alking
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Bestine = 100% heptane? It doesn't seem like it.
I'm fractionally distilling some bestine with a small amount of isopropanol and my first fraction is coming over at 70.0-70.2C. I actually didn't see
it until after it started condensing so it may be a bit lower than that, but either way that's 10c lower than the iso and definitely below that of
heptane. Am I correct to assume this is *not* 100% heptane? I can't explain it any other way. I just started the distillation so I have no idea if
this is just a small fraction or not at this point but we'll see. Any idea if they changed their formula, anyone else experience this? It doesn't
matter for my application, but I purchased it with the assumption that it was pure heptane and I'd like to know what I'm using. I'm also wondering if
my thermometer is off, but I've tested it recently and it seemed accurate.
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alking
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Well I just finished the distillation, nearly distilled it dry, and at *best* this is 1/4 heptane. >50% came over at 70c. I really hope there is no
benzene in this. I primarily got this thinking I would be able to condense it with RT water no problem, but that is not the case, I'm pretty
disappointed. I can still use it, but I have to use ice water or do it outside. Take this as a warning for anyone else purchasing bestine thinking the
manufacturer isn't lying.
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aga
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It would help to get good answers if the question was a bit clearer.
What is 'bestine' and what are you trying to do ?
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careysub
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Quote: Originally posted by aga  | It would help to get good answers if the question was a bit clearer.
What is 'bestine' and what are you trying to do ? |
He is referring to this product:
http://www.dickblick.com/products/bestine-solvent-and-thinne...
http://www.ebay.com/itm/like/262299681177?lpid=82&chn=ps...
http://www.artistsupplysource.com/category/57412/turpentine/
https://www.artsupplywarehouse.com/finelineDisplay.php?id=11...
Which claims to the 100% heptane:
http://www2.uwstout.edu/content/msds/Bestine-Solvent-Thinner...
The MSDS has a contact phone number. You could try and call and ask for the actual composition.
Its a very good price for heptane, if it *is* heptane.
[Edited on 11-3-2016 by careysub]
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aga
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Nice work careysub.
Took you approx 5 mins to know more about the stuff than the OP does.
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BromicAcid
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Note that the SDS on the manufacturer's website says it is 100% heptane but there is an asterisk which stipulates that the exact composition is a
trade secret. It's my understanding in that case so long as the added components do not add any additional hazard that they can be whatever the
company wants. If that is the case they're calling it heptane but it may well be just a specific fraction of petroleum distillate around the
'heptane' mark. Note that the SDS for Bestine as well as the SDS for the companies thinner on the company website both say that both products are
identical, but still containing their trade secrets.
http://www.realbesttest.com/
EDIT: Note that even their SDS for rubber cement on their website lists only 60-100% heptane as the composition. Obviously there is something else
in the rubber cement than heptane, otherwise I would feel slighted.
[Edited on 3/11/2016 by BromicAcid]
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careysub
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As long as the Bestine consists only of petroleum distillates I would not feel too bad about it not really being pure heptane. That reduces its
usefulness somewhat (vs having a pure substance of a single BP) but it will still serve as a solvent about equally well.
What convenient tests would work well to clarify its composition?
Measuring the density by weighing a known volume would be useful - but not really tell you much about its possible composition.
Shaking with water to see if any mass is lost would be probably more useful (test for any water soluble substances).
If there are any, it could be used to remove them.
Aldol condensation with NaOH to see if ketones are present?
What else?
(I am particularly interested in this thread as I have come Bestine.)
[Edited on 12-3-2016 by careysub]
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UC235
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Bestine is a solvent intended for removing rubber cement from surfaces so it would be against their best interest to use anything that wasn't
hydrotreated (fully saturated) alkanes. Consider it a fairly high-boiling ligroin. Benzene content is negligible if at all present or it would need a
dozen more warnings on it.
Of course, I'm swimming in heptanes from fractionating starting fluid, but I did buy a can of this stuff years ago.
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Dr.Bob
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"Heptane" could include all of the isomers of heptane, including n-heptane, which you are thinking of, but also 2-methylhexane, 3-methylhexane, 2,
3-dimethylpentane, and several other isomers. These would have a wide BP range, and likely include some hexanes and octanes. For the purposes of
dissolving rubber cement, there is no advantage of using a pure isomer, and mixtures are substantially cheaper than a "pure" isomer.
The best way to check it would be GC, most other analytical methods are not going to easily tell what amount of which isomers you have. There are
subtle differences in density and RI of the isomers, but unless you distilled each component carefully apart, those won't tell you much. But again,
for most chemistry, a mixture of hydrocarbons is fine. I used mixed hexanes for chromatography, extractions, and trituations daily.
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careysub
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Good observation Dr. Bob.
