Aluminium Potassium Sulfate Formula: Chemistry, Uses, and Why It’s Not the Same as Potassium Sulfate

If you’ve come across the term aluminium potassium sulfate formula while sourcing a potassium-rich compound for your agricultural or industrial operation, you might be wondering whether it’s the same high-purity potassium sulfate you need. The short answer is no. Aluminium potassium sulfate—commonly known as potash alum—has the chemical formula KAl(SO₄)₂·12H₂O (or sometimes the anhydrous form KAl(SO₄)₂), while potassium sulfate, the premium chlorine-free fertilizer and industrial chemical, is simply K₂SO₄. Despite the similar names, these two compounds have distinct chemistries, physical forms, and end-use applications. In this guide, we’ll break down the aluminium potassium sulfate formula, explore its uses and safety data, and clarify how it differs from the sulfate of potash that procurement managers in agriculture, glass manufacturing, aluminum recycling, and pharmaceuticals rely on every day.

What Is the Chemical Formula of Aluminium Potassium Sulfate?

The aluminium potassium sulfate formula most commonly encountered is the dodecahydrate: KAl(SO₄)₂·12H₂O. In its anhydrous state, it is KAl(SO₄)₂. This double sulfate salt crystallizes in regular octahedra and has been used for centuries in water purification, textile dyeing, leather tanning, and even as a component in baking powders. The compound contains roughly 10–11% alumina (Al₂O₃), 9–10% potassium oxide (K₂O), and the balance sulfate and water of crystallization. It is frequently sold in lump, crystal, or powder form and is widely available from chemical distributors worldwide.

In contrast, potassium sulfate (K₂SO₄) contains no aluminum. It is a binary salt with a typical K₂O content of 50% minimum, making it one of the most concentrated potassium sources available for chloride-sensitive crops like tobacco, potatoes, citrus, and grapes. The aluminium potassium sulfate formula is fundamentally different, which dictates its completely separate set of industrial applications.

Aluminium Potassium Sulfate vs Potassium Sulfate: Key Differences Every Buyer Should Know

Confusing these two chemicals can lead to costly procurement errors. Below is a side-by-side comparison of their essential properties.

Chemical Identity and Crystal Structure

• Aluminium Potassium Sulfate (Potash Alum): KAl(SO₄)₂·12H₂O, monoclinic crystal system, colorless octahedral crystals, loses water above 60°C, melts at 92.5°C in its own water of crystallization.
• Potassium Sulfate (SOP): K₂SO₄, orthorhombic or hexagonal crystal system, white powder or granular solid, melting point 1,069°C, highly stable.

Potassium Content (K₂O) and Nutrient Value

• Alum K₂O ≈ 9.9% (theoretical), never used as a fertilizer due to aluminum toxicity and low solubility of phosphate in soil presence.
• SOP K₂O ≥ 50%, chlorine-free, ideal for fertigation and broadcast application. Potassium sulfate fertilizer is a premium input for high-value horticulture.

Solubility and pH in Solution

Alum dissolves readily in water, forming a slightly acidic solution (pH 3–4) due to hydrolysis of the Al³⁺ ion. Potassium sulfate dissolves slowly and yields a near-neutral solution, making it compatible with sensitive irrigation systems.

Why Do Buyers Confuse Aluminium Potassium Sulfate with Potassium Sulfate?

The confusion arises primarily from overlapping terminology. The word “potassium sulfate” in both names is misleading; aluminium potassium sulfate is often listed on supplier websites simply as “potassium aluminum sulfate” or “alum,” and many international trade platforms group it under sulfate salts. A procurement officer searching for “potassium sulfate” for fertilizer may inadvertently land on listings for alum. Additionally, in some languages, “sulfate of potash” is loosely used, further blurring the lines.

When sourcing, always request the CAS number and full chemical formula. The CAS for anhydrous aluminium potassium sulfate is 10043-67-1, for the dodecahydrate it’s 7784-24-9. Potassium sulfate (SOP) has the CAS number 7778-80-5. Verifying these identifiers eliminates ambiguity during the purchasing process.

