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S.C. Wack
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Last time I checked ammonia forms salts with acids like HCl and HCN. Would you believe that if you could simply boil household ammonia and chloroform
and get HCN, this would be mentioned somewhere?
Really hot. Residence time is probably not long.
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Polverone
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Household ammonia is too dilute. 30% technical/lab grade works ok with ethanol as cosolvent or maybe no cosolvent but using PTC; IIRC extra base
(alkali hydroxide) is needed in either case. You can also prepare strong ammonia solution in place by reacting an ammonium salt with alkali hydroxide,
but this of course leaves you with an even messier mixture of chemicals.
I never attempted to isolate pure cyanides by this method, but you can definitely get a strong positive on the prussian blue test. It uses relatively
expensive materials and even in the best case the material thus prepared would contain more chloride than cyanide. It doesn't need extreme conditions,
hard-to-obtain materials, or fancy apparatus, but it still never seemed attractive enough (compared with cyanate reduction) to try developing into a
useful preparation.
PGP Key and corresponding e-mail address
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amchem2000
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| Quote: | Originally posted by Polverone
Household ammonia is too dilute. 30% technical/lab grade works ok with ethanol as cosolvent or maybe no cosolvent but using PTC; IIRC extra base
(alkali hydroxide) is needed in either case. You can also prepare strong ammonia solution in place by reacting an ammonium salt with alkali hydroxide,
but this of course leaves you with an even messier mixture of chemicals.
I never attempted to isolate pure cyanides by this method, but you can definitely get a strong positive on the prussian blue test. It uses relatively
expensive materials and even in the best case the material thus prepared would contain more chloride than cyanide. It doesn't need extreme conditions,
hard-to-obtain materials, or fancy apparatus, but it still never seemed attractive enough (compared with cyanate reduction) to try developing into a
useful preparation. |
=> Too dilute alright - so is the reaction slow or non-existent?
Since HCN evaporates at 26 oC and dilute HCL (in dilute ammonia solution) at much higher temperature, I assume that if we get the reaction started,
then we can capture HCN (gas) in another bottle containing K/NaOH solution in alcohol - precipitating K/NaCN! This I think should give very pure
K/NaCN (This knowledge is theoretical though).
=> The question is, at what temperature does the household ammonia solution and Chloroform start reacting (if they do at all) and how long does
that take?
=> The problem would get complicated (a) if the reaction happens at temperature beyond CHCl3's BP (61.2 oC). Since at that point, Ammonia and
Chloroform might just escape without reacting [what we capture in another bottle would then pretty much be everything from the previous bottle] (b) if
the reaction is too slow (like several hours) as in that case Cyanide is sitting in a strong alkali alcohol solution which might then decompose (or
polymerise).
Just a thought!
1) Where can we get strong ammonia solution
2) Forgive my ignorance - what is PTC?
I would really like to know someone has attempted this method successfully and if so the details of it.
BTW, just adding alkali to ammonia(dilute)+chloroform solution gives lot of heat [thats just alkali hydrolyzing] - but the end result had a layer of
brown solution. Could this be the CN polymer that someone mentioned here?
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12AX7
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Phase Transfer Catalyst.
Soap, in a very crude sense...
Tim
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kmno4
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| Quote: |
Correction1 -
NH3(aq) + CHCl3 => HCN + 3HCl(aq)
OR
Correction2 -
NH4OH + CHCl3 => HCN + 3HCl + H2O
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These are not good equations - you do not know basics of chemistry.
It is the same as you would write:
NaOH +...+...+... => H2SO4 +...+...+.....
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amchem2000
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| Quote: | Originally posted by kmno4
| Quote: |
Correction1 -
NH3(aq) + CHCl3 => HCN + 3HCl(aq)
OR
Correction2 -
NH4OH + CHCl3 => HCN + 3HCl + H2O
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These are not good equations - you do not know basics of chemistry.
It is the same as you would write:
NaOH +...+...+... => H2SO4 +...+...+.....
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They are not my equations. They were part of this thread since 2003. I am just asking if they work at all because of various other issues too.
In any case, I think they are 'good equations' but 'incomplete' and not really 'incorrect'. HCl could further react with ammonia giving ammonium
chloride salt while part of HCN escapes out due to low BP. Many possibilies but we are looking at one section (equation) trying to see if that is
significant enough to be considered here.
