The Gouy Method

The method is shown diagrammatically in Fig. 1. An elongated specimen is suspended so that one end is in a magnetic field of high intensity, while the other end is in a negligible field. On application of the field, the sample experiences a force, /, such that 

Principle of the Gouy method for measuring magnetic Busceptibilities. 

The force on the tube is generally measured by an analytical balance. For most types of work on solid powders a microbalance is not necessary. Numerous other devices have been suggested and used for measuring the force. 

The magnetic fields used are conveniently produced by an electromagnet. The strength used varies from about 5000 to 20,000 gauss. For work on inorganic solids it is essential that the field be variable, so that measurements may be made at several field strengths. 

The samples, which are often in powdered form, may be measured in glass tubes, a small correction being made for the diamagnetism of the glass. For a tube of 8 mm. external diameter, 12 cm. long, and a field of 8000 gauss, the forces exerted on samples, such as are discussed later 

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Results from magnetic susceptibiHty studies have been reported (50—53). Measurements (50) obtained by the Gouy method are shown in Figure 3. These are lower than those of other investigators. However, the temperature dependences of the magnetic susceptibiHties, for the various plutonium allotropes were similar. a-Plutonium single crystals show a slight anisotropy of (54). 

The uncorrected magnetic susceptibility of the cesium alum, determined by the Gouy method using the complex HgCo(NCS)4 as standard, is —0.12 c.g.s. units per gram this has been found to change to —0.03 c.g.s. units after 14 weeks.4... 

For the purpose of this calculation it was necessary to know the diffusion coefficient for ligand and whole molecules of hemocyanin (Table I) and the value of the diffusion coefficient for half molecules of hemocyanin. If the level of calcium ion is reduced in pH 9.6 glycine buffer to the point where no whole molecules remain, the half molecules always are contaminated with one-twelfth size (5S) subunits, so that it is impossible to measure directly the diffusion coefficient of half molecules. For a self-associating system, the Gouy method leads to an average diffusion coefficient which is the Z-average, defined by... 

Magnetic susceptibility and magnetization measurements are made by a variety of techniques. These include the Gouy method, the Faraday method, and change in flux methods. Excellent descriptions of the methods as well as their advantages and limitations are available. " ... 

Susceptibilities were determined by the Gouy method, extrapolated to infinite H (though the effect was small), and corrected for core diamagnetism with Selwood s values. Measurements on Lal2.42 between 1.2 and 80 °K. were made by the mutual inductance method. 

In Table II are assembled the compounds for which measurements have been made (so far by the Gouy method) and the results obtained. The behavior of the manganese compound, Mn (05115)2, is especially interesting. This compound has been investigated over the temperature range 4-530°K. (116, 216), and is found to be antiferromagnetic with a Neel temperature of 134 2°K. Earlier results are thereby superseded. 

Measured as Nujol mulls unless otherwise stated. Measured in methanol solution. Measured by the Gouy method on solid samples at 293-298 K unless otherwise stated. Measured in aqueous solution by the NMR method at 295 K. S... 

The Faraday method appears to have some definite advantages over the Gouy method for work on powdered samples. 

Magnetic susceptibility measurements were made on the several samples by the Gouy method. Susceptibility isotherms for two temperatures are shown in Fig. 9. These curves gives the susceptibility per gram of chromium in the several catalysts, as a function of chromium concentration. The expected rise of susceptibility with decreasing chromium concentration, and the position of point I are clearly shown, especially at low temperatures. In calculating the susceptibility of chromium in each sample it has been assumed that the susceptibilities of aluminum ions and oxide ions remain constant. This procedure is... 

The specific magnetization of these catalysts was so small that most of them could be studied by the Gouy method. The activity tests for the hydrogenation of benzene were carried out in apparatus like that previously described for similar tests on nickel-alumina catalysts. The reaction temperature was 175°. 

The diamagnetic susceptibility of alloys based on indium antimonide and arsenide was measured by the Gouy method for n-type and p-type samples over the temperature range 170-560°K. The relationship the susceptibility and the donor impurity density was determined for the composition 0.3 InAs-0.7 InSb doped with 2.7 10 -2.0-10 wt.<7( tellurium. A correlation between the molar ma etic susceptibility and the total charge Z was established. 

The measurements were conducted by the Gouy method under a vacuum of 10" torr over the temperature range 170-560 K, using the apparatus described previously [6]. Typical temperature relationships obtained are shown in Fig. 1, which shows that the magnetic susceptibility of the solid solutions, which are diamagnetic, usually varies only slightly with temperature. 

We determined also Ihe temperature dependence of the m netic susceptibiliiy of boron phosphide. The diamagnetic susceptibility was measured by the Gouy method in quartz ampoules in a magnetic field of 6500 Oe. Preliminary measurements demonstrated that this m -netic field was sufficient to suppress completely the influence of possible ferromz etic impurities. The measurement method was similar to that described in [9]. 

With large samples, the Gouy method can be very accurate, but this can also be a disadvantage when... 

The corrected magnetic susceptibihty of chromium(II) acetate hydrate determined by the Gouy method (using an aqueous slurry covered with a layer of petroleum ether to exclude air) is reported to be /moi = 94x 10 cm moF. ... 

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