How to Prepare Aluminium Hydroxide Gel Balanced Equation Principle and Laboratory Method
Aluminium hydroxide is an inorganic compound made up of aluminium ion and hydroxide ions. It is an amphoteric compound which means it can act as an acid as well as a base. Aluminium hydroxide minerals occur in nature. It holds the property of an antacid. The IUPAC name of the aluminium hydroxide is Aluminium trioxide.
Hydrophobicity is a property of aluminium hydroxide. In most cases, it produces lyophobic solutions. The hydrolysis of aluminium chloride can be used to prepare aluminium hydroxide gels.
3H₂O + AlCl₃ Al(OH)₃ + 3HCl
Aluminium Compounds
Aluminium is an inorganic element belonging to the thirteenth group. Aluminium reacts with nitrogen gas and forms an aluminium nitride
Al + N₂ → AlN
Aluminium reacts with the oxygen gas and forms aluminium trioxide also known as alumina.
Al + O₂ → Al₂O₃
Aluminium reacts with hydrochloric acid and forms aluminium trichloride as a product and hydrogen gas as a byproduct. This aluminium trichloride is used in the preparation of aluminium hydroxide gels.
Al + HCl → AlCl₃ + H₂
Aluminium reacts with the dilute sodium hydroxide solution and forms aluminium trihydroxide. This molecule is amphoteric in nature. Therefore, it further reacts with the dilute sodium hydroxide solution and forms sodium meta illuminate aa a product and hydrogen gas as a byproduct.
Al + NaOH (dil) → Al(OH)₃ → Na[Al(OH)₄] + H₂
Aluminium hydroxide reacts with the water molecules and forms a solution. This reaction can be used to clear drains. This reaction is also used to remove the obstructions from the drainage pipe.
AlCl₃ + H₂O → [Al (H₂O)₆]⁺³ + 3Cl⁻
Aluminium trichloride reacts with hydrochloric acid and forms white fumes.
AlCl₃ + HCl → white fumes
Structure of Aluminium Hydroxide
(Image will be uploaded soon)
Aluminium cation is attracted with three hydroxide anions.
Properties of Aluminium Hydroxide
The Colour of aluminium hydroxide is white.
Its density is 2.43 g/cm³.
Its melting point is 300 degrees celsius.
Its molar mass is 78.0036.
Aluminium Hydroxide Gel Preparation
Aluminium hydroxide is hydrophobic in nature. Generally, it forms lyophobic solutions. Aluminium hydroxide gel preparation can be done with the hydrolysis of aluminium chloride.
AlCl₃ + 3H₂O → Al(OH)₃ + 3HCl
Step by Step Aluminium Hydroxide Gel Preparation
Prepare the 2% aluminium chloride solution (by adding 2g of aluminium chloride in 100 ml water).
Add 100 ml distilled water to the conical flask.
Boil the water with the help of the wire gauze.
Add 10 ml of the above prepared 2% aluminium chloride solution. Add this solution with the help of the dropper of the burette. As aluminium compounds are violent in nature.
Constantly stir the solution while adding aluminium chloride.
Heat the solution until you see a coloured solution. The colour of the aluminium hydroxide solution is white.
Leave the mixture for cooling at normal temperature.
The cooling solution is called aluminium hydroxide gel.
Precaution You Need to keep During Aluminium Hydroxide Gel Preparation
Clean the conical flask with a steaming process to avoid any kind of impurities.
The byproduct (Hydrochloric Acid) formed in this reaction causes destabilization of the prepared gel. therefore, needs to be removed by the dialysis process.
Aluminium chloride solutions need to be added in a dropwise manner.
Uses of Aluminium Hydroxide Gel
It is used for treating gastric ulcers.
It is used in making vaccines.
It is used in cosmetics.
It serves as an intermediate compound in various reactions.
It is used as a flame retardant.
It is used in the manufacturing of certain drugs.
Side Effects of Aluminium Hydroxide Gel
Aluminium hydroxide is generally used as a medicine. But to some people, it shows side effects when consumed. These side effects involve:
Constipation is a possibility. Other issues, such as haemorrhoids and intestinal blockage, could result as a result of this. Contact your doctor or pharmacist right away if constipation persists or worsens.
If your doctor has prescribed this drug, ensure that he or she has determined that the benefits are more and the side effects are negligible. The majority of people who use this medication experience no significant side effects.
Exercise daily and drink ample amounts of water to avoid constipation. Constipation can be avoided by taking this medicine with a magnesium-containing antacid. Stool softeners may be beneficial as well. Other antacids, stool softeners, and laxatives might be discussed with your doctor or pharmacist.
In the intestines, aluminium-containing antacids bind to phosphate, a vital physiological component. If your kidneys are normal, this can result in low phosphate levels, especially if you take big dosages for a long time.
Get medical help right away if you experience any of the following side effects or symptoms of a serious medical problem: black/tarry stools, mental/mood disorders (e.g., confusion, deep sleep), pain with urination, stomach/abdominal pain, or vomit that looks like coffee grounds.
This medicine seldom causes a severe allergic reaction. However, if you witness any symptoms of some allergic response, such as a rash, redness, itching/swelling (particularly of the face/tongue/throat), extreme dizziness, or shortness of breath, go to the doctor right away.
This is a very important list of some potential adverse effects. Contact your doctor or pharmacist if you have any other side effects not listed above.
Aluminium Hydroxide: How to Use It
Before each dose, give the bottle a good shake. The flavour of the suspension may be improved by refrigerating it. Do not allow yourself to become frozen. This drug is most effective when taken without any other liquids. If necessary, dilute your dose with a little water.
