Using a mixture of normal red cells and plasma, of P.C.V. approximately 45
per cent, duplicate samples were spun at. 3000 r.p.m. for varying periods of time
Fu;. 4-The effects of variation in the speed and duration of centrifugation at different
levels of P.C.V. (‘‘observed venous hematocrit’’).
and the volume of trapped plasma was measured. Figure 3 illustrates a typical result., and it cats 1)e sects tha.t the rate of change with time is considerable at 30 minutes, smaller at. 1 hour and much smaller at 2 hours. Thus, small variations
in time of centrifugation around a. meats of 30 minutes can be expected to produce
a considerable scatter of results. However, at. 60 minutes the rate of change has diminished sufficiently for reproducible results to be attained with relative ease
(see below).