Diatom cleaning attemp

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jimur
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Diatom cleaning attemp

#1 Post by jimur » Tue Aug 14, 2018 10:20 am

Inspired by the current thread on mild cleaning and incineration of diatoms, I decided to try it minus incineration for now.
This sample was centrifuged with a 4:1 3% H2O2 / distilled water solution for three minutes, mixed and allowed to sit over night, then rinsed multiple times. Thanks for the inspiration guys. I knew if I hung out here some I learn stuff.
Not professional at all, but I'm very tickled with my first attempt.
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Re: Diatom cleaning attemp

#2 Post by Radazz » Tue Aug 14, 2018 1:20 pm

Nice job!
I’ve only tried this once, but it was a disaster.
Another day perhaps.
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Re: Diatom cleaning attemp

#3 Post by Hobbyst46 » Tue Aug 14, 2018 7:21 pm

Good luck! Once you pass the initial bumps, and work safely, you are on the road to enjoyment. Plenty of information about it here and in many other sources when you want it. Specifically, two recent detailed and well documented works are "Doing Diatoms a Different Way" (OP Charles) started Nov 29, 2016, and "Doing Diatoms" (OP rnabholz) started May 15, 2016.

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Re: Diatom cleaning attemp

#4 Post by photomicro » Wed Aug 15, 2018 9:07 am

Yes, cleaning diatoms can be fun, and there are many well tried and tested methods.

It may be worth interested parties looking at this resource, where amateurs of both great and little experience describe a number of methods, including hot acid protocols, but also the gentler methods, and some newly tried commercial cleaning products.

http://www.diatoms.co.uk/ad/archive.htm

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Re: Diatom cleaning attemp

#5 Post by billbillt » Wed Aug 15, 2018 10:18 pm

photomicro wrote:Yes, cleaning diatoms can be fun, and there are many well tried and tested methods.

It may be worth interested parties looking at this resource, where amateurs of both great and little experience describe a number of methods, including hot acid protocols, but also the gentler methods, and some newly tried commercial cleaning products.

http://www.diatoms.co.uk/ad/archive.htm
I had forgoten about this site.. Thanks for the memory jog!...

BillT

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Re: Diatom cleaning attemp

#6 Post by jimur » Thu Aug 16, 2018 9:13 am

Thanks for the encouraging words guys. It is indeed an enjoyable and educational pursuit for me. Perhaps in the not too distant future I can graduate to a little more involved and harsher chemical cleaning. For now I'll continue exploring H2O2
methods. Thanks for the great link photomicro.
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Re: Diatom cleaning attemp

#7 Post by rnabholz » Sat Aug 18, 2018 2:47 am

Hi jimur

I find the acids very intimidating, and so stayed away.

I have had very good results from H2O2 in the 30% strength teamed with Potassium Dichromate. Both require caution, but the H2O2 is relatively safe, minor temporary bleaching of exposed skin (20 minutes).

The PD is a powerful oxidizer, but used in very small amounts in large containers is manageable. Avoid the fumes and contact with the skin.

More on my experiences in the "Doing Diatoms" thread.

Keep up the good work.

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Re: Diatom cleaning attemp

#8 Post by jimur » Sat Aug 18, 2018 7:58 am

rnabholz wrote:Hi jimur

I find the acids very intimidating, and so stayed away.

I have had very good results from H2O2 in the 30% strength teamed with Potassium Dichromate. Both require caution but..........
Thanks for the info Rod. I may just try and locate the higher strength H2O2. Isn't PD used in developing by some photographers who shoot film? The name sounds familiar.
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Re: Diatom cleaning attemp

#9 Post by rnabholz » Sat Aug 18, 2018 11:32 am

You might be able to find higher the concentration H2O2 locally at a health food store. I order mine from Amazon.

Yes, Potassium Dichromate is used in photographic processing among other uses. I found mine in a reasonable quantity on Ebay. You will not need much, as it doesn't take much to get the reaction we are after. A half a baby aspirin sized dose in a 100ml's of H202/diatom batch is all it takes, and I suggest a 500ml or larger beaker and a catch tray to safely contain the reaction. You definitely don't want to do this in a test tube.

