182 



Pidpergffom 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 nam. 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 CI = 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-H20 and H20-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 CO2 (0.179) equals the CO2 (0.361 c.c.) as measured 

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

 large fraction (0.669) of which was CO2; hence the CO2 m that water 

 was 0.069X0.669X0.765 = 0.353. In other words, the CO2 in the 

 water = its volume X the CO2 fraction + the absorption coefficient. 



Practically all of this CO2 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 



trapped off in T contained 11x^^5— X 0.765 = 0.0855 ^•^' ^^ ^^2. 



This added to the 0.3963 c.c. brings the total up to 0,4818 c.c, and this 

 X0.8644 = 0.4165 c.c. per 10 c.c. or 41.65 c.c. per liter at 0° 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 C02-free air passing through it, and 



