Morris 1974 Edward Arnold

Morris JG (1974) A biologist's physical chemistry. 2nd ed. Edward Arnold, London:390 pp.

» A biologist's physical chemistry

Morris JG (1974) Edward Arnold

Abstract: The major innovation in this Edition is its 'conversion' to SI. Working biologists are understandably loth to exchange their familiar units, e.g. litre, °C, calorie, for the equivalents prescribed by this internationally agreed system of measurement which many physiologists consider less appropriate to their needs than to the requirements of the physical scientist. Yet .. the biologist cannot (and should not) nurture his prejudices when in the related disciplines of Chemistry and Physics his students are being instructed through the medium of SI.

• Bioblast editor: Gnaiger E

Selected quotes

• p 70 footnote: Although it is quite usual to talk of 'the osmotic pressure of a solution', this is in fact an irrational statement. In the first place, no isolated solution can 'possess' an osmotic pressure since the phenomenon of osmosis is only demonstrable in a system in which pure solvent and solvent in solution (or two solutions in which the solvent is at different activities, see p. 64) are separated by a semi-permeable membrane. In the second place, since the osmotic pressure is the pressure that must be imposed upon the solution to maintain its solvent in equilibrium with pure solvent at the same temperature (p. 74), it is disconcerting to have to refer to this pressure as if it were exhibited by the solution (in the same sense that a gas exhibits a pressure). There appears to be a need for a new and agreed term to denote the 'osmotic potential' of a solution — meanwhile in common with current usage we shall continue to refer to the osmotic pressure of a solution, whilst trusting that you will understand the true meaning of this rather unsatisfactory phrase.

Comment on first place: This represents a valid point, suggesting that 'pressure' should be replaced by the 'pressure difference' of the chemical transformation in an osmotic process.

Comment on second place: This is a refusal to accept the term 'pressure' for the osmotic pressure as a pressure difference which at equilibrium is opposed to and identical in magnitude to an applied barometric pressure. This refusal illustrates the paradigmatic opposition against the concept of isomorphic pressure, and the suggested alternative term 'osmotic potential' leads directly to the prevailing pressure-force confusion - see The linear flux-pressure law.