Experiment 66

Objective

To identify the presence of potassium ions in a sample by observing the formation of a white precipitate with tartaric acid.

Introduction

Potassium salts react with a high concentration of tartaric acid (H₂C₄H₄O₆) to form a white precipitate of potassium hydrogen tartrate (KHC₄H₄O₆). In some cases, this precipitate appears upon mixing the solution with a glass rod.

Reaction:

KCl + H2C4H4O6 → KHC4H4O6 ↓ + HCl

Materials

Chemicals

·       Potassium chloride (KCl)

·       Tartaric acid (H₂C₄H₄O₆)

·       Distilled water

Apparatus

·       Test tube

·       Test tube holder

·       Glass rod

Reagents

·       3–4 ml of the potassium sample solution in a test tube

·       5% tartaric acid solution prepared in a 250 ml beaker

Procedure

1.    Place 5–6 ml of the potassium sample solution in a test tube.

2.    Add tartaric acid to the sample.

3.    Mix the solution with a glass rod and shake well.

4.    Observe and record any changes in the reaction.

Observation

A white precipitate forms upon the addition of tartaric acid, indicating the presence of potassium ions.

Questions

1.    What is a potassium salt?

2.    What reaction occurs during the potassium test?

3.    What reagent is required in the potassium test?

4.    What color forms in the potassium test?