SECT. 1 



THE OCEANS AS A CHEMICAL SYSTEM 



13 



value, but in any case an upper limit. Unfortunately, the characters of the solid 

 phases were not established. An approach to equilibrium from the opposite 

 direction was then made by adding some of the precipitate to a fresh sea-water 

 aliquot and measuring the metal ion in solution until it reached a constant 

 value. Such concentrations should at least be minimal values. Where the two 

 values did not coincide, it was presumed that the equilibrium figure must lie 

 somewhere in between. His data are collated in Table IV. 



Table IV 

 Comparison of Calculated and Observed Concentrations of Metals at Saturation 

 with the Observed Concentrations in Sea-Water. (Adapted from Krauskopf, 



1956.) 



There are clouds of uncertainty about both the theoretical and measured 

 figures. In the former case, the activity coefficients are at best rough figures. 

 The effects of complex ion formation have been disregarded. Perhaps the pre- 

 sumed solid phases are in error. For example, silicate or phosphate associations 

 may yield with the metal ions a precipitate giving a lower value of the dissolved 

 cation. The solid phases may not be the simple compounds tabulated, but 

 possibly in some cases basic carbonates. In neither the experimental nor 

 theoretical cases were the effects of temperature taken into account. Both dealt 

 with temperatures 18°-25°C higher than the average oceanic value. 



Overriding these limitations, certain uniformities in the results affirm their 

 utility. In spite of the onerous burden of assumptions in obtaining both the 

 measured and calculated values of maximum concentrations, there is a close 

 agreement between them in most cases. The measured values are as a rule 



