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

[taricha]

blue= addition of total 5 ml H2O2; Red = addition of 2 g chopped (fine) potatoe

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.

did you mean to flip those? Red in the pic = h2o2 first, Blue = potato after?

 

[Randy Holmes-Farley]

The postulates and what the test indicate


1) The H2O2 breaks up cells.

Probably not the reason - no reaction when adding a potato - well known enzymatic catalyst for H2O2 break down

2) H2O2 can be both a reducer and oxidizer

still no evidence for or against. But it was in a high pH where H2O2 should be a reducer

Just got back from vacation and read the thread very quickly, but my interpretation is as follows:

1. Results are consistent with the known fact that H2O2 can oxidize certain trace metals in seawater (e.g., iron) and can reduce other trace metals in seawater (e.g., copper) and the reduction wins out in seawater ORP measurements. Remember, it is not even clear exactly which trace metals directly impact ORP as we sense it, but copper seems very likely to do so. A different trace element might also do a similar thing (e.g., manganese).

2,. I do not know that the potato result disproves the possibility of cell breakage, but I'm certainly leaning away from that possibility based on everything else, including the above.

Putting a little Cu++ in RO/DI water, or extra in seawater, then H2O2 might be interesting.

 

[taricha]

1. Results are consistent with the known fact that H2O2 can oxidize certain trace metals in seawater (e.g., iron) and can reduce other trace metals in seawater (e.g., copper) and the reduction wins out in seawater ORP measurements. Remember, it is not even clear exactly which trace metals directly impact ORP as we sense it, but copper seems very likely to do so. A different trace element might also do a similar thing (e.g., manganese).

I had not run across this explanation in these threads before, and it makes a lot of sense. Thanks.

 

[Randy Holmes-Farley]

I had not run across this explanation in these threads before, and it makes a lot of sense. Thanks.

We discussed it recently here:

Relationship Between H2O2 & Redox (ORP) . . . Help with Explanation?

There is no reaction , otherwise it would be heat expelled i think. Unless there are some pollutants and miniscule oxidation occurs. ORP meter measures net charge, and h202 introduces more negatively charged particles i think. p.s. i used to drop some h202 30% drops on mine shirt :D amazing how...

www.reef2reef.com

and

Relationship Between H2O2 & Redox (ORP) . . . Help with Explanation?

There is no reaction , otherwise it would be heat expelled i think. Unless there are some pollutants and miniscule oxidation occurs. ORP meter measures net charge, and h202 introduces more negatively charged particles i think. p.s. i used to drop some h202 30% drops on mine shirt :D amazing how...

www.reef2reef.com

 

[Lasse]

did you mean to flip those? Red in the pic = h2o2 first, Blue = potato after?

Your right - I probably got a minor cerebral haemorrhage when I wrote that. Red = H2O2 addition - blue is potato, I change in the original

Sincerely Lasse

 

[Lasse]

Now I have taken out 5 L of my old tank water. It should be like it is until at least tomorrow. The ORP need to stabilixze itself,

I have manganese at home - will do an experiment with that and RO water later on

Sincerely Lasse

 

[taricha]

We discussed it recently here:

Relationship Between H2O2 & Redox (ORP) . . . Help with Explanation?

There is no reaction , otherwise it would be heat expelled i think. Unless there are some pollutants and miniscule oxidation occurs. ORP meter measures net charge, and h202 introduces more negatively charged particles i think. p.s. i used to drop some h202 30% drops on mine shirt :D amazing how...

www.reef2reef.com

and

Relationship Between H2O2 & Redox (ORP) . . . Help with Explanation?

There is no reaction , otherwise it would be heat expelled i think. Unless there are some pollutants and miniscule oxidation occurs. ORP meter measures net charge, and h202 introduces more negatively charged particles i think. p.s. i used to drop some h202 30% drops on mine shirt :D amazing how...

www.reef2reef.com

hah, so I missed it a couple of times.

 

[Dan_P]

Just got back from vacation and read the thread very quickly, but my interpretation is as follows:

1. Results are consistent with the known fact that H2O2 can oxidize certain trace metals in seawater (e.g., iron) and can reduce other trace metals in seawater (e.g., copper) and the reduction wins out in seawater ORP measurements. Remember, it is not even clear exactly which trace metals directly impact ORP as we sense it, but copper seems very likely to do so. A different trace element might also do a similar thing (e.g., manganese).

