Step 7. Split into two 500-inl. polyethylene 

 bottles. 



3. Starch solution. 



Step 1. Make a suspension of 3 grams of sol- 

 uble starch in a small amount of cold distilled 

 water and stir into 300 ml. of boiling distilled 

 water. Cover and boil vigorously for a few 

 minutes. 



Step 2. Allow the solution to cool. Pour off 

 a portion of the supernatant liquid into a 

 125-ml. dropping bottle, and decant the remain- 

 der of the supernatant liquid into another 

 dropping bottle and store in a refrigerator. Dis- 

 card the residual portion. 



4. Potassium lodate or Potassium Biiodate 

 Solution. — The solution can be prepared from 

 0.3567 grams of powdered KIO3 (preweighed 

 in laboratory ashore) or from Hellige concen- 

 trated KH(I03)j reagent. Since the validity 

 of the titration results depends primarily on 

 the accuracy of the preparation of the KIO3 or 

 KH(I03) 2 solution, two batches of the standard 

 should be made, and one should be used as a 

 check on the other. If i^owdered potassium salt 

 is used, perform step 1; otherwise, proceed to 

 step 2. 



Step 1. Tap the vial lightly to shake the salt 

 to the bottom of the vial, and remove the screw- 

 cap while holding the vial over a fimnel which 

 has been placed in a 1,000-ml., Class "A", volu- 

 metric flask; then, holding the cap over the 

 funnel, wash the inside of the cap several times 

 with distilled water. Next, pour the salt from 

 the vial into the funnel, and wash down the 

 inside of the vial and the screwcap threads on 

 the outside of the vial at least five times to 

 insure the quantitative transfer of all the salt. 

 Finally, wash the funnel with distilled water 

 at least five times, draining each washing into 

 the flask; go to step 3. 



Step 2. Dilute the Hellige concentrated 

 KH( 103)2 reagent solution, following the in- 

 structions supplied with the boxed ampoule. 

 Care should be taken to quantitatively transfer 

 all the solution into a 1,000-ml., Class "A", 

 volumetric flask. 



Step 3. Dilute the KH (103)2, or KIO3, solu- 

 tion with distilled water to the 1,000-ml. mark 

 on the ^'olumetric flask. Seal the flask with a 

 rubber stoiJjjer that has been cleaned with dis- 

 tilled water, and mix well by inverting and 

 shaking several times. 



Step 4. Pour the solution into a clean dry 

 1,000-ml. amber glass stoppered bottle. 



5. Sodium Thiosulfate Solution. 



Step 1. Boil 6 or 7 liters of distilled water 

 for about 10 minutes to expel carbon dioxide. 



Step 2. Dissolve 15.0 grams of Na2S203 • SHoO 

 in 6 liters of the boiled water. 



Step 3. Add 6 grams of Na2C03 to stabilize 

 the solution. 



Step 4. Store the solution in an amber glass 

 bottle or black bottle out of contact with air 



or direct sunlight. Allow the solution to age for 

 several days before using. 



6. ION Sulfuric Acid.— Safety goggles must 

 be worn when diluting H2SO4. 



Step 1. Pour 600 ml. of cold distilled water 

 into a 1 -liter glass beaker, which has been placed 

 in a pan of cold water. 



Step 2. While stirring the distilled water, 

 sloioly add 280 ml. of concentrated H2SO4. 



Step 3. Allow solution to cool to room 

 temperature. 



Step 4. Pour into a 1,000-ml. graduated cylin- 

 der, and dilute to 1 liter with distilled water. 



Step 5. Transfer the liter of H2SO4 solution 

 into a beaker. Stir until well mixed. 



Step 6. Split the solution into two 500-ml. 

 polyethylene bottles. 



The above quantities of the reagents are 

 enough for titrating approximately 240 samples 

 by the (Macro) Winkler method. 



J-7 Treating (Macro) Winkler Oxygen 

 Samples. — As soon as the oxygen samples are 

 drawn (instructions for drawing oxygen sam- 

 ples are given in ch. E, Taking an Oceano- 

 graphic Station), they should be taken to 

 the ship's chemical laboratory and treated 

 immediately. 



Step 1. Remove the glass stopper from the 

 amber sample bottle, and add 2 ml. of MnCl2 

 reagent and 2 ml. of NaOH-Nal solution. In- 

 troduce the solutions 14 inch below the surface 

 of the liquid. A precipitate will form and sink 

 rapidly to the bottom of the bottle. 



Step 2. Stopper the bottle in such a mamier 

 that no air bubbles are trapped in the bottle; 

 then, shake bottle thoroughly to mix the 

 precipitate. 



Step 3. Repeat steps 1 and 2 with other oxy- 

 gen samples. After approximately 5 minutes, 

 reshake the sample to mix the precipitate 

 thoroughly. 



Step 4. Allow the precipitate to settle about 

 halfway down the bottle; then, remove glass 

 stopper from bottle, add 2 ml. of ION H2SO4, 

 restopper bottle, and shake thoroughly until all 

 precipitate is dissolved. The introduction of the 

 acid may cause bubble formation from the lib- 

 eration of CO2 and N2; this is of no concern, 

 however, as an aliquot of 100 or 50 ml. of the 

 sample is analyzed. 



The sample is now ready for titration. 



J-8 Analysis of Oxygen Samples by 

 (Macro) Winkler Technique.— Analysis of 



oxygen samples includes the following proc- 

 esses: (1) Blank Run, (2) Standardization, 

 (3) Titration of the Oxygen Sample, (4) 

 Calculation of dissolved oxygen. These proc- 

 esses are recorded on Oceanographic Log 

 Sheet-C (fig. J-3). The vessel, cruise, consec. 

 station number, and serial number are obtained 

 from the A-Sheet. 



J-3 



