Steps for disolved oxygen

What is the first step in collecting a water sample from a stream?

Find a stream.

What should you do after finding a stream?

Set up your equipment in a safe area.

What is used to collect the water sample?

A sample bottle.

When collecting water, in which direction should you face?

Face upstream.

What should you do with the sample bottle before filling it?

Rinse the sample bottle with stream water twice.

How should the sample bottle be filled?

Fill the bottle completely, cap it underwater if possible, and check for air bubbles.

What is the next step after filling the sample bottle?

Add the first dissolved oxygen reagents (follow the bottle labels and kit instructions for the exact number of drops).

What should you do after adding the first dissolved oxygen reagents?

Cap and invert several times.

What needs to settle after inverting the bottle?

The precipitate.

What reagent is added after the precipitate settles?

The acid reagent (the sulfuric acid reagent).

What indicates that the sample is 'fixed'?

When all precipitate dissolves after mixing.

What do you rinse with the fixed sample?

The titration vial.

To what mark do you fill the titration vial?

The 20 mL mark, reading the bottom of the meniscus.

How much titrant should be in the syringe?

Fill the titration syringe with titrant to 10.0 mL, ensuring no large air bubbles are present.

What is done with the titrator?

Insert the titrator into the vial cap.

How should the titrant be added during the titration?

Add titrant slowly while swirling.

What color indicates the sample is becoming ready for the starch indicator?

Pale yellow.

What should you do after adding the starch indicator?

Continue titrating drop by drop until the blue color disappears and the sample becomes clear.

How is the dissolved oxygen concentration determined?

By reading the amount of titrant remaining in the syringe, which indicates the concentration in mg/L.