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garage chemist
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Carbon Disulfide from sulfur and charcoal
Introduction
Four years ago, BromicAcid was the one who did several experiments on the amateur production of carbon disulfide. Although he once obtained a very
small amount of product, he was not able to devise a working method to produce useful amounts of this chemical.
Neither was I. We both heated sulfur and charcoal together in flasks and retorts, in hope to get a distillate of CS2. The only thing I ever managed to
do was foul up my glassware.
Paraffin and polyethylene did not give any CS2 with sulfur either, only large amounts of H2S.
We all knew from the beginning what the problem was: the reaction between charcoal and sulfur requires a temperature far above the boiling point of
sulfur, so that heating a charcoal- sulfur mixture in a retort always only results in the sulfur boiling off, without any noticeable reaction.
Our problem was firstly the lack of a suitable apparatus to react superheated sulfur vapor with charcoal, and secondly the inability to heat the
charcoal to the temperature of 900°C that is required for a sufficiently fast reaction between the two elements.
The first thing I realized was that a bunsen burner is unsuitable as a heat source to bring useful amounts of reactant to 900°C.
Placing several burners in a row under a quartz pipe results in a temperature of just about 650°C, as the synthesis of ketene on orgsyn shows.
One also has to abandon the "retort" apparatus design in favor of a hot-tube design.
This is a perfect application for a tube furnace.
In cooperation with Len1, I was able to, for the first time, produce a useful amount of carbon disulfide in an amateur laboratory and document the
process on the internet.
The uses of CS2 to the amateur chemist are many- apart from its very good solvent properties, it can also be chlorinated to carbon tetrachloride, a
substance that is very hard to get today.
Warnings
This is an unusually dangerous procedure. Carbon disulfide is very volatile, extremely flammable and has a self-ignition point of 100°C. Having to
make it at 900°C means that there WILL be a fire if there is a leak in a hot part of the apparatus!
An even greater danger is the toxicity of the hydrogen sulfide byproduct that the offgas contains. The condensation apparatus must be located under an
efficient fumehood!
Carbon disulfide is rather toxic as well.
As H2S and raw CS2 have very offensive odors, one surely understands that this is a very smelly procedure. Consider the neighbors.
Apparatus and Operation
The reaction vessel is a fused quartz tube, 26mm outer diameter and 1 meter from end to end, with two NS 29/32 male joints on both ends.
Note: If quartz joints are to be connected to borosilicate joints, the inner joint must be the one made of quartz, otherwise the
larger thermal expansion coefficient of borosilicate would break the outer joint upon heating.
The tube was filled with crushed (not powdered) beechwood charcoal on a length of 50cm, the charcoal was held in place at both sides via ceramic wool
plugs. The charcoal bed must not have too high an airflow resistance.
A closeup of some larger charcoal pieces- most of the rest was of much smaller size.
The tube was then placed in the tube furnace, and a 250ml borosilicate round-bottom flask filled with 120g sulfur attached to the left side.
Before the flask was attached, the charcoal bed was briefly heated to 800°C in the tube furnace to drive off any volatile matter it
contains. This is extremely important!
The charcoal contained a fair amount of adsorbed moisture- quite some water condensed to the left and right side of the charcoal bed. The condensed
water was driven off by heating both ends of the pipe with a bunsen burner until it was completely dry on the inside.
Failure to do this will result in large amounts of hydrogen sulfide being generated, by the reaction:
CS2 + 2 H2O ---> CO2 + 2 H2S
This reaction already takes place at 150°C and the equilibrium completely lies on the H2S side.
So precalcination of the charcoal bed and driving the moisture out of the system is very important both from a safety and yield perspective.
Some H2S will still be generated though.
On the right side, a 250ml three-neck round bottom flask was attached via a 45 degrees bent adapter. A Dimroth condenser was attached to the middle
neck, the third neck was stoppered.
From the top of the dimroth condenser, a hose led into the fume hood in order to dispose of the toxic offgas (contains H2S). The joints were later
greased. The black bucket was then filled with ice water for cooling, and ice-cold water circulated through the condenser.
With everything in place, the charcoal bed was then heated to 900°C and the sulfur heated with a bunsen burner in order to distill it into the pipe.
As the sulfur vapor reached the charcoal bed, a yellowish white fog soon appeared on the right side. Unreacted sulfur condensed directly after the
furnace and soaked into the ceramic wool. The electronic thermometer is also visible here.
The whole apparatus running:
We were delighted when we saw that drops of nearly colorless liquid were condensing on the inside of the flask- this was our product! The white fog
prevented us from seeing how much was accumulating until the end, when the ice bath was removed.
The Dimroth condenser contributed very little to the condensation- only very small amounts were condensing in it, almost all of the product was
condensing in the flask before.
We stopped after most of the sulfur had distilled into the pipe.
Upon removing the ice bath, we saw that a generous amount of yellowish liquid had accumulated in the flask. Success!
This was then transferred into a 100ml flask and distilled in a small distillation setup in order to remove the dissolved sulfur. Ice water was used
in the condenser.
The liquid passed over almost completely at a constant temperature of 46°C, confirming its identity.
A small amount of sulfur remained in the distillation flask.
The product: 44g of crystal clear carbon disulfide!
A few drops burning, it burns with a blue flame and deposits sulfur on the glass dish due to incomplete combustion:
Results and discussion
We weighed the unreacted sulfur in the sulfur boiler flask and in the tube back and determined a CS2 yield of about 50% in regard to the reacted
sulfur. I do not have my lab notes here at the moment- more exact values will be added later.
