Sciencemadness Discussion Board
Not logged in [Login ]
Go To Bottom

Printable Version  
 Pages:  1  ..  20    22    24  ..  31
Author: Subject: Preparation of cyanides
madmanhere
Harmless
*




Posts: 18
Registered: 21-2-2012
Member Is Offline

Mood: Meh..

[*] posted on 3-3-2012 at 21:56


Solubility in ethanol- 0.57g/100ml @ 19.5 'C
MSDS for KCN: http://www.sciencelab.com/msds.php?msdsId=9927707
View user's profile View All Posts By User
expInfi
Harmless
*




Posts: 36
Registered: 24-2-2012
Location: USA
Member Is Offline

Mood: Fine !

[*] posted on 3-3-2012 at 22:38


Quote: Originally posted by madmanhere  
Solubility in ethanol- 0.57g/100ml @ 19.5 'C
MSDS for KCN: http://www.sciencelab.com/msds.php?msdsId=9927707


Thank you !

1.What would you derive from this statement :
Potassium cyanide + hydrogen cyanide is a frictioin and impact-sensitive explosive in the context of "When liquid HCN drops to NaOH(aqs) it gives KCN and H2O."

2.Is this acid base reaction non-reversible below 26C while HCN inflow is in progress and after that?

3.Is temp the only factor which determines the reversibility of this reaction ? What is the role of Ph of NaOH solution (in other words the concentration) ?



[Edited on 4-3-2012 by expInfi]




alchemist
View user's profile View All Posts By User
expInfi
Harmless
*




Posts: 36
Registered: 24-2-2012
Location: USA
Member Is Offline

Mood: Fine !

[*] posted on 3-3-2012 at 22:42


I am trying to understand how can we prevent the KCN Solution from starting to release HCN back.



alchemist
View user's profile View All Posts By User
Nicodem
Super Moderator
*******




Posts: 4230
Registered: 28-12-2004
Member Is Offline

Mood: No Mood

[*] posted on 4-3-2012 at 03:20


Quote: Originally posted by expInfi  
I am trying to understand how can we prevent the KCN Solution from starting to release HCN back.

The pKa of the cyanide ion is 9.40 in water ( http://research.chem.psu.edu/brpgroup/pKa_compilation.pdf ). This number is enough to answer all of your questions above, except the one about temperature.

(It took me exactly 25 seconds of googling to find this information while you rather spent your time double-posting instead of looking for it. Makes me wander if you really have the skills and reason enough to mess with potassium cyanide?)
View user's profile View All Posts By User
expInfi
Harmless
*




Posts: 36
Registered: 24-2-2012
Location: USA
Member Is Offline

Mood: Fine !

[*] posted on 4-3-2012 at 08:14


Quote: Originally posted by Nicodem  
Quote: Originally posted by expInfi  
I am trying to understand how can we prevent the KCN Solution from starting to release HCN back.

The pKa of the cyanide ion is 9.40 in water ( http://research.chem.psu.edu/brpgroup/pKa_compilation.pdf ). This number is enough to answer all of your questions above, except the one about temperature.

(It took me exactly 25 seconds of googling to find this information while you rather spent your time double-posting instead of looking for it. Makes me wander if you really have the skills and reason enough to mess with potassium cyanide?)


I am sure that I do not have the skill to mess up with cyanide.Neither I am going to.I am trying to understand the theory.Thanks for the link.




alchemist
View user's profile View All Posts By User
AndersHoveland
Hazard to Other Members, due to repeated speculation and posting of untested highly dangerous procedures!
*****




Posts: 1986
Registered: 2-3-2011
Member Is Offline

Mood: No Mood

[*] posted on 7-3-2012 at 05:08


from chloroform and ammonia

CHCl3 + 5NH3 --> NH4CN + 4NH4Cl
View user's profile Visit user's homepage View All Posts By User
AJKOER
International Hazard
*****




Posts: 2914
Registered: 7-5-2011
Member Is Offline

Mood: No Mood

[*] posted on 7-3-2012 at 07:00


Quote: Originally posted by AndersHoveland  
from chloroform and ammonia

CHCl3 + 5NH3 --> NH4CN + 4NH4Cl


Do you have a reference, as the reaction as written is occurring in a non-aqueous medium.

Also, I previously noted a parallel reaction in an aqueous environment with CHI3, forming NH4COO as a path to HCN.

CHI3 + 4 NH3 + 2 H2O ---> 3 NH4I + NH4CHOO

Now, NH4CHOO --Heat--> HCN + 2 H2O

So, is there an intermediary in your proposed reaction as well? Does CHI3 also work?

