Test if it is possible to explain the know ORP reduction when adding H2O2 into a saltwater

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Lasse

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The H2O2 interacting with the bicarbonate?
pH was not dropping - redox was dropping unnatural in the RO sample. To be true - I have no idea why it drop. But it did not recover as it use to do in a reef,

Sincerely Lasse
 
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New water and the start looks different - higher ORP. But this IMO rather normal. I use branf new probes and they normally will have around a week before they stable on a true level.

RO water; magenta - change of test water

1628143780863.png

Tap water; magenta = change of test water; Olive = picking up a zip tie that had been dropped into the bucket

1628144121773.png

Will add some H2O2 this morning.

Sincerely Lasse
 
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Preliminary result from the new test run says that the rathe strong rise of ORP after adding H2O2 in the start in the first test run probably was caused of the low starting ORP. This new test run do not show a strong rise - if any. However not either a dip, The control - adding 5 ml H2O2 to my 300 L DT shows the normal dip

1628149258241.png


3) false reading because of local reaction between the metallic part of the redox probe.
As it is now - I think that this theory can be leaved busted. The dip we see in saltwater is not because of our measurement technique. At least have this investigation show that. I will test with a chopped potato later on in order to be more sure if the H2O2 breaks up the cells or not.

Will probably with adding bicarbonate once again.

Sincerely Lasse
 

DrZoidburg

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If I could add it might not just be the cells in potato it could react with the starches. In presence of catalyst like a transition metal Iron. Which is abundant in potatoes. Also sure it does oxidize cells. If you have haver had gotten peroxide on your hands and see the classic white spot it leaves on you. That is because it oxidized the skin, tiny capillaries, fats, etc under leaving bubbles and embolism. This not just one reaction it is several doing this. No blood flow turning white. I like this picture. I think I see where your going? Using a potato as the actual catalyst or am I over thinking this?
 

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Yes - there is no doubt that it oxidize cells but the question was if this was the source for the ORP dip we see in our aquarium when we add H2O2. The potato is not only rich in iron - it is rich in catalase too That´s the reason why I chose potato. Catalase is well known for a direct transition of H2O2 to O2 and H2O without any known oxygen radicals as intermediates. I was eager to know if the catalase direct transition into H2O and O cause a ORP drop - it did not.

The reason why I also test iron is that this reaction is another pathway for H2O2 breakdown - including intermediate forming of oxygen radicals. I was eager to see if this pathway cause an ORP drop.

Both addition did nothing - therefore maybe the breakdown pathways is of no interest in order to explain the observed ORP drop in a saltwater Aquarium.

Sincerely Lasse
 
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Test with new water and addition of H2O2 . RO water. Red - peroxide addition

1628190442255.png

Tap water Red Peroxide addition



1628190543893.png


No dip - a very weak rise.

After two runs - I think I´m sure that I do not get a dip in these example - if anything happens - it is a rise.

Now I will test with an addition of 1 g sodium bicarbonate to each bucket - skip both the iron and potato addition for the moment.

Sincerely Lasse
 

DrZoidburg

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Like you say earlier it could be big dip cause more ions in water. Try maybe with even stronger base like sodium hydroxide. At other end on spectrum with low ph buffered water with an acid. In both case would need something added to see if reducing or oxidizing though. May not see as big dip or rise with out something to be reacted. Try mash potato in these conditions. More surface area faster reaction. Also items that can be oxidized in acid conditions, and something that can be reduced in alkaline not just potato.
 
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Test with RO water Red = addition of H2O2. Black = addition of 1 g sodium bicarbonate

1628269095636.png


Test Tap water Red = addition of H2O2. Black = addition of 1 g sodium bicarbonate

1628269210948.png


In order to investigation if it is the bicarbonate addition itselfs or if it is the combination that is responsible for the drops in ORP in these experiments - I will set up an experiment with both pH and redox measurement. In this case I must do on type each time - and I will start with RO water

Sincerely Lasse
 
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Start a new experiment with RO water and both pH and ORP measurements. I will try with first a addition of sodium bicarbonate and addition of H2O2. try to figure out if the ORP drop I seen before after the addition of bicarbonate is caused of the bicarbonate soley or an reaction with the peroxide already present in the test solution.

However - and I know it from my days as a freshwater aquarist that it is very difficult to get a stable redings with ion weak freshwater. Especially if you use RO water. This happens this time too and it slowly reach the lower 6 in pH. I will let it stand as it is for the moment and see where it will stabilize itself.

Sincerely Lasse
 
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RAP
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Start new experiment - waiting for stability. red - start with new RO water. Blue - start with a new pH probe (just calibrated)

1628346979381.png

I will adjust the pH to around 8 with a sodium bicarbonate - very small amount.

Sincerely Lasse
 
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After adjusting the pH with very, very small amounts of bicarbonate - together less than 0.05 g - just a tip if a knife every addition I can conclude the well know factor that says that pH affect the redox. In this case with RO water and only bicarbonate in small amounts - the bicarbonat itself drop the redox. Next step is to add more bicarbonat - 0.8 g in one occasion. We will see what´s happen. pH now 8.48

1628409596305.png

Sincerely Lasse
 
Fritz
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Sumary of the pH/ORP test - RO water

Addition of bicarbonate affect the pH and the pH affect the ORP in the way that high pH - low ORP. However in my test - the first 5 bicarbonate addition was very small - below 0,05 g together, pH rise from 5.67 to 8.39 and ORP drop from 279 to 196 - very fast and only with a total addition of around 0.05 g NaHCO3. When nearly 0.7 g NaHCO3 was added - pH rise from 8.49 to around 8.80 and ORP drop from 195 to 175. This last addition indicate that the ORP drop is related to the pH rise. However - when 5 ml H2O2 was added pH slowly rise and the ORP decline - the drop was expected because the pH still rise but the drop seems to be a little to strong to solely be caused of the pH rise

Black - start of the experiment. Blue addition of total around 0.05 G NaHCO3; olive = addition of 0.7 g NaHCO3 and red = addition of H2O2 - 5 ml

1628450860891.png



Now I will continue with fresh mixed saltwater. Rd Sea Red bucket - around 34 psu

Note - the absolute pH is not exact because a wrong calibration. It is to high - however the changes is right.

Sincerely Lasse
 
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I´m sorry for slow working thread. I let the pH and redox probe adapt to the new mixed saltwater and make it to be 35 psu. I did the test with 5 ml H2O2 this morning and the result is not very easy to explain. However - before saying anything more and see how it works out during a day or two - I can only say that there was no dramatical drop in ORP. I did a 5 ml test with my aquarium too - just to see if the peroxide works the way it should. In that test - 5 ml in 310 L aquarium - the drop was dramatical - as always. I´ll come back with graph later on.

Sincerely Lasse
 
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The test with freshly mixed salt water - did not answer the question but maybe indicate an combination of chemical and biological factors. But not any clear results-

Black= start of experiment; Red= addition of total 5 ml H2O2; Blue = addition of 2 g chopped (fine) potato

(Note - I have edit it from a wrong description - I had flip the colours)

1628666786042.png

The addition of H2O2 did cause a ORP drop - but not so dramatically. Addition of a chopped potato did cause an ORP increase - but not very much.

Now - I will add some 4 years old tank water to the bucket in a first step.

Sincerely Lasse
 
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