bbartlog
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Question about copper, HCl... and sucrose
I did the following experiment:
- in each of two test tubes, place a 1980 US penny (3.11g copper) and 20g of 31% HCl
- in the second of the test tubes, added 1.0g of sucrose
The test tubes were then stoppered. After four months (during which the test tubes were occasionally shaken and/or opened), I removed the pennies and
rinsed them with water.
Penny in the first test tube weighed 2.85g (lost 0.26g mass) while the penny from the second test tube weighed 2.56g (lost 0.54g).
So my question is - what decomposition products of sucrose could oxidize the copper to make this happen? Why would sucrose increase the rate at which
HCl attacks copper? It certainly did decompose from the HCl (the liquid in the second test tube was black with gunk, humic acid or whatever gunk the
sucrose eventually turned into), but AFAIK the decomposition products are mostly reducing in nature. Formic acid, for example.
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Panache
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Your observation is statistically irrelevant as you need at least three samples of each experiment, averaged to one number, to differentiate the
experiments and claim a difference.
Even if the figures you quoted were averages of three, the experiment goes for a long period of time and the coins were not nitric acid stripped
before weighing. Such that you don't even know how much actual copper was in the penny or if all samples had a similar surface area available to the
acid.
If the immersion was quick, in the order of hours, then you could argue this point as unnecessary. However, over 4 months the argument for not needing
to strip as any difference would be small, fails, given the difference in the figures is still quite small.
To speculate as to the cause of a hypothetical difference is is not science, but i would guess any difference you find in this experiment is within
experimental error.
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zed
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The Copper content of 1980 US pennies is known. They are reputed to be 95% Copper.
Sucrose remaining sucrose, in the presence of acid is questionable.
Perhaps invert sugar is formed. Moreover, before a significant amount of copper was dissolved, it is conceivable that some fermentation may have
occurred.
How about applying a little qualitative analysis?
[Edited on 18-7-2010 by zed]
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bbartlog
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| Quote: | | Your observation is statistically irrelevant as you need at least three samples |
And you base this on what assumptions about random variation in the outcome? Really. I know a fair bit of statistics and I could certainly do multiple
trials in parallel if it seemed necessary, but you've basically just pulled this criticism out of thin air.
| Quote: | | the experiment goes for a long period of time...If the immersion was quick, in the order of hours, then you could argue this point as unnecessary.
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Why should that matter?
| Quote: | | Such that you don't even know how much actual copper was in the penny or if all samples had a similar surface area available to the acid.
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Considering that HCl is normally used to clean pennies to shiny brightness, that I weighed both coins prior to immersion (sure enough, 3.11g, per
spec... it might surprise you but most pennies, unless obviously corroded or mutilated, weigh in just as expected, down to the 1/100th of a gram), and
that the US Mint probably has pretty good quality control on the composition of their blanks, I don't think any of this is relevant either.
As it happens, I did this experiment because I had previously seen copper completely dissolve (in a day or so) in a heated solution of HCl and (what
started as) sucrose. Copper doesn't do that in straight HCl. But that really was an uncontrolled experiment (at least as regards the copper) and so I
prepped these two test tubes and set them aside.
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bbartlog
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| Quote: | Sucrose remaining sucrose, in the presence of acid is questionable.
Perhaps invert sugar is formed. Moreover, before a significant amount of copper was dissolved, it is conceivable that some fermentation may have
occurred.
How about applying a little qualitative analysis? |
Sucrose doesn't stay sucrose. First it hydrolyzes to glucose and fructose (rapidly), then it decomposes into other stuff, including levulinic and
formic acid, but also all sorts of other gunk. My question more or less is what exactly in this gunk would attack copper.
As for fermentation, I don't think anything can live in 31% HCl.
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blogfast25
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@bbartblog:
I think Panache's criticism is highly valid. As there was no prior reason to believe adding sucrose would make any difference, anything to enhance the
resolution of the experiment would be greatly desirable by repeating it a number of times and eliminating natural variation.