Some ppl on this forum claimed that it works. I just wanted to know what exactly did they do.
==========
BTW, kmno4, does prussian blue (ferric Ferro cyanide) react with dil H2SO4 directly upon heating? Or do we have to convert that to potassium ferro/i
cyanide first. You seem to have used the pottasium varient - did you try using prussian blue directly?
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Antwain
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I cant see why it would matter at all to be honest, besides I have read literature that prussian blue is in fact ferric ferrocyanide AND ferrous
ferricyanide (as I would have expected after one of my courses last year). So unless ferric ions interfere then you will have no problem - and i
should point out that you end up with loosely packed ferrous sulfate floating around in all its pale green-ness after the distillation of
ferrocyanide anyway.
Btw, the first time I tried to distill potassium ferrocyanide and sulfuric acid, but did not heat it adequately to drive off ALL the HCN the entire
residue (coke) bottle became filled with deep blue, starting from the contact with air at the top of the bottle and gradually diffusing into the rest
of the bottle. I still have to get around to destroying that at the end of the year... but since i just bought 10L of 'liquid pool chlorine' this
shouldn't be difficult.
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kmno4
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| Quote: | Originally posted by amchem2000
BTW, kmno4, does prussian blue (ferric Ferro cyanide) react with dil H2SO4 directly upon heating? Or do we have to convert that to potassium ferro/i
cyanide first. You seem to have used the pottasium varient - did you try using prussian blue directly? |
I do not know if they react at all.
" You seem to have used the pottasium varient - did you try using prussian blue directly?"
I do not understant this question. I use H2SO4/K4[Fe(CN)6] as starting materials.... And as I wrote before:
2K4[Fe(CN)6]+3H2SO4 -> 6HCN + FeK2[Fe(CN)6]+3K2SO4
But FeK2[Fe(CN)6] is not so useless as it seemed to me. It can be converted, in a simple way, into K2Na2[Fe(CN)6] with aid of NaOH:
FeK2[Fe(CN)6]+2NaOH ->K2Na2[Fe(CN)6] + Fe(OH)2 (I have done it recently - messy job but it works  )
.... and reused again (as dry salt) for making HCN.
ps1
in Ullmann's enc. you can find b.p. of mixtures HCN-H2O and it can be seen that it is important to distill off everything from reaction mixture up to
(almost) 100 C.
ps2
In "References" I gave old article about interaction between H2SO4 and K4[Fe(CN)6]
ps3
FeK2[Fe(CN)6] do not react (if even - veeeery slow) with ~40% H2SO4 (in boiling temp) - my own observation
BTW1
NaCN(aq) reacts easy with BzCl without cosolvent and heating but with addition of catalytic amount of TBACl and stirring 
BTW2
KCN reacts even with CH2Cl2 in acetone  I am going to do this reaction with
aquenous solution + TBACl
BTW3
This specific isonitrile reaction "NH3+NaOH+CHCl3" really gives NaCN in solution ( there is an article from ACS about it)
[Edited on 25-9-2007 by kmno4]
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amchem2000
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| Quote: | Originally posted by Antwain
This solution was distilled until about 100mL remained, at which time the 500mL flask was disconnected while still quite warm. A VERY strong smell of
ammonia was present. The solution was cooled in an ice bath, but simply gelled so it was added to a larger beaker and ~350mL of
ethanol added. This was filtered, which removed all but about 50mL of liquid. The gelatinous white powder was placed between two filter papers with
many sheets of paper towel on either side, and a brick placed on top. After half an hour the filter parers, which were only damp, were placed on a
warm heating mantle for around ~1/2hr. After this time the white powder was dry and was placed in a bottle (yield 33.3g, 0.51mol, 34%), however it had
attacked the steel top of the heating mantle, leaving a ring of ferrocyanide on the filter paper.
So in conclusion, I got a pretty crappy yield, of probably not entirely the right stuff (it felt and smelt like sodium acetate does when heated, which
is a worry because formate is one of the decomposition products) but there is definitely cyanide there as evidenced by it attacking my mantle. The
ammoniacal smell stopped after the addition of alcohol so if I do this again (I have enough ferro for one more attempt) I will be making a solution of
KOH in ethanol, and the KCN can precipitate out.
