The Sea-water and its Physical and Chemical Properties 

 Table 14. The specific heat of sea-water at 17-5^ 



49 



Salinity (°bo) 

 c„ 





 1000 



5 

 0-982 



10 

 0-968 



15 

 0-958 



20 

 0-951 



25 

 0-945 



30 

 0-939 



35 

 0-932 



40 

 0-926 



The dependence of Cp for sea-water on the temperature has not yet been closely 

 investigated, but presumably it is of the same form as that for pure water. Figure 26 

 shows the effect of temperature on Cj, for pure water and for sea-water with 35%o S. 

 The dependence of c^ on the pressure/? can be found using well known thermodynamic 



0-95 



0^4 



0-93 



10 20 30 40 50 



r, "C 

 Fig. 26. Specific heat for pure water and for sea water at 35o/(,p salinity. 



principles (Ekman, 1914). If the pressure/? is taken in decibars, and the density of the 

 water is p, the absolute temperature T, the coefficient of thermal expansion /S, and J 

 is the mechanical equivalent of heat (4-1863 x 10^ ergs/cal or dyn cm/cal), then 



dp pj \ 8t 



^' 



Ekman has calculated the value of c^ for atmospheric pressure and for pressures from 

 p = 2000 top = 10,000 decibars, corresponding to depths of about 2000 to 10,000 m 

 (Table 15). At great depths c^ differs appreciably from 1 and this must be taken into 

 account in accurate theoretical calculations. 



Table 15. Specific heat of sea-water at different pressures when ct = 28 (34-8%o) 



The relationship k = c^jc^ is also of interest. The specific heat/constant volume 

 c,; is a little less than Cp. From thermodynamics the equation 



Cp = c„ + ^^ 



pixj 



