SKC Limited Chromic Acid Test Kit - Manual (Page 11)

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Analysis
8. Check that comparator colour standards disc Chromium 66200 is inserted. Hold comparator
against good north daylight (not fluorescent lighting) and rotate comparator disc until match
with ‘sample’ solution is obtained.
9. The value appearing in the window of the comparator is the amount of hexavalent chromium
in milligrams per cubic metre (mg/m3) of air based on a sample volume of 120 litres. Note this
value.
10. Repeat steps 6 and 7 above using the solution from step 5. Note the reading for reference.
In ideal conditions there should be no reading from this solution as it was made with a clean
unused filter. If a reading is obtained this highlights a problem with procedures:
11. check on the purity of reagents and filters
12. check for contamination caused by unclean apparatus
13. Record results (see page 10).
14. Clean all apparatus between measurements and at the end of testing. The filter head should
be cleaned to avoid cross-contamination between samples.