[Edited on 12-8-2007 by Antwain] |
How do you know that the 'jelly' substance is cyanide? It could just be mostly KOH (after drying) as the MSDS states that KCN/NaCN decomposes in water
to KOH/NaOH + HCN.
Apparently anything short of looking at cyanide decomposes it to HCN - with water, air, CO2 etc.
NaCN (I think) does not precipitate but forms a jelly in the ethanol solution. How do u dry that jelly without decomposing NaCN? Using a hair dryer to
dry it will probably decompose the substance.
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amchem2000
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| Quote: | Originally posted by kmno4
NaCN can be made in the same way as KCN, from K4[Fe....] and H2SO4/H3PO4. Diffrence is that NaCN crystallises as hydrate ( NaCNx0,5H2O or x1H2O) from
EtOH so H2O must be quickly evaporated or hydrate should be kept at lower (<10 C) temperature. But it is much easier filter off NaCN than KCN,
because of its much larger crystalls. It has also lower molar mass: 49g NaCN corresponds 65g KCN and there are less problems with stirring/filtering
suspentions.
Generally, cyanides should not be kept/heated for a long time in strongly alkaline solutions - they decompose to brown products (propably polymeric
CxNy ).
BTW.
Carl Scheele (discoverer of HCN and many others chemicals...) described smell and taste of HCN, ha ! It was hard man, almost dead
because of Cl2... Great oldschool chemist
On the picture: about 60g NaCN (two runs). One run takes about 4-5 hours (from starting distilation to placing dry NaCN in a jar)
Everything can be done....
 |
Same here. How do u know the content in the bottle isn't mostly NaOH? How will you evaporate the water from the 'jelly' substance (NaCN?) obtained in
ethanol+NaOH solution?
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kmno4
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Where have I written that it is 'jelly' ? My observations and easiness of filtering out NaCN hydrate say that it has crystalline form. Heating this
hydrate up to ~80C causes its melting (looks like white thick honey, but not so tasty ) and (during stirring with spoon) as H2O goes away, it spills into white powder. At this moment it looks like (previously prepared) KCN.
About KCN --> see page 4 of "Preparation of cyanides". Proof of content ? Read BTW1 in my last post (and yield of the precious nitrile was good
). Of course, some can say: it is bullshit, not NaCN in a jar but washing
powder... But this powder works
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amchem2000
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- What is BzCl and TBACl (forgive my ignorance)?
- The reaction for HCN ad NaOH is thus (simplyfying to 1 equation),
HCN + NaOH <=> NaCN + H2O
with equilibrium biased towards the right side.
When heated dry (under burner, drier or open air), the HCN evaporates/boils faster than H2O. As a result, at the end of the drying process, you are
left with mostly NaOH (and perhaps its sister products like Na2CO3 etc) and very little NaCN [Since NaCN decomposes very fast in the presence of H2O
with 'drying']. The product might pass the prussian blue test but will be very low in NaCN - something like <5-10% (even that I doubt).
If you know that your yield is more than that, then it will be curious to know how you dried it.
Could you please explain your steps with amount of time spent on each step and the exact details?
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Antwain
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| Quote: | Originally posted by amchem2000
How do you know that the 'jelly' substance is cyanide? It could just be mostly KOH (after drying) as the MSDS states that KCN/NaCN decomposes in water
to KOH/NaOH + HCN.
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Ummm.... rubbish?
Yes it is decomposed by CO2 + moisture
Yes other weak acids decompose it easily to HCN
Yes, it is strongly hydrolised in solution by the good old weak acid strong base (oversimplified) theory.
And yes, it polymerises and generally turns into things you do not want.
But, that is a load of crap. HCN will react very strongly towards the right hand side of this equilibrium, especially with an excess of base.
K/NaOH + HCN <------> K/NaCN + H2O
Also, I just properly read your last post. H2O, pKa~15; HCN, pKa~7
Once there is a good excess of a few % of hydroxide, there should be next to no HCN escaping. Since I designed the reaction with an excess of
hydroxide I think loss of HCN was unlikely.