2,. I do not know that the potato result disproves the possibility of cell breakage, but I'm certainly leaning away from that possibility based on everything else, including the above.

Putting a little Cu++ in RO/DI water, or extra in seawater, then H2O2 might be interesting.

The ORP drop is robust in just a NaCl solution.

 

[Lasse]

Now I have add 5 ml H2O2 to 5 L old water in a bucket. Anyone who expected a simple result is wrong. I also add 5 ml to my 310 L aquarium (where the water was collected from yesterday) and the result was the expected - a prominent dip, I´ll come back with the diagrams later on. I will let the test continue for a while.

The difference between my tank and the bucket is that I have light - including wavelengths below 400 nm - in the tank - not in the bucket. I will test with addition of H2O2 in the tank when the light is out - just for exclude or confirm that light can be a cause.

Sincerely Lasse

 

[Hans-Werner]

t has been a lot of discussion and speculation why ORP drops directly after H2O2 have been added. In my aquarium - around 320 L - i always get a drop when I fill up my oxidator

I add first 1 ml H2O2 and after around 38 minutes I hade 1 ml each 10 minutes. The ORP rise after the first 1 ml 12% H2O2 but after that - no change in the other 4 occasions of H2O2 adding (red marking).

I am sorry, Lasse, I have only read your initial posts which I comment. I have expected exactly this. My theory is that not the water causes the drop in ORP but the bacterial cover on the electrode. When you use a fresh and sterile probe I expected exactly this result. You can read in literature that ORP electrodes must be clean and sterile, otherwise what you are measuring is just the ORP of the biofilm on the probe.

We also got and still get some remarks that ORP drops after water changes with Tropic Marin salt. I always suspected this to be a reaction to increased bacterial activity which I ascribed to the addition of fresh trace elements.

When adding oxygen, the same may occur, heterotrophic bacteria show increased activity. Instead of increasing ORP which in fact in the water occurs, the biofilm creates its own reduced ORP which the electrode measures.

I suggest to use a cleaned or new and sterile probe and watch the changes in reaction over days and weeks in the tank (or a container which has growing bacteria and biological activity) while the biofilm on the probe grows.

 

[Lasse]

Interesting theory - and I am able to test it ! This can explain a lot of observations I have done - one is that it always take a week or two before a new electrode have adapt itself and shoe a redox potential around 300 - 400. After a cleaning with a tooth brush - it always take some time before the ORP is normal again.

i will put my new electrode into the sump and compare reactions as a first test.

But even if it is the ORP in the biofilm covering the electrode - it is interesting because the change take less than 1 minute! and maybe you just take the ORP in all biofilms in your aquarium - now it becomes very, very, very interesting!

I will test

Sincerely Lasse

 

[Hans-Werner]

Thank you, Lasse! Meanwhile I have rushed through the whole thread. I have seen nothing that contradicts my theory yet.

Wow, good chance. I really look forward to your results!

 

[Dan_P]

Now I have add 5 ml H2O2 to 5 L old water in a bucket. Anyone who expected a simple result is wrong. I also add 5 ml to my 310 L aquarium (where the water was collected from yesterday) and the result was the expected - a prominent dip, I´ll come back with the diagrams later on. I will let the test continue for a while.

The difference between my tank and the bucket is that I have light - including wavelengths below 400 nm - in the tank - not in the bucket. I will test with addition of H2O2 in the tank when the light is out - just for exclude or confirm that light can be a cause.

Sincerely Lasse

Great experiment. It raises many questions and gives us a long list of experiments to perform.

Freshly prepared Instant Ocean also had a dip, which dark clean water. This means, as you pointed out, there can be a couple factors involved. Also, you haven’t controlled this experiment for all the other differences between old dark water vs freshly sampled illuminated aquarium water. The experiment can only be interpreted as bucket of old water is different than aquarium water. The illumination effect is a guess and as I said ignores other factors that differ between the two water samples. Nonetheless, I believe you are inching closer to important Information.

For fun, I bet ORP will respond similarly when H2O2 is added to dark aquarium water (Based on Instant Ocean results).

 

[Lasse]

I look in my cabinet - and voila - a brand new redox probe ( I bought a lot when the fish farm I worked on get out of business. They had a lot new as reserves. Always wonder - what shall I use all of these too - now I know the answer ) I have a free redox port (actually - I hav 4 ) - I will connect this new to one of my expansion boxes and run it on the main system - close to the old redox probe.