Why don't you do that, starting with clean pennies, perhaps over a shorter time? Or why not make it more interesting still and conduct an F.E.D.?
Eight treatments (tests) would allow you to test 3 variables independently AND establish natural variation at the same time: 
http://en.wikipedia.org/wiki/Factorial_experiment
You wrote:
"And you base this on what assumptions about random variation in the outcome?"
bbartblog, that's precisely the problem: that you have NO IDEA of natural variation in your experiment space, thus are unable to conclude anything
meaningful about the observed difference! 
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bbartlog
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It would indeed be easy enough to repeat the experiment with eight or twenty samples, but it will have to wait until after I move in two weeks (and
results even longer unless I run the whole thing at 100C or w/e). As for having no idea of the natural variation in my experiment space: it seems like
this objection should require at least some sort of speculation (consistent with physical law) as to factors that would result in a difference. Am I
supposed to have coated one of my pennies with lard? Left one of the test tubes in the refrigerator? Pennies in acid are a chaotic system subject to
self-catalyzed disintegration, such that even small differences in manufacture can result in a twofold change in mass loss? Anyway, while I think this
objection is dubious I don't mind running a factorial experiment as suggested. Varying the amount of sucrose could be informative in trying to
determine whether the organics are actually forming a stable copper compound or are just acting catalytically (assuming, of course, that they really
make any difference at all...).
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blogfast25
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Quote: Originally posted by bbartlog  | As for having no idea of the natural variation in my experiment space: it seems like this objection should require at least some sort of speculation
(consistent with physical law) as to factors that would result in a difference.
|
No, none whatsoever: all measurements, even the simplest ones, are subject to natural variation (mainly because all the other variables which you keep
constant in reality do fluctuate a bit). No prior idea of the size of natural variation is needed when you start up a new experiment: replication will
provide that. As the experiment stands right now it's strictly speaking impossible to infer whether the observed difference is real (causal) or due to
natural variation. I'm surprised that for such a long term experiment you didn't include replicas. Replicas could also confirm/infirm other
non-quantitative observations you may have made.
But once you've run an F.E.D. (for instance) it's valid to use the observed natural variation to gauge significance in future, closely related
experiments.
I'm also intrigued to know what it is you're trying to figure out: adding sucrose to HCl isn't something one chooses to do 'at random'.
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bbartlog
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Just trying to get some insight into what happened in a previous experiment. In that case, I wanted to see whether I could get formic acid from table
sugar and HCl. The prep I based the experiment on was the one for levulinic acid in Organic Syntheses (see: http://www.orgsyn.org/orgsyn/prep.asp?prep=cv1p0335). In their case the formic acid is a byproduct, and while the reaction they outline shows it
being produced in equimolar quantity to the levulinic acid, there's no way to know from their writeup whether that's really true since they didn't
collect it. I figured I'd just distill it out of the mess and not try to extract the levulinic acid(*).
Obviously the atom economy would be atrocious but the cheapness of the reagents made it seem like a good idea at the time. Then I cracked a
flat-bottomed 1L flask while trying to clean out the last of the black cake of carbonaceous products and I decided it wasn't as neat an idea as it
seemed - it really makes quite a mess.
But anyway, one of the cockamamie things I did was to add several copper pennies (I forget why I did this... need better notes) to the solution, and
observed that they completely disappeared over a 24 hour period while the flask was in a steam bath. Knowing from previous experience that boiling 31%
HCl attacks copper only very slowly unless oxygen is added, I thought this was odd. So I did the trial mentioned in the first post, above, thinking
that I might see something that would provide more information, or more generally just substantiate the idea that sucrose somehow helps HCl dissolve
copper.
