Simultaneous measurements of viscosity and density in solutions undergoing change.

The magnetic suspension densimeter-viscometer has been modified so that the variations of viscosity and density in solutions undergoing change are determined continuously as a function of time. The changes in values for both of these properties are also obtained when solutions of varying composition are passed through the sample cell (<0.5 ml). The new method measures the torque on the magnetically suspended buoy which is held stationary in a stable velocity gradient; this procedure also facilitates the measurement of the density with greater accuracy. Preliminary results relating to the conformation changes of ribonuclease A in the presence of guanidinium chloride and a disulfide cleaving agent are presented.