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NeonPulse
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so i made an attempt at making potassium dichromate via heating Cr2O3 with KOH and KClO3. went fairly well during the initial 10 mins heating but at
one point it got too hot and the whole thing ended in a spectacular runaway which was bubbling very violently and ended up ejected much of the red
hot molten mixture up like a volcano. it was relatively contained in the work area with a bit of paper on which my notes were written getting splashed
and catching fire and some scorch marks on the sleeve of my labcoat the only damage.
I was able to retrieve much of the now rock hard mixture off the burner and sides of the crucible and the little balls of it on the board, to
continue the synthesis. the rest of the synthesis was pretty un eventful. thats my excitement for yesterday. one screenshot shows the mixture left in
the stainless steel crucible still glowing red hot.
 
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JJay
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Oh wow, that doesn't sound like much fun to clean up! Did you get a decent product?
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tsathoggua1
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Me, with the WP? not a clue. It might have been for a moment, but obviously not ALL of the argon backpurge before beginning to heat prior to sealing
must have been purged, for the ampoule gave a CRACK! loud enough to wake my sleeping old man, and afterwards, only a few tiny fragments of glass,
coated in phosphorus, were ever discovered, the rest of it, ampoule and all, ended up atomized in a fine cloud of glass dust from the obsservation of
said event, and as for the phosphorus, part of it obviously burnt to a huge cloud of smoke instantly, being dispersed finely, and the rest, well some
of it rebounded off my face shield and coveralls to splatter across a wooden cabinet, leaving a trail of burn marks an inch or two or three in
circumference. And a little caught my hair (this is not because of inadequate protective gear, rather, due to the great length of my hair. Its a face
shield that goes down below my shoulders, not a 'near-to-stomach shield'  and I
ended up with some hair burnt extra-crispy and the stink of burning proteins, but other than that no harm done (to me) whatsoever, can't say the same
for the cabinet, that took a trail of burning splatters.
Was more hacked off about the loss of the ampoule I'd made, and the loss of a few grams of white phosphorus and having to go reset the fire alarm set
off by the P2O5. No damage to the face-upper torso shield, the WP seems to have rebounded off of it and gone on to toast that cabinet. Only a few g of
WP, a few thousandths of my supply of red P went into its creation, other than that, not a problem, just an irritation.
What else....annoyingly, a NaOH/KOH melt, producing NaK alloy electrolytically brutally attacked the nickel alloy electrodes (guitar fret wire pieces,
and the end of it that started out blunt, used as anode ended up being corroded so badly it was a razor sharp point when withdrawn from the ~200 'C
melt. The point on it was as sharp as any hypodermic needle tip and the end at least as fine as one of the 28 gauge needle sometimes used for my pain
medication, and I imagine lengths of such electrolytically sharpened fretwire, being triangular rougly, would make, for those who wished to do so,
fantastic ammunition for a shotgun cartridge, that would autostabilize in flight due to the T-like profile of the remainder of the fret wire other
than the sharpened tip. Like a beehive flechette round fired from tanks etc.
I'd rather have had the wire undamaged though since it was the only long piece I have, but still, will come in handy for poking blocked condensers
open.
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JJay
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I'm not seeing what went wrong exactly; what is another chemist to learn from these experiences with white phosphorus and NaK? To use PPE when
handling dangerous substances? I mean, it's not quite, "Today I accidentally killed my dog while distilling some prussic acid in my grandmother's
basement  Good thing I was wearing a gas mask." I am interested in phosphorus
chemistry, but I don't have any phosphorus, so I'm not *that* interested in it. But if you have exciting stories about phosphorus and NaK, I am sure
people are interested in them.
I was thinking about actually trying a similar potassium dichromate synthesis but with potassium nitrate, so I am really quite interested in the
synthesis with potassium chlorate. Chromium chemistry seems to be a popular topic right now, and it's plenty dangerous enough if you like that sort of
thing.
[Edited on 13-4-2017 by JJay]
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NeonPulse
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the synthesis was fairly straight forward and the yield is 14g- i attribute this lowered figure to the obvious losses in the first stage. this was the
second time around attempting this synthesis.
