Sciencemadness Discussion Board

Testing for KCN

Umbrellaterm - 20-11-2020 at 04:45

Hello.
What are some simple DIY testing methods for potassium cyanide?
I want to be sure it’s high purity above ,as well , (ofc) being indeed cyanide.

Fyndium - 20-11-2020 at 05:20

Chemplayer used a mixture of iron(III)chloride and iron(II)sulfate to indicate a cyanide presence. I also have a cyanide batch lying around and once I get to it, I need to determine it's purity.

Umbrellaterm - 20-11-2020 at 05:29

Quote: Originally posted by Fyndium  
Chemplayer used a mixture of iron(III)chloride and iron(II)sulfate to indicate a cyanide presence. I also have a cyanide batch lying around and once I get to it, I need to determine it's purity.

Can you share the details on how to go about doing that with those two reagents?

I need to know that it’s purity is above 95% at least.

Do you know if that’s the only method apart from prussian blue?

Antigua - 20-11-2020 at 05:32

Maybe that could be of use to you? https://www.911metallurgist.com/blog/free-cyanide-vs-total-c...
Titration using silver nitrate would let you assay the purity as well as identity of the compound.

Fluorite - 20-11-2020 at 05:36

Vitamin b12?

teodor - 20-11-2020 at 08:04

I see it is much dependent on what you have as impurities, like Cl-, ferrocyanide, SCN- etc. But classical literatire, e.g. Treadwell contain all the method on volumetric determination of presence these compounds in mixtures. So, look Treadwell, Volume II.

Edit: I prepared AgNO3 solution for volumetric purposes by dissolving high purity Ag in chlorine-free HNO3. This way it is easier to get known concentration of the solution. (AgNO3 is hygroscopic).

[Edited on 20-11-2020 by teodor]

[Edited on 20-11-2020 by teodor]

chornedsnorkack - 20-11-2020 at 13:44

High purity also requires proving absence of all likely impurities. Qualitatively proving that it is mostly cyanide does not prove that it is high purity KCN and does not, for example, contain a small impurity of NaCN.

Bedlasky - 20-11-2020 at 14:29

Quote: Originally posted by teodor  
I see it is much dependent on what you have as impurities, like Cl-, ferrocyanide, SCN- etc. But classical literatire, e.g. Treadwell contain all the method on volumetric determination of presence these compounds in mixtures. So, look Treadwell, Volume II.

Edit: I prepared AgNO3 solution for volumetric purposes by dissolving high purity Ag in chlorine-free HNO3. This way it is easier to get known concentration of the solution. (AgNO3 is hygroscopic).

[Edited on 20-11-2020 by teodor]

[Edited on 20-11-2020 by teodor]


Liebig-Deniges method is used for determination of CN-.

https://nvlpubs.nist.gov/nistpubs/jres/7/jresv7n5p913_A2b.pd...

Umbrellaterm - 21-11-2020 at 01:15

Guys I don’t know what you get out of trolling me but it’s plain stupid in my eyes.
ANYWAY, anyone with knowledge are welcome to contact me on bort@ctemplar.com and discuss this further. Iam willing to PAY.

zed - 21-11-2020 at 08:05

Hnuh?

You think these guys are messing with you?

Has it occured to you, that your question isn't a common one?

Try the search engine. Quite likely, there have been discussions on this topic in the past.

Oh, one was insanely nearby.

https://www.sciencemadness.org/whisper/viewthread.php?tid=23

A 31 page discussion, on cyanides.

[Edited on 21-11-2020 by zed]

chornedsnorkack - 21-11-2020 at 08:55

Making sure that it is " indeed cyanide" is the easy part. There are several simple qualitative tests to show presence of cyanide.
Making sure that it is pure KCN is harder. How do you tell apart pure KCN from impure KCN which is 94 % KCN and 6 % various impurities? If you don´t know which impurities they might be?
There are analysis methods to measure different impurities, but those are different depending on which impurity.
Liebig-Deniges method measures the amount of CN-. Which means that you might measure all impurities which are not cyanides, without knowing what the impurities are, just by measuring the amount of KCN and comparing with total. But the problem here is that NaCN is also an "impurity", so measuring just CN- does not give you the purity of KCN.

Bedlasky - 21-11-2020 at 08:56

I don't trolling you. Liebig-Deniges method is one of the basic classical analytical methods.
Quote: Originally posted by chornedsnorkack  
But the problem here is that NaCN is also an "impurity", so measuring just CN- does not give you the purity of KCN.


Sodium can be determined gravimetricaly as sodium antimonate:

https://www.jbc.org/content/41/2/263.full.pdf

Potassium can be determined gravimetricaly by several methods. For example as perchlorate using alcoholic solution of HClO4.

https://books.google.cz/books?id=7RoSBQAAQBAJ&pg=PA723&a...

Or as potassium phosphotungstate:

https://www.jbc.org/content/156/2/765.full.pdf

https://www.jbc.org/content/169/3/539.full.pdf

But these two methods use acids, so firstly it would be better to oxidize CN- to OCN- by H2O2.

[Edited on 21-11-2020 by Bedlasky]