[Edited on 30-9-2007 by Antwain]
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amchem2000
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| Quote: | Originally posted by Antwain
:::
Also, I forgot to post after my experiment... I was expecting a yield of ~70g theoretical. what I now have is a slurry in some ethanol which is ~25g
and is probably only <5g of something (white powder), and 700mL of 80% ethanol solution with god only knows what in it. Sodium cyanide is quoted as
being 'slightly soluble in ethanol' by merck and other sources, but is soluble in water 1:1@0*C, 2:1@100*C. Also sodium formate is 'almost insoluble
in ethanol' and sodium hydroxide dissolves 1g in 7.2mL ethanol. Also given that the solution I had poured like conc. NaOH, ie. like honey, I wonder if
maybe I never made much cyanide. A lot of gas bubbled through the solution (possibly because the base was too concentrated and it clogged) but I had a
bleach soaked cotton ball in the release tube and a fan blowing into the shed.
I have NO experience with practical gas chemistry so any help would be useful.
PS. I am currently thinking of using an upturned funnel, which is a pain because of the diameter of the beaker or whatever required + I can think of a
bunch of ways in which this could fail and release HCN, or bubbling it through a long thin coloumn, of which I have none. |
Antwain,
- Take about 15-20g of K-Ferricyanide
- Add lots of 30% H2SO4
- place in boiling water bath
- Put the tube from this into another bottle having denatured alcohol+NaOH. Place some part of the tube and the Alc+NaOH bottle in ice water.
- After about 1 hour bubbling, there will be virtually zero 'precipitate' (You would expect atleast few grams). The solution would turn a little green
though.
- FerriCyanide+H2SO4 solution would turn into very deep blue to black color.
==========
- Clearly 'bubbling' doesn't do the trick.
- Any analysis on the colors obtained [green and deep blue/black]?
==========
Basically what did you do next.
Edit: Summarizing my understanding of Antwain's experiment. Description found to have lot of inconsistencies (pointed by kmno4 and Antwain).
[Edited on 2-10-2007 by amchem2000]
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kmno4
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| Quote: |
Antwain,
- Took about 15-20g of K-Ferricyanide
(...)
|
Antwain took K4[Fe(CN)6] (ferro...) not K3[Fe(CN)6] (ferri...)
I think your ignorantion is too big to play with such things.
In Ullmann I have found also HCN/CN(-) equ. in diluted solutions. As you see, much less than 1% excess of (for example) NaOH is needed to prevent HCN
formation. Smell of HCN is caused mainly by atmospheric CO2.
BTW.
TBACl is [N(n-Bu)4]Cl, one of the PTC catatysts. BzCN is øCH2CN.
[Edited on 1-10-2007 by kmno4]
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amchem2000
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| Quote: | Originally posted by kmno4
| Quote: |
Antwain,
- Took about 15-20g of K-Ferricyanide
(...)
|
Antwain took K4[Fe(CN)6] (ferro...) not K3[Fe(CN)6] (ferri...)
[Edited on 1-10-2007 by kmno4] |
=> Doesn't this work for ferri?
=> What about other questions? Like if one should condense the 'HCN bubbles' to a liquid before introducing it to NaOH solution?
=========
I came across another equation which some people claimed to have worked -
K3[Fe(CN)6] + 3KOH = 6KCN + Fe(OH)3(ppt)
Did anyone try this route? It also looks safer (without involving HCN) and better.
However, mixing the two chemicals in water and heating may not do anything.
=========
Edit: Found the flaw in the equation - one book mentioned that Ferri gets converted to Ferro in the presense of alkali.
[Edited on 2-10-2007 by amchem2000]
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12AX7
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What's the Kf of CN vs. OH? OH is pretty substantial, but so is CN.
Tim
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Antwain
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@amchem2000
Ok, first of all I con't remember if I posted my first attempt and don't have time to check, but a water bath is NOT HOT ENOUGH. I used a water bath
the first time and so much cyanide was left in the distillation flask that it was not destroyed by adding several hundred mL of bleach, it is still
deep blue. Use an oil bath (or sand of whatever, I prefer oil). Ferric ferricyanide is deep brown, god only knows what else you had in there.
Don't know if it works with ferricyanide, but making ferrocyanide is easy enough. *see post below
Also, I can't remember my exact reasoning, but I decided that ethanol+ NaOH was not acceptable. I think that NaCN is too soluble or NaOH not soluble
enough.
