Sciencemadness Discussion Board

Colour of potassium nitrite

Akhil jain - 19-3-2018 at 00:24

I made potassium nitrite yesterday and posted that video on my channel .
If you will see the video you will observe that the filtered solution of potassium nitrite was slight yellow in colour.
Is it due to the tar contained in charcoal or is it the characteristic colour of potassium nitrite?
And won't tar be burnt in that reaction . Plz see the video carefully and answer this question .

hissingnoise - 19-3-2018 at 03:19

The yellow tint is normal for alkali metal nitrites as a quick glance at their wiki would've told you had you bothered to look...

XeonTheMGPony - 19-3-2018 at 03:25

this would be a case to add a simple link to the video in question, or a link to your channel on signiture.

As stated when making a substance it is your duty to research both starting materials and their properties, and the expected target substances properties.

In the case of your research you'd have easily found your answer.





Yes, a slight yellow tinge is what they tend to look like.

Akhil jain - 19-3-2018 at 04:02

I know that wikipedia says that potassium nitrite is slight yellow in colour . And I have also seen sodium nitrite in lab it was also slight yellow in colour . I want to ask someone who has worked before with nitrites and has a good experience of it

Texium - 19-3-2018 at 04:12

Sounds more like you're fishing for views

Tsjerk - 19-3-2018 at 05:18

Stop the fishing dude, I hope you don't need more explanation about why. Also; it doesn't work, everyone here knows what you are trying to do.

My potassium nitrite is completely colorless.

Akhil jain - 19-3-2018 at 06:12

I am not fishing views over here . Enough you have spoken . Enough is enough . It's too much now.
Even the lab grade sodium nitrite is slightly yelloe and you say it is colourless. I think many people have problem with my posts because they are not interested in that topic .
You can only see that I am fishing views over here but cannot see that first of all I am posting videos for nothing and giving correct information .
People cannot see other people getting benefit and I think you are one of them
And if I am sharing my videos or my creations with my SM members I don't think that's fishing . I think that's sharing of ideas on a correct platform. The people who are interested will like it . The people who are not interested will ignore it .

[Edited on 19-3-2018 by Akhil jain]

Tsjerk - 19-3-2018 at 06:20

I will take a picture of mine tonight.

aga - 19-3-2018 at 06:33

The video/yellow colour is this one: https://youtu.be/9J9Rlz5xahI?t=245

My nitrite was prepared using the classic lead reduction method :
http://www.sciencemadness.org/talk/viewthread.php?tid=52&...

The yellow tint is almost impossible to see unless you sneak up on it and take a peek while it's back is turned.

nitrite.jpg - 28kB

On the left is some sodium nitrate, probably prepared with nitric acid & some sodium salt (can't remember).

On the right is the sodium nitrite prepared a couple of years back, using some of the same nitrate seen on the left.

@Akhil: if you're convinced there's no Fe present, try the activated carbon trick to see if it clears that yellow solution up a little.

With the best will in the world, a straight combustion-in-air reaction is going to generate a hell of a lot of side-products, no matter how well you calculate the stoichimetry.

aga - 19-3-2018 at 06:40

Quote: Originally posted by Akhil jain  
... I am posting videos for nothing and giving correct information ....

Erm, that's bending the fabric of Reality further than even my brain can imagine after 16 pints of strong lager.

"... the Correct method to prepare potassium nitrite ..." for example.

I guess H.T. Vulte never imagined just setting fire to stuff when he wrote his book "Laboratory Manual of Inorganic Preparations" back in 1895.

Edit:

Seeing as simply burning KNO3 + C does produce some KNO2, it might be worthwhile heating that mixture in a stream of argon (to remove the CO/CO2 as it is produced).

Might be a much better way than using lead.

[Edited on 19-3-2018 by aga]

TheMrbunGee - 19-3-2018 at 06:56

Might it be just the products of side reactions burning charcoal? how pure was your charcoal..?

Tsjerk - 19-3-2018 at 07:24

OK, I actually watched your video and I'm pretty certain the yellow color is due to the charcoal.

Akhil jain - 19-3-2018 at 09:25

Guys my charcoal was simple charcoal it was not lab grade charcoal . And I would try clearing it by activated charcoal but I don't have activated charcoal .
Does anyone know how to activate simple charcoal.

