SKC Limited Chromic Acid Test Kit - Manual (Page 10)

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Analysis
The comparator
The Lovibond 2000 comparator fitted with chromium VI comparator disc 26620 covers the range
0-0.1 mg chromium VI per cubic metre of air in steps of:
0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10
This is suitable for the measurement of 120 litres of sample drawn at 2 litre/minute for 60 minutes.
Removing the filter paper for analysis
1. Transfer your sampling system to clean, non hazardous area to perform the analysis.
2. Remove filter using forceps, taking care not to cause damage, and place filter into 50 ml plastic
beaker.
3. Using 10 ml measuring cylinder, add 8 ml 0.25M sulphuric acid to the beaker.
4. Wait 10 minutes for dissolution of any hexavalent to take place, swirling solution occasionally.
5. Using 5 ml measuring cylinder add 2 ml diphenylcarbazide solution to beaker and swirl to mix.
Allow to stand 10 minutes.
6. Transfer one new unused filter membrane to a clean 50 ml plastic beaker using forceps and
repeat steps 2 - 4 above.
7. Fill a comparator cell to 10 ml mark with ‘sample’ solution and place in right hand compartment
of Lovibond comparator. Place a second cell containing deionised water in left hand
compartment.