Figure J-4. ( Micro) Winkler apparatus. 



Figure JS. Details of the microburette and the digital 

 counter. 



tapered ground glass ball and socket joint. The 

 microburette is held in the proper position in- 

 side the box by clamps, and the magnetic stirrer 

 is installed to swing out so the sample flask can 

 be positioned beneath the delivery tube of the 

 microburette. 



All equipment should be clamped or attached 

 rigidly to the titration bench, and sea racks 

 should be secured to the top of the table to hold 

 reagent bottles and sample flasks. 



J-14 Preparing the Reagents. — Reagents re- 

 quired for the (Micro) Winkler titration proc- 

 ess are the same as those required for the 

 (Macro) Winkler titration method with the ex- 

 ception of the sodium thiosulfate solution. Pre- 

 pare the Manganous reagent, the Sodium 

 Iodide-Sodium Hydroxide solution, the Starch 

 solution, the Potassium lodate (or biiodate) 

 solution, and the ION Sulfuric acid by instruc- 

 tions listed in paragraph J-6, Preparing the 

 Reagents. The Sodium Thiosulfate solution for 

 the (Micro) Winkler titration method usually 

 will be prepared in 70 grams per liter concen- 

 tration ; however, in areas where the dissolved 

 oxygen content of the sample is more than 10 

 ml./L, a stronger concentration should be used. 

 To prepare the solution proceed as follows: 



Step 1. Boil W2 liters of distilled water for 

 about 10 minutes to expel carbon dioxide. 



Step 2. Dissolve the NaaSjOs • 5H2O in about 



J-8 



