Picene
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Solvent systems.
I am trying to come up with a mixed solvent system to dissolve metal salts in dodecane.
Trick is, it has to be relatively safe to put in your mouth.
The obvious choice is Crown Ethers, but they are damn expensive. The expense could be forgiven, save that they are also toxic when ingested.
The mechanism of their toxicity is their ability to leach cations from the body, but I hypothesize this wouldn't necessarily be a problem If the crown
ether is already saturated with cations. I just don't know what the difference in affinity will be between the crown ethers and my own spit, nor do I
know where to find such information
Does anyone have any experience/reccomendations with/for mixed solvent systems to dissolve lithium and potassium salts? Any help or input would be
appreciated.
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DDTea
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How safe should it be when put into your mouth? I mean, are you planning to swallow it? How long will you leave it in your mouth? Should
it taste good? 
"In the end the proud scientist or philosopher who cannot be bothered to make his thought accessible has no choice but to retire to the heights in
which dwell the Great Misunderstood and the Great Ignored, there to rail in Olympic superiority at the folly of mankind." - Reginald Kapp.
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ScienceSquirrel
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What sort of metal cations do you want to dissolve in dodecane?
The approach for an alkali metal like potassium will be different to say a transition metal like iron.
Paraffin hydrocarbons of low molecular weight are quite toxic if swallowed in quantity.
Many years ago a local farmworker drank a pint of diesel for a bet, he was dead on arrival at the local hospital twenty minutes or so later.
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DDTea
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On that note: if you're putting it in your mouth, only use even-numbered carbon chains, not odd-numbered. I don't remember how they're broken down,
but odd-numbered carbon chains lead to some toxic metabolite or other...that's not to say all even-numbered chains are somehow safe, though 
"In the end the proud scientist or philosopher who cannot be bothered to make his thought accessible has no choice but to retire to the heights in
which dwell the Great Misunderstood and the Great Ignored, there to rail in Olympic superiority at the folly of mankind." - Reginald Kapp.
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Picene
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I should really be more clear here, lest I risk coming off as suicidal.
The goal of the project is to develop a set of flammable mixtures that can be used for fire arts.
Some of these mixtures can be slightly more toxic. Copper chloride is nasty enough not ever want in your mouth, but would give nice green for fire
spinning or dancing.
Potassium and magnesium salts, however, are just non-toxic enough that I'd love to use them for fire breathing. Lithium sulfate would be nice too, but
lithium crown 4 is rather... volatile.
Only problem is dissolving them in the fire breathing medium, which is jet fuel (saturated c12-c14 hydrocarbons).
They dont stay in your mouth for long, and you dont swallow them, but a fair amount of the aerosol gets on your skin. Concentrations of the salts need
not be high. Just something to give a little carmine or purple tinge.
I don't have the bio background to be able to assess how readily crown ether complexes would cross my buccal mucosa. Alternative ideas for making a
good, flammable, complex liquid mixture would also be appreciated.
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DDTea
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Picene: depending on how often you're doing this, you should consider the chronic/long-term toxicity of these salts and solvents. It might not be so
bad for a single demonstration, but if you're doing them often it could be unsafe. Definitely, at minimum, check the MSDS's of everything you're
using.
You might not even have to dissolve the salts. What about using some kind of suspension?
"In the end the proud scientist or philosopher who cannot be bothered to make his thought accessible has no choice but to retire to the heights in
which dwell the Great Misunderstood and the Great Ignored, there to rail in Olympic superiority at the folly of mankind." - Reginald Kapp.
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ScienceSquirrel
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I think that triethyl borate would give you a spectacular green flame.
It can be prepared quite easily as a solution by dissolving boric acid in ethanol.
Heating or the presence of a strong acid will produce higher yields and more quickly but you will have to purify it if you use the acid.
It is readily soluble in ethanol and produces a brilliant apple green flame.
I am not sure about the toxicity but I would be loathe to put it in my mouth!
http://en.wikipedia.org/wiki/Triethyl_borate
Copper acetylacetonate is readily soluble in most organic solvents and would give good flame colouration.
http://www.chemicalland21.com/specialtychem/perchem/COPPER%2...
Not sure about putting that one in my mouth at all!
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zed
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In my opinion, this is a thoroughly dangerous idea.
Heavy metal poisoning is easily acquired, and damn hard to get rid of.
Potassium Chloride is very do-able; not toxic. Maybe Potassium Iodide too. Not very toxic. Lithium salts, are somewhat more toxic.
Also note, solubility may not be your friend.
Fine suspensions of materials that are highly insoluble AND indigestible, might be more safely used, in most cases.
These materials could touch your mucus membranes, and pass through your digestive tract, unabsorbed. Sparing you an agonizing death.
Still none too healthy. Because, after your colored flame display, a cloud of vaporized metal salts will be hanging around your head. Giving you an
opportunity to breath in the ions, that you just spit out.
