Middle molecular solutes

Contaminant species Particulate matter and suspensions Colloidal impurities High-molecular-weight organics Middle-molecular-weight organics Low-molecular-weight organics Multivalent ionic solutes Acids... 

Other groups also used gel filtration exchange to measure middle molecules and perform in vitro toxicity tests (C7, D21). However, many of the middle molecular weight substances isolated by these techniques proved to be much smaller than anticipated. This discrepancy was due to the intrinsic inadequacies of the standard gel filtration techniques for the isolation of middle molecules, as pointed out by Furst et al. (F13) and later by Schoots et al. (S13). These investigators used analytical techniques to demonstrate that middle molecular fractions obtained by gel filtration comprised many low-molecular-weight solutes, such as carbohydrates, amino acids, polyols, aromatic substances, and other UV-absorbing solutes, and also sodium chloride, acetate, phosphate, and sulfate (S10). Thus these fractions do not exclusively represent middle molecules. 

Figure 2.70. Typical examples of chromatograms. The solution is branched polyethylene in tetrahydrofuran. Top light-scattering intensity 1 (LS 90°) and refractive index difference A (Rl). Middle molecular weight M. Bottom radius of gyration R, plotted as a function of the retention volume Vr. (From Ref. 9.)...

Henderson, L. W., Clark, W. R., and Cheung, A. K. (2001). Quantification of middle molecular weight solute removal in dialysis. Semin. Dial. 14, 294. 

Molecular liquids. The bottom layer, carbon tetrachloride (CCI4), and the top layer, octane (CbHis), are nonpolar molecular liquids that are not soliirle in water. The middle layer is a water solution of blue copper sulfate. 

Towards the middle of 1929, Mark was clearly close to establishing a viscosity equation. He and H. Fikentscher published a somewhat complex relationship of viscosity, and molecular volume (33). It was based on the Einstein relationship of viscosity and solute concentration. 

In solution, the two end chromophores of a polymer chain produce a molecular-weight effect even without energy migration, because the end rings have only one neighbor and thus yield fewer excimers than the middle chromophores. The probability M for an aryl vinyl polymer with N repeat units is given by... 

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