Preparation:
Ammonium chloride can be prepared by the neutralization reaction between ammonia (NH₃) and hydrochloric acid (HCl):
NH3(g)+HCl(g)→NH4Cl(s)
Industrially, it is often produced as a byproduct of the Solvay process, which manufactures sodium carbonate (soda ash).
Properties:
White crystalline solid with a saline taste.
Soluble in water, with solubility increasing with temperature.
Slightly soluble in alcohol and insoluble in acetone.
Melting point: 338°C (640°F).
Sublimates at around 520°C (968°F).
Storage:
Store in a cool, dry, well-ventilated area away from heat and moisture.
Keep in a tightly sealed container to avoid moisture absorption.
Uses:
Medical: Used as a urinary acidifier to treat kidney disorders such as kidney stones.
Pharmaceuticals: Acts as an expectorant in cough medicine to help clear mucus.
Textile and Leather Industries: Used as a mordant to help dye adhere to fabrics.
Food Industry: Serves as a flavoring agent and acidity regulator.
Batteries: Used as an electrolyte in zinc-carbon batteries.
Assay (Determination of Concentration/Purity):
Common Method - Acid-Base Titration:
1.Prepare a Standard Solution:
Dissolve a known amount of a strong base (e.g., sodium hydroxide, NaOH) in water to create a standard solution of known concentration.
2.Take the NH₄Cl Sample:
Accurately weigh a sample of NH₄Cl and dissolve it in a known volume of water.
3.Add an Indicator:
Add a pH indicator (e.g., phenolphthalein) to the NH₄Cl solution. The indicator changes color when the solution reaches neutrality.
4.Titrate:
Slowly add the NaOH standard solution to the NH₄Cl solution while stirring.
The NH₄Cl reacts with NaOH, forming water and ammonium hydroxide (NH₄OH).
The endpoint is indicated by the color change of the indicator, signaling the neutralization of the solution.
5.Calculate the Concentration:
Measure the volume of NaOH used in the titration.
Use the stoichiometry of the reaction and the volume of NaOH to calculate the concentration or purity of the NH₄Cl sample.