The method you are referring to with KOH + ferrocyanide sounds like one I saw using K2CO3. I wont promise you this, but I really think the reverse
reaction would happen, ie ferric hydroxide would dissolve in KCN. The method I saw requires fusion, and pouring off molten KCN. It doesn't sound much
safer to me, and ferro/ferricyanide is libel to decompose to C and N at the temperatures required, I wouldn't expect a great yield.
[Edited on 2-10-2007 by Antwain]
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kmno4
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| Quote: | Originally posted by Antwain
(...)Filter off the zinc and crystalise the ZnSO4 + k4[Fe(CN)6]. Having ZnSO4 in there shouldn't matter.
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Yeah.
And cows can fly....
ZnSO4 reacts with K4[Fe(CN)6].
[Edited on 2-10-2007 by kmno4]
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Antwain
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Your (accurate) sarcasm has been duly noted.
How about metabisulfite then? Easy to obtain from your local home brew section. Probably easier to get than zinc anyway. Serves me right for posting
when I should be asleep 
(incidentally, I expect that zinc ferrocyanide would work in place of potassium ferrocyanide)
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Pixicious
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How would you suggest building an oxygen-free crucible?
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Pixicious
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Sorry for the second post. This one is for Meyer.
I'm not a chemist but it appears in the second process (although it is weird this doesn't appear on wikipedia since it appears to be a 1839 process
but only in its infancy in commerical production now) that you need a temperature of 900-1000C, which I believe is a greater temperature than that of
glass.
The formulas are fine but I couldn't tell you anything more. This is just a passing interest for me.
EDIT:
| Quote: |
OK, the process is too tedious as an amateur method of sodium cyanide production when compared to the discussed NaOCN reduction with carbon. Not only
because of the need of oxygen free nitrogen, but also due to the messy workup. Still, I find it fascinating that Fe (or in situ formed Fe when Fe2O3
is used) can catalyze the reaction. How does it "capture" N2? Does iron form or equilibrates with Fe(II) nitride when heated in N2 atmosphere?
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Couldn't it be possible to fill a cruitable (upside down ofc) with Nitrogen which is obtained by a reaction of Ammonia Chloride and Sodium Hydroxide
in a mixture of water which is sent through an iron catalyst to seperate the Hydrogen and Nitrogen. The mixture required is placed on top of a lid and
the lid is very carefully and securely attached to the upside down cruitable. The cruitable can then be shaken, dropped and carelessly handled without
air or more importantly oxygen added to the mixture. Then this is put in side a furnance at temperatures of 950-1000*C. Afterward the container has
cooled it is opened and a yeld of 30-40% NaCN is removed.
DO NOT TRY THIS AT HOME. I AM NOT AN EXPERIENCED CHEMIST. THIS COULD EXPLODE.
[Edited on 6-2-2008 by Pixicious]
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franklyn
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Cyanogen Cyanide chemistry
The Chemistry of Cyanogen Compounds and Their Manufacture and Estimation
Herbert E. Williams - 1915
http://books.google.com/books/pdf/The_Chemistry_of_Cyanogen_...
Also covers fulminate compounds
Page 177 gives this reference for Cyanuric chloride, needs phosphorus pentachloride though.
Beilstein, A., 116, 357
.
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Pixicious
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| Quote: |
- Any analysis on the colors obtained [green and deep blue/black]?
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I've read it could be a reaction between iron and the other substances.
K4[Fe(CN)6] + H2SO4 -> FeSO4 + 2HCN + 4KCN
Iron Sulphate is one possibility. After checking Wiki it could be the reason for the green colour.
Can someone say the formula above may be correct? What may be the other colours in his "mixture" I know HCN is formed when ferrocyanide and sulphuric
acid are mixed. KCN was just the letters which were left. Iron Sulphuate was used because it seemed to fit the equation and was green in colour.
Sorry I couldn't have been more help.
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grind
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There is another way to make KCN. I´ve tried this:
Make a concentrated solution of KOH in absolute ethanol. Cool this with ice/NaCl. Now slowly drop in a solution of acetone cyanohydrine in ethanol.
KCN is precipitated. Filter, wash with little ethanol, dry in vacuum at first at RT, later at 80°C. This yields 50% of very pure KCN.
(CH3)2C(OH)CN + KOH ---> KCN + CH3COCH3 + H2O
The only problem would be the accessibility of the cyanohydrine, but this method works fine.
[Edited on 23-2-2008 by grind]
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