Potash Alum

Potash Alum also known as Potassium Aluminum Sulfate is a chemical compound commonly used as potassium sulfate dodecahydrate. It has an octahedral structure in a neutral solution and changes into a cubic structure in an alkali solution. This compound is a double salt and is frequently utilized in medicine and water treatment procedures. It is often termed as ‘fitkari‘.

In this article, we will have a detailed description of the Potash Alum, properties of potash alum, uses of the potash alum, and how the potash alum is prepared.

• 258.192 g/mol (anhydrous)
• 474.37 g/mol (dodecahydrate)

IUPAC Name	Aluminum Potassium Sulfate Dodecahydrate
Chemical Formula	K2SO4.Al2(SO4)3.24H2O
Molar Mass	948 gm/mol
Density	1.725 g/cm3
Melting Point	92 to 95 °C (198 to 203 °F; 365 to 368 K)
Boiling Point	200 °C (392 °F; 473 K)

What is Potash Alum?

Potash Alum also termed as Potassium Alum contains a wide variety of highly complex species, such as aluminum polymers, which influence the kind of product, which in turn depends on various factors like dosage, pH, rate of hydroxide supplementation, and mixing. Alum’s flexibility also makes it exceptionally adaptable, allowing for the manipulation of different coagulation mechanisms.

Potash alum is an essential member of the alum class of compounds and is often used as an astringent, antiseptic, water purifier, fire retardant, and in tanning leather. The FDA (Food and Drug Administration) considers potash alum safe and uses it to manufacture various products.

Structure of Potash Alum

Potash alum has an octahedral structure in its hydrated form and a cubic structure in an alkali solution. The structure of a potash alum is given below:

Some key features of potash alum structure include:

• Octahedral shape: Potash alum crystals are octahedral, with each molecule surrounded by six water molecules.

• Dodecahydrate form: Potash alum is commonly encountered as the dodecahydrate, meaning that each molecule of the compound is associated with twelve molecules of water

• Colorless and highly soluble: Potash alum is almost colorless and highly soluble in water.

• Heat-sensitive: The compound turns red when heated to a certain degree.

Properties of Potash Alum

Some of the important properties of potash alum are listed below:

Potash Alum Properties
Appearance	Colorless, crystalline solid
Taste	Sour taste
Nature	Acidic
Structure	Octahedral
IUPAC Name	Aluminum Potassium Sulfate Dodecahydrate
Density	1.757 g/mL at 25 °C (77 °F)
Melting point	92 to 95 °C (198 to 203 °F)
Boiling point	200 °C (392 °F)

Formula of Potash Alum

The chemical formula of potash alum is K₂SO₄.Al₂(SO₄)₃.24H₂O

Molecular Weight of Potash Alum

The molecular weight of potash alum or potassium aluminum sulfate is 948 grams per mole.

Equivalent Weight of Potash Alum

The equivalent weight of potash alum is 118.59 grams.

Potash Alum in Water

Potash Alum is highly soluble in water and forms an octahedral structure. In water treatment, potash alum is used as a coagulant to precipitate contaminants and impurities.

Potash Alum Dissociation

When potash alum is dissolved in water, it undergoes a process called dissociation, where it breaks down into its simplest ions. In the case of potash alum, the dissociation process can be represented as follows:

K₂SO_4.Al₂(SO₄)₃.24H₂O → 2K⁺ + 2SO₄^2- + 2Al³⁺ + 3SO₄^2- + 24H₂O

In this dissociated state, potash alum has the following ions:

• Potassium ions (K⁺ ): Carry a positive charge and are attracted to negatively charged particles.

• Sulfate ions (SO₄^2-): Carry a negative charge and are attracted towards positively charged particles.

• Aluminum ions (Al³⁺): Carry a positive charge and are attracted towards negatively charged particles.

These ions move around in the water solution and interact with other ions and molecules, depending on the conditions and the presence of other solutes.

Potash Alum Reaction

The chemical reaction for the formation of potash alum (potassium aluminum sulfate dodecahydrate) is as follows:

K₂SO_4(aq) + Al₂(SO₄)_3(aq) + 24H₂O → K₂​SO₄​.Al₂​(SO₄​)₃​.24H₂​O_(s)

This reaction occurs when a concentrated solution containing equimolar amounts of potassium sulfate and aluminum sulfate is allowed to crystallize. The resulting potash alum is a colorless, crystalline solid with a sour taste and an octahedral crystal structure.

