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Chemist_Cup_Noodles
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Oh my god do I love the look of chromates and dichromates. For the life of me I can't find a good source of the anion, or even of chromium itself in
order to make some. Maybe I'll just have to buy some and recrystallize it. I do wish that chromates were more soluble though. Anyone know good
solvents for them? The mineral crocoite (lead chromate) is beautiful but insoluble in water.
But crystalgrower, if those are your crystals I'd love to hear the details on how you made and grew them. Chromium is seriously one of my favorite
transition metals.
I'll be honest-- We're throwing science at the wall here to see what sticks. No idea what it'll do.
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crystal grower
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Quote: Originally posted by Chemist_Cup_Noodles  | Oh my god do I love the look of chromates and dichromates. For the life of me I can't find a good source of the anion, or even of chromium itself in
order to make some. Maybe I'll just have to buy some and recrystallize it. I do wish that chromates were more soluble though. Anyone know good
solvents for them? The mineral crocoite (lead chromate) is beautiful but insoluble in water.
But crystalgrower, if those are your crystals I'd love to hear the details on how you made and grew them. Chromium is seriously one of my favorite
transition metals. |
Frankly, these crystals have come from solution which I have forgotten somewhere in mess in my lab and when I found it after few months, there was a
pretty surprise waiting for me  . So time is best recipe IMO.
But if you want to try to grow these crystals a lot faster, you can try this procedure: http://chem.pieceofscience.com/?p=937. And Im sure you can get better results than mine. Although k2cr2o7 has only little water solubilty at room
temperatures, the solubilty rises drastically with bigger temperatures, so repeated cooling seems to be very effective for crystal growing.
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Chemist_Cup_Noodles
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| Quote: Originally posted by crystal grower |
Frankly, these crystals have come from solution which I have forgotten somewhere in mess in my lab and when I found it after few months, there was a
pretty surprise waiting for me . So time is best recipe IMO.
But if you want to try to grow these crystals a lot faster, you can try this procedure: http://chem.pieceofscience.com/?p=937. And Im sure you can get better results than mine. Although k2cr2o7 has only little water solubilty at room
temperatures, the solubilty rises drastically with bigger temperatures, so repeated cooling seems to be very effective for crystal growing.
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Ooh, I'm really liking this website you linked me to. Very very good work. Sleek interface, great content. I see you have quite a wealth of
experiments on this page, wow. Where do you source most of your chemicals and glassware? Do you synthesize your own intermediaries or buy them? And it
says you're in highschool? Damn son, making me feel bad.
Anyway, being a novice chemist I've always seen the word "alum" thrown around, especially in this thread, but always preceded by potassium and
aluminum. I never really understood what exactly it meant. So I never realized that alum was a group of compounds! These are something to behold,
truly. I've just cracked open my new bottle of H2SO4 so I'm eager to use it to make some of these now. So by my understanding,
an alum is any +3 oxidation state ion and one +1 oxidation state ion with two -2 sulfate ions.
On a side note, spring is being annoying. I've had several solutions that I've left open to air in order to try and let them evaporate faster, but
with all this rain it's too damn humid. Also, bugs won't stop flying into them, dying, and in some cases they start to dissolve if it's reactive
enough. Little bastards, contaminating my hard work.
Edit: I like these so much I think I'll start a topic for them on the General Chemistry board. I think I'll just call it Alum Crystals Thread.
[Edited on 28-4-2016 by Chemist_Cup_Noodles]
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crystal grower
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Thanks  .
Our sources are various, we buy something o f course, other stuff we synthese ourselves, and also a lot of experiments has hegi done at university
lab.
Sometimes we must improvise a little, but we are trying our best to be as profesional as possible. We also accept any donations, though finding a
sponsor is very hard of course.
A lot of that great synthesis is Hegi's work so don't think that Im some super chem-kid  lol.
You're partially right with the alums, you can find a good explanation on wikipwedia: https://en.m.wikipedia.org/wiki/Alum
And to tell something about the "spring problems" you mentioned, just look properly at the third photo of the p. dichromate crystals that i have taken
(that small fly in it ).
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Cucurbit
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Nice bichromate crystals!
