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Reflux-and-Chill
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Here they are:
 
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NEMO-Chemistry
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Quote: Originally posted by aga  | Too complicated.
Better to just make some copper sulphate from your sulphuric acid with electrolysis.
Nitric acid is less of a worry than conc sulphuric !
Edit:
Also, Reflux-and-Chill has had plenty of time to boil 125ml of water, add/dissolve crystals, filter, leave to cool ...
... so will probably post his results pretty soon ... ?
[Edited on 16-6-2016 by aga] |
Nitric acid is a paranoia thing now we are not meant to have it. Apart from being complicated do you see any reason it wont work?
I know he is posting his results but still good practice to do any way. AND I get to add to my reagents  .
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Reflux-and-Chill
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Neither nitric nor sulphuric acid have to represent a major concern if handled and stored with care. SAFETY FIRST, people!
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NEMO-Chemistry
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Conc Nitric isnt legal for the public in the UK  , i misread the Amazon advert and
got two, lots of two litres each by mistake! It was worded in a way that sloppy reading made me think i was getting 2 ltr total.
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Reflux-and-Chill
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How many liters did you end up receiving?
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NEMO-Chemistry
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4 Ltr, the advert said 1ltr bottle packaging, i missed the bit about it being for 2 bottles! The advert used a different company bottle as the
picture.
But the acid is clear and seems ok, dosnt fume and dosnt have any orange in it, which i thought a bit odd for 68%. Anyway its way more than i will use
in a reasonable time frame and conc sulphuric is allowed so easy to get at the moment.
I probally prefer to have nitrate salts rather than nitric acid, then i can make the acid as i need it, i will keep 1-2 LTR conc anyway.
If i go electrolysis then i have to clean battery carbon rods and likely to get an even more impure product, plus wet chemistry seems a bit quicker.
I normally use an extension lead for electric to the shed, so thats one reason i am sort of confined to weekend chemistry for anything needing
electric or anything that requires a bit of time.
Also i would like some copper compounds anyway. I am half way through trying to make a dry glove box for copper nitrate crystals.
I was tempted to flush the box with propane but instead will use sodium hydroxide for the desiccator. Hopefully if i put the everything including the
final storage bottle in, i might be able to get some fairly dry copper nitrate crystals.
Cool crystals by the way.
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aga
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Woohoo ! Well done Reflux-and-Chill !
That works out at a yield of 82%, which is pretty close to the 84% i ended up with, although that is probably because i started with 5x as much
'dirty' crystals.
     
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Reflux-and-Chill
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Fuming nitric acid is a solution that contains more than 86% nitric acid, so don't worry about the lack of fumes. If you want to find out the
concentration, you could titrate it against a known concentration of Sodium Hydroxide using a simple indicator like Phenolphthalein.
Thanks.
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Reflux-and-Chill
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WOW, aga! That looks awesome!!! It seems that you did great job with this.
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NEMO-Chemistry
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Wow, how many crystallization did you do? definitely a skill worth developing, i wasnt expecting to see so much crap on the filter paper.
Copper salts have a great colour dont they.
So my target is around the 80% mark, how long did they take to crystallize? I hope to have it done and dusted by 8pm Sunday night.
[Edited on 16-6-2016 by NEMO-Chemistry]
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aga
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It's just one recrystallisation, although my cock-up with the .5H2O meant that it would not all fit in one 250ml beaker.
The photo of the crystals drying is the second portion, with the already-dried 'main' portion in the container behind it (container=1 litre disposable
drinks cup).
The process with copper sulphate is easy enough to describe in just a few words, without pictures.
The photos are really just to show that it was actually done rather than just photograph two piles of the same crystals.
As can be seen in the photo of the filtration step, crystals have already formed : copper sulphate doesn't hang around much when recrystallising due
to the solvent losing heat.
By the morning you will get a large crop of small crystals, usually fused into a single lump, which is why it's best to use plastic
containers in this step : you'can't squeeze glass.
[Edited on 16-6-2016 by aga]
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Reflux-and-Chill
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It was actually done, but I can see why you would think these are two piles of the same crystals (they do look very similar). The second pile
are in fact the recrystallized crystals that I filtered out of my beaker. I know they are, because what else could they be? This is my first time
doing this and you don't need to be so passive-aggressive, just because my crystals look like crap compared to yours. Thank you.
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DJF90
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| Quote: Originally posted by aga |
By the morning you will get a large crop of small crystals, usually fused into a single lump, which is why it's best to use plastic
containers in this step : you'can't squeeze glass.
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This is why (process) chemists use stirring when (re)crystallising compounds.
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aga
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What ! they want even smaller crystals !
Makes sense i suppose : they're likely going to dissolve and use them straight away.
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aga
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It is what it is.
The photos i posted show what the process looks like, and may be of some use to somebody one day.
Yes, there is a lot of crap in the filter.
[Edited on 16-6-2016 by aga]
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aga
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They don't: yours look much better, much more professional.
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DJF90
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| Quote: Originally posted by aga |
What ! they want even smaller crystals !
