Viscosimetric determination

Viscosimetric determination of activity is used only with pectic enzymes displaying the random-action pattern. The activity is mostly expressed as the time required for attaining a 50% decrease of viscosity (in s) or as the amount of enzyme required for attaining a certain decrease of viscosity per unit time.223... 

Deviations of (r02) ( ) M can also be brought about by other causes, for example by chain branching as an extreme case we can think of a highly complex branched structure in which the many branches are again branched, so that it can hardly be defined as a chain. The conformation statistics is then no longer applicable, and for such polymers a value of a near to 0 has even be found this means that V ( ) M, just as with small molecules. Viscosimetric determination of M is then no longer applicable, since [q] is independent of M. 

Viscosity. The first viscosimetric determinations made by Guba (1943) and Roth (1947) have not shown clearly the very high viscosity of fish actomyosin. It has only been observed (Hamoir, 1949) and investigated (Hamoir, 1955) recently. 

M. Laskowski and M. Seidel. Viscosimetric determination of thymonucleodepolymerase. Arch. Biochem. 7 465-473 (1945). 

The viscosimetric determination of the molecular weight, which we have applied in our experiments, has accuracy of 5 per cent and does not allow the differentiation of molecular weights of 22,700, 19,000, and 9,000 for the corresponding types of mbbers. This suggests that the cleavage of C=C bonds, located at distances of 420, 280, and 100 units from the macromolecule end, would not affect the measured molecular weight. 

Gans, C. Schnee, J. Scherf, U. Staikos, G. Pierri, E. Dondos, A. Viscosimetric determination of the statistical segment length of wormlike polymers. Polymer, 1998, iPfi/ , 4155 158. 

Viscosimetric determinations. The Newtonian intrinsic viscosity of the xanthan molecule was determined by measuring the viscosities of several dilute polymer solutions with a Contraves Low-Shear viscometer. Extrapolation at zero polymer concentration of the reduced specific viscosity gave the value of the intrinsic viscosity, and the Huggins constant was calculated from the slope of the curve. 

Therefore the critical concentration is proportional to the reciprocal intrinsic viscosity. The factor of 2.5 assumes that the polymer coils behave like hard spheres in solution. Viscosimetric measurements for the determination of the intrinsic viscosity have to be performed in dilute solutions at concentrations clearly below c for an exact linear extrapolation according to the Huggins equation (Eq. 4.9). This condition is fulfilled for example in Fig. 4.2, where it is shown that the data points for the viscosimetric determination are below the critical concentration calculated from Eq. (7.7). 

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