Gouy balance

Amongst a wide range of interest in optics, Brownian motion, and experimental physics, Gouy also had a strong intrigue for the phenomena of magnetism.

Gouy derived a mathematical expression showing that force is proportional to volume susceptibility for the interaction of material in a uniform magnetic field in 1889.

From this derivation, Gouy proposed that balance measurements taken for tubes of material suspended in a magnetic field could evaluate his expression for volume susceptibility.

Gouy became interested by this hypothesis and subsequently formulated an interaction expression of materials within cylinder designations in uniform magnetic fields, displaying how the force would be proportional to volume susceptibility.

For unknown reasons, he never introducethis concept himself, although it was eventually replicated by others over its simplicity, thus emerging as a regular means to measure magnetic susceptibility.

The Gouy balance measures the apparent change in the mass of the sample as it is repelled or attracted by the region of high magnetic field between the poles.

A sample with a paramagnetic compound will be pulled down towards the magnetic, and provide a positive difference in apparent mass mb – ma.

[3] In a practical device, the whole assembly of balance and magnet is enclosed in a glass box to ensure that the weight measurement is not affected by air currents.

[7] Since it requires a large and powerful electromagnet, the Gouy balance is a stationary instrument permanently set up on a bench.