50 



Dittmar's item CaCOg, which was presum- 

 ably included in order to express the fact 

 that there is on the whole an excess of bases 

 over acids, is obviously incomplete as it 

 stands. From the most recent measurements 

 we gather that a 3 per cent, sodium chloride 

 solution, in equilibrium as regards COj 

 tension with air (which holds good approxi- 

 mately for sea-water), dissolves at 77° F. 

 about 0-07 part of calcium carbonate per 

 thousand. Hence there cannot be as much 

 as 0-123 part per thousand in sea-water. The 

 surplus base should rather be regarded as a 

 mixture of calcium and magnesium bicar- 

 bonates, existing in equilibrium with a certain 

 amount of free COg, and of the products of 

 their hydrolytic dissociation, viz. calcium 

 and magnesium hydroxides. It is the two 