(*) - I still haven't finished the workup; I have ~500ml of very slightly yellow, strongly acidic distillate sitting on the shelf, which probably
contains some formic acid but certainly contains quite a bit more HCl (their azeotropes have very similar boiling points). At some point I'll try to
add chloroform and distill out the chloroform/formic acid azeotrope and see if I can achieve separation that way...
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blogfast25
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Interesting. You're trying to find out whether dissolution of copper by HCl is aided (perhaps catalytically?) by the presence of sucrose.
Why not run the tests (with/without sucrose) at BP? That would be quicker and closer to the actual conditions or your synthesis. At RT you may be well
below activation energy (the numbers of your experiment seem to suggest that). Of course the formic or levulinic acid may be the real 'catalyst'...
Well worth investigating, IMHO.
Perhaps you added the copper to aid boiling (like 'boiling stones')?
Levulinic acid should make some interesting salts... Another rainy Sunday project.
Looking at the synth write up, with all that carbonisation going on, there must be a better way...
[Edited on 19-7-2010 by blogfast25]
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zed
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Glucose and Fructose are reducing sugars. They react as aldehydes. Generally, in the presence of dissolved Copper ions, they are oxidized to acids,
while the Copper is precipitated as a solid red Copper oxide.
I believe this is the basis of both Fehling's and Benedict's tests.
I'm imagining that as soon as HCl dissolves Copper from the surface of the penny.......The reducing sugars present, may be knocking it out of solution
as a fairly insoluble oxide. Eventually, black gunk. If HCl is regenerated during the process, and Copper Ions are constantly being depleted from
the solution.......The Native Copper present, could disappear pretty quickly.
It would be interesting to see what your organic fraction consists of.
Hadn't thought of it as a potential preparative method, but it has possibilities.
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Panache
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Rereading my original post i can see how you may have taken some sort of personal affront at my concise derision. I assure you however there was
nothing personal involved whatsoever. Fortunately i don't have to rebut what you said as blogast25 has done it better than i could so hopefully
things clear.
I assumed you posted your inquiry because you wanted an answer or a discussion, the answer is we don't know based on your experiment because your data
is incomplete, thats it, nothing more than that. Take it or leave it however it remains such that you cannot glean or infer anything further about
the system you describe because that's all your data offers. if you want more you need more results.
What was the other system you observed that seemed to dissolve copper so effectively?
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blogfast25
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@ Panache:
You were a little abrupt but I saw no derision. We should all stick to the facts: being a scientist means coming in for flak sometimes, a
self-correcting truth machine cannot operate otherwise!
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zed
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Upon further consideration, it would appear that there might be further reactions taking place at the metal's surface.
Aside from the action of the reducing sugars upon the copper ions present.......There could be dissolving-metal reductions taking place at the penny's
surface. The Cu/HCl system you have created, is not dissimilar to the system that Heinzelman used to reduce Nitropropenes to Oximes, via Iron dust
and HCl. Also, some Zinc is also being dissolved during the reaction, and it may play a role.
In short, it is a surprisingly complicated system, and it may involve some dissolving metal reductions, which to the best of my knowledge....are not
well understood.
So, the pungent question is....."What are the organic products?"
Since I'm in the U.S., I can buy sucrose for about a dollar a kilo. That's real cheap.
Now, tell me what kind of nifty reagents I can make it into, via your dissolving Copper reaction!
This is O-Chem. Often, the results come first. Theory follows, much later. Sometimes a century later.
[Edited on 20-7-2010 by zed]
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Panache
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| Quote: Originally posted by zed |
Since I'm in the U.S., I can buy sucrose for about a dollar a kilo. That's real cheap.
[Edited on 20-7-2010 by zed] |
Yes your sugar producers are about the most inefficient farmers in the world yet for some strange reason they thrive whereas all the other great sugar
producing communities struggle.