Rhodanide - 19-3-2018 at 10:56

Quote: Originally posted by aga  
The video/yellow colour is this one: https://youtu.be/9J9Rlz5xahI?t=245

My nitrite was prepared using the classic lead reduction method :
http://www.sciencemadness.org/talk/viewthread.php?tid=52&...

The yellow tint is almost impossible to see unless you sneak up on it and take a peek while it's back is turned.



On the left is some sodium nitrate, probably prepared with nitric acid & some sodium salt (can't remember).

On the right is the sodium nitrite prepared a couple of years back, using some of the same nitrate seen on the left.

@Akhil: if you're convinced there's no Fe present, try the activated carbon trick to see if it clears that yellow solution up a little.

With the best will in the world, a straight combustion-in-air reaction is going to generate a hell of a lot of side-products, no matter how well you calculate the stoichimetry.


From my experience working with bulk NaNO2 (above 1 pound or .45 kg), I can confirm that there absolutely is a yellow color. Mine is technical grade, but the only impurity that I know of is an anti-caking agent (insoluble anyways). The solid takes on a slight yellow color, even when cracking open the bottle for the 1st time. Even the water solution of it takes on a pale yellow color.

aga - 19-3-2018 at 11:05

Quote: Originally posted by Rhodanide  
... there absolutely is a yellow color. Mine is technical grade...

Yay !

My amateur chemfumbling made a better grade than Technical !
Quote: Originally posted by Akhil jain  
... activate simple charcoal.

ISTR it was a lot of work.

https://www.sciencemadness.org/whisper/viewthread.php?tid=63...

Edit:

OMG ! Just re-read that thread and i pyrolysed some bread even back then !

Rough (but experienced) stab at a way to make Great Activated Carbon :-

Pyrolyse some bread.
Stick it in a tub of water
Freeze it
Thaw it out.
Ball-mill it.

Chances are that it makes an A.C. with an I.N. of over 1,000.

Maybe repeating the freeze-thaw-ball-mill part will get it way up there.

Deffo got to try that one.

[Edited on 19-3-2018 by aga]

LearnedAmateur - 19-3-2018 at 11:12

The food grade sodium nitrite I have is slight yellow in colour. Since both K+ and Na+ are colourless, I’d presume it would be the same either way.

aga - 19-3-2018 at 11:17

Quote: Originally posted by LearnedAmateur  
The food grade sodium nitrite I have is slight yellow in colour. ....


Please post a photo for comparison.

Akhil jain - 19-3-2018 at 11:24

That's a so long discussion aga on AC

aga - 19-3-2018 at 11:35

Sorry it was not simple.

Edit:

Condensed version :-

Pyrolyse some bread.
Stick it in a tub of water
Freeze it
Thaw it out.
Grind it up.

(maybe grind before freezing)

[Edited on 19-3-2018 by aga]

LearnedAmateur - 19-3-2018 at 11:41

Only got about 50-60 grams left, gotta get some more soon.

Apparently it’s 99.9% pure, it’ll have to be high for food use but in any case it’ll be at least 98%.
E00698F3-915C-468C-82FA-E95CE27954F9.jpeg - 1MB

[Edited on 19-3-2018 by LearnedAmateur]

aga - 19-3-2018 at 11:45

Thanks LearnedAmateur !

That yellow stuff looks highly granular, like cubic crystals.

Very much like the wiki image shows.

I guess mine is more white and fluffy due to idiocy and/or Pb salt contamination.

LearnedAmateur - 19-3-2018 at 12:05

Yeah it’s got the consistency of table sugar as far as I can see, just a little smaller. Time to bust out the ghetto microscope for a better look! Sucks though because it doesn’t exactly show true colour and it gets in the way of the flash, but I’ve got some cool pictures with it before.

0F94E14C-123C-4DC9-B0C9-EFA855BE8077.jpeg - 878kB

S.C. Wack - 19-3-2018 at 14:04

There are references that say nitrite is white to yellow, but most just say slightly yellow or yellow white. I think white to yellow actually means somewhere in between. All of either cation that I've seen is the same color, like the ~yellow of the site. Same as a few pounds of food grade on hand.

(the color is best viewed with, or on, something white)

BTW aga there is a difference between what prepchem says Biltz said on the reduction of nitrate, and what he actually wrote.

