62 



Papers from the Department of Marine Biology. 



pressure is multiplied by the correction in the table. Degrees and 

 fractions of a degree may be estimated, because 1 makes about as 

 much difference in the correction as 4 or 5 mm. pressure. 



The mode of calculation is perhaps best shown by the following 

 example: The analysis was made on 10 c.c. of sea-water of Cl = 19.375 

 per kilo, and the room was 20, so the absorption coefficient was 0.765. 

 The length of the graduated portion of the burette B was 9 cm., so 

 the meniscus correction (Hg-H 2 and H 2 0-gas) was 0.0125 c.c. and 

 the capillary depression 3 mm. The barometer minus the capillary 

 depression was 725 mm. The water above the mercury meniscus was 

 0.0565+0.0125 = 0.069 c.c. The total gas (0.54) minus the gas after 

 absorption of C0 2 (0.179) equals the C0 2 (0.361 c.c.) as measured 

 directly; but the 0.069 c.c. of water was hi equilibrium with a gas, a 

 large fraction (0.669) of which was C0 2 ; hence the C0 2 in that water 

 was 0.069X0.669X0.765 = 0.353. In other words, the C0 2 in the 

 water = its volume X the C0 2 fraction+the absorption coefficient. 



Practically all of this C0 2 was pumped out and then reabsorbed; 

 hence the amount originally pumped out was 0.361+0.0353 = 0.3963 

 c.c., and this amount expanded to 39 c.c. was in equilibrium with 11 

 c.c. of water at the end of the first shaking. Hence this 11 c.c. finally 



Ci QOf*Q 



trapped off in T contained 11 X ' X 0.765 = 0.0855 c.c. of C0 2 . 



o9 



This added to the 0.3963 c.c. brings the total up to 0.4818 c.c., and this 

 X 0.8644 = 0.4165 c.c. per 10 c.c. or 41.65 c.c. per liter at and 760 

 mm. This correction of 0.8644 goes outside the table, but the table 

 is probably extensive enough for most determinations, especially at a 

 lower altitude, and the logarithm of the corrections for a more extended 

 range may be found in the Chemiker Kalender or Landolt-Bornstein. 

 The apparatus was tested by making an artificial sea-water of 

 neutral salts, distilled water that had just been boiled 15 minutes in a 

 quartz vessel and cooled with C0 2 -free air passing through it, and 