Maybe its because for every dollar worth of sugar your incredibly powerful sugar mafia produces they have managed to convince the American people they
should give them a further five dollars. Why? Fuck knows but let your congressmen know that you would also like five dollars for every dollar you
earn, and if its not forthcoming then STOP ROBBING THE DEVELOPING WORLD OF WHAT LITTLE IT HAS (and at the same time Australian sugar growers).
Maybe you could make a far-reaching correlation connecting all your fat people walking around to the fact that buying sugar is cheaper than breathing
into the USA (Unfortunately we have more fat people again here in Australia but cannot blame cheap sugar, i have a solution to the obesity problem
though, lifted from the Family Guy 'PUT DOWN THE FORK!').
While you're at it ask the Distinguished Gentlemen 'what the fuck is with all the guns?', i'd like to know.
Back on topic sugar chemistry is such an old area, cmps that are absolutely harmless by themselves become potent systems if the right combination of
conditions prevail. The Maynard browning reactions are very interesting field of food chemistry.
what a grumpy old man rant.
8)
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zed
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It isn't just sugar. Most foods are remarkably inexpensive in the U.S.. We have a relatively small population, a temperate climate, vast areas of
fertile farmlands, a reasonable infrastructure, AND it still rains here.
It might take some shopping around, but for that same dollar, I can often buy a dozen medium eggs or a dozen hot dogs. I could alternately a buy a
loaf of bread, or possibly a quart of non-fat milk. A kilo of chicken, or 1/2 a kilo of ground beef is a possibility. Over the holidays, as a
come-on, when I bought 50 dollars worth of groceries, I was allowed to buy a 10 kilo Turkey for about 50cents per kilo. Less than 5 dollars for the
whole bird.
Even Canadians, our next-door neighbors, are surprised by the low prices for food here.
The average U.S. wage may not be high, and the international rate of exchange isn't what it once was. But, within the US., when it comes to food, the
dollar buys a lot.
Now, I've got me a few kilos of Sucrose. What interesting reagents can I turn it into?
Because, regardless of food prices, chemical reagents aren't cheap here anymore.
At least, not from the typical chemical lab supplier.
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unionised
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"We have a relatively small population, a temperate climate, vast areas of fertile farmlands, a reasonable infrastructure, AND it still rains here."
Not to mention a 20 billion dollar farm subsidy, of which 61 million goes to sugar producers.
(data from here)
http://en.wikipedia.org/wiki/Agricultural_subsidy
And I know the EU is no better- but we admit to being socialist.
Of course the original topic is more interesting than this debate.
[Edited on 21-7-10 by unionised]
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mr.crow
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You can turn it into ethanol
Double, double toil and trouble; Fire burn, and caldron bubble
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bbartlog
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The tariff on sugar imports and the trade embargo against Cuba represent bigger indirect subsidies than those mentioned in Wikipedia. But the sugar
producers themselves are not nearly powerful enough to maintain this sorry state of affairs; they only have some local influence, mostly in Louisiana
and Florida. The main villain is the corn lobby (ADM et. al.) which does not want cheap world sugar competing with its high fructose corn syrup.
Even so sugar is relatively cheap. I already made some ethanol. Some other possibilities are formic acid, levulinic acid, and hydroxymethylfurfural...
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zed
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Two potential bio-diesel type fuels and formic acid.
Some folks have been touting ethyl-levulinate as a potential biodiesel fuel. You can make it out of any sugar type material, even cellulose.....AKA
wood pulp or old paper.
Some of these same folks would like to design and build a factory for you. You got cash? We can get you in on the ground floor!
Yet, for all of the hullaballou, nobody actually seems to be selling Ethyl-Levulinate for Biodiesel. Unless of course, you consider 80 dollars a
gallon a reasonable price for Diesel fuel.
Still, the following links to a DOE study on Levulinic acid products. It is an interesting read.
http://www.osti.gov/bridge/purl.cover.jsp;jsessionid=1F74097...
A quick check on the price of 88% formic acid, reveals that several U.S. chem suppliers are now quoting a price of 100 to 150 US dollars per 500ML.
