Acetaldehyde synthesis

Thx DJF90!

Melgar for your silver mirror tests you do not need to make silver nitrate, just use your silver coin as an anode in KNO3 solution, you will be amazed how fast the silver turns into Ag2O, then dissolve it in aq. NH3!

I finally made some acetaldehyde in pure form!

I used the setup that I posted in my previous attempts, but this time I drew it for better understanding, sorry for the shitty line leading!

The glass tube was filled with copper oxide pressed into small granules of about the diameter of 3mm. Copper oxide was made with anodic oxidation, as it seemed to me that this way the oxide is extremely fine.

At the startup I gradually increased the temp of the khantal wire (setpoint of TC1) to 500°C, but the rate of acetaldehyde evolution is also acceptable at 400°C so I decreased the temp to 450 and kept at that. (the acetaldehyde is decompose @400°C to CO and CH4 but this was external temp control, so the temepature in the tube during operation is surely below 350C or so I think...)
It should be noted that I melted a small capillary, made of glass that protrude into the glass tube and tried to control the temperature that way (TC2), but as it turned out it was a bad idea and totally unnecessary. And I have not got a temerature controller with such a high response that this layout would require.

I directly avoided the heating of the catalyst, so the heating element(Khantal wire) and the catalyst bed was separated (Heating part~15cm, catalyst bed~15cm).

Identifying tests:

1 I led the gases into cc H2SO4! which was first get a yellow colour then got hot and charred after about 20min.

2 I led the gas into ammonical AgNO3 and heated it, a solid black precipitate was formed.

3 I led the gases into ccNaOH, first it got a yellow tint then turned into red and a tacky melted polymer with an apple like smell settled on the bottom.

4 The gas absorbs in aq ammonia and the solution on drying give a crystaline compound.

5 The NaOCl solution gets warm and turns yellow upon absorbing the gas.

6 If you drop some ccH2SO4 into the condensate (pure acetaldehyde) the condensate immediately starts boiling and if you do not stopper the bottle immediately you only get char, othervise you get two layers, a black layer at the bottom, and a yellow-white layer above it, which smells like pinewood three?!

7 I also lead the gas into Ca(OH)2 with HCHO followed the org synt volt 2 instructions, and after the required weight increase of the reaction mixture I poured some additional HCHO solution into it, (because the HCHO smell was totally disappeared after the addition), and got a yellow colour, which after keeping the mixture @ 45°C for an hour turned intense red. and a fine yellow powder settled at the bottom. (I did not have the time to isolate the product.....)

It seems to me that I forgot something, but I always have this feeling, anyways

So based on this reactions the dehydrogenation mehod, which is noted for lower by products, works at home, and can be reproduced by anyone..

After the tests, the setup was being run for additional 12 hours, during which I collected 69g of acetaldehyde, I poured it into a vial with a srew cap, upon opening the vial the liquid began to boil which is not literally means boiling, If you open the vial and follow a dust particle with your eyes you can see that it goes up and down, and a condensate on the vial walls can also be observed, furthermore on every opening of the vial I heared a 'shssssss'.

Which amazed me is that after the refrigerator there was still a lot of acetaldehyde uncondensed, I do not know how much, I can only say that the best is to use it as is, I am sure that I do not bother condensing it next time...

I will make some pentaeritriol and modify the setup to make acetic acid from ethanol with car exhaust catalyst (Pt on Al2O3) in my next project, wich I wanted for a long time, and after this success I seems to me that it wont be that hard

Any comments or improvements would be appreciated!


Attachment: acetaldehyde exp setup.rar (34kB)
This file has been downloaded 1172 times

I do acetaldehyde synth yesterday in mybody from vodka

Here are the HSGC MS results of the two samples made by completely different apparatus.. to my deepest suprise.. the composition of the two samples are identical.. eeh!!

5micro liter of the pre chilled stuff with a chilled syringe was injected to a HS ampoule and heated to 300°C the absorbing component of the GC tube was of poly ethylene glycol.

The components on the main spectrum in ascending order of the retention time:

Acetaldehyde: 1,93 min.. I can say.. that lab quality acetaldehyde can be made at home which is just awseome

Acetone: 2,17min

Butanal: 2,45min

Ethyl acetate: 2,513min

Diethyl acetal: 2,54min

Then: 2 butanon, ethyl alcohol, paraldehyde (4,8min), metaldehyde, dioxolane.

