Electromagnetic Fields’ Impact on Salt Crystals

Authors: Parth Lamsal, Charles Liu, Samson Lo, Nathaniel Chan (Lancaster Royal Grammar School)

Supervisor: Mr. King (Lancaster Royal Grammar School)

Research Objective

The purpose of this study is to investigate how exposure to coil-generated magnetic fields (0 A, 2 A, 4 A current settings) influences the crystallisation of three salts: Sodium Chloride (NaCl), Potassium Nitrate (KNO₃), and Magnesium Sulfate (MgSO₄). The research focuses on observable differences in crystal morphology and coverage between control (no current) and driven coil conditions.

Although the original aim was to isolate electromagnetic effects, in practice the main observable factor was coil heating, which accelerated evaporation and modified crystal size and structure. Nevertheless, the study demonstrates how current-induced changes to the experimental environment can alter the crystallisation process.

Key Concepts

Crystallisation Process

Crystallisation is the process by which solute particles leave a solution and form an ordered solid lattice. It involves two main steps:- Nucleation: first formation of crystal nuclei.- Crystal Growth: enlargement of crystals as more ions join the lattice.Factors such as temperature, evaporation rate, and presence of external fields can influence crystal size, habit, and uniformity.

Magnetic Field

A magnetic field is generated by moving charges (current). In a coil, the field is strongest inside and near the centre. The strength is proportional to current. Theoretically, a magnetic field could affect ion motion or convection in solution. In practice, the heating from current flow (Joule heating, P = I²R) also strongly affects evaporation rate.

Joule Heating

When current flows through the coil, resistance causes energy dissipation as heat. This heat is transferred to the air and to the crystallising dish placed above, increasing the evaporation rate of the solution. At 2 A the effect was mild, while at 4 A the coil overheated and interrupted the run.

Evaporation and Supersaturation

As water evaporates from the solution, the concentration of dissolved salt rises. Once supersaturation is reached, ions begin to nucleate and form crystals. Faster evaporation leads to earlier and more widespread nucleation, often producing smaller but more numerous crystals.

Morphology

Crystal morphology refers to the external shape and structure of crystals. NaCl typically forms cubic crystals, KNO₃ tends towards needle-like forms, and MgSO₄ can form acicular or prismatic crystals. Heating can change the habit, producing sharper edges or irregular branching.

Electromagnetic Field

Although our experiment used DC current (so a static magnetic field plus heating), an electromagnetic field generally refers to coupled electric and magnetic fields. In industrial contexts, AC or oscillating fields can affect diffusion, ion transport, and convection more strongly than static fields.

Fluid Dynamics & Diffusion

Local heating can create convection currents in the dish. This affects how ions are transported to nucleation sites. In our experiment, higher current likely created stronger convection and faster drying at the centre.

Literature Review

Lopez advanced crystallisation research by improving nucleation control and using process intensification techniques (see: Nucleation and Crystal Growth: Recent Advances and Future Trends).

Marek Bruna investigated Al alloys with EMFs at 0.1–0.2 T, finding mechanical properties improved at 0.2 T (see: Affecting the Crystallization of Al-based alloys by Electromagnetic Field | Request PDF).

Abdrakhamov explored alternating EMF effects on oxides and salts, proposing that field orientation and intensity influence growth (see: To the mechanism of influence of an alternating electromagnetic field on crystallization process of oxide refractory melts).

Experimental Setup

Materials

• Sodium Chloride (NaCl)

• Potassium Nitrate (KNO3)

• Magnesium Sulfate (MgSO4)

Equipment

• Beakers (400mL and 100mL)

• Crystallization

• Crystallization dishes

• Solenoid (copper wire coil)

• DC power supply

• Wires

• Ammeter

• Voltmeter

• Distilled water

• Funnel and filter paper

• Buchner funnel

• Buchner flask

• Optical microscope

• Stopwatch

• Ruler

• Stand

• Camera

• Lab stands and clamps

Controlled Variables

Solution preparation: 100 g salt in 400 mL hot distilled water.

Volume per dish: equal aliquots (~30 mL).

Room temperature (ambient, uncontrolled).

Same dish type and size.

Same placement above the end of the coil.

Independent Variable

Current applied to coil: 0 A, 2 A, 4 A.

Individual PSUs were swapped for 2A and 4A .

Dependent Variables

Observed morphology, size, and distribution of crystals.

Electromagnet Setup

In this experiment, a premade school coil of approximately 120 turns was used, with an iron core (about 1.5 cm in length, 1 cm × 1 cm cross-section) inserted into the coil to concentrate the magnetic flux. The coil was then mounted horizontally using clamps so that the end face of the iron core pointed upwards. A metallic dish of thickness 2 mm was placed directly on top of the exposed iron core, such that the bottom of the dish made full contact with the core surface, with no significant air gap.

Additionally, a light bulb was placed in series with the coil at 4 A to act as a visual indicator of circuit health, allowing us to monitor for potential short circuits and overheating.

Field Strength Calculations

It was observed that at 2 A, the coil experienced only moderate heating, while at 4 A the coil overheated and failed, preventing further sustained measurements..

