Krogh 1935; Yoder and Dresher 1934; Pomeroy 

 and Kirschman 1945) for this determination. 

 The oxygen samples taken from the M/V Pom - 

 pano were collected in the conventional 

 300-milliliter B. 0. D. bottles. Using 

 50-milliliter burettes, 100-milliliter 

 aliquots were titrated. 



Since then many analyses have had to 

 be made on samples of limited volume. For 

 this reason a semimicro method is now em- 

 ployed. Samples are collected in 60-milli- 

 liter pyrex reagent bottles. Since their 

 volumes vary considerably, each one has to 

 be calibrated and the appropriate volume cor- 

 rection included in the final calculations. 



The semimicro determination is carried 

 out as follows: 



Reagents: 



a. NaOH-Nal reagent. Dissolve 

 900 gm. of Nal and 400 gm. of NaOH in 

 550 ml. of water. 



b. MnCl2 reagent. Add 40 gm. 

 of MnClj to 10 ml. of 6N HCl and di- 

 lute to 100 ml. with distilled water. 

 Stir until solution is complete. 



c. 0.003N sodium thiosulfate 

 reagent. This reagent is standardized 

 with potassium biniodate or recrystal- 

 lized potassium dichromate. 



d Starch reagent. Prepared by 

 dissolving 1 gm. of starch in a satu- 

 rated NaCl solution. 



1. Very carefully displace the bottom 

 layer of the sample with 0.6 ml. of NaOH-Nal 

 reagent. Make this addition with a 2-milli- 

 liter automatic pipette. 



2, In the same manner add 0.6 ml. 

 the MnCl2 reagent. 



of 



3. Displace the portion of sample in 

 the bottle neck by carefully replacing the 

 glass stopper. If air should be inadvertent- 

 ly trapped in the bottle, discard sample. 



4. Shake sample, being careful not to 

 introduce air. 



5. After 5 minutes add 2.5 ml. of 

 12N HCl with an automatic pipette. 



6. Replace stopper displacing excess 

 sample and shake vigorously. 



7. Draw out a 10-mill iliter portion 

 with a 10-milliliter volumetric pipette and 

 add to a 50-milliliter Erlenmeyer flask. 



8. Using a 5-milliliter micro bu- 

 rette, titrate the 10-milliliter portion 

 with approximately 0,003N sodium thiosul- 

 fate. As the end point is approached, add 

 3 drops of starch solution. The titration 

 is complete when the blue coloration disap- 

 pears. 



9. Convert the burette readings to 

 oxygen concentration units (ml/1 or ppm) 

 with the aid of the oxygen conversion chart. 

 Do not forget to correct for sample bottle 

 volume. 



Total Carbon Dioxide 



For the determination of total CO2 we 

 used the Van Slyke volumetric blood gas 

 apparatus and followed the method of Green- 

 berg, Moberg, and Allen (1932). The tech- 

 nique is as follows: 



1. Rinse the apparatus' reaction 

 chamber with a small portion of the sample. 

 Discard the washings and eliminate all air 

 from the apparatus by completely filling 

 with Hg. 



2. Introduce 1 ml. of Hg into the 

 cup by opening the connecting valve between 

 the cup and reaction chamber. Remove with 

 filter paper any water entering the cup 

 with the Hg. 



3. Add exactly 10 ml. of sample to 

 reaction chamber. For measuring and intro- 

 ducing sample, use a 10-milliliter pipette, 

 accurately calibrated to deliver between 

 marks, and having a stopcock seal between 

 either the upper or lower end. Place a rub- 

 ber tip on the end of the pipette to prevent 

 air from entering. Remove any portion of 

 the sample on top of the Hg seal with a 

 piece of filter paper. 



4. Run 1 ml. of C02-free 0.2N lactic 

 acid—' into the cup on top of the mercury. 



3/ The CO2 Is removed in the Van Slyke 

 apparatus after which the solution is 

 kept under oil. 