I would like to add that I used denaturated alcohol, which is mainly adulterated in my country with methyl ethyl ketone (2 butanone), that explains the 2 butanone peak, the ethyl alcohol peak is evident

Also I would like to add that more acetaldehyde can be produced by the lamp method according to the results, but it can be attributed also to error of measurements, I mean messing with prechilled 5micro litre syringe can really cause difference at paralell measurements.

More ethyl acetate is produced by the lamp method due to higher temperatures, also the amount of paraldehyde and the tetramer is more that I cannot explain taking into consideration the increase in the amount of ethyl acetate, these impurities are only a few percent of the total sample though.

Based on the results both setups are recommended for a trial to every home chemist

JIMMY! Great experiment! I was going to suggest something similar, but don't have that kind of analytical equipment to hand. I've seen people rabbiting on about the idea of building mini catalytic reactors but rarely hear about practical attempts and have never seen a spectrum from one.

I'm kind of busy and can't read back to your other posts right now, but did you try depositing the copper onto zeolite for the cake? This is mentioned all over the patents regarding copper catalysts, as well as how trace impurities in the copper affects the process. Like, I think zinc helps produce MEK or butanal in the product, or something along those lines.

From memory, they use ?ZSM-10? zeolite as the support. The vast surface area the structure presents accelerates the catalysis. The specific pore size seems to also influence the selectivity of the process.

Of coarse, the patents also discuss how they deposited the copper from solution (easy stuff). Google around "ethanol copper zeolite patent" and you'll be underway in no time.

DCM, I've never seen bearing a flammable sticker in real life. I have a tank of paint stripper, a container of pure DCM for everyday solvent cleaning and an up to date reagent grade bottle from a laboratory supplier. None of them have flammable stickers. But it has now been upgraded to a potential carcinogen. Meaning it can have a skull and cross-bone sticker in place of it's old harmful cross. I bet all the older chemists aren't impressed! I'm not! Hopefully it's not another benzene. I haven't seen these stickers on paint stripper yet, which is odd as they are very high concentration sources of the solvent. They're still using the harmful sticker on both stripper and the reagent bottles.

I have a bone to pick with people constantly referring to things as toxic, when they're actually more like harmful. It seems anything with the potential to cause any harm is upgraded to toxic now. Whilst things that do present real risks (like cancer) still have a harmful sticker on them. Since irritant also exists, it makes me question precisely what harmful is still being used for by these people. To me, toxic means it creates a long lasting risk at everyday exposures. So benzene would be toxic to me, as it damages DNA and creates a long lasting, carcinogenic risk. DCM would fall into the same category for myself. Following that pattern of logic, I'd nominate DCM for a harmful cross (with harmful / irritant under it) and a skull and cross-bones (with carcinogen under it), as it is both immediately irritating and slightly dangerous in terms of exposure but also capable of longterm damage. Cyanide would be harmful, as (despite it being extremely dangerous) it does not accumulate or present a longterm risk. I would seriously love for them to produce a new sticker visually indicating something is a suspect carcinogen, like a simple double helix (or to write this under the skull and cross-bone, as they already do under the blanket, seriously outdated term poison). I would also like to see the NFPA 704 rating system used on the containers. It's on the sides of the trucks, it should be on the containers people will actually be handling. I worry when I see MSDS that take the safe route out and blanket list everything as dangerous to cover against liable action. It's like saying a relatively harmless drug is in the same category as heroin. Causing users of the former to think the latter will be the same in terms of risk. Failing those changes to the stickers, or in addition to them, I'd like to see an accumulation sticker to indicate whether acute exposure is going to build up. And I want all of those changes regulated by someone other than the chemical companies, who will plaster them all over everything as the carcinogens start lining up. Either way, what I'm saying is that I'm not happy with the level of information the quick references provide, and think it could easily be improved upon. And students should be taught precisely what each of the few new variations means.

