Concentration, definition magnetic

Ignition of manganous nitrate at 200° would be expect to yield pyrolusite. The actual result in this series is that while the manganese clearly has an oxidation state of - -4 at high concenti ations, yet the oxidation state is definitely 4-3 at low concentrations. Both magnetic and chemical analysis are in j eement on this point. Another curious... 

More than 30 years ago, Scott, Obenhaus, and Wilson (135) suggested that for lithium chloride, a solute to solvent ratio of 1 10 corresponded to a definite composition, and they quoted earlier measurements (134) as indicating two distinct, definite values for the magnetic susceptibility of lithium chloride above and below the concentration, corresponding to a decahydrate in solution. Likewise, anomalies were also found in the density of such solutions. Scott, Obenhaus, and Wilson also quoted Hiittig and Keller (83) who found that the densities, refractive indices, and coefficient of extinction of lithium halide solutions showed discontinuous changes with concentration for molar ratios of water to solute of 6, 30, and 75. 

A wide variety of chemical and spectroscopic techniques has been used to determine functionality in humic substances. Although nuclear magnetic resonance (NMR) spectroscopy has been used for a much shorter period of time than most other techniques for determining functional group concentrations, this technique has provided far more definitive information than all other methods combined. However, substantially more work must be done to obtain the quantitative data that are necessary for both structural elucidation and geochemical studies. In order to increase the accuracy of functional group concentration measurements, the effect of variations in nuclear Overhauser enhancement (NOE) and relaxation times must be evaluated. Preliminary results suggest that spectra of fractions isolated from humic substances should be better resolved and more readily interpreted than spectra of unfractionated samples. 

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