Be patient waiting for the reaction, it can sometimes take a bit for it to kick off. Resist the urge to add more PD. I have had it take an hour or longer to start, and I have seen it take less than a minute. Weird, but adding more PD can cause it to get pretty exciting when it goes, and not good exciting... That is where the catch tray comes in.

The reaction usually is over in a couple of minutes, bubbling, heat and steam, yielding an orange solution. From there it is just a matter of multiple rinses to clear and you are all set.

Rod

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Re: Diatom cleaning attemp

#10 Post by Hobbyst46 » Sat Aug 18, 2018 7:49 pm

I wonder, was it ever demonstrated that the addition of dichromate to H2O2 at the final stage of cleaning diatoms is significant and essential? I have seen this trick in the Sterrenburg Protocol, perhaps in other protocols as well, and I have read that is was successfully applied as described in the (very interesting) posts "Doing Diatoms" and "Doing Diatoms A Different way" in the forum. Yet I have a reservation, perhaps unjustified.
It is known that dichromate reacts chemically with H2O2, irrespective of diatoms and other organic chemicals. So, effervescence, froth, rapid heating etc are expected, at least due to the reaction between the dichromate and surplus, unreacted H2O2. Thus dichromate gets rid of the unused excess of H2O2 in the flask, but does it also serve as cleaner? does it eliminate organic stuff and debris, which previous heating or even boiling with H2O2 did not decompose?
Because (and I now enter a fox-hole against incoming sling-rocks and comments) I believe that there are safer ways than the dichromate to get rid of the excess H2O2.

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Re: Diatom cleaning attemp

#11 Post by photomicro » Sat Aug 18, 2018 8:34 pm

Hobbyst46 wrote:I wonder, was it ever demonstrated that the addition of dichromate to H2O2 at the final stage of cleaning diatoms is significant and essential? I have seen this trick in the Sterrenburg Protocol, perhaps in other protocols as well, and I have read that is was successfully applied as described in the (very interesting) posts "Doing Diatoms" and "Doing Diatoms A Different way" in the forum. Yet I have a reservation, perhaps unjustified.
It is known that dichromate reacts chemically with H2O2, irrespective of diatoms and other organic chemicals. So, effervescence, froth, rapid heating etc are expected, at least due to the reaction between the dichromate and surplus, unreacted H2O2. Thus dichromate gets rid of the unused excess of H2O2 in the flask, but does it also serve as cleaner? does it eliminate organic stuff and debris, which previous heating or even boiling with H2O2 did not decompose?
Because (and I now enter a fox-hole against incoming sling-rocks and comments) I believe that there are safer ways than the dichromate to get rid of the excess H2O2.

It is surely a stronger oxidising agent, hence should clear some of the organic material left.

As regards getting rid of unused peroxide, a simpler way of doing this is just to leave it, as it will eventually decompose into water and oxygen over time. You would remove excess chemicals left by several rinses with distilled (or similar) water, especially as you don't want any residues before mounting.

This is a good reference if you have not seen it before;

https://www.mccrone.com/mm/an-introduct ... diatoms-2/

Mike

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Re: Diatom cleaning attemp

#12 Post by Hobbyst46 » Sat Aug 18, 2018 10:00 pm

photomicro wrote:It is surely a stronger oxidising agent, hence should clear some of the organic material left.
Thanks a lot for the link to the McCrone book! I already scanned it looking for the dichromate role! but found no explanation.
AFAIK, dichromate is a strong oxidizer at strong acidic pH. However, I guess that the pH of the diatom suspension in H2O2 is fairly neutral. The composition and processes in mixtures of dichromate and H2O2 depend on the pH and are quite complex. Surely some drastic interaction occurs upon the addition of the (tiny) amount of dichromate, but who is the oxidizing agent in the mixture? and did it oxidize diatoms or other unwanted material? This is perhaps tinkering or "digging", yet...

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Re: Diatom cleaning attemp

#13 Post by rnabholz » Sat Aug 18, 2018 10:13 pm

Regarding the necessity of potassium dichromate in the process, I can't say that I have done extended study, but there is basis for it in the work of folks much smarter than me.

I found the process while searching for an alternative to drain cleaner which was a fail for me. I came up in an academic paper, and credited Albert van Der Werff as the originator. Searching his name + dichromate will bring up references, most of which seem to be behind pay walls.

For what it's worth.

