 | As a measure of the mean molecular weight of a polymeric substance, Fikentscher derived the k value from measurements of the relative viscosity of solutions of polymer solutions. The k value is calculated by applying the following equation:
where c = concentration in g/100 ml;  = viscosity of the solution;  = viscosity of the solvent; k = value acc. to Fikentscher (K = 1000* k)
For Walsroder Nitrocellulose and Walsroder NC-Chips the k value calculated from Fikentscher’s equation is multiplied by 1000 and stated as the K value.
To determine the K value, dissolve 2 g of dried nitrocellulose in 100 ml acetone (with high-viscosity grades an appropriately smaller quantity), and determine the viscosity of the solution at 25°C, using for example a Höppler falling-ball viscometer. Then determine the viscosity of the pure solvent in the same viscometer. Insert the viscosity readings and the nitrocellulose concentrations into the above equation and calculate the k value. The K value is obtained by multiplying the k value by 1000.
Literature: Fikentscher, Cellulosechemie 13,(1932) 58
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