196 



CARNEGIE INSTITUTION OF WASHINGTON. 



the temperature, excess base, or condition of the tide, in this series of de- 

 terminations. The total CO2, however, shows an unmistakable diurnal 

 variation, which is doubtless caused by photosynthetic action, as McClendon 

 has pointed out.^ During the day CO2 is withdrawn from the water by 

 plants, owing to the action of the chlorophyll, and the deficit is afterwards 

 made up by animals, the respiration of plants, or by CO2 from other sources. 

 The average diurnal variation for 5 days was about 4.3 per cent of the total CO2. 

 It is therefore evident that organic factors greatly affect the CO2 content of 

 the sea-water at Tortugas, if they do not wholly determine it. 



Table 1. — Determinations on sea-water at Loggerhead Key, Tortugas. 



\t, temperature, °C. ; CI, chlorine, grams per kilogram; D, density; Ph, hydrogen-ion concentration 

 expressed as —log [H+]; ^Zfc., excess base, in terms of a normal solution, or alkalinity titrated 

 with acid, using methyl red and blowing out CO2; CO2, total, gram per liter.] 



Date, time, and condition of water, 



CI 



D 



Pu+ 



Alk. 



CO2 



10 

 11 

 12 

 13 

 14 

 15 

 16 

 17 

 18 

 19 

 20 



21 

 22 

 23 



24 

 25 



June 10, 

 11, 

 11, 

 12, 

 13, 

 13, 

 13, 

 13, 

 14, 



14, 

 14, 

 15, 

 15, 

 16, 

 16, 

 16, 

 16, 

 16, 

 17, 

 17, 



17, 

 17, 

 18, 



18, 

 18, 



3^30" p. m.; cloudy.. 

 12 noon; fair 



5*'30'" p. m. ; cloudy. . 

 12 noon; after rain 



6''45 ""a. m. ; after rain 



9 50 a. m.; cloudy. . . . 

 12 50 p. m.; cloudy. . . 



4 10 p. m 



9 45 a. m. ; after rain 



and wind 



.3'^45"' p. m. ; wind ... 



5 15 p. m.; wind 



6 30 a. m. ; wind 



11 a. m 



"••lO" a. m. ; fair 



8 15 a. m. ; fair 



11 a. m. ; fair 



4*^15'" p. m.; fair 



5 45 p. m. ; fair 



6 30 a. m 



10 15 a. m.; slightly 



cloudy 



4*'45™ p. m.; rainj'. . . . 



7 p. m.; after rain . . . . 

 7'' 15™ a. m.; after 

 shower 



11 a. m. ; rain 



1 p. m.; rain 



26.6 

 27.6 

 28.2 

 27.4 

 27.1 

 27.1 

 27.5 

 27.6 



27.0 



27.4 

 27.8 

 26.5 

 26.8 

 26.8 

 27.0 

 27.0 

 28.1 

 27.8 

 27.1 



27.3 

 26.8 

 27.6 



26.8 

 26.8 

 26.6 



20.01 

 20.00 

 20.05 

 19.90 

 19.28 

 19.90 

 20.07 

 19.96 



19.89 

 19.87 

 20.00 

 19.94 

 19.31 

 19.99 

 20.00 

 19.99 

 20.05 

 19.98 

 19.99 



20.09 

 19.16 

 19.77 



20.04 

 19.81 

 19.73 



1.02373 

 1.02339 

 1.02326 

 1.02332 

 1.02258 

 1.02342 

 1.02352 

 1.02334 



1 . 02344 

 1.02328 

 1.02333 

 1.02.366 

 1.02371 

 1.02368 

 1.02.359 

 1.02357 

 1.02.330 

 1.02330 

 1 . 02354 



1.02361 

 1 . 02239 

 1.02308 



1.02370 

 1.023.39 

 1.02334 



8.23 

 8.19 

 8.19 

 8.21 

 8.20 



8.19 

 8.22 

 8.21 

 8.21 

 8.21 

 8.07 

 8.19 

 8.20 

 8.23 

 8.21 

 8.20 



8.18 

 8.20 

 8.19 



8.18 



0.002370 

 . 002368 

 .002398 

 .002394 

 .002394 

 .002410 

 .002402 



.002406 

 .002402 

 .002412 

 .002435 

 .002424 

 .022368 

 .002414 

 . 002440 

 .002374 

 .002410 

 .002414 



.002.396 

 .002306 

 .002326 



.002418 

 .002400 

 . 002374 



0.0890 

 .0925 



.0902 

 .0924 

 .0913 

 .0900 

 .0897 



.0881 

 .0863 

 .0873 

 .0910 

 .0869 

 .0904 

 .0896 

 .0888 

 .0873 

 .0873 

 .0928 



.0910 

 .0857 

 .0893 



.0918 

 .0928 

 .0879 



The average value of total CO2 found was 0.0895 gram per liter at about 

 27.2° C, whereas the writer previously found 0.0952 gram per liter for water 

 averaging 19.1° C, including some deeper waters, collected in the Gulf south 

 of Pensacola. The Tortugas water appears to be slightly deficient in CO2, 

 from the standpoint of equilibrium with the atmosphere, if the other samples 

 are assumed to be near the equilibrium requirements, as they seem to be 

 when tested by the equation of Fox for the solubility of CO2 in sea-water. In 

 other words, the Tortugas water appears to be very slightly modified Gulf 

 water. 



1 Diurnal changes in the sea at Tortugas, Florida. Proc. Nat. Acad. Sci., vol. 3, p. 692, 1917. 



