Instructions for Use

Pour

• Unscrew Cap. 
• Extract the plug carefully. Use a firm grip to avoid dropping.
• Rinse inside and outside of the bottom part of the blind plug with 5-10mL of water while holding it over the beaker to capture the liquid.
• Pour entire contents of the Standardette® Solution into the beaker.
• Rinse the inside of the ampule 5 times with intermediate swirling into the beaker. Use 5- 10mL of water for each rinse.
• Top up volume in beaker to ~80mL with DI water.

Titrate

• Rinse a 50mL burette twice with approximately 10mL of the Thiosulfate solution.
• Clamp the burette in position and fill the burette to just above the zero mark with the Thiosulfate solution.
• Release any bubbles from the tip of the burette.
• Bring the Thiosulfate solution meniscus down to or below the zero mark, read, and record the burette reading to the nearest 0.01mL.
• Add 3g of ACS grade Potassium iodade followed by 4mL of 1:1 HCl.Ensure that the Potassium iodade is entirely free of Iodate ions.
• Titrate while stirring. Solution will be dark brown.
• Add 1mL of Starch solution (0.4%SS + 0.3%CH2O) when solution becomes light brown in color.
• Stir vigorously as the endpoint approaches, adding fractions of a drop of titrant using a glass stir rod.
• Look for a fading and lagging endpoint. There will be a very slight blue starch color remaining which will fade in approximately 5 minutes.
• Read the burette to the nearest 0.01mL.
• Complete the titration in exactly 3 minutes.
• Correct the volume of titrant to 20°C.

 
Calculate

• Normality = Meq on the label /mL of Thiosulfate solution used