Applications of Aluminium Potassium Sulfate (Alum) in Industry

Understanding what alum is used for helps clarify why it shouldn’t be substituted for SOP. Key industrial applications include:

• Water Treatment: Alum acts as a flocculant to remove suspended solids. The Al³⁺ ions form a gelatinous precipitate of Al(OH)₃ that traps impurities.
• Paper Manufacturing: Used as a sizing agent and pH controller in paper pulp.
• Textile and Leather: Mordant in dyeing and tanning agent for leather hides.
• Food Additive: E522 in baking powders, pickling, and maraschino cherries—though this use is tightly regulated.
• Cosmetics and Pharmaceuticals: Astringent in styptic pencils and aftershaves; adjuvant in some vaccines.

None of these uses overlap with potassium sulfate’s role as a chlorine-free fertilizer, glass fining agent, or pharmaceutical excipient—reinforcing why correct product identification is critical.

Aluminium Potassium Sulfate SDS and Safety Considerations

Many buyers search for an aluminum potassium sulfate SDS when assessing handling requirements. The Safety Data Sheet for alum highlights:

• Hazard Classification: Generally non-hazardous under GHS, though may cause mild skin and eye irritation. Not flammable.
• Inhalation: Dust may irritate respiratory tract; use local exhaust ventilation.
• Storage: Keep in a cool, dry area away from strong bases and moisture to prevent caking.
• Environmental Precautions: Large spills may acidify water bodies; aluminum ions are toxic to aquatic life at low concentrations.

In comparison, the SDS for high-purity potassium sulfate from Hailei Chemical indicates a non-hazardous substance with no special ecological risks when handled as recommended. Neither compound is classified as dangerous goods for transport. Nevertheless, always refer to the manufacturer’s SDS for the specific grade you purchase.

What Is Potassium Sulfate Fertilizer and Why Choose Chlorine-Free?

While alum contains potassium, what is potassium sulfate fertilizer exactly? It’s a binary source of potassium (K) and sulfur (S) with zero chloride. The K₂SO₄ molecule delivers 44–46% K₂O (Hailei Chemical guarantees 50% minimum) and 18% sulfur. This combination makes it indispensable for:

• Chloride-sensitive crops: Tobacco, tea, coffee, citrus, grapes, potatoes, and many fruit trees suffer from chloride toxicity, which reduces yield and quality. SOP eliminates this risk.
• Hydroponics and fertigation: Fully water-soluble grades dissolve without residue, supporting precise nutrient management.
• Soil health: Unlike potassium chloride (MOP), SOP does not increase soil salinity or degrade soil structure over time.

For specialty fertilizer importers, sourcing SOP with guaranteed analysis and consistent granule size is a business-critical decision. Hailei Chemical’s sulfate of potash meets international standards, with options in powder, granular, and soluble crystal forms.

Price Potassium Sulfate: Factors Influencing Cost

When exploring the price potassium sulfate market, it’s essential to understand what drives variability. Unlike aluminium potassium sulfate, which is relatively inexpensive due to its broad manufacturing base, SOP pricing reflects these key factors:

• Raw Material Source: SOP can be produced via the Mannheim process (KCl + H₂SO₄), from natural brines (Great Salt Lake), or from sulfate-bearing minerals like langbeinite. Each route has different production costs.
• K₂O Purity: Higher guaranteed K₂O content (>52%) commands a premium. Hailei Chemical’s product delivers a minimum 50% K₂O, offering a strong value-to-performance ratio for bulk buyers.
• Granulation and Bulk Density: Compacted granular SOP for mechanical spreading costs more than standard powder. Packaging (25 kg, 50 kg, jumbo bags) also affects unit cost.
• Logistics and Shipping: Being a Chinese exporter, our competitive freight rates from Qingdao port often offset raw material differentials, making us a reliable partner for buyers in Southeast Asia, the Middle East, Africa, and South America.

Procurement managers should always request a full specification sheet alongside the price quotation to ensure you’re comparing like-for-like grades. The aluminium potassium sulfate formula might be cheap, but it cannot replace the agronomic or industrial performance of genuine SOP.

How Is Potassium Supplied in Agriculture and Industry?

Your question how is potassium supplied goes to the heart of chemical sourcing. Potassium for agricultural use is primarily supplied as muriate of potash (KCl), sulfate of potash (K₂SO₄), and potassium nitrate (KNO₃). For industrial applications like glass manufacturing, aluminum recycling, and pharmaceuticals, SOP is the preferred form because of its purity and lack of corrosive chloride ions.

