Diffractometric measurements of the tonicity volume relations of human red cells in hypotonic systems.

Red cell volumes in media sufficiently hypotonic to produce partial hemolysis have been measured with a high speed hematocrit and by an improved diffraction method. A comparison of the results shows that the upward departures from the linear relation based on the van't Hoff-Mariotte law are not observed when the volumes are measured diffractometrically. Downward departures are observed at low tonicities by both methods. These results provide strong evidence that the upward departures are due to the inclusion of semirigid ghosts in the column of packed red cells which is measured when the volumes are found with the hematocrit.