In terms of extracting DCM from paint stripper, get the cheapest, nastiest stuff you can. They usually have more DCM in them. It's usually around 50-70%. It will also be mixed with a polymer to make it thick enough to paint onto vertical surfaces without it immediately running off or evaporating away. Before you distill it, wash it with some water. The water should start looking like someone's cum in it. There'll be opaque white goo floating around in it (the polymer). Throw out the wash, distill the remaining organic. Using a saline wash may help prevent loss of DCM, as some of it will end up in the aqueous phase using pure water. If you go straight to distillation with the polymer, you may cake it onto the flask. It boils like crazy under only moderate vacuum, but it's also not going to liquefy at the condenser all that well, so it'll end up spitting out the pumps exhaust. Go with atmospheric distillation given that it boils so close to body temperature and doesn't break down. It's a fairly 'fun' distillation given how easy it is compared to oxygen sensitive, high BP things that bump under vacuum.

Bulk pyridines from a catalytic reactor? One thing that really interested me about this method of producing aldehyde was that the product is part of the one pot pyridine synthesis (throw it all together, stir away). One can cheaply and easily ferment hundreds of liters of ~20% alcohol at home in a week or two using raw sugar and distillers yeast. The excess water can be quickly and cost effectively stripped by dumping in a bag of plaster I believe, then decanting from the cake. The remaining liquid can then yield 100% ethanol under a more reasonably sized vacuum distillation (which breaks the azeotropic mix). You could also simply warm up the drum with an immersion heater (even the plastic ones will take the heat) and gently strip the azeotrope off, then run it through a smaller volume vacuum distillation in the glass. Homebrewers of moonshine go as simple as putting a plastic bucket of alcohol inside another plastic bucket with a lid and then warm up the alcohol containing bucket, letting the azeotrope condense on the sides of the outer bucket. Catalytically produce aldehyde from the vacuum distilled azeotrope, feed it into the one pot. I wonder if this same catalytic method works for methanol to formaldehyde (another component of the one pot). Yes, I know about the niacin method. But this seems reasonably realistic if you wanted larger volumes of pyridine. Or, for myself, just for the fun of doing something involving both biology and chemistry. I've brewed up huge volumes of alcohol using distillers turbo yeast and raw sugar in a big 210l plastic storage drum with an aquarium heater. The drum was formerly used to internationally transport olives. Yum! And even featured a very nice screw on lid that could easily be ported for an air pump, lock or vapor outlet; with your condenser possibly being as simple as a roll of PB / PEX plastic plumbing pipe, secured to the lid using a push fit cold header tank connector (they sell them specifically for this pipe and they feature a rubber gasket). I just loosely put the lid on and let it go. It was so tough I could kick it around the floor and barely scratch it. It all cost next to nothing and took next to no effort. I 'sterilized' with a quick rinse of boiling water. I rolled the culture up in a 15l container before hand, using more clean methods (e.g. boiled water), then inoculated the 210l of water at 50% of the recommended sugar concentration, so as to avoid thermal death. Then poured in the remaining 50% once it had calmed down a little. I was using 25kg sacks of sugar from a bakery supplier (real, real cheap). The water in the bulk drum was straight from the tap. The rate of fermentation was hilarious. You can also yield other useful building blocks, solvents and reagents from the process. It's like a total synthesis, but without the total overkill. The appeal of going from something as simple as sugar, water and yeast is high for myself. In addition, yeasts can perform other interesting feats of biochemical manipulation. And the raw product of this method is a highly valued resource for those who enjoy getting very drunk, very quickly, very cheaply. Might I suggest sampling some 100% ethanol, or buying a nebulizer and blowing O2 through it at the same time (you could use the pump that comes will a full kit for aerating the fermentation, not that it really needs it, but it might help churn up the mix). Caution, ethanol + pure O2 + drunk people = extreme fire hazard. These methods would also be very easy to lay down at the small scale, starting from some off the shelf alcoholics grade, no name vodka. The fermentation is bulletproof, it's about the oldest, most well studied biochemical method committed to text. You'd yield around 40 liters of 100% ethanol from a 210l drum fermentation. And foaming isn't an issue at all given how simple the sugar supply is; it doesn't foam. I also doubt you'll get into that much trouble, if any, distilling your own alcohol if you can demonstrate that it's not intended for consumption (which is what the tax is there for). When it comes to chemicals, the law is more concerned with why you have it and how safely you can handle it rather than the fact you have it in the first place.

[Edited on 20-6-2010 by peach]

Quote: Originally posted by Ephoton

you are right there meglar TCCA makes nitriles from aminoacids very easily.