As a leading exporter, Hailei Chemical supplies potassium sulfate in multiple forms:

• Industrial Grade (99% min purity): Used as a flux in specialty glass production, where it lowers melting temperature without introducing chlorides that attack furnace refractories.
• Pharmaceutical Grade: Meets USP/BP/EP monographs for use as an excipient in tablet formulations and osmotic drug delivery systems.
• Soluble Grade (low water-insoluble matter): Designed for liquid fertilizers and drip irrigation; turbidity below 30 NTU in solution.

In contrast, aluminium potassium sulfate is rarely, if ever, used to supply potassium because the aluminum ions would be phytotoxic and counterproductive. It remains a specialty chemical for water treatment and niche industrial processes.

Potassium Sulfate in Aluminum Recycling and Glass Manufacturing

A unique angle that often surprises buyers is the role of K₂SO₄—not alum—in aluminum recycling. When melting aluminum scrap, a molten salt flux is used to protect the metal from oxidation and to strip away impurities. Potassium sulfate, combined with sodium chloride in precise ratios, forms a low-melting eutectic that floats on the melt surface. The aluminium potassium sulfate formula is entirely unsuitable here because its hydrated form would violently decompose at the high temperatures of molten aluminum (≈700°C), releasing steam and disrupting the process. Only anhydrous K₂SO₄ provides the thermal stability required.

Similarly, in glass manufacturing, potassium sulfate serves as a refining agent. It reduces furnace temperature and eliminates bubbles, improving the clarity of high-quality container and optical glass. The absence of chloride ensures no corrosive attack on the furnace lining or color deviation in the final product. This is an application where Hailei Chemical’s consistent particle size distribution and high purity directly translate to cost savings for glass producers.

Pharmaceutical and Food-Grade Applications of Potassium Sulfate

The pharmaceutical industry uses potassium sulfate as an excipient in sustained-release tablets and as a component of oral rehydration salts. The rigorous requirements—heavy metal limits, microbial purity, and compliance with pharmacopeia monographs—demand a supplier with robust quality management systems. This is not a market that aluminium potassium sulfate can serve. Alum’s astringent properties and aluminum content make it pharmacologically active in ways that are undesirable for most drug formulations.

Hailei Chemical’s SOP meets USP/EP specifications, and our customers in the pharmaceutical and food supplement sectors value our batch-to-batch consistency and comprehensive certificates of analysis. If your application demands the finest potassium sulfate, our technical support team can guide you through the grade selection process.

Why Choose Hailei Chemical for Your Potassium Sulfate Requirements?

With over two decades of experience in the fine chemical export sector, Weifang Hailei Fine Chemical Co., Ltd. understands that B2B buyers need more than a low price—they need a partner who ensures supply security, regulatory compliance, and technical expertise. Our potassium sulfate is produced under strict ISO 9001 quality management, and each shipment is accompanied by a detailed COA, packing list, and, if required, a certificate of origin.

• Verified Product: 50% K₂O minimum, chlorine-free, pH neutral.
• Flexible Packaging: 25 kg, 50 kg PE-lined PP bags, 1,000–1,250 kg jumbo bags, custom labeling.
• Global Logistics: 20+ years of containerized and break-bulk shipping experience from China’s main ports.
• Sample Support: Free samples for lab evaluation, so you can validate quality before large-scale procurement.

Final Thoughts: Don’t Let a Formula Confusion Derail Your Sourcing

The aluminium potassium sulfate formula (KAl(SO₄)₂·12H₂O) defines a compound with a rich history in industrial chemistry, but it is not a substitute for potassium sulfate (K₂SO₄) in agriculture, glass, aluminum recycling, or pharmaceuticals. By clearly understanding these differences and verifying CAS numbers, buyers can avoid costly mistakes and secure the precise material their operations demand.

Ready to source premium chlorine-free potassium sulfate from Hailei Chemical? Whether you need a container load for your fertilizer blending facility or a full truckload of industrial-grade SOP for glass production, our team is here to deliver. Request a quotation today and let’s discuss your specifications, volume requirements, and delivery timeline—backed by the technical support and consistent quality that global buyers trust.