The first try was using sodium nitrate as the oxidiser and it did seem to be inferior and the reduced yellow solution released quite some NO2 upon
acidification which suggests that NaNO2 was formed as well. there was also quite a lot of un reacted Cr2O3 on my filter so it probably needed longer
heating even though it was heated full blast for about an hour. i had a problem with the workup so i had to ditch that attempt.
i did not have any KNO3 around to use this instead. i would say the chlorate method is probably better but i think slow and steady heating is the way
to go. also use a large crucible! i only had a smallish batch 25g Cr2O3/ 28g KCLO3/30g KOH and thought that the size would easily handle the mixture
but obviously i was wrong.
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tsathoggua1
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The moral of the tale is to (probably) heat the OPEN ampoule a bit, to drive out the inert gas until P vapor is slightly exiting the amp, covering the
end with a jet of inert gas and fusing with a secondary torch. Perhaps using one of those micro torches to expel the air and then seal it before
suckback of air occurs. The ampoule was small, made from a 2ml (bulb size) pipette, the phosphorus being introduced as a suspension via cannula as in
a volatile solvent, not quite sure what, but an inert for contact cleaning, rapid drying spray, kept mildly warm for a while to expel the solvent (it
boils off in moments) by keeping the UNfused ampoule in the oven for a little while, away from direct flame.
On sealing it, then heating, the change occured from red to white unusually quickly. I noticed an odd change in appearance of the red phosphorus, it
changed from its usual color to a dark color, like that of mercury sulfide, before transition to white P, and then all of a sudden the amp went off
with a bang, loud enough to wake my sleeping father. Really glad of that face shield, since it got peppered with glass, as the amp ended up atomized,
not much left of it, the resultant crack when it went off was sufficient to reduce it to dust, only a few small fragments left.
I'm curious about the change in the red phosphorus observed shortly before the disintegration of the ampoule. It darkened very significantly. Could
this perhaps have been the beginnings of a transition to violet phosphorus?
This is afterall a thread for chemistry going wrong. It was chemistry. It went wrong. Scratch one ampoule, spend the rest of the night scratchING the
jet-trail of burn marks off one of the nearby wooden carbinets. Personally I think it sort of decorative, in a way only a mad scientist could
appreciate 
As for chromium chemistry, I do have a synthesis of chromyl chloride planned actually, since I happen to have ended up with some very resistant
bottles (the caps, that is) that seal well, especially wrapped in teflon tape.
The NaK is on hold for now. Well, probably. I do have a melt in a crucible to drill a hole in and see if there was any deposited under the surface of
the melt, but it proved too reactive to isolate, forming large (about a half inch) bubble-like blobs which collapsed in on themselves in showers of
sparks immediately. Unfortunately my power supply has blown something inside, and its beyond my ability to fix it. My old man is going to take a look
at it, if its buggered, I'll buy myself a welding supply and use it to drive a constant-current DC source with variable yields. The lack of a power
supply is driving me nuts I was spending all night, most nights, beavering away
with it. Did get some sodium and sodium-calcium alloy out of it though.
NaK is, as well known, more reactive than Na or K, but bloody hell, just HOW reactive coming out of the melt is understated if anything. Small amounts
spark and burn the second they touch air, larger bubbles of it can make quite a mess. Had to clean the walls after every experiment in NaK
electrolysis due to the spatter of KOH and NaOH.
On to something a little tamer, until I get a power supply back up and running, got a manganese thermite planned for today. Zinc-plated one of my
carbon crucibles as a temporary shield between the carbon and the manganese oxide hydroxide. Finishing drying off the oxide in preparation for
reduction.
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JJay
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Quote: Originally posted by NeonPulse  | the synthesis was fairly straight forward and the yield is 14g- i attribute this lowered figure to the obvious losses in the first stage. this was the
second time around attempting this synthesis.
The first try was using sodium nitrate as the oxidiser and it did seem to be inferior and the reduced yellow solution released quite some NO2 upon
acidification which suggests that NaNO2 was formed as well. there was also quite a lot of un reacted Cr2O3 on my filter so it probably needed longer
heating even though it was heated full blast for about an hour. i had a problem with the workup so i had to ditch that attempt.
i did not have any KNO3 around to use this instead. i would say the chlorate method is probably better but i think slow and steady heating is the way
to go. also use a large crucible! i only had a smallish batch 25g Cr2O3/ 28g KCLO3/30g KOH and thought that the size would easily handle the mixture
but obviously i was wrong. |
Good to know. I figured that using a large crucible would help, but I didn't know it needed to be anywhere close to that large with that size batch.
I have been tossing around the idea of making a few mL of chromyl chloride for an ampule, but it wouldn't be my reagent of choice for any oxidation
that I can think of, and I definitely don't want to be posting in this section about how I dropped a liter of chromyl chloride on concrete and ruined
my new Asics.
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tsathoggua1
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Trust me, thats really not pretty if it happens. Had just that occur once due to a flask failure, cracked right round the middle of the distillation
flask and the bottom dropped out, and likewise the reaction mixture. Wasted a lot of dichromate and the best part of a liter of 98% sulfuric, plus
scratch one desk. Nearly hit me too, thankfully I was quick enough to get out of the way. Not a mixture I'd like being covered with at ~120 'C
It is useful stuff though, the Etard reaction can selectively oxidize alcohols to aldehydes. Needs care in the choice of solvent though, chlorinated
hydrocarbons, CH2Cl2 especially is a good choice.
[Edited on 16-4-2017 by tsathoggua1]
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JJay
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I'd probably use a different reagent for that. Pretty much any chromium based oxidizer can oxidize primary alcohols to aldehydes, but they also
oxidize aldehydes to carboxylic acids in aqueous conditions.
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tsathoggua1
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CrrO2Cl2 is NOT compatible with H2O. It fumes in air, releasing HCl, and best used in anhydrous DCM. There is no way of using CrO2Cl2 in aq.
conditions. Don't let water get to the stuff, its messy and downright unpleasant.
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JJay
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Chromyl chloride hydrolyzes to hydrochloric acid and chromic acid in water. That combination can certainly oxidize alcohols to carboxylic acids.
Chromyl chloride isn't "compatible" with the things you would be oxidizing with it either, so I'm not sure what you are getting at. What do you clean
up a liter of spilled chromyl chloride with anyway?
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j_sum1
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A litre!? Ouch!
I'd use plenty of PPE including a respirator and flood the scene with a solution of sodium sulfite.
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tsathoggua1
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What do you clean it up with? you run like the devil himself were nipping at your heels.
And it was a liter of CrO2Cl2, plus a liter of sulfuric (98%), and the corresponding quantities of NaCl and dichromate, potassium dichromate IIRC. Was
quite some years back. And I just got the hell out of the way and let it hydrolyse, sealed off the room for the next few days and vented it out.
Couldn't have gotten close enough at the moment of flask failure. Its not pretty on that scale!!
Thankfully my receiving flask had stayed intact as had condenser. So I did get to keep some of my distilled chromyl chloride at least
[Edited on 17-4-2017 by tsathoggua1]
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Rhodanide
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Not a disaster, but...
Tried to filter excess Cu(OH)2 from concentrated Schweitzers reagent solution.
Used paper filter.
Filter dissolved.
Noticed incredibly obvious fuck-up.
Cried self to sleep.
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j_sum1
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That cracked me up.
Well done, Tetra.
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JJay
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Today I managed to get sulfuric acid on several of my fingers.
The first time it was from picking up a rag I had used to wipe up a tiny amount of spilled sulfuric acid. I remember thinking, "Something tingles,"
and then realized what I was holding. I washed my fingers under water and then rubbed sodium carbonate on them and washed them some more. It left
these big watery sulfuric acid blisters that were apparently full of dilute sulfuric acid. The second time I was holding a graduated cylinder (rather
stupidly) with no gloves and pouring sulfuric acid and I noticed that my thumb was getting carbonized, although I didn't feel any pain. I put it under
water for a while and got another sulfuric acid blister.
This was the first time I had ever gotten sulfuric acid on my hands, and I think I've handled quite a bit of sulfuric acid... and it happened twice
within a period of about 10 minutes.
I was worried that I was going to have some nasty painful wounds, but after half an hour or so, the blisters dried up and my skin re-laminated itself.
The skin on my fingers is still a little dry but other than that everything seems ok. I actually don't have particularly heavy-duty hands, but I sure
am glad I didn't rub my eye or something.
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NedsHead
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Does this count? https://youtu.be/VRoYCpjMPyk?t=56s
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gdflp
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The viscosity of conc sulfuric acid can be a real pain sometimes. If you aren't careful, it's easy to get that one drop which clings to the pouring
spout, then runs down the side of the container when you put it down. With good quality, clear acid, most of the time I don't notice unless I put it
down on a piece of paper towel; a habit I've gotten into for that very reason.
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Sulaiman
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I have adopted the habit of rinsing the outside of my acid bottles after use,
I use self-adhesive paper labels but a quick rinse so far has not caused label damage,
and anything that comes into contact with conc. sulfuric acid
( stir rod, thermometer, funnel, measuring cylinder etc.)
I dunk under water then rinse, immediately after use.
... usually ...
CAUTION : Hobby Chemist, not Professional or even Amateur
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JJay
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It is easy to get lackadaisical around sulfuric acid if you handle it all the time. After all, it's not *that* dangerous compared to strong sodium
hydroxide solutions or hydrogen peroxide. At the same time, it is one of the strongest commonly available acids and can cause extremely serious
injuries. I wipe off the bottle, graduated cylinders, etc. after using them, but of course I should remember to put the rag used for doing so into
water immediately rather than leaving it at arm's reach. It would also probably be a good idea to use a wet rag....
I sometimes do the paper towel trick also, and it is a good one.
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tsathoggua1
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Excluding getting it in the eyes, I'm surprised that NaOH, concentrated or otherwise is rated as more hazardous than concentrated sulfuric. At least
with NaOH there is a quick window within which to wash it off thoroughly, due to the greasy layer of saponified fats produced. The only time it gives
me the willies a bit in terms of caution required is when not in solution but in the molten state,, fused NaOH at a few hundred degrees 'C is
definitely rather nasty stuff. I'd still give concentrated H2SO4 my vote for the more dangerous substance however.
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JJay
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There's a window to wash off most mineral acids (note: no one should ever attempt to replicate anything in this video or conduct similar experiments
with caustic substances): https://www.youtube.com/watch?v=XeVZQoJ5FdE
I have never personally gotten any sodium hydroxide on my skin other than a prill once or twice, but I have read that concentrated sodium hydroxide is
extremely dangerous....
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mayko
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I usually put solutions in the microwave to get them up to boiling, even if I'm going to continue heating on a hotplate later. This is what I did the
other day, when I put a 600 mL beaker in the microwave, containing ~250 mL of tribasic sodium citrate solution in excess sodium hydroxide, and a few
inches of wooden dowel to act as a nucleation site for bubbles. I left the room for a few minutes (maybe 3 at the outside) as it heated.
When I returned, there was a charred, caramel smell in the air. Looking in the microwave, the liquid in the beaker was hot and brown, and the dowel
was not at first visible. My first thought was that the very basic, boiling liquid had dissolved the wood. On closer inspection, though, I saw that
the dowel had in fact been burnt into two pieces and fallen into the liquid. The burn mark looked to coincide with the level of the liquid.
Has anyone seen this sort of thing before? My (speculative) explanation is that a bit of solution landed on the wood, dried, and then the residual
sodium hydroxide absorbed microwave energy until it melted, charring the wood. The carbon produced would then act as an accelerating energy sink.
al-khemie is not a terrorist organization
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j_sum1
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I dunno. But if it was me I would try to replicate this -- and watch it this time.
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mayko
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I tried recreating it on a small scale with concentrated NaOH; nothing happened with the stick but the beaker cracked, apparently from thermal stress,
and I had to figure out how to move a cracked, liable to disintegrate container full of hot lye rescuing the TSC is probably my top priority right this second.
al-khemie is not a terrorist organization
"Chemicals, chemicals... I need chemicals!" - George Hayduke
"Wubbalubba dub-dub!" - Rick Sanchez
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