Evans method magnetic susceptibility

It is thus evident that, in order to interpret the results obtained by one of the relaxation methods, a thorough investigation of the unperturbed equilibrium properties is required. In general, solution magnetic susceptibilities measured by the NMR method of Evans [83, 84] are used to this end, the equilibrium constant for the equilibrium in Eq. (37) being determined by ... 

Magnetic susceptibilities of solutions — These are useful parameters for determining equilibrium constants for reactions involving spin changes. The Evans nmr method utilizes the observed shift in the resonance line (say of a proton of t-BuOH or hexamethyldisilox-ane) in solution when a paramagnetic substance is added. The paramagnetic shift A/ is related to the magnetic moment (jj, of the solution at TK by the approximate expression... 

Fig. 1. Linear plot of solution magnetic susceptibility obtained by the Evans method.

In solutions, nuclear magnetic resonance is of use from the H paramagnetic shift (AAv) of a reference compound, corrected for the diamagnetic contribution of the ligands, the paramagnetic susceptibility is evaluable using the Evans method [10]... 

Bertini et report a detailed study of the magnetic properties of myglobin, in which they determined the axial and orthorhombic terms of the paramagnetic susceptibility tensor using a combination of hyperfine chemical shift measurements and static suscetibility measurements (Evans Method). The determination of the magnetic anisotropy provided a measurement of the residual dipolar couplings and also permitted a separation of the contact and pseudocontact chemical shift contributions of resonances of the Fe(III) ligands. 

Finally, we should note that the shifts in resonance frequencies caused by paramagnetic substances can be used to measure the magnetic susceptibilities of those materials [76]. The method, commonly known as Evans method, involves the use of two equally concentrated solutions of an inert substance, typically 2% of f-butanol, one also containing the paramagnetic material. One solution is placed in a capillary, inside the other. Two resonances for the butyl groups are then observed, and the shift between them is attributed to the magnetic material, and is in fact directly proportional to the differenee in volume suseeptibilities for... 

Grind a very pure Mn(II) sulphate or chloride to a very fine size. Pack in the Gouy tube and measure the susceptibility by the Gouy or Evans methods (Sec.2.1.3) and calculate the magnetic moment. 

---