Sciencemadness Discussion Board

Lithium salt red fire

alexleyenda - 17-12-2013 at 22:46

Hi,
I try to figure out a way to make red flames and I don't want to waste money buying strontium salts ( I live in canada so I get a 15$ shipping bill for 4$ of strontium -_- ), so today I made LiCl out of lithium from batteries and HCl (quite entertaining let's say!) and it turns lighters flames red as it should.

The problem is I look for an effect that looks like boric acid dissolved in methanol that makes big green flames with only a little amount of "dye". ( like that http://www.youtube.com/watch?v=dUG2RlELnhg ) The thing is, I tested LiCl in methanol and it didn't change the color at all ( it didn't seem soluble either, it may explain why...).
Is there any solvent in which it could work?

I also tought about trying with LiOH which should be soluble in methanol. Do you think that could work?


Thanks

Fantasma4500 - 18-12-2013 at 04:50

indeed indeed..

controlling the heat dissolve lithium in methanol, this will make (highly toxic) lithium methoxide..

otherwise mix up lithium chloride with methanol and dump it in a gas canon, this i saw being linked to on some pyro forum.. looked pretty nice, and they had some special name for it..

about the methoxide

http://www.youtube.com/watch?v=c7M-Nf6cYwY

again.. add small amounts of lithium to methanol and you can control it, i had no problems, but i recall people having accidents doing this..?

blogfast25 - 18-12-2013 at 06:21

@Alex:

LiCl is quite soluble in methanol (17 g per 100 ml, acc. Wiki). I've made Li coloured flames for spectroscopy with such solutions. You probably didn't add enough LiCl or your expectations re. flame colour intensity were too high. The spectral line intensity of the Li carmine line may be lower than the Sr line (but I'd have to look that up, to be sure).

MrHomeScientist - 18-12-2013 at 06:45

Part of the reason the boric acid / methanol flame looks so good is that these two compounds react to form trimethyl borate, which acts as a strong colorant throughout the whole solution. In my experience with flame colors you won't get anything near as good as this green flame with other salts, because they simply dissolve instead of reacting. I usually see the usual methanol flame to begin with, then as this burns down you get more and more of your color to show up. Careful what you burn this in too - I used a Petri dish once that shattered under the thermal stress and spilled flaming methanol onto my work surface :o Always work outside!

I tried making a video on flame colors once, but never could get a good blue. I've tried both Li and Sr salts and Sr definitely gives a more rich color, but Li is adequate if that's all you have.

blogfast25 - 18-12-2013 at 07:46

Quote: Originally posted by MrHomeScientist  
- I used a Petri dish once that shattered under the thermal stress and spilled flaming methanol onto my work surface :o Always work outside!



Always use a metal or dedicated glass spirits burner for methanol/ethanol, it's quite a hot flame.

I bought an old fashioned spectrometer (Bunsen - Kirchoff style) last weekend, so I'll be messing with coloured flames shortly too, this time actually measuring wavelengths of specific lines.




[Edited on 18-12-2013 by blogfast25]

MrHomeScientist - 18-12-2013 at 09:51

Yeah, I was lulled into a false sense of security by methanol's cool blue, barely visible flame.

That's an awesome looking piece of equipment! Can't wait to see some experiments with it.

blogfast25 - 18-12-2013 at 10:23

Quote: Originally posted by MrHomeScientist  

That's an awesome looking piece of equipment! Can't wait to see some experiments with it.


Well, you're in luck because I can't wait to do some good stuff with it. I want to see the Rb and Cs lines, using Lepidolite as a starting material.

alexleyenda - 18-12-2013 at 10:51

I'll try dissolving LiCl again in warm methanol and i'll add more. The methoxide methode seems interesting, i'll definitely try that later even if my LiCl does work as it seems to give much better red flames than the salts. By the way I looked at the msds of lithium methoxide and it isnt toxic, just corrosive as any basic salt and flammable.

Anyways thanks to everyone for all these useful and interesting answers and explanations, it's my first post and I already love this place :D

alexleyenda - 18-12-2013 at 11:28

I tested it again, once again the flames were blue, but i let it run for a minute and then I saw the most awesome fire I've ever seen... I made some tests and found that LiCl in methanol doesn't produce red flames, the red flames appear only when enough methanol burnt and dry LiCl cristalises around the pot above the flames. Only then the flames heat the LiCl and become a kind of reddish magenta. I even tryed stopping the fire at this point and pouring the methanol solution in another pot and once again the flames were blue until some LiCl dried.

Tsjerk - 18-12-2013 at 11:37

But how about reacting lithium metal with methanol? The borate/methanol mixture is supposed to give its bright green flames because it contains a real borate compound, and the red flames from the lithiumchloride gives its red color only when the chloride starts to crystallize. So wouldn't give lithium methoxide give a red flame? I know lithium tert -butoxide does.

alexleyenda - 18-12-2013 at 11:52

As it was said it should work and I will definitely try it later when i'll have some time. I even have perfect conditions to try it, the temperature is around -15°C these days
it'll help keep the mixture cold :D

Tsjerk - 18-12-2013 at 12:38

Do you have the equipment to do a reflux? I only did the synthesis of sodium ethoxide, but I didn't found it to be that violent. Just use a reflux setup to keep to much alcohol from evaporating and use an excess of alcohol to keep the temperature from rising to high. If you find the solution to dilute you can evaporate excess alcohol.

alexleyenda - 18-12-2013 at 13:47

Not atm, but I got a graham condenser on the way, it might not be the best for that purpose but it should get the job done. Thanks for the tip. And by the way, how did you get your sodium? I already tried hard to make some and failed. I tried with NaOH + Mg ( in fact I definitely made some this way, but didn't manage to isolate it from the mixture, the reaction was awesome though) and by frightening molten NaOH electrolysis.

