Holmarc's Magnetic Susceptibility - Gouy's Method Apparatus (Model No: HO-ED-EM-08) is designed for the determination of magnetic susceptibility of solid samples. The apparatus consists of a pair of electromagnets with constant current power supply and a tube in which the sample powder is taken. The magnetic field is measured using a digital Gauss meter. The sample weight measurements are taken with the help of a Gouy balance.
In the Gouy's method of susceptibility measurement, the solid sample in the form of a long cylinder is hung from the pan of a balance and is placed in such a way that one end of the sample is between the pole pieces of the magnet 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 gain or loss in sample weight.
A sample with a para magnetic compound will be pulled down towards the magnet and will provide a positive difference in apparent mass. Diamagnetic compounds can either exhibit no apparent change in weight or a negative change, as the sample is slightly repelled by the applied magnetic field. With a para magnetic sample, the magnetic induction is stronger than the applied field and magnetic susceptibility is positive. A diamagnetic sample has a magnetic induction much weaker than the applied field, and a respective negative magnetic susceptibility.
Introduce the gauss meter probe between the poles of electromagnet. Change the current from zero up to its maximum value and from maximum to zero. Note the corresponding field strength from gauss meter at different intervals. Plot a graph Magnetic field Vs Current.
Mass susceptibility of the solution, χ'solution can be obtained from this relation.
χ'solution = ( ms / ms + mw ) χ'salt + ( mw / ms + mw ) χ'water
where χ'water = -0.72 x 10-6, ms is the mass of the salt dissolved in ms of water.
|Material||Magnetic Susceptibility x 10-5 (cm3·mol-1)|
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. The sample is suspended between the magnetic poles through an attached string. The experimental procedure requires two separate reading to be performed. An initial balance reading is performed on the sample of interest without a magnetic field. A subsequent balance reading is taken with an applied magnetic field. The apparent change in mass from the two balance readings is the result of magnetic force on the sample.