conducting experiments.
| Criteria | FeCl2 (iron(II) chloride) | FeCl3 (iron(III) chloride) |
|---|---|---|
| CAS | 7758-94-3 | 7705-08-0 (compound base) |
| Common solution colors | Light green / pale green | Golden brown / brown |
| Iron oxidation state | Fe2+ (easily oxidized) | Fe3+ (more durable in air) |
| With NaOH | White-blue precipitate → brown upon oxidation | Reddish-brown precipitate Fe(OH)3 |
| The role of water treatment (overview) | Coagulation/reduction of some systems; oxidation control is required. | Coagulation is common, and the solution is darker in color. |
If you are designing a coagulant dosage, don't just switch to "the same iron group" and ignore the oxidation state: Fe2+ Fe3+ Other factors include pH behavior, sludge color, and additional oxidation requirements. Jar testing based on actual wastewater remains a safe step before large-scale infiltration.
Applications and usage instructions
FeCl2 (ferrous chloride) is found in:
- Water/Wastewater Treatment: Coagulation, decolorization assistance, or removal of certain heavy metals — dosage and pH must be tested according to the water source.
- Lab and preparation: Fe source2+Oxidation-reduction reactions, ion identification.
- Some industrial/textile dyeing processes (as needed): It depends on the batch specifications and documentation requirements (COA, MSDS).
Practical storage: Keep in a tightly sealed container, away from air and strong sunlight, and do not store near strong alkalis. Fe solution2+ less durable than iron.3+Leaving the lid open for too long may cause discoloration. This is a general operating guideline. Not a complete factory SOP. — You will need internal procedures, PPE, and MSDS for the shipment.
Do you need industrial-grade FeCl2 (15–30%) with a Certificate of Analysis/MDS?
Loc Thien supplies ferrous chloride on a B2B basis — pricing varies depending on concentration, packaging, and delivery area. See product information at hoachatlocthien.com/san-pham/fecl2-sat-ii-clorua.
Technical/Purchasing Hotline: (+84) 979 891 929.
Top Q&A
What is the standard color for FeCl2 solution?
Often light green / pale greenYellow or brown color suggests iron.2+ partially oxidized to Fe3+It is advisable to compare the batch COA and storage conditions, not just rely on subjective color comparison.
Does FeCl2 form a precipitate?
FeCl2 salt dissolves well in waterTherefore, a clean solution usually does not "precipitate FeCl2". The precipitate you see after adding alkali or when oxidation/pH increases is usually iron hydroxide (Fe(OH)).2 / Fe(OH)3).
What color is the FeCl2 precipitate when NaOH is added?
Precipitate of Fe(OH)2 often white or bluish white, transfer grayish blue, Already nâu when oxidized in air to Fe(OH)3This is a sign of iron.2+ Common in labs.
How can you distinguish between FeCl2 and FeCl3 visually?
FeCl2 solutions are usually pale green; FeCl3 solutions are usually yellowish-brown/brown. With NaOH: FeCl2 gives a bluish-white precipitate (which turns brown later), FeCl3 gives a reddish-brown precipitate immediately. Confirmation with a Certificate of Analysis (COA) or further analysis is still recommended when used in production.
Is a yellow FeCl2 solution still usable?
Yellow/brown usually means it contains iron.3+Depending on the application: some coagulation systems still accept the mixture, but only if the process requires Fe.2+ If it's a pure (lab, reduction reaction), you need to re-evaluate or obtain a new batch. Contact technical support with a COA before large-scale injection.
What are the common concentrations of FeCl2 in industrial applications?
Catalogs often contain solutions of approximately... 15-30%Precise concentrations according to the COA for each batch. B2B pricing is based on requirements, packaging, and delivery area — no fixed individual prices are listed on the website.
What is the CAS value of iron(II) chloride?
CAS 7758-94-3 (ferrous chloride / iron(II) chloride). When comparing MSDS/COA documents and import records, ensure the correct CAS number and form (liquid/solid, concentration) match the order.
Where can I buy FeCl2, and what documents do I need?
You can view Loc Thien's product page here: FeCl2 iron(II) chloridePrepare your requirements for concentration, volume, delivery address, and COA/MSDS request per batch. Hotline: (+84) 979 891 929.
This content is for technical reference and basic chemistry education purposes only. It does not replace safety procedures, jar tests, or plant operating instructions (SOPs). Always use PPE and adhere to the MSDS of the batch being used.
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