I am not a total believer as there is a significant secondary reaction:

NH4CHOO --Heat--> NH3 + H2O + CO

[Edited on 7-3-2012 by AJKOER]
View user's profile View All Posts By User
AndersHoveland
Hazard to Other Members, due to repeated speculation and posting of untested highly dangerous procedures!
*****




Posts: 1986
Registered: 2-3-2011
Member Is Offline

Mood: No Mood

[*] posted on 9-3-2012 at 02:41


Chloroform will react with ammonia much more readily than chloromethane will.

http://www.sciencemadness.org/talk/viewthread.php?tid=6915

Quote: Originally posted by Polverone  

The "easiest thing ever" that I have found, from my good friend the Hive, is that when certain chlorine-containing solvents are gently heated and stirred for a long time with a mixture of aqueous ammonia and sodium (or potassium) hydroxide, they will form NaCl or KCl and NaCN or KCN



It is not really extremely difficult to prepare anhydrous NH3 gas (NH4Cl + CaO).

While cyanide can be produced in the presence of water, less water gives much better yields. One would think that the yields from CHCl3 would be higher than CHI3 in the presence of water, because CHI3 is much more reactive, and has a tendancy to just readily hydrolyse in water by itself (chloroform takes many days to hydrolyse in water, and only then if it is completely dissolved since it has a low solubility)

The room temperature reaction between chloroform and ammonia is still relatively slow (more than 2 days).
Quote:

Ammonium cyanide is also formed by passing a mixture of the vapors of chloroform and ammonia gas through a tube heated to 300 °. When chloroform is passed with excess of ammonia through a heated tube, no action takes place till the temperature approaches a red heat, when chloride and cyanide of ammonium are formed.


Quote:

Hydrogen cyanide is formed by passing ammonia and chloroform vapour through a hot tube Heintz, Ann. 100, 369 , or by heating chloroform and alcoholic ammonia to 180-190 °. Cloez, Jahresber. 1858, 345.


Supposedly heating formic acid with dry ammonium chloride can form HCN. Pelouze and Döbereiner, Ann. 2, 90

An aqueous solution of copper acetate with ammonia heated to 180 ° in a sealed tube for two hours gives cuprous cyanide, Cu2(CN)2. Vittenet, Bull

Heating urea with zinc dust forms zinc cyanide.
Aufschläger, Monats. 13, 268

[Edited on 9-3-2012 by AndersHoveland]
View user's profile Visit user's homepage View All Posts By User
seashell1982
Harmless
*




Posts: 21
Registered: 31-1-2012
Member Is Offline

Mood: No Mood

[*] posted on 12-3-2012 at 19:03


What type of gas mask should I use to protect against HCN? Link? Thanks.
View user's profile View All Posts By User
entropy51
Gone, but not forgotten
*****




Posts: 1612
Registered: 30-5-2009
Member Is Offline

Mood: Fissile

[*] posted on 12-3-2012 at 19:15


Quote: Originally posted by RisingSun96815  
What type of gas mask should I use to protect against HCN? Link? Thanks.
You would trust a gas mask to protect you against HCN? Seriously?

Be sure the authorities know how to contact your next of kin.
View user's profile View All Posts By User
AndersHoveland
Hazard to Other Members, due to repeated speculation and posting of untested highly dangerous procedures!
*****




Posts: 1986
Registered: 2-3-2011
Member Is Offline

Mood: No Mood

[*] posted on 12-3-2012 at 20:34


One would need a specially designed fumehood, ideally the type that is completely insulated, with gloves built into the window. And even then a respirator (gas mask) would still be advised.
View user's profile Visit user's homepage View All Posts By User
ScienceSquirrel
Super Moderator
Thread Pruned
13-3-2012 at 05:28
AJKOER
International Hazard
*****




Posts: 2914
Registered: 7-5-2011
Member Is Offline

Mood: No Mood

[*] posted on 13-3-2012 at 10:13


AndersHoveland:

Thanks for the wealth of info on the CHCl3 + NH3 reaction.

(I'm glad I dragged it out of you)
View user's profile View All Posts By User
Mira
Harmless
*




Posts: 3
Registered: 23-3-2012
Member Is Offline

Mood: No Mood

[*] posted on 12-4-2012 at 05:15


I am surprised to see the over estimation of toxicity around HCN given in this thread.I have worked with HCN with fumehood and without.I mean I had taken the flask in my hand and walked for a few seconds to the other chamber with heated H3PO4 and Ferro.cyanide in it without a fumehood.I understand the indication of low safety system I worked in ,that I am delivering here.But I fear if a chemist actually believes that it is something that you be around and you are going to die , is a kind of silly.But , yes I understand if that over estimation is done to prevent people without proper background to get into a trap that they are not really aware of.
View user's profile View All Posts By User
cyanureeves
International Hazard
*****




