The Gouy’s method involves measuring the force on the sample by a magnetic field and is dependent on the tendency of a sample to concentrate a magnetic field within itself.
The solid sample in the form of a long cylinder (area of cross section A) is hung from the pan of a balance and is placed such that one end of the sample is between the pole-pieces of the magnet (field H) and the other one is outside the field. The force exerted on the sample by the inhomogeneous magnetic field is obtained by measuring the apparent change ( m ) in the mass of the sample. The susceptibility χ is given By 2χ = 2 Δ mg/AH If the sample is in the form of powder, it is filled in a long nonmagnetic tube which is then suspended from the pan of the balance.
