16 



PHYSICAL PROPERTIES OF SEA WATER 



coefficient decreases rapidly with increasing temperature and increases 

 slowly with increasing salinity. At a salinity of 35.00°/oo the viscosity 

 at 0°C is 18.9 X IQ-^ g/cm/sec, and at 25°C it is 9.6 X IQ-^ g/cm/sec. 

 The effect of pressure is small. 



This coefficient of viscosity is valid onlj^ if the water is in laminar 

 motion, but, as stated above, since turbulent motion prevails in the sea, 

 an ''eddy" coefficient must be introduced which is many times larger 

 (p. 19). 



Diffusion. In a solution in which the concentration of a dissolved 

 substance varies in space, the amount of that substance which per second 

 diffuses through a surface of area 1 cm^ is proportional to the change 



1334 



X 1.336 



1 1 3381- 



1340 



10 15 



CHLORINITY %. 



10 15 



CHLORINITY. (%o) 



20 



A B 



Fig. 3. A. Refractive index of sea water as a function of temperature and salinity. 

 B. Specific conductance, reciprocal ohms per cubic centimeter, of sea water as a func- 

 tion of temperature and chlorinity. 



in concentration per centimeter along a line normal to that surface 

 {dM /dt = —b dC/dn). In the c.g.s. sj^stem, M is measured in grams per 

 square centimeter, and the concentration C in grams per cubic centimeter. 

 The coefficient of proportionality (6) is called the coefficient of diffusion; 

 for water it is equal to about 2 X 10~^ cm^/sec, depending upon the 

 character of the solute, and is nearly independent of temperature. 

 Within the range of concentrations encountered in the sea the coefficient 

 is also nearly independent of the salinity. 



The statement concerning the coefficient of thermal conductivity in 

 the sea applies also to the coefficient of diffusion. Where turbulent 

 motion prevails it is necessary to introduce an ''eddy" coefficient that is 

 many times larger and that is mainly dependent on the state of motion. 



Surface Tension. The surface tension of sea water is slightly 

 greater than that of pure water at the same temperature. 



