THE SOLUBILITY OF CALCITE IN SEA-WATER. 



317 



Incidentally to the titrations, direct determinations of the total carbon 

 dioxide in the cold and warm solutions were made at the conclusions of 

 the runs, giving 0.101 gm. and 0.078 gm. of C0 2 per liter in the cold and 

 warm solutions, respectively. 



The results obtained show that under otherwise similar conditions 

 there is a tendency for the colder sea-water to retain more carbonate in 

 solution than the warmer sea-water. What was not expected, however, is 

 the fact that the colder water did not dissolve fresh calcite, but appears 

 rather to have remained almost unchanged during the 40 days' run. In 

 other words, ordinary sea-water appears to contain so much carbonate that 

 in contact with the atmosphere at i° C. it neither has nor acquires an appre- 

 ciable solvent action on calcite. At higher temperatures it undergoes a slow 

 diminution in its content of carbonates on being agitated in contact with 

 outdoor air. 



Table 2. — Calcite added to sea-water at room temperature and air passed daily. 



To compare with the above determinations, I had, fortunately, been 

 able to make a few titrations at sea. At two points in the Caribbean, 

 about 13 N., 8i° W., the normality of the carbonates was found to be 

 0.00236 and 0.00238 at 25 C. Water from the Pacific off Payta, Peru, at 

 24° C.j gave 0.00226. These values are a little higher than those found in 

 the laboratory after a few days' agitation and suggest a condition of satura- 

 tion, if not supersaturation, with respect to atmospheric conditions. They 

 throw no light on the variations with temperature, however. 

 Table 3. — Dittmar'' s results for surface waters. 1 



^-Challenger Reports, vol. I, p. 135. Dittmar showed that deep waters have 

 a slightly higher alkalinity than surface waters, p. 206. 



Dittmar made determinations of the "alkalinity," i. e., carbonates, in 

 130 samples of water collected on the Challenger. For reference I have recal- 

 culated and give in table 3 results for surface waters only. 