(explore your links and my www button)

[Edited on 20-3-2018 by S.C. Wack]

aga - 19-3-2018 at 14:07

Quote: Originally posted by S.C. Wack  
... there is a difference between what prepchem says Biltz said on the reduction of nitrate, and what he actually wrote.

Damn.

Wish i could find that stuff.

Could there be a reference ? Who's Biltz ?

Texium - 19-3-2018 at 14:09

My sodium nitrite (I think it's reagent grade but I can't remember- it was a group-buy thing) is just barely yellow enough to notice- less yellow than the picture that LearnedAmateur posted. Perhaps the differences in color are just due to differences in crystal size and/or hydration.

[Edited on 3-19-2018 by Texium (zts16)]

LearnedAmateur - 19-3-2018 at 14:37

When I get around to ordering some more, I’ll try and grow a crystal out of it to see if there’s much colour through a repeating lattice. Shouldn’t be difficult considering it’s barely hygroscopic, definitely won’t form a solution when left to air (we all know how bad LDPE bags are for keeping moisture out).

I guess it’s like with colourless solids, they’re clear when crystalline and white when powdered, lots of interfaces for light to reflect off, so weak colours are likely intensified in the latter case. Can’t find any images of a macroscopic NaNO2 crystal so it’s up for experimentation.

aga - 19-3-2018 at 14:42

Sounds like a Challenge !

Reminds me: made some potassium rhodizonate some time ago, so best stick it in some vinegar and see how contaminated my NaNO2 is, thence to photos in solution and crystals.

Magpie - 19-3-2018 at 14:59

I made KNO2 by reducing the nitrate with lead. I also bought some lab grade from Post Apple Scientific. Both hav a slight yellow cast.

TheMrbunGee - 19-3-2018 at 23:20

My NaNO2 is slightly yellow, but not even close to that yellow as OP KNO2, those are impurities. May be N oxides or some kind of tars from charcoal.

When I played with self made low quality black powder - yellow/brown residue was always left after burning it. It might be because of S, but charcoal might also be blamed.

woelen - 20-3-2018 at 00:23

I have NaNO2 from two sources. One of them is reagent grade. Both are pale yellow, it is a true yellow color and not brownish.
I also have KNO2. This also is yellow, but this has a faint brownish cast.

Color (like whiteness) does not tell everything. Your NaNO2 or KNO2 can be very impure, e.g. it can contain a lot of NaNO3 or KNO3.
With NaNO2 it is important to assess its purity. You can do that by titration with KMnO4. KMnO4 is quickly reduced to Mn(2+) by nitrite ion at low pH.
Best way to do this is make a dilute solution of KMnO4 in very cold dilute H2SO4 (e.g. 2% H2SO4) of known concentration of KMnO4. Dissolve a well measured weight of your nitrite in a well measured volume of water and drip this in the solution of KMnO4 while stirring strongly. Continue until the color of the MnO4(-) ion just disappears.
Do not work the other way around. If you add your acidic KMnO4-solution to the solution of NaNO2 or KNO2 then you'll lose bubbles of NOx and this will make your titration very inaccurate.

RawWork - 20-3-2018 at 05:05

Add sodium hydroxide until color dissappears, this means contaminant is some nonmetal like N (it's compounds). If it doesn't, then contaminant is some metal (transition or rare earth, their compounds).

hissingnoise - 20-3-2018 at 05:35

Quote: Originally posted by TheMrbunGee  
May be N oxides...

Indeed, since both alkali nitrites are hygroscopic there may be some hydrolysis releasing traces of NO2.

LearnedAmateur - 20-3-2018 at 07:50

I don’t think NaNO2 hydrolyses, not from what I’ve heard. The mechanism behind its ‘conversion’ is through HNO2, nitrous acid, which is weak enough to be liberated by just about any household acid. It’s quite unstable above 0-5C, decomposing via 2 HNO2 -> H2O + NO2 + NO, at least that’s what makes sense to me. In fact, it would technically be a dehydration reaction, wouldn’t it?

Edit: actually I’d say you’re partly right there, since you’ve got some NO2 and SO3 floating around in the atmosphere from pollution, they could make their way into the nitrite, forming acidic vapours with atmospheric moisture.

[Edited on 20-3-2018 by LearnedAmateur]