For amusement here is a list of all of the heptanes and their boiling points in ascending order (ignoring enantiomers):
2,2-Dimethylpentane (neoheptane) 79.2
2,4-Dimethylpentane 80
2,2,3-Trimethylbutane 81
3,3-Dimethylpentane 86
2,3-Dimethylpentane 89
2-Methylhexane (isoheptane) 89.6
3-Methylhexane, 91.6
3-Ethylpentane 93
Heptane (n-heptane), 98.1
All above 70 C however. n-Hexane is the highest BP hexane at 69 C, so maybe it is largely n-hexane.
Sounds like you might want to fractionate your Bestine into low and high BP portions for convenience. I may do that with mine.
[Edited on 12-3-2016 by careysub]
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Ozone
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I will note that the rubber cement smells clearly like heptane (or, at least it used to).
O3
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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alking
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| Quote: Originally posted by aga | Nice work careysub.
Took you approx 5 mins to know more about the stuff than the OP does. |
No need to be a dick. Did it occur to you the reason I'm posting this is because I read the sds? I wouldn't have made this post if it said
something else than '100% heptane' or the product in hand had the appropriate bp range. Maybe I should have explained what it is, but you not
knowing doesn't somehow impart a lack of understanding on me.
| Quote: Originally posted by Dr.Bob | "Heptane" could include all of the isomers of heptane, including n-heptane, which you are thinking of, but also 2-methylhexane, 3-methylhexane, 2,
3-dimethylpentane, and several other isomers. These would have a wide BP range, and likely include some hexanes and octanes. For the purposes of
dissolving rubber cement, there is no advantage of using a pure isomer, and mixtures are substantially cheaper than a "pure" isomer.
The best way to check it would be GC, most other analytical methods are not going to easily tell what amount of which isomers you have. There are
subtle differences in density and RI of the isomers, but unless you distilled each component carefully apart, those won't tell you much. But again,
for most chemistry, a mixture of hydrocarbons is fine. I used mixed hexanes for chromatography, extractions, and trituations daily.
|
That is a good point about isomers, but still out of the boiling point range as someone else pointed out. I was wondering if it were a hexane mix as
well, maybe they just cut it with hexane depending upon availability. After about halfway through the distillation, which was at ~70.6 iirc, I just
cranked it up to get it all through and so I really don't know what the fractions were after that besides 98.7 or so to which I stopped the
distillation. I'll probably do a test later and actually try to figure out the different fractions present and the amounts of each.
| Quote: Originally posted by BromicAcid | It's my understanding in that case so long as the added components do not add any additional hazard that they can be whatever the company wants.
[Edited on 3/11/2016 by BromicAcid] |
That's my main concern is that it is more hazardous. If this is a petroleum fraction from 70-100c then it would have to contain benzene which has a bp
of 80c or so (I can't remember specifically off hand). I really have no idea on the regulations on this, and I really don't trust companies to follow
them anyway if it's in their interest not to. I recently purchased a popular brand of naptha, naptha being classified as bp fractions from 30-90c, and
the sds said it was specifically 60-90c fractions, yet when I distilled it it didn't start coming over until 90c, most of it came off >100c, and a
large portion all the way up to 135c and there was a bunch of black tar and waxes left in the pot  . Anyway, hopefully it's just some kind of blend, as long as it's ~60-100c and no more dangerous than hexane/heptane
that's fine w/me.
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BromicAcid
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Of course, all of this assumes you have proper position of your thermometer, an accurate thermometer, and that you had sufficient reflux to get a
constant head temperature. If you're just doing a quick distill with a vigreux then your measured head temp might be off by quite a bit.
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It's accurate within a degree at *most*, iirc from previous tests it's accurate within 0.2c even. I've tested it against boiling water, I also
compared it against a mercury(or similar) thermometer during the naptha distill I mentioned (actually two mercury thermometers) and they all
registered ~135c. I've tested numerous probes with this thermometer in ice water too, although not this specific one; I've had this thermometer for
years and have used it for all kinds of applications and temperature ranges. It's cheap, but it's never given me the slightest issue.
It held 70.2-70.4c rock solid for about ~70ml of the ~125ml that I started with in the pot until I cranked the heat all of the way up, it definitely
was a clean separation up until that point and only stopped being because I essentially stopped fractionating it. The probe was just below the still
head as well so I can't see how it would be inaccurate due to its position and I did not record a measurement until condensation began to drip and the
thermometer settled its reading(there is a small delay over a mercury thermometer, from 5-20s generally, so I always wait for the thermometer to
settle). If anything it would have read too high I would think. Lastly even if they were off though it's not going to be nearly 30c off, or even ~8c
assuming it's the lowest bp heptane fraction, and as I mentioned earlier it finished at ~98.5C which is right where you would expect it to with only
heptane and water remaining.
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I have yet to do any further tests, but I did come across mention the other day that a solution of ethanol + heptane actually lowers the bp to ~70-72c
(I forget the exact number now) so it is possible that bestine is in fact 100% heptane and I had more isopropyl mixed in that I thought, I especially
do not remember now anyway.
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