They clearly are not interested in small accounts. For 1600 or so US Dollars you could purchase 200 Liters. About eight bucks per liter.
[Edited on 22-7-2010 by zed]
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Panache
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Wood to methanol, methanol to dimethyl ether and voila! i think toronto is running their buses atm with DME as a trial. To boot you have a ready
supply then of the king of inhalants!!
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blogfast25
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| Quote: Originally posted by Panache | | Wood to methanol, methanol to dimethyl ether and voila! i think toronto is running their buses atm with DME as a trial. To boot you have a ready
supply then of the king of inhalants!! |
King of inhalants?
Elaborate, please...
Regarding Levulinic acid, can it be purified fairly easily? I'm looking for a home made standard for acid-base titrations. Oxalic
acid is slightly out of my range, unless I had pure glycol. Purifying washing soda is a possibility. Levulinic acid seems fairly easy to produce...
Anyway, I just found the procedure for converting sucrose to oxalic acid with nitric and V2O5 by Julius B. Cohen and that's well within my means. Used
to buy oxalic as an undergraduate from a pharmacy, now they won't sell pure to any individual, I think...
[Edited on 22-7-2010 by blogfast25]
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zed
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CH3(C=O)CH2CH2COOH
Levulinic acid? I imagine you could distill it, it's a liquid. Spooky thing though. The way I remember it, it used to say on the bottle "If you
get this material in your eye, you will lose it."
Am I mistaken?
At any rate, my buddys, The Fun Guy Pharmacists, were once very interested in levulinic acid. That, was a little over forty years ago. Back in the
days when there were far fewer laws, and spiffy academic credentials could generally nullify most of the ones that actually existed.
Levulinic acid, was the key ingredient in using the Fischer Indole Synthesis, to produce 2-Methyl-N,N-Dialkyl-Tryptamines. Completely legal
materials, that guys like Shulgin were postulating, should be psycho-active.
Phenylhydrazine+Levulinic Acid---> Phenylhydrazone
Phenylhydrazone+Acid+ Reflux----->2-MethylIndole-3-Acetic acid.
Indole Acetic Acid+Thionyl Chloride, followed by reaction with Amine----> Amide
Reduction of Amide via NaBH4&AlCl3----->N,N-Dialkyl-Tryptamine
Hey! The synthesis worked. But, both the Dipropyl and Di-isopropyl 2-Methyl Tryptamines proved to be largely inactive. The advice from on high?
Try synthesizing the lower analogs. The Fun Guy Pharmacists, lost heart.
Later, I produced a lower analog on my own. Though I managed to do it with "softer" chemistry.
When I discovered that Aldrich was offering 5-N,N-Diethylamino-2-Pentanone for sale, I bought some.
In blink, I had converted it to its phenylhydrazone, and I had cyclized the Phenylhydrazone, to produce a bunch of 2-Methyl-N,N-Diethyl-Tryptamine.
Oh Baby!
Turned out to be inactive. At least, inactive in the ways, that I was hoping it would be active in. Oh well. All of that money would have corrupted
the artistic soul in me.
So, perhaps 2-Methyl-IndoleAcetic Acid is a bodacious Auxin? It could happen! All of that clever chemistry should eventually yield something.
Right?
Well, it isn't an effective Auxin. Too bad.
Leaves us with a problem. What can we do with all that levulinic acid?
Could Aminate and reduce the ketone function, then protect the amine,
followed by reducing the carboxylic acid function to an aldehyde.
CH3(CNHR)CH2CH2CH=O
Thereafter, cyclization of the aldehyde's phenylhydrazone, would produce AMT or one of its analogs. Not entirely legal in my jurisdiction. But an
interesting idea. Though it hardly solves the bigger problem.
The world seems to be able to produce mountains of Levulinic Acid, but to date, folks haven't really figured out, how best to use it.
.
[Edited on 22-7-2010 by zed]
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