[Edited on 18-12-2013 by alexleyenda]

blogfast25 - 18-12-2013 at 13:53

Try sprinkling finely ground LiCl directly into your flame. You should get some flare up each time the solid hits the flame. Same with NaCl.

DubaiAmateurRocketry - 18-12-2013 at 13:57

Lithium for red color ? Cool, I have done some and here are some of my videos.

Lithium perchlorate burning with hexamethylene tetramine.
http://www.youtube.com/watch?v=iQ22fX6g6JU

Lithium perchlorate burning with magnesium
http://www.youtube.com/watch?v=P1T0-hNZpG0

Tsjerk - 18-12-2013 at 14:19

I got my sodium from a commercial source, I (unfortunately) never made it myself. My tries to isolate it from sodium azide failed as the reaction was to violent :)

DubaiAmateurRocketry - 18-12-2013 at 14:56

Quote: Originally posted by Tsjerk  
I got my sodium from a commercial source, I (unfortunately) never made it myself. My tries to isolate it from sodium azide failed as the reaction was to violent :)


Sodium is one of these things we have to buy if you want to use it for something. Its just cheaper/ more pure than the way we make our selves :)

nezza - 19-12-2013 at 06:55

Halides are among the best salts to use for flame colouration because of their relative volatility. Lithium chloride in methanol gives a beautiful carmine red flame colour as in the attached video. In pyrotechnics chlorine donors are almost always added to mixtures to give flame colours. I have tried small scale burns of barium and strontium nitrate with and without a relaitvely neutral coloured chloride salt (Not sodium chloride) and the mixtures with chloride in give much better colours. For a really intense green Barium chlorate takes some beating and obviously trimethyl borate as a methanolic solution.

Attachment: Lithium flame.mp4 (604kB)
This file has been downloaded 750 times

blogfast25 - 19-12-2013 at 07:30

Quote: Originally posted by nezza  
Halides are among the best salts to use for flame colouration because of their relative volatility. Lithium chloride in methanol gives a beautiful carmine red flame colour as in the attached video. In pyrotechnics chlorine donors are almost always added to mixtures to give flame colours. I have tried small scale burns of barium and strontium nitrate with and without a relaitvely neutral coloured chloride salt (Not sodium chloride) and the mixtures with chloride in give much better colours. For a really intense green Barium chlorate takes some beating and obviously trimethyl borate as a methanolic solution.



Nice vid, nezza. That's roughly how I remember LiCl in methanol for my past spectroscopy experiments. For those, mixed salts solutions are really useful too.

alexleyenda - 19-12-2013 at 11:13

Yep, that's pretty much what I got once some salt dried around the flame. :)

alexleyenda - 23-12-2013 at 19:42

update:I tried lithium methoxide and just as LiCl it needed to dry before colouring the flame. Anyways, it doesnt matter too much, it's just a bit more trouble. It even was less efficient than LiCl.

[Edited on 24-12-2013 by alexleyenda]

annaandherdad - 19-10-2019 at 07:59

I hope to add something of interest to this old thread. My daughter has been doing the flame test in chemistry class, and it got me interested in it. Here are some random thoughts.

Looking at youtube videos led to the question of why sodium makes such a strong yellow flame while potassium has a rather weak (lilac) color. The atomic transition is 3p->3s in sodium, why wouldn't the 4p->4s in potassium be comparable in strength? The answer is that it is, but the line is in the infrared so you can't see it.

So I went to the NIST data base of atomic energy levels and calculated the wavelengths of the p->s transitions for the alkali atoms, and here's what I got:

Li 2p->2s 671 671
Na 3p->3s 589 590
K 4p->4s 767 771
Rb 5p->5s 780 795
Cs 6p->6s 853 895

What's given in this table are the wavelengths in nanometers of the two lines of the doublet, which are split by the fine structure. Things to notice: 1. Potassium and beyond, the lines are in the infrared, as noted on the youtube video; 2. the fine structure splitting gets much bigger as you move down the periodic table; 3. the function is not monotonic, the wavelength decreases from lithium to sodium, then increases. Can anyone explain item 3?

So the nice color of lithium flames must come mainly from the 2p->2s transition at 671nm. It has the right color.

More questions. These spectral lines come from atomic alkali atoms, not ions. So in the lithium flame that this thread talks about, the lithium chloride is broken into Li + Cl, atoms not ions, and then Li is knocked into the first excited state, 2s->2p, with an energy difference of about 1.8ev. Of course it also gets knocked into other excited states, but this is the first one and presumably the excited state with the highest population, since all the others require more energy. It would seem to me that at the temperature of the flame, which can't be more than about 0.2ev, the chance of getting into even the first excited state on a single collision would be very small. The fractional population of the 2p state ought to be something like exp(-1.8/0.2)=10^-4. Is this a correct analysis of the kinetics, does anyone know?

And there is also the question of why we don't see spectral lines from the chlorine or from the hydrogen or carbon in the flame (or oxygen, if you're using methanol). In the case of hydrogen, the first excited state is 10ev above the ground state, compare to the 1.8ev for Li and you see why you don't see anything from excited hydrogen (in any case, the 2p->1s line in hydrogen is in the UV). It is just energetics that explain why we don't see chlorine lines etc? Actually, the methanol (or methane) flame is blue. What causes this color?

By the way, youtube is full of dread warnings about using methanol for the flame test, because there was some accident (or more than one) in some chemistry class in the US recently. Seems like it was a fire.

rockyit98 - 20-10-2019 at 04:03

Lithium Grease burn with red color .soap with yellow Na some times lilac (pink) from kids or high quality soap which contain only potassium.red from road salt calcium chloride.if your samples have Na impurity look through cobalt blue glass.it filter out Na color.