Preparation of Potash Alum

Typically, alunite is the mineral from which potash alum is derived. But potassium alum is also made industrially these days. Adding potassium sulfate to concentrated aluminum sulfate solution is one of the most popular preparation techniques. Potassium chloride can be used instead of potassium sulfate if the sulfate has a higher iron content.

Lab Preparation of Potash Alum

The laboratory preparation of potash alum involves the following steps and materials:

Materials Required

The materials required to prepare potash alum are potassium sulfate, aluminum sulfate, sulfuric acid, and distilled water. These chemicals are weighed and dissolved in separate containers.

Procedure

The procedure for the preparation of Potash Alum is as follows:

• First, dissolve about 5g of potassium sulfate in a minimum quantity of distilled water in a beaker.
• In a separate conical flask, dissolve 50g of aluminum sulfate in warm water.
• Then about 3 ml of dilute sulfuric acid is added to make the solution clear.
• The two solutions are then mixed, and the resulting solution is filtered if unclear.
• The concentrated solution is then cooled slowly to allow the potash alum to crystallize.

Cooling and Crystallization

The solution obtained in the preparation of potash alum is cooled slowly, allowing the potash alum to crystallize. The crystals that form are collected using a vacuum pump, washed with a 50/50 ethanol-water mixture, and allowed to dry.

Determining the Yield

The mass of the potash alum crystals is determined, and the percentage yield is calculated based on the theoretical yield.

Observation

The following properties of Potash Alum were observed after its preparation:

Potash Alum
Color	Colourless
Structure	Octahedral
Acidic Property	Changes Blue litmus to red
Solubility	Soluble in water

Precautions

The safety measures that need to be taken while preparing Potash Alum in the Lab are as follows

• Wear protective gear: Put on safety goggles, a lab coat, and gloves to protect yourself from potential chemical splashes or skin contact.

• Handle chemicals carefully: When handling chemicals, always use a funnel to minimize spills and ensure proper containment of the reagents.

• Heat the mixture properly: Heat the mixture gradually and stir continuously to ensure even heating and prevent localized.

• Dispose of waste properly: Dispose of all waste materials, such as used glassware and chemical residues, according to laboratory safety procedures and local regulations.

Uses of Potash Alum

Potash alum has various applications in everyday life. Some of the uses of potash alum are:

• Water purification: Potash alum is used to remove impurities and suspended particles.

• Dyeing: Potash alum is used in the dyeing process to fix the color of the dye to the fabric.

• Tanning leather: Potash alum is used in the tanning process to make leather more durable and resistant to decay.

• Fire retardant: Potash alum is used as a fire retardant for textiles and wood.

• Medicine: Potash alum has been used in traditional medicine for various purposes.

• Baking Powder: Potash alum is a component of baking powder, where it acts as a leavening agent and acid-neutralizing agent.

• Deodorant: It is used as a deodorant due to its ability to absorb moisture and reduce odor.

• Paper Marbling: It is used in the dyeing process for paper marbling, where it helps create a permanent bond between the dye and the material.

Read More,

• Potassium and Calcium
• Potassium Dichromate
• Potassium Bromide Formula

Potash Alum-FAQs

1. What is Potash Alum Used for?

Potash alum is commonly used as a mordant in dyeing fabrics, in water purification, and in traditional remedies for skin conditions due to its astringent properties.

2. Is Potash Alum also Called Fitkari?

Potash Alum is commonly known as Fitkari in Hindi, and people use it for various household and medicinal purposes.

3. What is Action of Heat on Potash Alum?

When heated, potash alum undergoes dehydration, losing water molecules and forming anhydrous alum, which is a white powder.

4. What are Alums?

Alums are a class of chemical compounds, including potash alum, characterized by double sulfates with a specific crystalline structure.

5. Is Potash Alum Harmful?

People generally consider potash alum safe when used in moderate amounts for its intended purposes. However, excessive consumption or inappropriate use may have adverse effects.

6. What is Shape of Crystals of Potash Alum?

Potash alum crystals typically form octahedral shapes, meaning they have eight faces. This characteristic shape is a result of the crystal structure of potash alum.

7. What is Chemical Name of a Potash Alum?

Chemical Name of Potash Alum is Potassium Aluminum Sulfate.

8. What is Molecular Mass of a Potash Alum?

The molecular mass of Potash Alum is Approximately 948.73 g/mol.