Finely powdered Magnesium Metal, suspended in a hydrocarbon, might produce an interesting effect. White lightning. Of course, it might kill you too.
Do your initial experiments using disposable clones. They aren't legally consider people; so.....if their heads are blown off, it's no big deal!
[Edited on 7-10-2010 by zed]
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Panache
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i just did a flame test on mercuruchrome in ethanol .....and.......boring orange.
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unionised
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"I think that triethyl borate would give you a spectacular green flame."
Possibly twice. Once as a fire breathing show and the second time when they cremate your remains.
Anyway, there are at least two big problems here.
Saturated hydrocarbons burn with smoky flames and lots of soot (Not as bad as unsaturated ones but still smoky). So the hot soot will give rise to
lot's of yellow/orange light which will wash out any colour you might otherwise see.
You could get round that using alcohol as a fuel.
The second problem is that saliva will contain enough sodium ions that all you are ever likely to see is a yellow flame.
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Picene
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Unionized:
When you breathe fire, you make a very fine fuel-air mixture which burns rapidly and with minimal soot.
You make a great point: Sodium from your mouth WOULD impart significant yellow coloration in any general purpose solvent system. That sort of limits
me to crown ethers. 18-crown-6 would selectively dissolve potassium ions and not sodium ions.
Zed: I am not going to be using heavy metals. There are plenty of food grade sources for metal ions.
The mechanism of toxicity for crown ethers is their high affinity for a specific cation which allows them to leach them from the body. Raw 18 crown 6
has a high enough potassium affinity to sequester almost all available K+ in a solution, as well as drawing it across your cell membrane. This pretty
effectively blocks your cells ability to polarize or absorb glucose.
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Picene
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AAAND the moral of the story is: don't be lazy, do your homework.
From: "Variability of crown ether toxicity Wung-Wai Tso, Wai-Ping Fung and Man-Yin Wong Tso, Journal of Inorganic Biochemistry Volume 14, Issue 3,
1981, Pages 237-244 "
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"Similar to nigericin and other natural ionophores, the mode of action of crown ether in inhibiting growth may involve an interference with the
cation-translocating mechanism [7]_ This implies that the damaged cell has to create a new route to reestablish its cationic gradient across the
membrane before growth can resume. An alternative method is for the cell to replenish the ions that leaked out due to the presence of crown ether. The
cell wall-inhibitory antibiotics are known to cause a marked reduction of intracellular potassium ion content [2t]Indeed the adverse effect of
them as well as ionophores has been found to be reversed by the addition of excess potassium They are as follows: (a) The cation
crown complex exhibits differential toxicity when compared to their corresponding crown ethers so that the potassium 18-crown-6 complex has less
toxicity," |
From "Effect of Some Potassium Selective Crown Ethers on the Permeability and Structure of a Phospholipid Membrane, Szögyi M, Cserháti T, Tölgyesi
F. Lipids. 1993 Sep;28(9):847-51."
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"The objectives of our study were to determine the effect of new crown ethers on the permeability and melting properties of dipalmitoyl
phosphatidylcholine {DPPC) liposomes and to assess the effect of the lipophilicity of crown ethers on their membrane-modifying properties."
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Regrettably, they don't actually test out 18-crown-6, rather a number of substituted crowns of variable lipophilicity. The gist of the article is that
highly lipophilic crown ethers not only sequester metal cations, but bind with the cell membrane and alter it's ion permeability, which doesn't sound
particularly fun.
A little more digging found an article that specifically addresses just this topic. "Effect of macrocyclic compounds on the ionic permeability of
artificial and natural membranes. Tosteson D C Federation proceedings (1968)"
But, as might be expected from an article published in 1968, its not electronically available. I am waiting for a paper copy to be faxed over, will
update then.
[Edited on 8-10-2010 by Picene] [Edited to improve readability and include full sources]
[Edited on 8-10-2010 by Picene]
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ScienceSquirrel
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Quote: Originally posted by unionised  | "I think that triethyl borate would give you a spectacular green flame."
Possibly twice. Once as a fire breathing show and the second time when they cremate your remains.
Anyway, there are at least two big problems here.
Saturated hydrocarbons burn with smoky flames and lots of soot (Not as bad as unsaturated ones but still smoky). So the hot soot will give rise to
lot's of yellow/orange light which will wash out any colour you might otherwise see.
You could get round that using alcohol as a fuel.
The second problem is that saliva will contain enough sodium ions that all you are ever likely to see is a yellow flame.
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I stated that I would be reluctant to put it in my mouth.
However Picene mentions fire dancing and spinning as well.
A torch made of glass wool or some other inert absorbent material soaked in a solution made by refluxing methanol with 10% w/v of boric oxide would
burn with a spectacular green plume.
It would be pretty safe as well.
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