This contains aluminium, which can interfere with the absorption of other medications (such as digoxin, iron, tetracycline antibiotics, pazopanib, and quinolone antibiotics like ciprofloxacin). To avoid this problem, talk to your doctor or pharmacist about how to schedule your medications.
If your acid problems persist or worsen after one week of use, or if you suspect you have a significant medical concern, seek medical help right away.
Did You Know?
Aluminium hydroxide reacts with both acid and base.
Aluminium hydroxide is used in coating TiO2 nanoparticles.
Aluminium hydroxide is used to reduce phosphate levels in people with certain kidney conditions.
Aluminium hydroxide consumption reduces the absorption of the other medicines in the body. Therefore, two-hour gaps before and after taking aluminium hydroxide should be maintained for consuming other medicines with this.
Hence the article is very useful for the students to understand the properties, structure of aluminium hydroxide. Step by Step procedure of preparation of aluminium hydroxide gel is given in the above article.
FAQs on Aluminium Hydroxide Gel Preparation and Chemical Reaction
1. What is aluminium hydroxide gel preparation?
Aluminium hydroxide gel preparation is the laboratory process of producing a colloidal gel of Al(OH)3 by precipitating aluminium salts with a base. It is commonly prepared by reacting aluminium chloride with ammonium hydroxide:
AlCl3(aq) + 3NH4OH(aq) → Al(OH)3(s) + 3NH4Cl(aq)
The white gelatinous precipitate formed is washed to remove soluble impurities and dispersed in water to form aluminium hydroxide gel, widely used as an antacid and pharmaceutical suspension.
2. What is the chemical formula of aluminium hydroxide?
The chemical formula of aluminium hydroxide is Al(OH)3. It consists of one aluminium ion (Al3+) combined with three hydroxide ions (OH-). Aluminium hydroxide is a white, gelatinous, amphoteric compound that acts as both a weak acid and a weak base in chemical reactions.
3. How do you prepare aluminium hydroxide gel in the laboratory?
Aluminium hydroxide gel is prepared by adding a dilute base to a solution of an aluminium salt to form a gelatinous precipitate of Al(OH)3.
Steps in aluminium hydroxide gel preparation:
- Prepare a dilute aqueous solution of AlCl3.
- Add dilute NH4OH solution slowly with constant stirring.
- Formation of white gelatinous precipitate: AlCl3(aq) + 3NH4OH(aq) → Al(OH)3(s) + 3NH4Cl(aq).
- Wash the precipitate with distilled water to remove soluble ammonium chloride.
- Disperse the washed precipitate in purified water to obtain aluminium hydroxide gel.
4. Why is aluminium hydroxide called an amphoteric hydroxide?
Aluminium hydroxide is called an amphoteric hydroxide because it reacts with both acids and bases.
Reactions with acids:
Al(OH)3(s) + 3HCl(aq) → AlCl3(aq) + 3H2O(l)
Reactions with bases:
Al(OH)3(s) + NaOH(aq) → Na[Al(OH)4](aq)
This dual behavior explains its role in neutralization reactions and its pharmaceutical use as an antacid.
5. What is the balanced chemical equation for the formation of aluminium hydroxide from aluminium chloride?
The balanced chemical equation for aluminium hydroxide formation from aluminium chloride is AlCl3(aq) + 3NH4OH(aq) → Al(OH)3(s) + 3NH4Cl(aq).
This is a precipitation reaction in which insoluble aluminium hydroxide forms as a white gelatinous solid, while ammonium chloride remains dissolved in solution.
6. What is the principle behind aluminium hydroxide gel preparation?
The principle behind aluminium hydroxide gel preparation is precipitation by double decomposition when an aluminium salt reacts with a weak base.
When aluminium chloride reacts with ammonium hydroxide, insoluble Al(OH)3 precipitates due to its low solubility product (Ksp). The gelatinous nature of the precipitate allows it to form a colloidal gel upon dispersion in water.
7. What are the uses of aluminium hydroxide gel?
Aluminium hydroxide gel is mainly used as an antacid and pharmaceutical suspending agent.
Major uses:
- Neutralizes excess stomach acid: Al(OH)3 + 3HCl → AlCl3 + 3H2O.
- Used in treatment of gastric ulcers and hyperacidity.
- Acts as a phosphate binder in medical therapy.
- Used in vaccine formulations as an adjuvant.
8. Why is ammonium hydroxide preferred in aluminium hydroxide gel preparation?
Ammonium hydroxide is preferred because it produces a pure, easily washable precipitate of Al(OH)3 without introducing strongly basic metal ions.
Using sodium hydroxide may form soluble sodium aluminate due to amphoteric behavior:
Al(OH)3(s) + NaOH(aq) → Na[Al(OH)4](aq)
Ammonium hydroxide is a weak base and helps control precipitation, preventing dissolution of the formed aluminium hydroxide.
9. What are the properties of aluminium hydroxide gel?
Aluminium hydroxide gel is a white, gelatinous, amorphous precipitate that is insoluble in water but soluble in acids and strong bases.
Key properties:
- Chemical formula: Al(OH)3
- Amphoteric nature
- Low solubility in water
- Forms colloidal dispersion (gel) in water
- Neutralizes gastric acid
10. What precautions should be taken during aluminium hydroxide gel preparation?
The main precautions in aluminium hydroxide gel preparation are controlled addition of base, thorough washing, and avoidance of excess alkali.
Important precautions:
- Add NH4OH slowly with constant stirring.
- Avoid excess base to prevent dissolution of precipitate.
- Wash the precipitate to remove soluble impurities like NH4Cl.
- Use distilled water to maintain purity.
- Store the gel in well-closed containers to prevent contamination.
