448
MALCOLM S. GORDON
Bradley and Munro (1965), Horne (1965), and Weale (1967). Whalley
(1967) surveys recent developments in studies of nonliving systems.
Chapters 9 and 10 in Johnson et al. (1954) remain the most penetrating
and comprehensive reviews of pressure effects on biological systems.
Knight-Jones and Morgan (1966) and Morita (1967) review much of
the more recent biological literature. A brief summary of the major
effects of pressure follows.
Pure water and complex electrolyte solutions such as seawater up to
salinities of at least 410/,, (presumably also, therefore, the body fluids
of fishes ) all have comparable compressibilities. Over the temperature
range from 0" to 25"C, increase in pressure from 1 to lo00 atm produces a decrease in specific volume of 3 4 % (Newton and Kennedy,
1965).
The compression of solutions like seawater appears to decrease the
average size of hydrogen-bonded aggregations of water molecules in
the solutions and to increase the number of such aggregations. This
change in solvent structure produces viscosity versus pressure curves
which initially decrease, go through a minimum, then increase. The
pressures at which the minima occur vary with temperature, as does
the magnitude of the maximum viscosity decrease. At 0°C the viscosity
decrease reaches a minimum about 44% below viscosity at 1 atm at
a pressure of about 700 atm. The decrease is smaller at higher temperatures (Home, 1965).
The pressure-induced changes in water structure combine with
pressure-induced changes in degree of hydration of dissolved ionic
substances to produce changes in both the electrical and the colligative
properties of the solutions. For example, the specific conductance of
3596, salinity seawater at 25°C increases about 6% between pressures
of 1 and 1000 atm. The activation energy for electrical conduction in
seawater decreases by a comparable amount over the same pressure
range (Horne, 1965). The freezing point depression of pure water, fish
body fluids, and seawater increases 9°C between 1 and loo0 atm
( Hodgman, 1962-1963; Scholander et al., 1957).
Increased pressure produces a multiplicity of effects on the properties
and chemical reactivities of solutes present in aqueous solutions. Essentially all of the drastic effects of pressure on solutes, such as denaturation of proteins, occur at pressures far higher than the 1100-atm limit
present in the ocean. Less drastic effects which do occur within this
range include changes in solubility, changes in rate constants for reactions, and changes in equilibrium constants. Most of these changes
appear to be in large part attributable to the occurrence of volume
changes associated with the processes. Processes involving volume de-
MALCOLM S. GORDON
Bradley and Munro (1965), Horne (1965), and Weale (1967). Whalley
(1967) surveys recent developments in studies of nonliving systems.
Chapters 9 and 10 in Johnson et al. (1954) remain the most penetrating
and comprehensive reviews of pressure effects on biological systems.
Knight-Jones and Morgan (1966) and Morita (1967) review much of
the more recent biological literature. A brief summary of the major
effects of pressure follows.
Pure water and complex electrolyte solutions such as seawater up to
salinities of at least 410/,, (presumably also, therefore, the body fluids
of fishes ) all have comparable compressibilities. Over the temperature
range from 0" to 25"C, increase in pressure from 1 to lo00 atm produces a decrease in specific volume of 3 4 % (Newton and Kennedy,
1965).
The compression of solutions like seawater appears to decrease the
average size of hydrogen-bonded aggregations of water molecules in
the solutions and to increase the number of such aggregations. This
change in solvent structure produces viscosity versus pressure curves
which initially decrease, go through a minimum, then increase. The
pressures at which the minima occur vary with temperature, as does
the magnitude of the maximum viscosity decrease. At 0°C the viscosity
decrease reaches a minimum about 44% below viscosity at 1 atm at
a pressure of about 700 atm. The decrease is smaller at higher temperatures (Home, 1965).
The pressure-induced changes in water structure combine with
pressure-induced changes in degree of hydration of dissolved ionic
substances to produce changes in both the electrical and the colligative
properties of the solutions. For example, the specific conductance of
3596, salinity seawater at 25°C increases about 6% between pressures
of 1 and 1000 atm. The activation energy for electrical conduction in
seawater decreases by a comparable amount over the same pressure
range (Horne, 1965). The freezing point depression of pure water, fish
body fluids, and seawater increases 9°C between 1 and loo0 atm
( Hodgman, 1962-1963; Scholander et al., 1957).
Increased pressure produces a multiplicity of effects on the properties
and chemical reactivities of solutes present in aqueous solutions. Essentially all of the drastic effects of pressure on solutes, such as denaturation of proteins, occur at pressures far higher than the 1100-atm limit
present in the ocean. Less drastic effects which do occur within this
range include changes in solubility, changes in rate constants for reactions, and changes in equilibrium constants. Most of these changes
appear to be in large part attributable to the occurrence of volume
changes associated with the processes. Processes involving volume de-