Posts: 736
Registered: 29-8-2010
Location: Mars
Member Is Offline

Mood: No Mood

[*] posted on 12-4-2012 at 15:54


Mira i am all ears,then you have distilled ferrocyanide with H3PO4? did you distill it into hydroxide and ethanol? please elaborate and do you mean that acid and ferrocyanide will not release gas without heat?
View user's profile View All Posts By User
seashell1982
Harmless
*




Posts: 21
Registered: 31-1-2012
Member Is Offline

Mood: No Mood

[*] posted on 28-4-2012 at 07:12


Quote: Originally posted by Magpie  
I suggest you test it using a Prussian Blue test as follows:

1.Place about 1 mL of water in a small test tube.
2. Add a smidgen (few mg) of FeSO4*7H20 or other soluble ferrous salt and stir until dissolved.
3. Acidify with a few drops of 1M HCl.
4. Add a smidgen of your product and stir.

An intense dark blue color indicates the presence of cyanide.

I should also point out that it is necessary for some ferric ions be present also. So I add a drop or two of 0.5M FeCl3 to be sure.
How should I dispose of this when I'm finished? It sounds like there is a small amount, but because there is some ferric chloride I don't won't to put it down the drain.
View user's profile View All Posts By User
cyanureeves
International Hazard
*****




Posts: 736
Registered: 29-8-2010
Location: Mars
Member Is Offline

Mood: No Mood

[*] posted on 28-4-2012 at 09:12


i think household bleach will neutralize cyanide. iron chloride isnt that toxic is it?
View user's profile View All Posts By User
seashell1982
Harmless
*




Posts: 21
Registered: 31-1-2012
Member Is Offline

Mood: No Mood

[*] posted on 28-4-2012 at 18:15


Quote: Originally posted by cyanureeves  
i think household bleach will neutralize cyanide. iron chloride isnt that toxic is it?
From what I've read elsewhere, ferric chloride etches copper, and therefore could damage plumbing.
View user's profile View All Posts By User
Zan Divine
Hazard to Others
***




Posts: 170
Registered: 3-12-2011
Location: New York
Member Is Offline

Mood: Wishing all the worst that life has to offer to that SOB Wayne Lapierre

[*] posted on 3-6-2012 at 14:45


Cyanureeves,
What she meant is that after you add your acid to your ferrocyanide, no HCN is evolved. HCN comes out as the temperature is increased.

Bleach is the suggested reagent to destroy cyanide. Oxidizes it to cyanate. pH control is important to prevent runaway reaction.

Mira,
I couldn't agree more. I've synthesized 200 g lots of liquid HCN a half dozen times on an open benchtop. The reaction vessel was a closed system and a vent tube ran out the window.

Incidentally, my experience is that HCN vapors lead directly into aqueous NaOH always give contamination by black polymers. On the other hand, if I collect the liquid HCN and then drip that into aq. NaOH I get a clear solution.

Remember never to collect it as an anhydrous form. Make sure some water is present in the collector (a few drops of sulfuric acid is also a good idea) to prevent uncontrolled polymerization.

I'm genetically predisposed to being able to smell cyanide. I love the smell. Reminds me of delicious almond pastries.

OK...on to the anecdotal stuff. My former boss got a mouthful of anhydrous HCN at his job at Dupont decades back. He spit it out and rinsed his mouth out. He's pushing 80 today. I got a big lungful of HCN gas maybe 20 years ago. The room started to go dim. I took a step toward a labmate to say "cyanide" and just as quickly as it started it was done. Yeah, cyanides are poisonous, but not a big deal by any stretch if you have the appropriate glassware, grease your joints, use keck clips & and take common sense precautions.




[Edited on 4-6-2012 by Zan Divine]




He who makes a beast of himself gets rid of some of the pain of being a man. --HST

View user's profile View All Posts By User
cyanureeves
International Hazard
*****




Posts: 736
Registered: 29-8-2010
Location: Mars
Member Is Offline

Mood: No Mood

[*] posted on 3-6-2012 at 17:50


thanks divine and i didnt know mira was a woman. i am about ready to go ahead with this process but use phosphoric acid instead. i got a laser thermometer to check the heat and make sure it doesnt boil. i am going to test run with water and set my hot plate to just under boiling heat and have it ready. i got stoppers that fit the thermometer port where i will add a small amount of water for when it starts getting dry like myfanwy experienced. i want so much to see cyanide dissolve gold so,so bad because i think it is almost magical. i will be so happy to have this experience so much that i have it up there with a grand canyon and a carribean experience. when this will be accomplished then i will learn more about acid/base extractions.as it is right now i am not disappointed with the bubbling hcn through ethanol/hydroxide method because it gold plates really good but i know it can be better.
View user's profile View All Posts By User
Zan Divine
Hazard to Others
***