It will probably be up an working this evening. When it is installed - I will let i be in the aquarium for a while - maybe repeat the addition of 5 ml H2O2 every second - or third - day.

Sincerely Lasse

 

[Lasse]

This happen in my tank Red addition of 5 ml H2O2 in 310 L

This with the same water standing in a bucket for 1 night and the ne electrode RFed - addition of 5 ml H2O2 in 5 L

no order at all so to speak

Sincerely Lasse

 

[taricha]

Here's some data which anyone is free to disregard as unreliable noise. My tank water is anomalous in the hobby with regards to h2o2. I put the probe in, and h2o2 increases ORP of my tank water (almost always - one time it did not). The ORP rose whether I put the probe in scrubbed and new or left it in for weeks.

here's my tank water (1L, glass beaker, stirrer) 0.1mL h2O2 added at 7.5 min.

Here's two metals additions to my tank water. Red line is an hour after recommended dose of Seachem Reef Trace (contains a bunch of things except Fe). Tan yellow Line is same but with brightwell Ferrion (Fe edta). Neither seems to dramatically change the ORP response.

0.1mL H2O2 in 1L, added at ~7 min, (and a 2nd again at ~15min that had no additional effect)

here's ingredients for Reef Trace

Then, attempting to flip the ORP effect and make h2o2 lower it, I took my tank water and added some CuCl2 solution. I estimate the final concentration was 5uM CuCl2 (~0.3ppm Cu maybe.)

After ORP stabilized, I added 0.1mL H2O2 to the L water at 14 min. The ORP inrease was significantly blunted.

...so tripled the amount of CuCl2 solution in the next L of tank water (~0.9ppm Cu)

The addition of h2o2 at ~6min caused the ORP to drop.

I'm not sure this illuminates much if we already knew that copper in seawater would be reduced by h2o2. My water is weird compared to the hobby, its ORP increases upon h2o2 addition, and to reverse that I had to add what I think is a huge amount of Cu.
Where this might lend support for the idea that various metals concentrations in tank water are determining the ORP response to h2o2, is if an ICP test shows my water has a high level of some metal(s) known to be oxidized by h2o2. And then that might both explain why my water doesn't do what the rest of the hobby does, and why I had to add so much Cu to cause the h2o2 effect to flip.

 

[taricha]

This with the same water standing in a bucket for 1 night and the ne electrode RFed - addition of 5 ml H2O2 in 5 L

no order at all so to speak

So which do you think?
if you put the water in the bucket for some hours and shine reef lighting on it will it keep acting like reef water?
Or if you repeat in a clean glass container instead of a plastic bucket would it continue acting like your reef water?

 

[Randy Holmes-Farley]

Where this might lend support for the idea that various metals concentrations in tank water are determining the ORP response to h2o2, is if an ICP test shows my water has a high level of some metal(s) known to be oxidized by h2o2. And then that might both explain why my water doesn't do what the rest of the hobby does, and why I had to add so much Cu to cause the h2o2 effect to flip.

Yes, that makes sense to me.

 

[Lasse]

I am sorry, Lasse, I have only read your initial posts which I comment. I have expected exactly this. My theory is that not the water causes the drop in ORP but the bacterial cover on the electrode. When you use a fresh and sterile probe I expected exactly this result. You can read in literature that ORP electrodes must be clean and sterile, otherwise what you are measuring is just the ORP of the biofilm on the probe.

We also got and still get some remarks that ORP drops after water changes with Tropic Marin salt. I always suspected this to be a reaction to increased bacterial activity which I ascribed to the addition of fresh trace elements.

When adding oxygen, the same may occur, heterotrophic bacteria show increased activity. Instead of increasing ORP which in fact in the water occurs, the biofilm creates its own reduced ORP which the electrode measures.

I suggest to use a cleaned or new and sterile probe and watch the changes in reaction over days and weeks in the tank (or a container which has growing bacteria and biological activity) while the biofilm on the probe grows.

Its maybe more in this than I first thought. First test show a huge difference between the old and new electrode. However I´m not sure that this redox port is total OK. Will test with another port too. This is interesting!

Sincerely Lasse

 

[Lasse]

My Cu tests

Sincerely Lasse