calcium oxalate crystals by precipitation

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Lomonaut
Posts: 100
Joined: Sat Jan 27, 2018 5:30 pm

calcium oxalate crystals by precipitation

#1 Post by Lomonaut » Sat Jul 10, 2021 10:20 pm

I prepared these crystals by precipitation, rather than evaporation. A drop of oxalic acid solution on the slide, then a drop of calcium chloride solution at the side of the coverslip. By slow diffusion these crystals appear because of their low solubility.
Better on a slide than in the body: kidney stones :shock:

So many other combinations between anions and cations are possible! I tried calcium sulfate (gypsum) from calcium chloride and magnesium sulfate and that worked great, but no pictures.

Calcium carbonate (from CaCl2 + Na2CO3 aq) formed tiny crystals, crystal formation must have been too quick... I know diffusion can be slowed down by a gel - and hey, I found some glycerin-gelatine that I made 40+ years ago that looks and smells as fresh as on day 1 :) So, that's high on the priority list: use gel to increase crystal size.

Test shots with my new optiphot, improvised with an old enlarger objective as photo eyepiece (50 mm Componon), some PVC and paper cylinders, Olympus E-500, 20x DIC (and POL of course).
Attachments
CaOxalaat3.jpg
CaOxalaat3.jpg (100.6 KiB) Viewed 1295 times
CaOxalaat2.jpg
CaOxalaat2.jpg (96.94 KiB) Viewed 1295 times

MichaelG.
Posts: 3981
Joined: Mon Apr 10, 2017 8:24 am
Location: North Wales

Re: calcium oxalate crystals by precipitation

#2 Post by MichaelG. » Sun Jul 11, 2021 6:05 am

Very interesting, thanks
… and very sharp corners ! [ouch]

MichaelG.
Too many 'projects'

Hobbyst46
Posts: 4277
Joined: Mon Aug 21, 2017 9:02 pm

Re: calcium oxalate crystals by precipitation

#3 Post by Hobbyst46 » Sun Jul 11, 2021 9:02 am

Very nice experiment !
Sometimes tiny crystals are formed when the solution contains crystallization nuclei - like dust particles, or when the process is disturbed by a mechanical shock.
But I doubt that any of these happened. Indeed, slow diffusion is the way to go, on a slide.

Lomonaut
Posts: 100
Joined: Sat Jan 27, 2018 5:30 pm

Re: calcium oxalate crystals by precipitation

#4 Post by Lomonaut » Sun Jul 11, 2021 10:44 pm

I should print a T-shirt with 'SLOW DIFFUSION: The Way to go' :lol:

You're right about dust, there is some debris visible. I'd better filter the solutions, perhaps with a syringe and cotton pad.

Thanks for the feedback!

Lomonaut
Posts: 100
Joined: Sat Jan 27, 2018 5:30 pm

Re: calcium oxalate crystals by precipitation

#5 Post by Lomonaut » Sat Jul 24, 2021 5:34 pm

Here's a shot of gypsum, from calcium chloride + magnesium sulfate (any soluble sulfate and calcium salt will work), with my new old Nikon 10x/0.30 e-planachromat.
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gypsum1.jpg
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