Tuesday 17 December 2013

Tips In Using A Dissolved Oxygen Test Kit

By Cornelia White


It is normal for people to use the dissolved oxygen test kit. This is especially true if the person wants to identify what the state of an aquatic ecosystem is. The result of this testing will surely help a lot in assessing productivity and pollution within areas like streams, rivers, and lakes. For the testing, here are the steps to follow.

First of all, prepare the BOD bottle. One will need to fill this up with a sample H2O. Simply dip the said bottle on the aquatic ecosystem one plans on testing. Wait for the bottle to fill up while ensuring that there are no bubbles coming inside. Tilt the bottle from side to side so that one can let the bubbles escape.

Prepare the manganese sulfate as well. Add this to the sample using a calibrated pipette. The said pipette should be inserted into the H2O's surface, squeeze it slowly after that. When doing this, one has to make sure that no air bubbles are being introduced in this sample to avoid altering the result.

The next preparation that one has to do involves the alkali-iodide-azide reagent. This reagent will be mixed to the sample as well. For the person to be able to add the said reagent into the sample easily, one is required to have the calibrated pipette. Utilize a pipette to add the reagent the same way one added the manganese sulfate.

Carefully put the stopper into the bottle, making sure that there are no air introduced inside. One should then turn the BOD bottle upside down. Do this step several times just to mix its contents. Do not forget to check whether the sample has bubbles or not. If there are air bubbles, then that means one needs to discard the said sample and then start over.

Add sulfuric acid to one's sample as well. Just like how one has added the other elements into the sample before, one will also have to use the pipette when it comes to adding the sulfuric acid. This time, one needs to tip the acquired pipette above the H2O surface instead of inserting it below. Stopper the bottle and turn it over to mix the contents.

There should be an Erlenmeyer flask prepared beforehand too. The person will then have to place 201ml of the sample solution into the Erlenmeyer flask. Make sure to get the right amount for this to get better results. For the person to get the right amount for the sample solution, utilize a graduated cylinder. After that, add sodium thiosulfate with the pipette to change this into a pale straw color.

Adding starch solution is the next step to this testing. The most ideal amount of the starch solution to add to the sample is two ml. When one adds the said solution, one's sample should turn blue as well. One should then continue to add sodium thiosulfate until this solution becomes clear in color.

Do not forget to record how many sodium thiosulfate one has added to the solution. With this, one must be able to calculate the element content of the said sample. Since the person is going to use this dissolved oxygen test kit, assume that every sodium thiosulfate equates to one ml per liter of dissolved oxygen.




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