I requested a reference for this in the references section. You need pyridine tho

Quote: Originally posted by mr.crow

Quote: Originally posted by Ephoton   you are right there meglar TCCA makes nitriles from aminoacids very easily. I requested a reference for this in the references section. You need pyridine tho

See! Everyone loves pyridine!

Quote: Originally posted by peach

I have a bone to pick with people constantly referring to things as toxic, when they're actually more like harmful. [...] Cyanide would be harmful, as (despite it being extremely dangerous) it does not accumulate or present a longterm risk.

I also read patents how to make catalysts that for example increase the ethyl acetate yield, but I think the only product of value of catalytic dehydrogenation of ethanol is acetaldehyde, if I were to make ethyl acetate I surely will not make it this way.

The making of some hundred of pressed copper oxide pellets was really a pain. I was glad when I finished, that I will not have to in my rest of my life. I have the shivers of the simple thought of a 4%Zn 6%Mn 10%Co 80%Cu homemade catalyst, but If you have the time to make it I will be happy to try it out

I took a photo about the CuO catalyst, (before and after shots)
I also took some catalyst pellets after a 12 hours of run and broke them to show that also the inside parts are reduced, so It must be porous.

Attachment: CuO catalyst.doc (96kB)
This file has been downloaded 1059 times

[Edited on 21-6-2010 by Jimmymajesty]

Quote: Originally posted by watson.fawkes

Under this theory, cyanide would be non-toxic.

It'd be classed as harmful, since it neither accumulates or causes permanent damage; it actually burns off quickly compared to other chemicals. Alcohol and tobacco (do they have a chemically additive sticker? ) are both harmful and toxic at levels that are used everyday by vast numbers of people. They are also both flammable, alcohol for obvious reasons and cigarettes because they contain burn enhancers. They are responsible for hundreds of millions of deaths and they lack all three labels. As is table salt lacking it's harmful / toxic sticker due to the heart disease it causes when exposure is at realistically prominent, everyday excesses.

Quote:

The making of some hundred of pressed copper oxide pellets was really a pain. I was glad when I finished, that I will not have to in my rest of my life. I have the shivers of the simple thought of a 4%Zn 6%Mn 10%Co 80%Cu homemade catalyst, but If you have the time to make it I will be happy to try it out

Quote: Originally posted by jon

cyanide became safe to handle?? did i just read that???? or am i on drugs?

They're now planning to use H2S for a form of suspended animation of seriously injured casualties on the way to surgery. They worked out that a very precise dose of H2S antagonizes (blocks) the sites that would be damaged by oxidation when normal homeostasis wasn't functioning. They've been testing it on mice and the results are so positive they're going to human trials. I think they'll be injecting it dissolved in solution. The 'victim' also needs cooling in an ice bath.

I don't want to start arguing, but it's somewhat ironic you're calling it jargon when you'd likely have a fit on me if I started using none standardized names for reagents and solvents. I know what you're saying, but I think jon is joking.

He's actually illustrating my own point perfectly well. In that people now assume harmful means safe to handle. Whilst genuine lab suppliers are still shipping things that should now be labeled toxic as harmful. It may as well not exist as a label.

And I know none of this has anything to do with aldehydes and I hope I haven't annoyed you. I didn't mean to do so if I did, I just don't like the blanket use of the word toxic, as it desensitizes people to the real risks. I'll shut up now.

[Edited on 28-6-2010 by peach]

I never succeeded in recovering the acetaldehyde from dilute solutions, I usually got an unpleasant smell, that is far away from the smell of pure acetaldehyde. Also the acetaldehyde does not like to be acidified/basified you will get either a yellow solution with and acrid smell or an orange sticky polymer with an apple like smell, depending on the pH that you disturb poor little CH3CHO molecule

Quote: Originally posted by Hoveland

What is the reaction with acetaldehyde when the pH goes to high or too low? I found an excellent explanation about aldehydes: http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/aldk... which did not seem to tell what these reactions might be, but as a side note, I did learn "Although the addition of water to an alkene is exothermic and gives a stable product (an alcohol), the uncatalyzed reaction is extremely slow due to a high activation energy . The reverse reaction (dehydration of an alcohol) is even slower, and because of the kinetic barrier, both reactions are practical only in the presence of a strong acid."

Practical Preparation

Quote: Originally posted by jon

cyanide became safe to handle?? did i just read that???? or am i on drugs?

