EXPLORATION 2D:

WEST-GAEKE METHOD: evaluation of SO₂ content in Air (45 min)

	Pipet exactly 10 mL of the absorbing solution into the scrubber (absorber).
	Connect the air pump to the scrubber
	Aspirate the air sample through the absorber at a rate 3.5 L/min. The location of your sampling will be given by the instructor. Stop when your total air volume is 38.2 L.
	Transfer the absorbing solution to the plastic sample container.
	Repeat the sampling for another 10 mL of absorbing solution.
	Transfer both absorbing solutions to the testing tubes marked "1" and "2".
	Add 10 mL of absorbing regent (0.1 M sodium tetrachloromercurate) to the tube marked (0). This is going to be your blank solution.
	Add 1 mL of acid-bleached pararosaniline solution and 1 mL of formaldehyde for each tube. Wait 20 min for color development.
	Measure the absorbance at 570 nm.

 

Sampling	time	volume of air [L]	absorbance at 570 nm
1
2

CALCULATION:

Convert the volume of air sampled to the volume at standard temperature and pressure. Compute the microliters of SO₂ in the sample by dividing the absorbance by the slope of the calibration plot (assume that your experimental conditions are STP conditions). Then the concentration by  volume is: