AndrewOfWallachia
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Failed attempt at making chloroform[?]
For context, I originally posted this on that cesspit of a site called reddit, because I didn't think this issue was of enough import to bother the
ScienceMadness halls of wisdom with it. However after two very foolish passive-aggressive comments (which completely failed to answer my question) my
post was removed because apparently chloroform is on the same level as amphetamine to them and talking about making it is illegal. [Maker preserve
us!] Anyways, here's my predicament:
Today I attempted to produce chloroform by the haloform reaction. Using NaClO Bleach and Acetone.
The bleach I used was very dilute this is the only variety you can get where I live, it's reasonable to assume its concentration is around 4.5%. Based
on this I calculated the weight of Acetone I needed for the reaction (12g) for 1 L of bleach. I chilled both Acetone and Bleach below zero and then I
combined them in a clean glass bottle in an ice-bath. The bottle was shaken vigorously and I left it's cap ajar so that no pressure is built up.
The reaction temperature did not exceed 20 C which I assume is normal due to the cooled reagents and very low concentration of NaClO. I initially the
solution became cloudy and washed white, this should be completely normal it's the solution forming an emulsion with the immiscible chloroform
droplets, I assumed. HOWEVER, when I checked the reaction hours later I found out that was in fact not chloroform but a very fine solid white
precipitate which had settled on the bottom. Both now and during the reaction I could notice a very, very small amount of gas being constantly
released from the solution (at most 3 barely visible bubbles at a time). I have absolutely no idea what went wrong here and what the white precipitate
was, what I am most worried about is the gas being released, although tiny amount it seems to have been released constantly over the course of
multiple hours. If you have any idea what the hell could have caused this or what the reaction products were please explain your theories.
For your information, I immediately disposed of the reaction mixture (safely) once I realized something was not going according to plan.
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Keras
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Are you sure your bleach is pure? And is it really sodium hypochlorite and not some sort of TCCA-based thing?
Also, chloroform is soluble in cold water (~ 10 g/L) so if your bleach is not concentrated enough, all your chloroform goes into solution…
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AndrewOfWallachia
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Quote: Originally posted by Keras  | Are you sure your bleach is pure? And is it really sodium hypochlorite and not some sort of TCCA-based thing?
Also, chloroform is soluble in cold water (~ 10 g/L) so if your bleach is not concentrated enough, all your chloroform goes into solution…
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To be totally honest the bottle says "<5% Chlorine-based bleach(-ing agent)" The nomenclature here is flimsy because in Romanian the key word is
"Înălbitor" which can be interpreted both as bleach and bleaching agent. It would make the most sense for it to be Sodium Hypochlorite but it's
indeed not listed exactly what it is.
Regarding your theory that the chloroform just stayed in solution, I doubt it because according to my calculations I should have gotten around 23 g of
Chloroform form the reaction, which was in 1 liter of solution. So even if the water was constantly cold, which it was not I still would have gotten
around 13 g of Chloro- that would have fallen out of solution. Plus what I really am perplexed about is the white precipitate.
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unionised
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Saturating the mixture with salt will reduce the solubility of the chloroform.
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Sulaiman
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how efficient is that.?
I ask because my first haloform attempt gave a few drops of chloroform with the bulk lost in solution,
so I tried with 35% (from memory) hypochlorite to reduce the water content,
suuuper exothermic - not practical,
So the 'plan' for my next attempt is/was dilute hypochlorite then distillation,
salting out would be much easier and safer.
CAUTION : Hobby Chemist, not Professional or even Amateur
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Precipitates
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| Quote: Originally posted by AndrewOfWallachia |
To be totally honest the bottle says "<5% Chlorine-based bleach(-ing agent)" The nomenclature here is flimsy because in Romanian the key word is
"Înălbitor" which can be interpreted both as bleach and bleaching agent. It would make the most sense for it to be Sodium Hypochlorite but it's
indeed not listed exactly what it is.