Rod

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Re: Diatom cleaning attemp

#14 Post by Hobbyst46 » Sat Aug 18, 2018 10:27 pm

Thanks Rod - I will try and search. Curiosity killed the cat... ;)

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Re: Diatom cleaning attemp

#15 Post by zzffnn » Sat Aug 18, 2018 11:13 pm

Hobbyst46,

If you are boiling 30% H2O2, I don't think you have to try dichromate. Dichromate is supposed to help oxygen production, which is what boiling does as well. I am not 100% sure, though I am guessing it dichromate + 30% H2O2 may provide more oxidation. Your boiling results look good enough though, such that you likely don't need dichromate.

I personally would prefer boiling as it involves less harmful chemicals and is a chemically simpler process. You would want eventually to remove trace dichromate as it is toxic, but trace H2O2 would disintegrate itself.

I had quite some chemistry courses in college to be very comfortable with it, but I am no chemist by trade. Member eiman is a good chemist, if you need to ask to be sure.

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Re: Diatom cleaning attemp

#16 Post by KurtM » Sun Aug 19, 2018 12:49 am

Hey Rod, good to see you -- sure miss your diatom images!

I pick up food grade 35% H202 at a local health food store/cafe, and am perfectly satisfied with the results I get.
Cheers,
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Re: Diatom cleaning attemp

#17 Post by jimur » Sun Aug 19, 2018 11:38 am

photomicro wrote:
This is a good reference if you have not seen it before;

https://www.mccrone.com/mm/an-introduct ... diatoms-2/

Mike
Really appreciate that link Mike. A very good resource.
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Re: Diatom cleaning attemp

#18 Post by jimur » Sun Aug 19, 2018 12:35 pm

rnabholz wrote:
Be patient waiting for the reaction, it can sometimes take a bit for it to kick off. Resist the urge to add more PD. I have had it take an hour or longer to start, and ..........

Rod
Thanks for the heads up on the reaction times. After a minute or two it would most likely catch me off guard. I should make it a point to always use a catch tray.
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Re: Diatom cleaning attemp

#19 Post by Hobbyst46 » Sun Aug 19, 2018 2:05 pm

Hobbyst46 wrote:Thanks Rod - I will try and search. Curiosity killed the cat... ;)
Apparently the original protocol is described here:
"A new method of concentrating and cleaning diatoms and other organisms" A. van der Werff
Pages 276-277 | Published online: 01 Dec 2017
https://doi.org/10.1080/03680770.1950.11895297

Internationale Vereinigung für theoretische und angewandte Limnologie: Verhandlungen, 12(1), pp. 276–277 (1955)
Quite old.
Alternative publication name:
Societas lnternationalis Limnologiae: International Association for Theoretical and Applied Limnology

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Re: Diatom cleaning attemp

#20 Post by rnabholz » Mon Aug 20, 2018 2:47 pm

jimur wrote:
rnabholz wrote:
Be patient waiting for the reaction, it can sometimes take a bit for it to kick off. Resist the urge to add more PD. I have had it take an hour or longer to start, and ..........

Rod

Thanks for the heads up on the reaction times. After a minute or two it would most likely catch me off guard. I should make it a point to always use a catch tray.

And a significantly over sized container will save you some trouble too.

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Re: Diatom cleaning attemp

#21 Post by rnabholz » Mon Aug 20, 2018 3:06 pm

Hobbyst46 wrote:
Hobbyst46 wrote:Thanks Rod - I will try and search. Curiosity killed the cat... ;)
Apparently the original protocol is described here:
"A new method of concentrating and cleaning diatoms and other organisms" A. van der Werff
Pages 276-277 | Published online: 01 Dec 2017
https://doi.org/10.1080/03680770.1950.11895297

Internationale Vereinigung für theoretische und angewandte Limnologie: Verhandlungen, 12(1), pp. 276–277 (1955)
Quite old.
Alternative publication name:
Societas lnternationalis Limnologiae: International Association for Theoretical and Applied Limnology
Thanks for the investigation work.

I have also seen the protocol referenced in summaries academic papers on Diatom studies. It seems it has been out there a while.