And poor insect - unless it's a mosquito, I hate those 
Which reminds me of something... many years ago I used potassium bichromate for gum prints, and got a nice crystal after evaporation of leftovers.
I'll see if I can find it and take a picture tomorrow.
And Cup_noodles, I can't wait to see some pics of your alum crystals!
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The Volatile Chemist
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Ammonium Chloride surprisingly makes needle-like crystals, something at least I hadn't seen before.
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crystal grower
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@the volatile chemist
Once i grew nh4cl crystals with needle like shape too, and they had hashtag reminding layout ### .
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The Volatile Chemist
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Yeah, they were kinda unique, It might've had to do with excess ammonia or HCl,
to be honest I forget which I used. What other shape grew for you besides needle-like? I just got a crust with beads, and then the needle-shaped ones.
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crystal grower
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these are crystals of nh4cl that I´ve grown few years ago (I didnt care much about the procedure in that time, I just dissolved some sal ammoniac in
the water and waited what it will do ).
It´s interesting that it crystallized into "three forms". At the very buttom a crust was formed, above a # like needles crzstallized and at the top
were something like prisms and another crystastals crzstallized on them (reminding me sceptre quartz)
Sal ammoniac is really interesting stuff and I´ll maybe write an article about it in near future .
 
[Edited on 1-5-2016 by crystal grower]
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Cucurbit
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Very nice ammonium chloride crystals!
Here's this potassium bichromate crystal. Old, impure and damaged... in my memory it was much nicer but hey, I promised to post a picture!
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The Volatile Chemist
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Yes, it is quite interesting stuff. Unfortunately, I only just recently realized that the crap on the sides of the crystallizing dish was soap from my
ammonia supply. So the stuff I collected is garbage...
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Velzee
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Potassium ferrioxalate crystals, contaminated with potassium oxalate and chloride:
 
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"All truth passes through three stages. First, it is ridiculed. Second, it is violently opposed. Third, it is accepted as being self-evident."
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Bezaleel
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Praseodymium sulphate octahydrate
On pg 3 of this thread, Nezza posted a beam-shaped crystal of Pr2(SO4)3.8H2O.
Mine appear to have a somewhat different form. Here are 4 pictures of the same crystal. I needed to stop growing it further, because I ran out of
solution.
The long side is less than 1 cm long.
[Edited on 9-2-2017 by Bezaleel]
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crystal grower
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| Quote: Originally posted by Bezaleel | On pg 3 of this thread, Nezza posted a beam-shaped crystal of Pr2(SO4)3.8H2O.
Mine appear to have a somewhat different form. Here are 4 pictures of the same crystal. I needed to stop growing it further, because I ran out of
solution.
The long side is less than 1 cm long.
[Edited on 9-2-2017 by Bezaleel] |
Oh my god, this one is just beautiful. Awesome clean crystal faces
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woelen
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These look very good. How long did it take to grow these crystals?
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Bezaleel
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I took a seed crystal from the solution, about 1mm in thickness, which was just big enough to tie a thread around. It was suspended in the solution
from which it had formed for almost 1 week (6 days, if I remember well - I started somewhere last week). The solution evaporated in the boiler room
with a larger beaker over it to keep out most of the home dust in the air. The air in the boiler room is relatively dry and the temperature is quite
constant (between 19 and 22C). Evaporation speed was about 30ml from the 100ml when the crystal was first suspended from the monofilament thread.
Maybe it's interesting to know that a plastic beaker is preferred over a glass one, because in an earlier experiment with a solution of the very same
Pr-sulphate, the solution crept upwards along the walls of that glass beaker (more than 8 cm up!). It forms ugly crusts on glass beaker walls. I also
think that a plastic (PE) beaker makes it easier for the crystals to nucleate. In glass beakers, my rare earth solutions super saturate almost without
exception.
The pH of the solution is 6.
Also of interest may be the dissolution behaviour. In order to get all of the Pr2(SO4)3.8H2O dissolved, about 20% more solution was needed than the
volume from which the first tiny seed crystals appeared. I am tempted to conclude that the dissolution-crystallisation cycle has some hysteresis.
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