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Phys. Rev. Lett. 71, 4267–4270 (1993)

Equilibrium sedimentation profiles of screened charged colloids: A test of the hard-sphere equation of state

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Roberto Piazza, Tommaso Bellini, and Vittorio Degiorgio
Dipartimento di Elettronica, Università di Pavia, 27100 Pavia, Italy

Received 18 June 1993; published in the issue dated 20 December 1993

Equilibrium sedimentation profiles of concentrated suspensions of charged colloids are accurately determined by measuring the intensity of the depolarized light scattered by optically anisotropic particles. From the data we derive the osmotic pressure Π versus the particle volume fraction Φ. The Π(Φ) values obtained with strongly screened colloids are in excellent agreement with the predicted hard-sphere equation of state. The data show that, besides gravitation, there is an additional force acting on the particles, probably due to the buildup of an electrostatic sedimentation potential.

© 1993 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.71.4267
DOI:
10.1103/PhysRevLett.71.4267
PACS:
82.70.Kj, 64.70.-p