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Re: Diatom cleaning attemp

#22 Post by Hobbyst46 » Mon Aug 20, 2018 6:20 pm

rnabholz wrote:
Hobbyst46 wrote:
Hobbyst46 wrote:Thanks Rod - I will try and search. Curiosity killed the cat... ;)
Apparently the original protocol is described here:
"A new method of concentrating and cleaning diatoms and other organisms" A. van der Werff
Pages 276-277 | Published online: 01 Dec 2017
https://doi.org/10.1080/03680770.1950.11895297

Internationale Vereinigung für theoretische und angewandte Limnologie: Verhandlungen, 12(1), pp. 276–277 (1955)
Quite old.
Alternative publication name:
Societas lnternationalis Limnologiae: International Association for Theoretical and Applied Limnology
Thanks for the investigation work.

I have also seen the protocol referenced in summaries academic papers on Diatom studies. It seems it has been out there a while.
The original van Der Werff article being very short and hard to acquire, I looked in some more modern literature. There has been some research in France in 2005-2006 on mixing H2O2 with tiny amounts of dichromate (by N. Frikha and coworkers). They provide evidence that indeed, dichromate combines with H2O2 in a catalytic way: It accelerates the decomposition of H2O2 to oxygen and water, releasing considerable heat. When it is finished, dichromate remains in the mixture (this explains the yellow color of the final liquid after the dichromate reaction). For catalysis, a tiny amount of the agent (dichromate) is sufficient, even if the amount of residual H2O2 is large by comparison.

the research indicated that the reaction rate and the rate of heating of the liquid depend on several conditions (so that, in my opinion the time to start and the intensity could vary from time to time as mentioned by rnabholz). The reaction can get out of control (called "runaway process"). So, although the products are not toxic, it should indeed be carefully approached.

But IMHO, these results show that dichromate does not serve here as oxidizer. Neither does it amplify the oxidative power of H2O2. It does heat the mixture and create a lot of oxygen bubbles. But oxygen bubbles are not powerful oxidizer in this case. They just remove the debris mechanically. So, I agree with zzffnn, that it is equivalent to boiling and that for cleaning diatoms, warming the H2O2-diatom mixture in a water bath, even to the boiling point of the water, is safer and better controlled than the (spectacular) reaction with dichromate.

Like mentioned in protocols, I think that heating the H2O2-containing mixture should be done gradually, taking precaution against splashes of hot corrosive liquid, and only when there is no strong foaming at room temperature. And I agree with photomicro that getting rid of the excess of H2O2 is not an issue, no need to employ dichromate for that. My opinion, until other evidence is found, I would omit the dichromate from the protocol.

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Re: Diatom cleaning attemp

#23 Post by KurtM » Tue Aug 21, 2018 12:55 am

In your discussions of potassium dichromate in H202, there's one possible factor you utterly fail to address: magic. The additional cleaning action is a result of magic that happens when you dump a few of those mysterious little crystals into your diatom-H202 soup. You can tell it's magic by the way the color instantly changes from tan-ish to deep purple.

Seriously, I like to think the furiously hot boiling grand finale puts a finishing touch on clearing and separation of the valves and girdles, and in this case of using a less than professional grade boiling acid process I'll take all the help I can get. Mind you, I have zero training in chemistry, not very bright besides, and really don't know what the heck I'm doing. But the reaction is entertaining, makes it easier to pretend I do know what I'm doing, and I get very nice diatom strews slides in the end.
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Re: Diatom cleaning attemp

#24 Post by rnabholz » Tue Aug 21, 2018 3:23 am

I will be watching for news of your trials with the H2O2 only process, and I am rooting for you. I am more than willing to remove a step in the processing if it is found to be unnecessary.

That said, I find myself with Kurt on this for now. Adding PD to room temperature H2O2 and diatom material and watching the bubbling and steam that results, it is hard to believe that it has no effect. I have witnessed a reduction in remaining visible organic particles post reaction. I believe the thermal spike does help separate stubborn girdles and valves as well.

The issues I had in the beginning managing the reaction were completely the result of my ignorance and inexperience with the chemicals and process. I caution those inquiring only to save them the same troubles, not to paint a picture of great peril or impending doom for all that dare tread here ;^). Use a significantly over sized vessel, and conservative amount of PD, and be patient, and all will be well.

In the end this process is very productive for me,and produced nice clean and separated frustules, but I am open to making a change should it be proven just as effective.

Good discussion.

Rod

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