Re: Clean Diatoms


leszekwolnik <leszek@...>
 

Hi Bill

This question of giving advice is very difficult and we'll have to stress how a moments inattention or just plain mischance can result in very serious injury. I feel the advice is warranted as I hope it will help prevent accidents rather than initiate them.

I stopped discussing hot acids on a previous group once a poster announced that he was going to use boiling acid in test tubes in a hand centrifuge which he was then going to whirl around his head pretending the whole gizmo was a football rattle.

Ouch!

Leszek

--- In diatom_forum@..., "bill2penn" <dailey@...> wrote:

Hi Leszek,
Yes, please do add some information that can be included. I have actually been very hesitant to add my own detailed descriptions using strong acids since they can be very dangerous if misused, and I don't want to be held liable for any accidents that might occur.
Bill


--- In diatom_forum@..., "leszekwolnik" <leszek@> wrote:

Hi Bill

I'll add some brief details and pictures on the sulphuric acid step as well if I may as I find that step quite fraught and needing as many precautions as possible.

I'll try and get some pictures and notes done over the next few days.

Leszek



--- In diatom_forum@..., "bill2penn" <dailey@> wrote:

Hello Charles,
Thanks for the kind words. I will try to put together a detailed writeup with pictures this weekend. But let me comment on some of your details.

First, you've pretty much got the sequence correct.I will give a few comments on some parts right now but do plan on writing up a more detailed description with some pictures.

Step 1. Turn the diatomite into mud. This mud should NOT contain any significant chunks or pieces that you can see since those will typically not be broken down later in the processing and will cause issues with bumping and such. Sometimes a very coarse sieve is useful to sieve this mud and get out larger pieces and rocks, roots, etc. You must make sure to use a large enough sieve to let the diatom clumps through, but keep the larger chunks at junk.

Step 3. You really do need to use hot concentrated sulfuric acid to clean some samples. You are correct to be very, very cautious when doing this. I do all my acid cooking on my back patio as far away from the house as possible. Wear heavy gloves and face protection!

I'll provide details of "gold panning" and sieving in my future writeup.

Bill



--- In diatom_forum@..., "charles" <suslavage@> wrote:

Hello Bill,

I hope the following makes sense, some questions some comments, if not feel free to us a big stick.

Your first step is to breakup the diatomite using either the freeze thaw method or you recommend sodium acetate cryohydrate as an alternative. Which ever method is employed how do you determine when this step is complete. I feel this first step is complete when the material looks like a slurry, with no large chunks remaining.

Before continuing on to step 2 I will wash the material with several changes of distilled water to reduce the volume. Less junk in the mix should allow the following steps to work more effectively. That is my thought. I also make a test slide or two to look for anything interesting that might be destroyed by the acids.

Step 2 is to boil for 20 minutes in HCl. This is to eliminate some of the mineral contend? After boiling the material do you check your progress with the LM? If so do you look for anything special? Will you repeat this step?

I keep a bucket of water handy and use acid resistant gloves and plastic safety goggles, long sleeve shirt, long pants, and shoes, California is a shoe free environment.

Step 3 is to heat in concentrated H2SO4, sulfuric acid, and then to add sodium nitrate or potassium perchlorate. This I believe is to oxidize any organic material in the sample. I have used hydrogen peroxide, 24 hour soak, as a substitute because I believe the addition of the potassium perchlorate is potentially dangerous if not done correctly.

I do not have a lab with a fume hood so I work on the patio in open air. Even so I still worry about fumes and keep a safe distance. Safe I define as I can't smell it.

Step 4 is new, heat to simmer with Sparkleen 1. I have noted that at this point some diatoms and I am surprised that it seems to be by species are still encrusted. I would describe this coating as a cake of rust, I know it is not but that is descriptive. Other then the use of Sparkleen, which I have not as yet tried. I have tried to go back to the freeze thaw cycling to remove this with little success or warm hydrogen peroxide for an extended period which seems to clean some species but not all. Have you observed this clean vs. unclean by species?

Step 5 is to separate fractions by gold panning. Your old methodology recommended to sieve using a 400 mesh. You are now recommending `gold panning'. By fractions I believe you mean to separate diatoms from quarts and other heavy debris. How do you deal with the larger heavier diatoms?

Lastly Sieve if necessary.

For steps 5 and 6 I use a decanting process through a sieve, 400 mesh. This works very well if I go slow. I will then sieve what remains from the decanting through a 125 micron sieve to capture the big ones. I do get a lot of additional stuff but some of it is fun stuff, large radiolaria.

I think the rule in all of the above is to be flexible because every sample will be different even if collected from the same location, formation. What I am trying to learn is what to look for as I step through the cleaning process.

Charles

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