Posts: 170
Registered: 3-12-2011
Location: New York
Member Is Offline

Mood: Wishing all the worst that life has to offer to that SOB Wayne Lapierre

[*] posted on 4-6-2012 at 05:34


Typical run:
422 g (1 mol) K4[Fe(CN)6] added to 2 L round bottom with stir-bar. Add a solution of conc. H2SO4 (200 mL) in H2O (600 mL) in one portion. Attach distillation head cooled with ice-water. Reaction appratus vented by tubing running out the window. Slowly heat the stirred blue suspension. You don't need to go much above 50 - 60 degrees C. Foaming occurs in the first hour or longer as cyanide is distilled out and collected in an ice-cooled flask containing 5 mL H2O and a couple mL H2SO4. Foaming subsides after a couple hours and then the suspension thickens. Adjust stirring as necessary. After 4 hours, 147 g HCN (80%) has been collected as a water-white liquid.

Dispose of residue in accordance with local laws.

Depending on your intended use, gold dissolution, electroplating bath, etc. you can convert it to the appropriate salt.

[Edited on 4-6-2012 by Zan Divine]




He who makes a beast of himself gets rid of some of the pain of being a man. --HST

View user's profile View All Posts By User
kmno4
International Hazard
*****




Posts: 1405
Registered: 1-6-2005
Location: Silly, stupid country
Member Is Offline

Mood: No Mood

[*] posted on 4-6-2012 at 13:08


Quote: Originally posted by Zan Divine  
Typical run:
(...)

This "thypical" procedure will not work because of obvious reasons.




Klaszczę w dłonie, by było mnie więcej....
View user's profile View All Posts By User
cyanureeves
International Hazard
*****




Posts: 736
Registered: 29-8-2010
Location: Mars
Member Is Offline

Mood: No Mood

[*] posted on 4-6-2012 at 16:11


and the obvious reason would be all the hcn flying out the window. wouldn't it? unless the reaction vessel is the recipient vessel but regardless, why the ventilation?if it's because of quantities of acids then i dont know why.

[Edited on 5-6-2012 by cyanureeves]
View user's profile View All Posts By User
Zan Divine
Hazard to Others
***




Posts: 170
Registered: 3-12-2011
Location: New York
Member Is Offline

Mood: Wishing all the worst that life has to offer to that SOB Wayne Lapierre

[*] posted on 4-6-2012 at 18:57


Quote: Originally posted by kmno4  
Quote: Originally posted by Zan Divine  
Typical run:
(...)

This "thypical" procedure will not work because of obvious reasons.


You both don't seem to grasp the fact that I was reporting an actual run. Why would HCN "fly out the window"?. The cooling water in the condenser is below the bp of HCN and the receiver certainly is way below.

When I discuss preparations, they are preparations that I have done. As I said earlier, I've done this a half dozen times. A little background...I've probably got as much or more experience with synthesis as anybody here. 26 years of nothing but custom synthesis of cancer, malaria & AIDS drugs, oxygen-selective absorbents, organometallics, pesticides, labeled compounds. You name it, I've made it. So, before you say that something I'm saying is not legitimate, you should be prepared to back your statement up.

The vent line is obvious, isn't it? You don't want a sealed system that can pressurize. Unless you are doing a pressure reaction, reaction vessels are always vented one way or another.

You do know the bp of HCN, don't you?

Why would anyone doubt the veracity of this trivial preparation?








[Edited on 5-6-2012 by Zan Divine]




He who makes a beast of himself gets rid of some of the pain of being a man. --HST

View user's profile View All Posts By User
seashell1982
Harmless
*




Posts: 21
Registered: 31-1-2012
Member Is Offline

Mood: No Mood

[*] posted on 6-6-2012 at 04:37


Quote: Originally posted by Zan Divine  

Bleach is the suggested reagent to destroy cyanide. Oxidizes it to cyanate. pH control is important to prevent runaway reaction.
How do you control the pH? I'm assuming you're adding some kind of cyanide salt to household bleach (pH 12.6). What exactly do you mean by runaway reaction?
View user's profile View All Posts By User
Zan Divine
Hazard to Others
***




Posts: 170
Registered: 3-12-2011
Location: New York
Member Is Offline

Mood: Wishing all the worst that life has to offer to that SOB Wayne Lapierre

[*] posted on 6-6-2012 at 07:39


Take a look at:
http://shorinternational.com/cyanodestruct.php

The reaction is complex. At different pH's it gives different products. pH can be controlled by the usual methods (add some NaOH or HCl). But, read the cautions...

If pH is too low you may produce ClCN. If pH is too high, reaction is very fast and excessive N2 pressure may result.

[Edited on 6-6-2012 by Zan Divine]




He who makes a beast of himself gets rid of some of the pain of being a man. --HST

View user's profile View All Posts By User
 Pages:  1  ..  20    22    24  ..  31

  Go To Top