Help! PCC method...

Hello all, I'll begin with the formality of introducing myself as "a long-time lurker, 1st-time post-er". I have a question which should be simple, but I can't seem to find a proven, precise method on ANY search engines... Lots of theory and stoichiometric equations, but nothing specific enough for me to confidently proceed... So here goes:

I've succeeded with the pyridinium chlorochromate (PCC) prep, and am ready to oxidize my dry ethyl alcohol; I intend to use celite, silica, 4A sieves. I've read all the literature I could find for oxidizing primary alcohols to aldehydes, but it seems like nobody's bothered to describe a specific workup procedure, since its such a straightforward reaction. I don't want to waste my reagent! Not a fan of CrO3

Can anyone point me in the right direction? I've got an arsenal of pure, dry solvents to chose from, EXCEPT that I lack diethyl ether... just have petroleum ether(s) available.

The original paper [Tetrahedron Letters, No. 31, Corey, E.J. and Suggs, W., 'Pyridinium Chlorochromate...'] describes a TINY-scale procedure, with 1.5mmol PCC in 2mL DCM, and '1 mmol in 0.5 to 1.5 ml of CH2Cl2' of Alcohol X...

Does anyone have experience with this? I'm not comfortable with blindly scaling-up the given molar ratios; I'm thinking more along the lines of ~1mol of PCC.

Any help would be greatly appreciated, and I'd be glad to post results and pics.

Quote: Originally posted by cold_electrician

I've succeeded with the pyridinium chlorochromate (PCC) prep, and am ready to oxidize my dry ethyl alcohol; I intend to use celite, silica, 4A sieves. I've read all the literature I could find for oxidizing primary alcohols to aldehydes, but it seems like nobody's bothered to describe a specific workup procedure, since its such a straightforward reaction. I don't want to waste my reagent! Not a fan of CrO3 Can anyone point me in the right direction? I've got an arsenal of pure, dry solvents to chose from, EXCEPT that I lack diethyl ether... just have petroleum ether(s) available.

Quote: Originally posted by cold_electrician

Does anyone have experience with this? I'm not comfortable with blindly scaling-up the given molar ratios; I'm thinking more along the lines of ~1mol of PCC.

Quote: Originally posted by hissingnoise

I don't know the metaldehyde content of slugkiller pellets but heating to ~80°C breaks the tetramer so that acetaldehyde might be (carefully) distilled from the material!

Quote: Originally posted by S.C. Wack

How many grams of acetylene in a #3 cylinder?

Acetaldehyde from Acetone

Substitution of Sodium Dichromate

As you all know, this week I am especially obsessed with acetaldehyde- and I would like to make some of my own

This looks like the best and most productive way I've seen so far.

http://www.scribd.com/doc/45868796/preparation-of-Acetaldehy...

Problem- I don't have any sodium dicromate

Possibilities: I have ammonium dichromate. If I adjust the stoiciometry- could this work? I also have potassium chromate. I know acids convert this into a dichromate. If K dichormate will work, can I just throw some extra acid in solution 1 and hope it works?

Thanks in advance!

Quote: Originally posted by ScienceHideout

http://www.scribd.com/doc/45868796/preparation-of-Acetaldehy...

So? Even if it is a school report, it is a valueable resource. The author of this has quite a few other respectable documents. Of course, not as venerable as an O-Chem text book, but in my mind- this procedure it describes is useful.

I have seen other sources that use dichromates to make acetaldehyde from acetone- so why do we have to declare that this is half-assed becuase it lists 8 synonyms for water?

That or he is a pretty sucky chemist!

But us chemists like to experiment- We know that you can make acetaldehyde from this procedure, as stated in the very first post in this entire topic.


So, if we give this persons procedure the benefit of the doubt, perhaps we can make it better, and perhaps rewrite a scholarly paper on it!

[Edited on 24-11-2012 by ScienceHideout]

[Edited on 24-11-2012 by ScienceHideout]

Quote: Originally posted by ScienceHideout

Check this out: http://lecturedemos.chem.umass.edu/chemReactions5_4.html The only thing that I can't quite figure out is how to capture the acetaldehyde that is formed. Perhaps we can condense it along with acetone, convert it to the trimer, and reproduce te acetaldehyde?