Safety and Ethics

Electrical Safety

The coil was powered using a DC supply limited to 4 A. Excessive current, particularly at 4 A, caused significant heating, so the coil and connecting wires were continuously monitored. Insulated leads and secure clamps were used to prevent short circuits. A small in-series light bulb was connected as a visual indicator of overcurrent or short-circuiting.

Thermal Safety

The coil and surrounding metal parts became hot during operation, especially at 4 A. Gloves and eye protection were worn when handling hot equipment, and care was taken to avoid touching the coil directly while it was powered.

Magnetic Field Safety

The magnetic field generated was weak, estimated to be less than 0.02 T at the dish surface, posing minimal risk to personnel. Sensitive electronic devices were kept away from the coil during operation.

Chemical Safety

Saturated salt solutions were handled carefully, with goggles and gloves worn to prevent contact with skin or eyes. Potassium nitrate, being an oxidiser, was handled cautiously to avoid contamination or ignition. Hot solutions were transferred using funnels and handled with tongs or heat-resistant equipment.

Environmental and Ethical Considerations

Solutions were disposed of according to local waste disposal guidelines, and no toxic salts were used. The experiment did not involve any living organisms or pose ethical risk to humans. All procedures were supervised and designed to minimise environmental and personal risk.

Procedure

Set 1 (I = 0A)

Initially we poured out 400mL of distilled water into each beaker, heating them each up to 60 degree Celsius.

100g of each salt was then poured into their respective beaker. Then using a magnetic stirrer to ensure the salts fully dissolve.

Each solution was then poured into a reagent bottle.

100mL of each solution was then heated in an evaporating basin to near boiling and then poured in an crystallising basin to crystallise.

48 hours later, we came and filtered the crystals formed. Smaller crystals such as Magnesium Sulphate were filtered out by using a Buchner funnel.

We then observed each salt crystal underneath a microscope, noting characteristics to use as our control variable for future crystals.

Set 2 (I = 2A)

We clamped the coil to the stand to make sure the dish on top would balance whilst connected to the PSU. A light bulb was also in circuit for a visual representation of the circuit's health.

The dish was then placed on top, and the sunlight was later blocked to control the environment.

48 hours later, we came to collect the crystals that formed. Due to moderate heating from the coil, the excess water evaporated.

We then proceeded to view them underneath the microscope.

Set 3 (I = 4A)

Set 3 repeated Set 2's set up, whilst swapping out PSU models to set the current at 4A.

Additionally, after the 48 hours, the light bulb was turned off, whilst the crystals in the dish were not fully crystallised. Therefore we concluded that the coil had overheated.

This then meant filtering out the crystals like Set 1 rather than to scrape them off in Set 2.

Data Collection

Observed differences qualitatively. At 0 A, crystals formed slowly and uniformly. At 2 A, more numerous, sharper crystals were observed, consistent with faster evaporation. At 4 A, partial crystallisation occurred before the coil overheated and stopped. No quantitative timing or size distribution measurements were made.

Error Analysis

Coil Heating and Evaporation (2 A)

At 2 A, the coil produced moderate heating.

Increased temperature accelerated evaporation of the salt solutions, affecting crystal nucleation and growth rates.

Evaporation was not directly controlled, so variations in crystal size, coverage, and morphology could be partly due to thermal effects rather than magnetic fields.

Overheating and Run Termination (4 A)

At 4 A, the coil overheated, causing the experiment to stop prematurely.

Joule heating scales as equation3, so 4 A produced roughly four times the heating of 2 A.

The interruption prevented full crystallisation, producing incomplete crystal growth and uneven coverage.

Dish Thickness and Air Gap

The dish was 2 mm thick, acting as a non-magnetic “gap” between the coil’s iron core and the solution.

Even small misalignments or imperfect contact between the dish and core could reduce the effective magnetic field at the crystal surface.

Any air pockets, surface irregularities, or material inconsistencies introduce uncertainty in the end-field strength.

Iron Core Permeability

The soft iron core’s relative permeability eqaiution4 was assumed to be ~200.

Actual permeability varies with purity, shape, temperature, and prior magnetisation.

Variations in equation4(x)​ affect the magnetic flux density inside the core and at its end, adding uncertainty to the calculated equation5​.

End-Field Approximation

The magnetic field at the exposed end was approximated as ~50% of the internal field.

This simplification ignores fringing effects and non-uniformity across the dish area.

Real end-field strength may differ by ±50% or more from this estimate.

Current and Power Fluctuations

Resistance of the coil increases with temperature; at 4 A, actual current may have decreased slightly over time.

This would reduce the real magnetic flux below the theoretical calculation.

Solution and Environmental Factors

Ambient temperature and humidity were uncontrolled.

Minor differences in solution preparation, stirring, or placement could affect nucleation timing and crystal morphology, independent of the magnetic field.

Conclusion

The experiment demonstrated that applying current to a coil under crystallisation dishes altered the appearance of salt crystals. The most consistent explanation is heating-driven changes to evaporation. Direct magnetic effects cannot be claimed. Nevertheless, the project illustrates how simple lab setups can influence crystallisation pathways and provides a foundation for more controlled experiments.