Crystallization of Salol (Phenyl Salicylate)

Observing crystal growth under a microscope in real time

Crystallization Intermediate (High School) 30 min ~$10.00

Objective

Observe the real-time growth of salol crystals under a microscope, studying nucleation, crystal growth rates, and the effect of temperature on crystal morphology.

Background

Salol (phenyl salicylate) has a melting point of 43°C, making it perfect for observing crystallization under a microscope in real time. It can be melted on a microscope slide and watched as it crystallizes, with the crystal fronts growing visibly. Supercooling is easily demonstrated.

Safety Warnings

  • Salol can irritate skin — wash hands after handling
  • Handle microscope slides carefully — breakage risk
  • Do not overheat salol (decomposes above 70°C)

Required PPE

goggles

Materials

  • Salol (phenyl salicylate) (2 g)
    Melting point 43°C
  • Microscope slides (3)
  • Cover slips (3)

Equipment

Microscope (at least 40x) Hot plate or warm water bath Tweezers Timer

Procedure

1

Place a small amount of salol on a microscope slide. Warm gently on the hot plate until the salol melts (43°C). Place a cover slip on top.

5 min Do not overheat — decomposes above 70°C
2

Place the slide on the microscope stage. Focus at low magnification (40x). Allow to cool.

3 min
3

Watch for nucleation points — small bright spots where crystal growth begins.

5 min
4

Observe the crystal growth fronts expanding across the field of view. Time the growth rate.

5 min
5

Touch a cold metal object to one edge of the slide to create a temperature gradient. Observe how crystal morphology changes with cooling rate.

5 min
6

Draw or photograph the crystal patterns. Note the needle-like or fan-shaped morphology.

5 min

Expected Results

Needle-like or fan-shaped crystal fronts should be visible growing across the field of view in real time. Faster cooling produces finer needles; slower cooling produces larger, more regular crystals. Supercooling may be observed (liquid persists below 43°C until nucleation occurs).

Cleanup

Allow slides to cool completely. Scrape off salol and dispose in solid waste. Clean slides with ethanol.

Details

Category
Crystallization
Difficulty
Intermediate (High School)
Duration
30 min
Est. Cost
$10.00
Steps
6
Materials
3

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Frequently Asked Questions

What is the objective of Crystallization of Salol (Phenyl Salicylate)?
Observe the real-time growth of salol crystals under a microscope, studying nucleation, crystal growth rates, and the effect of temperature on crystal morphology.
How difficult is Crystallization of Salol (Phenyl Salicylate)?
This experiment is rated as Intermediate (High School). It takes approximately 30 minutes to complete.
What safety precautions are needed for Crystallization of Salol (Phenyl Salicylate)?
Key safety precautions include: Salol can irritate skin — wash hands after handling; Handle microscope slides carefully — breakage risk; Do not overheat salol (decomposes above 70°C).
What materials are needed for Crystallization of Salol (Phenyl Salicylate)?
The main materials required are: Salol (phenyl salicylate), Microscope slides, Cover slips.
What results should I expect from Crystallization of Salol (Phenyl Salicylate)?
Needle-like or fan-shaped crystal fronts should be visible growing across the field of view in real time. Faster cooling produces finer needles; slower cooling produces larger, more regular crystals. Supercooling may be observed (liquid persists below 43°C until nucleation occurs).