SOME CRITERIA OF ACCURACY FOR THE MEASUREMENT OF THE OSMOTIC PRESSURE OF COLLOIDS IN BIOLOGICAL FLUIDS

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Abstract
The inconsistency of published values for the osmotic pressure of colloids of similar biological fluids indicates a need for standardization of methods. Criteria of accuracy and of equilibrium are suggested, and details of the procedures evolved are presented. Dynamic methods of estimating the osmotic pressure are to be avoided. The micro-osmometer of Krogh, which employs collodion sacs, is satisfactory. The preparation of membranes of suitable permeability is described. The specific permeability number of a membrane is defined as the number of cc. of water filtered per second through an area of 1 sq. cm. and thickness of 1 cm. at a pressure of 1 atm. Membranes possessing permeability numbers in the range from 10 X 10-8 to 50 X 10-8 are suitable. It is suggested that henceforth, in connection with such measurements, the permeability numbers of membranes, and such other data as will allow others properly to evaluate the accuracy of the determinations, should be published.

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