Viskoznost: izbrani modeli in načini merjenja

V članku so opisane osnove obravnave dinamične viskoznosti raztopin. Predstavljena je razlaga viskoznosti v raztopinah in štirje modeli, ki obravnavajo odvisnost viskoznosti od volumskega deleža topljenca. Da bi bili masna koncentracija in volumski delež povezana, je vpeljana intrinzična viskoznost. Nato je predstavljenih sedem merilcev viskoznosti, ki temeljijo na Stokesovi sili ali Poiseuillovem zakonu. Pri vsakem merilniku je opisan princip delovanja in pričakovano merilno območje, količina vzorca ter negotovost meritve. Na koncu so predstavljeni še izbran pomen viskoznosti v farmacevtski industriji in načini, kako lahko viskoznost raztopine zmanjšamo z dodatkom aditivov.

Viscosity: selected models and measurement methods

This article presents selected aspects of dynamic viscosity of solutions. Interpretation of viscosity in solutions is presented, introducing four models explaining viscosity dependence on volume fraction. To connect mass concentration and volume fraction, intrinsic viscosity is introduced. Then, seven viscometers are presented which rely on Stokes’ drag force or Poiseuille’s law. Working principle of each viscometer in explained as well as their measuaring interval, sample consuption and measurement limitations. At the end, the selected relevance of viscosity in industry is presented, such as in farmaceutical industry, and how the viscosity of solution can be reduced by adding additives.