Regarding your theory that the chloroform just stayed in solution, I doubt it because according to my calculations I should have gotten around 23 g of
Chloroform form the reaction, which was in 1 liter of solution. So even if the water was constantly cold, which it was not I still would have gotten
around 13 g of Chloro- that would have fallen out of solution. Plus what I really am perplexed about is the white precipitate.
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Very dilute bleach may be way less than 5% - I titrated thin bleach before and it was around 2%, and had a similar <5% label.
Random white precipitates (probably from a weird additive in the bleach) have been seen before, including in the following thread:
https://www.sciencemadness.org/talk/viewthread.php?tid=67020
| Quote: Originally posted by AndrewOfWallachia |
what I am most worried about is the gas being released, although tiny amount it seems to have been released constantly over the course of multiple
hours. |
In Nilered's video lots of bubbles can be seen in the final solution (3.30), so perhaps normal.
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Keras
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Is not inhibitor, right?
Well, okay albus in Latin is ‘white’, so makes sense.
I think you should start not from standard bleach, but from calcium hypochlorite, which is sold as pool chlorinating agent. Much like if you were
attempting making potassium chlorate. Because it is solid, you can get a much more concentrated solution and a lot more of chloroform.
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AndrewOfWallachia
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| Quote: Originally posted by Keras |
Is not inhibitor, right?
Well, okay albus in Latin is ‘white’, so makes sense.
I think you should start not from standard bleach, but from calcium hypochlorite, which is sold as pool chlorinating agent. Much like if you were
attempting making potassium chlorate. Because it is solid, you can get a much more concentrated solution and a lot more of chloroform.
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Nope, don't worry it's not inhibitor. Your conjecture was correct, "Înălbitor" could be very roughly literally translated as "En-whiten-er".
Regarding Calcium Hypochlorite, I honestly don't think I get that reliably because even when pool cleaning supplies are sold here for some reason
manufacturers don't like listing active substances, much less actual concentrations. Is it perhaps possible that I can concentrate the Bleach by
boiling off some of the water and only then attempting the process?
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Sir_Gawain
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No, boiling bleach will instantly destroy the hypochlorite.
“Alchemy is trying to turn things yellow; chemistry is trying to avoid things turning yellow.” -Tom deP.
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bnull
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| Quote: Originally posted by AndrewOfWallachia | | Regarding Calcium Hypochlorite, I honestly don't think I get that reliably because even when pool cleaning supplies are sold here for some reason
manufacturers don't like listing active substances, much less actual concentrations. |
Bleaching powder or pool chlorine--at least the brand I buy here--is 60-80% calcium hypochlorite, the remainder being mainly sodium chloride (this one
was a surprise) and calcium chloride.
If you can get your hands in some TCCA, the synthesis of chloroform using it was discussed in this 2006 thread (found it!).
Quod scripsi, scripsi.
B. N. Ull
P.S.: Did you know that we have a Library?
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Boffis
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I have just finished making over 1kg of chloroform from ordinary sodium hypochlorite and after some experimentation I settled on a simple procedure
that is very reliable providing you carry it out as per my instructions. The optimum concentration of bleach is about 10-11% w/w NaOCl. if the bleach
is stronger than 10-11% the can will become too hot and the yield will suffer. 7-8% "thin bleach" also works; remember to pro-rata the acetone
quantity. Experiments with calcium hypochlorite bleaching powder worked fairly well but the amount of filtering required due to insoluble impurities
is a problems and sodium hypochlorite is cheaper anyway.
Take a 5 litre plastic jerry can and fill it with, fresh, 10% sodium hypochlorite bleach (bought from farm store in 25L drums) leaving about 200-300ml
of head space. Place the can in the chest freezer overnight. Then add 180ml of acetone, replace the cap and shake and allow to stand for about 1-2hour
in a cool place. At first nothing appears to happen then after about 5 minutes the can becomes warm and the clear yellow solulution becomes milky
white. After 1-2 hours pour out into a large beaker/ beakers/ glass jugs, steel bucket as available, allow to settle for a few minute and decant most
of the aqueous liquid. The heavy organic layer and the last of the cloudy aqueous fluid are poured into a separating funnel and the chloroform run
off. The yield was fairly consistently about 230g of crude chloroform. Save the aqueous phase.
