evil_lurker
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Maximum "safe" concentration of peroxides in ether?
I'm getting ready to distill off a couple liters of starting fluid later this week.
However before I do so I plan on testing the starting fluid for peroxide formation using test strips.
Should the ether show peroxide formation, what is the maximum ppm level that would allow for safe distillation?
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Magpie
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I don't know the maximum "safe" concentration. And I am not familiar with distillation of ether from starting fluid.
I have prepared small amounts of ether from ethyl alcohol. Distillation occurs during the reaction and then the distillate is redistilled to purify
the ether. Ether's boiling point is very low (39C?) so the pot liquid never gets very hot. I understand this is the key: never distill to
dryness!. That way any peroxides in the pot never get hot enough to explode. Also remember that dry peroxides can be detonated by friction
as a localized high temperature is produced that way.
You can test for the presence of peroxides using iodide. I have added about 1000 ppm BHT to my meager supplies of ether and THF (also an ether). I
was able to buy some BHT off the internet. Its not real cheap, however, but it helps me sleep well.
The single most important condition for a successful synthesis is good mixing - Nicodem
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evil_lurker
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I should be ok I would assume since from my understanding the primary contents of what I am attempting to distill (walmart starting fluid) is
heptane.... the ether content is only around 25%.
http://msds.walmartstores.com/cache/28009_1.pdf
According to the MSDS, it is stored in an iron can and does contain BHT as a stabilizer so it should be safe.
The Prestone brand should have a higher ether content, the MSDS (also available from that website) lists a 30-60% ether content, however it is unknown
if it is stabilized.
I'm going to call them and find out.
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evil_lurker
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Well didn't get too much info outta prestone. Seem as though all starting fluid manufacturers have pretty much have reduced the amount of ether in
their products to less than 25% or so... walmart brand is probably going to be the best bang for the buck.
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Fleaker
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I'm sure you know not to distill to dryness. As far as the maximum amount allowable? Who knows? It unlikely to explode if it's dissolved in the
ether--main worries are dry distillation, and You can stabilize with BHT and try the copper wire trick (don't even know if it's effective). The
boiling point ranges with ether, I've seen it come over at 35C and all the way to 42C, with the wide rangeindicating its lack of purity. Fractioning
at 37.5C does however yield purity ether.
Magpie adding 1000ppm (perhaps we should denote that differently  maybe 1/1000?
lol) is gross overkill. I have a liter of ether from Fisher and I believe it says BHT "50 ppm". I'll check next time I use it.
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Magpie
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Yes, Fleaker, I suppose you are right about the overkill on BHT. I bought it first for use with my THF. Lyondell sells this by the railroad tanker
so I went to their website for guidance:
http://www.lyondell.com/html/products/products/thf.shtml
Their MSDS says "<0.1% BHT" then in another place says "a minimum of 200 ppm BHT."
Besides, putting in even 1000ppm was just such a tiny smidgen on the end of my spatula. 
I just used the same dose for my diethyl ether. At first I thought this level might affect my Grignard success but it didn't. I suppose all
commercial ether has some stabilizer even the "anhydrous" grade which is probably targeted to Grignards.
The single most important condition for a successful synthesis is good mixing - Nicodem
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nitroglycol
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| Quote: | Originally posted by evil_lurker
Well didn't get too much info outta prestone. Seem as though all starting fluid manufacturers have pretty much have reduced the amount of ether in
their products to less than 25% or so... walmart brand is probably going to be the best bang for the buck. |
Motomaster (from Canadian Tire) is 30-60% ether, according to the MSDS, so if you live in Canada or close to the border it might be worthwhile checking it out. I'm rather curious about the large range, though;
could it be that the stuff sold in the far north (where the winters are more extreme and hence cars are harder to start) has more ether than the stuff
sold in BC or southern Ontario where it's relatively mild?
[Edited on 6-8-2006 by nitroglycol]
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evil_lurker
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Well, perhaps I didn't do the distillation correctly, but my yield from 6 cans of Supertech brand ether was about 150ml crude product boiling over a
range of 31-38C. Distillation was stopped when the water bath temperature reached 50C and very little product was coming over. The actual amount of
liquid that came outta the 6 cans was about 2L or so.
Peroxide test was negative using test strips.
It appears that it has some ether in it, but for the most part its higher boiling solvents such as heptane.
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leu
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As far as the original question as to what a safe level of peroxides is there is no safe level of peroxides in any ether or alcohol, though these
compounds have been isolated in the past by procedures that sometimes killed or injured those doing the isolation  This simple fact is illustrated by those who attempt to make acetone peroxide, which is the peroxide formed in
isopropyl ether, some manage to survive, some don't
Chemistry is our Covalent Bond
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Nicodem
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Evil_lurker, if you intent using ether as a solvent than in many aplications you can just as well use the heptane/Et2O mixture. It does not dissolve
well the solid organic compounds since it is kind of like petroleum ether, but if your reagents are liquid that it will make no difference wheter you
use pure ether or if it is highly dilluted with heptane or other alkanes. You should consider if it is even worth distilling that thing.
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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evil_lurker
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The whole purpose for my aquisition of ether is for the preparation of grignard reagents, so I want it as pure, dry, and free of contaminants as
possible.
Due to governmental (read DEA) restrictions, hazmat fees, and general cost, purchasing ready made ether is simply out of the question.
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triphenylphosphineoxide
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From P.A. Claret EXPERIMENTAL CHEMISTRY PART 2 Small-Scale Organic Preparations
Test For Peroxides in ether:..... can be detected by shaking with acidified solutiion of potassium iodide containing starch as indicator, iodine is
liberated if peroxides are present
Removal of.....: Shake the ether with ferrous sulphate, acidified with sulphuric acid retest after seperation.
I have used ether with peroxides concentrations as high as 9ppm for a gentle reflux lasting three hours, without problem.
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unionised
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If you do the initial distillation from a mixture of the crude ether and FeSO4/H2O/H2SO4 then, if there are any peroxides, they will be left behind
during the distillation and destroyed.
you can then redistil the product (now free of peroxides) to get it pure.
Another aproach I have heard about is to add something involatile like oil to the stuff then distill out the ether. Any peroxides are left behing but
they are safely diluted by the oil.
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HOTPLATE
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Distill Tetrahydrofuran
How can tetrahydrofuran be distilled safely and is there an additive that can be used for storage like ether to stop explosive peroxide formation.I
have read that some labs throw away any tetrahydrofuran that is not used on the first opening.
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Magpie
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Also search under peroxide.
[Edited on 26-10-2008 by Magpie]
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starman
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@ Magpie that thread leads to "forum does not exist" (for me anyway)
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Magpie
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I think one of the mods merged it with this latest inquiry.
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