Makes sense i suppose : they're likely going to dissolve and use them straight away. |
Not necessarily smaller crystals, but it helps give a narrower particle size distribution and greatly improves handling properties compared to large
crystalline chunks. Suspensions of the crystals in the mother liquors have to be pumped through transfer lines from the reaction vessel to the filter
unit. In addition, any subsequent use of the product (whether used in another reaction on scale, or sold/used as a reagent/substrate/building
block/pharmaceutical) will benefit from the improved handling and dissolution properties that the smaller crystalline solids will possess (in
comparison to having to grind/mill/dissolve larger chunks of solid material).
The only reason a chemist would perform crystallisation without agitation would be for the purposes of growing an aesthetically appealing
crystal specimen or for preparation of a single crystal suitable for X-ray diffraction experiments (structure determination).
EDIT: One caveat to using agitation - mag stirring will return a (finely) ground solid due to action of the stirrer bar. Best use mechanical stirring.
[Edited on 16-6-2016 by DJF90]
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elementcollector1
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I'm going for a big ol' single crystal of CuSO4, so I'll probably pop back in a few days or a week from now with my own pics. Wasn't
concentrating on yield, but it looks about right. : P
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
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Reflux-and-Chill
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aga, y u trollin' so much?
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NEMO-Chemistry
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Out of interest makes you think he is trolling? Not being funny i guess i didnt interpret his reply the way you did. The net is a funny thing and its
hard to read peoples intent of word without a facial expression to accompany the words.
Also i get the feeling some/alot of the older members (time wise) are pretty mistrustful of newer members, but then again this is mainly chemistry
based site so you need to use caution with questions until they know you i spose.
I think there has been 'kewles' etal on here previously (a kewel i believe is a druggy????). Any way nice crystals and i think you misread what he was
saying.
One last thing dont take things to heart, at the end of the day aga did the experiment also, he has some experience and the way he presented his
information was good.
Us newbies can learn from this and when i post mine up at the weekend i will try and follow a similar write up. Lats be brutal here, two piles of
crystals show you did the crystallization, but agas gave more information by providing a pictorial reference.
I admit not easy to photo things when your busy doing, but as a newbie i was surprised to see so much crud on the paper, now when i do mine i am
expecting more but now i wont think its abnormal to get so much.
I am not being critical of you, i just think sometimes it helps to step back and see the bigger picture.
I kinda promised in another thread i wasnt going to do copper sulphate crystals!! Bah looks like thats gone out the window .
But better to practice on cheapo copper sulphate than hard won crystals from a plant extraction . Only got to chop the copper wire today, but weekend is lab time!!
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aga
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People tend to do better if they treat Honestly with other People, virtual or otherwise.
'Better' as in learn more.
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Reflux-and-Chill
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I think I got it; the second pile of crystals never dissolved, and the ones that did never recrystallized...but not like that matters anymore. This
has been very educational. Thank you all for your help and time, farewell!
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myristicinaldehyde
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Tried this myself, but got smaller crystals than I hoped. Next time, cover the beaker!
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MrHomeScientist
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Going back to DJF90's remark about purity:
| Quote: | | There is no point in trying to purify a material if you cannot assess the improvement in purity that the process has afforded |
I know at the amateur level it's difficult to specify the exact purity of a substance (99% vs 99.9%), but in my experience with copper sulfate at
least there is a pretty clear improvement visually. When dissolving 'root killer' grade hardware store copper sulfate, there is always a green/brown
residue that remains and refuses to dissolve. Whatever this is would contaminate reactions, so is worth my time to remove with at least one
recrystallization. This results in clean, pure blue, well-formed crystals that clearly appear a good deal more pure. Not even considering the beauty
of the process!
While I agree with your statement up to a point (doing 17 recrystallizations with no way of measuring the improvement is pointless), I do believe at
least one recrystallization is always warranted. It certainly can't hurt, and you know it will always increase purity to some extent.
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experimental
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Recently I bought 1 Kg of technical grade copper sulfate, which turned out to be quite dirty. Just dissolving some in water left a sand-like deposit
on the bottom of the flask, so I decided to recrystallize it.
I did the same procedure that aga explained in this thread, but had to work in batches of 200 g each and to dry the crystals I used a buchner funnel.
After each batch the glass frit of the buchner was visibly dirty, so I washed it with some hydrochloric acid.
Everything went well, but the saturated solution of CuSO4 where the crystals formed accumulated after each batch and I was left with nearly 600 mL.
So I tried to make a second crop, evaporated 200 mL of it down to about 75 mL (when a crust of crystals started to form on the surface) and left it to
cool, without any hot filtration this time.
And here is where the problems started: the next day I found dual-colored crystal in the beaker! Most of the crystals were the usual color of CuSO4,
but a smaller amount of lighter colored crystals were also present.
Can any of you guess what happened and how to recover more copper sulfate in such a situation? My explanation is that some hydrochloric acid remained
in the glass frit and in subsequent batches I somehow made copper chloride.
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