Quote: Originally posted by Organikum

Dehydrogenation of EtOH: Coppercatalysts with ZnO, CoO and CrO3 as structural promotors. The reaction temperature is limited to 270°C - 330°C for to reach a selectivity towards acetaldehyde of 95%. Yields (per pass) are limited to 30% to 50% this way. The hydrogen produced as byproduct is clean enough for use in catalytic hydrogenations. The preparation of the catalyst is a standard procedure for precipitating metal catalysts onto a metal support - I think I got it from some patents. It is tried and true. (it cost me a damned long time to find out what "structural promotors" means) If you precipitate copper on zinc you will see that the copper grows on the zinc in form of fractal "trees" providing a huge surface area later in the dehydrogenation. Thats the whole trick of the "structural promotion" of zinc. A coppertube filled with copper-scrubpads works fine if the amounts of acetaldhyde needed are not to large (less than one liter) - important is to activate the copper by first oxidising it - blowing air through the tube at red dull heat - and reducing it again what can be conveniantly done by passing ammonia or hydrogen through the hot tube. It actually works also without this activation step. but yields are low.

Quote: Originally posted by Polverone

Navarone, Navarone's Ghost, Anubis: Your writing is sloppy, riddled with errors, and provides little of interest even when one ignores its technical blemishes. I have valuable advice for you: The next time you post anywhere other than Whimsy, provide enough details to show that you've already investigated the topic you are talking about. The investigation could be an experiment that you have conducted, or that you have seen someone else conducted, or even something that you read in a book or journal or on a reputable website. Whatever you post about, you should make a respectable effort to spell words correctly and in their entirety, and to use such perfect punctuation and grammar that no 7th grade teacher of English would hesitate to give you an "A." If you don't post about a technical subject, and don't post in Whimsy, then your prose should be rich and beautiful in addition to technically flawless. If Vladimir Nabokov's ghost isn't green with envy, you have failed. I hate cluttering up perfectly good threads with this sort of off-topic discussion, so let me be extra-clear: If you are incapable of following the above advice, kindly go home and eat bleach and die.

Quote: Originally posted by Nitro-esteban

Could potassium permanganate be used to oxidize ethanol or other alcohols? I have plenty of it but it is a carcinogen so I don't want experiment with it unless there is a good chance that it will work.

Here is some pictures if people are interested:

<img src="http://i1103.photobucket.com/albums/g469/plante1999/DSC00187_zps1749ce00.jpg" width="800" />




I'm actually doing a test with non-regenarated dilute palladium chloride solution and propylene, due to my easy access to it, see the mapp pro thread.

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[Edited on 7/8/13 by bfesser]

[Edited on 8-7-2013 by plante1999]

Ok, so I did another test, with ice cooled water, and it still didn't condensed much acetaldehyde, It did however made lots of HCl gas, I really need more copper acetate buffer in the reaction mixture, I'm pretty sure I also need to add new HCl now. I pretty much made the same smell as when you oppen a bottle of 30% HCl in the summer.

I will need to pass the gas in water I guess.

When the procedure will be successful, I will work on making formaldehyde from Silver and methanol, and make pentaerythriol, for the pyro out there. However, I will probably try to polymerise each to paraformaldehyde and metaldehyde respectively. If anyone want to help me in this project, there is a link in my signature.

here some pictures:

The makeshift apparatus, the white on the reaction flask is due to burning residue:

<img src="http://i1103.photobucket.com/albums/g469/plante1999/DSC00193_zps7d85ec01.jpg" width="800" />


The catalyst solution being used up:




The catalyst solution being regenerated:



The regenerated solution:



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[Edited on 7/14/13 by bfesser]

Using acetone

Formation of Lactate from Sugars

Quote: Originally posted by Random

Is there a procedure for formation of lactic acid from glucose? Could saccharose be used too? Lactobacillus can be obtained from yoghurt i guess.

Oxidation of lactate to acetaldehyde with H2O2

Quote: Originally posted by bbartlog

Lactic acid can be oxidized directly to acetaldehyde without prior conversion to pyruvic acid, by adding dilute hydrogen peroxide to ammonium lactate solution. At one time this was used as a method for assaying lactic acid in blood (a hundred years ago). Too lazy to dig up the reference but I think Dakin actually published something on this topic. [Edited on 12-10-2013 by bbartlog]