Why do COD tubes have a yellow solid stuck to the inside glass surface?

Document ID

Document ID TE1085

Published Date

Published Date 04/30/2019
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Question
Why do COD tubes have a yellow solid stuck to the inside glass surface?
Summary
COD tube vials with yellow orange solids
Answer
After manufacture, this reagent is a turbid, light orange/yellow liquid. Solids stuck to the sides of the tube indicate that they were shipped or stored on their side, this does not present a problem in the test procedure.

After preparing the sample and blank by adding 2.00 mL of sample/deionized water to the tube the vials should be closed tightly and inverted several times to mix. The yellow solids will re-enter solution during these inversions. Hold the vials by the cap, as the glass vials get very hot during mixing.

Test a COD Standard Solution to confirm expected response.

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