Washing causes losses as chloroform is slightly soluble in water and the best method of purification is to treat with 25-30% of its volume of conc.
sulphuric acid. Stir them together in a large beaker at room temperature for 2 to 3 hours, separate the spent acid and distill the crude chloroform.
The vast majority of the chloroform distills over in a range of about 0.5 degrees, 60.5 to 61C on my thermometer. 1240g of crude chloroform gave 1034g
of distilled product plus a small addition flask residue (about 90-100g) and some low boil fraction (about 15-20g). The flask residue was treated with
potassium bicarbonate to neutralise and sulphuric acid present and then filtered into a smaall bottle, it will be added to the next batch should I
prepare one. The spent acid was neutralisd by pouring into the aqueous residues, this caused a small amount of immiscible organic liquid to separate.
It appears to be a mixture of chloroform and a pleasant smelling substance presumably an alkali induced polymerisation product of acetone but the
volume was very small, 5-6ml per 5L of bleach.
Attempts were made to recover more chloroform from the milky aqueous phase by distillation, steam distillation and solvent extraction; the latter one
was the only one that worked. The aqueous phase was extracted with ligroin twice, using about 50ml per litre of fluid for each extraction. The ligroin
from the second extraction being used for the first extraction of the next litre and so on. The ligroin was then dried with magnesium sulphate and
fractionally distilled to recover the chloroform from the ligroin (Bp range 160-200 C, low odour white spirit, shellsolve etc can be used) but the
recovery of further chloroform was only about 1.5ml per litre of fluid and in the end I gave up and simply used the aqueous phase to neutralise the
spent acid (caution: do this outside as much chlorine is evolved due to the acid induced reaction of chlorate ions with chloride ions in the bleach)
Do not use excess acetone, it does not improve yields it just makes the crude product harder to purify!
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Sir_Gawain
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That pleasant-smelling side product might be chlorobutanol. It forms from a reaction between chloroform and acetone, and smells like camphor.
“Alchemy is trying to turn things yellow; chemistry is trying to avoid things turning yellow.” -Tom deP.
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4-Stroke
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| Quote: Originally posted by Boffis | | Do not use excess acetone, it does not improve yields it just makes the crude product harder to purify! |
In fact, it is better to use a bit of an excess of bleach to make sure that all the acetone reacts, because unlike acetone, it is not miscible with
chloroform, meaning that it will be a lot easier to separate. But as it was noted before, chloroform is still slightly soluble in water so don't add
too much excess or you will lose yield.
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Boffis
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Hi 4-Stroke, you are quite correct a small excess of hypochlorite is preferrable. In my procedure above I have assumed the 10% claim at face value and
used a standard mnufacturers datasheet to get the density. I then calculated the theoretical amount of acetone required and exactly that amount.
Because hypochlorite bleach decays with time when freshly purchased it is usually a bit stronger than the claimed concentration. The excess simple
represents wasted reagent, the solubility of chloroform in pure water might be 10g per litre but in strong bleach/sodium chloride it is much less. My
experiments with recovering chloroform from the spent liquor found only a small amount, 1.5ml per litre in the best instance, so I think that the
solubility of chloroform in 10-11% bleach is little more than 2g/litre.
@ Sir_Gawain. Thats an interesting possibility I hadn't thought about. I originally expected there to be a modest residue in the final distillation
flask consisting of acetone polymers such as diacetone alcohol, phorone etc. But given the low temperatures and relatively short contact period (an
hour or two) that might be a better possibility. Its hard to say what it smelt like because it still contained some chloroform.
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