This leaves the question: where did the other half of the reacted sulfur go?
During the process, we briefly attached a washing bottle filled with water to the offgas hose, and almost no bubbling was observed. However, this was
during a period of low flux through the tube- at the beginning of the synthesis, we had a very large flux, and it is possible that during this time a
considerable amount of CS2 escaped uncondensed.
Another theory would be that the sulfur was lost to H2S.
There certainly was a strong smell of H2S in our garden, at the exhaust of the fume hood!
This would mean that there still were some hydrogen-containing compounds in the charcoal after calcination.
Ullmanns Encyclopedia says that the offgas contains H2S, so this seems to be the case to an extent.
Problems and possible improvements
At the entry side of the tube, a large amount of highly viscous liquid sulfur accumulated in the portion of the tube not inside the furnace. The next
time, I will certainly completely insert the entry side of the tube into the furnace to prevent this.
Ice water does not seem to be cold enough to completely condense all of the CS2, as seen by the only 50% yield.
The next time, I will lead the offgas through a cold trap cooled with ice and salt in order to try and condense some additional CS2.
The dimroth consenser also seemed quite useless, as it wasn't contributing to condensation- maybe I will leave it away the next time.
The sulfur boiler could be improved by connecting the flask to the pipe via a 45° bent adapter so that it is inclined in such a way that it can hold
more sulfur- I would then be able to use ca. 200g sulfur per run. The adapter would have to be insulated with glass wool.
I will soon do the preparation a second time and make pictures of the improved procedure.
[Edited on 22-5-2008 by garage chemist]
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Polverone
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Excellent work, gc! You and len1 have really convinced me of the utility of electrically heated high-temperature apparatus for the advanced amateur
lab. It seems many barriers come down when you're willing to build and operate electrical furnaces.
PGP Key and corresponding e-mail address
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garage chemist
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Thank you. Yes, I am a big advocate of electrically generated heat in the laboratory in cases where the bunsen burner just doesn't do the job.
For 900°C, even nichrome wire will be sufficient, it doesn't have to be Kanthal. You could wind the nichrome wire directly onto the quartz pipe and
wrap it all in ceramic wool blanket.
Temperature measurement is crucial though. You have to get or make a thermocouple.
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DerAlte
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A splendid example of experimental chemistry, Garage Chemist. As Poverone says, a tube furnace of this nature is a great asset. If it were not for the
cost of quartz or ceramic tubes, I feel more would attempt to build such an apparatus. The ability to easily control temperature compared with other
forms of heating is a great bonus.
Der Alte.
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Magpie
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Excellent work, as usual, GC! You and Len are certainly setting the standard for home chemistry. Thanks for the nice write-up and great pictures.
There is nothing that thrills me more than see a home chemist overcome the oftentimes considerable obstacles to making a reagent.
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BromicAcid
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Excellent to see this in action! Finally, useable amounts of CS<sub>2</sub> at home!
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Klute
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Bravo Stephan! Very impressive!
You just keep on knocking barriers down! Would you have been born 100 years ago, your name would be all over scholar chemistry books 
Any plans with the CS2 at the moment? Chlorination? IIRC it it's an excellent solvent for Friedel-Krafts alkylations also.
Be carefull with that bloody H2S by the way...
\"You can battle with a demon, you can embrace a demon; what the hell can you do with a fucking spiritual computer?\"
-Alice Parr
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Fleaker
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Bravo indeed Stefan, and Len too! NERV and I are both very impressed; this is something we have long wanted to do.
Did you two collaborate in person?
"We weighed the unreacted sulfur..."
"We were delighted when we saw that ..."
It sounds like Len made a trip to Europe. :-)
I wonder if the other half of the unreacted sulfur isn't stuck in the walls of your quartz tube or adsorbed onto your charcoal? What type of charcoal
did you use? Would activated carbon of high purity work for this as well?
Neither flask nor beaker.
"Kid, you don't even know just what you don't know. "
--The Dark Lord Sauron
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Magpie
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| Quote: |
You just keep on knocking barriers down! Would you have been born 100 years ago, your name would be all over scholar chemistry books
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I agree, Klute. Stefan's lab always has the look of a seriously productive workspace. It reminds me of some those pictures of Wohler's laboratory.
Yes, Fleaker, I was also wondering if Len was there in person. If so, I'm doubly jealous! 
[Edited on 22-5-2008 by Magpie]
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garage chemist
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Yes, Len and I did collaborate in person. He made a trip to europe and visited me, some german labware suppliers, and friends in europe.
No, we removed the unreacted sulfur from the tube as good as possible, and at 900°C really no sulfur is being adsorbed to the charcoal- it rapidly
reacts with it, after all, and the product is a gas then. We briefly heated the charcoal to 1000°C after the experiment and absolutely no gasses
were being given off. After cooling down, the recovered charcoal was completely odorless. I can try burning some of it in order to see if it gives any
SO2, but I'm sure this will not be the case.
Upon reading some old literature on early manufacturing methods for CS2, they say that the sulfur first reacts with the impurities, especially
hydrogen and oxygen, in the charcoal before it reacts with the carbon. So one probably gets more H2S at the beginning.
I actually already had some 400ml of pure commercial carbon disulfide in my cupboard for years, and did some experiments with it- synthesis of
thiocarbanilide, and phenyl isothiocyanate from this- but it was expensive, and very difficult to obtain, so I want to be able to make my own CS2, a
goal that I have now accomplished.
I might do its chlorination then, to obtain trichloromethylsulfenyl chloride and thiophosgene. CCl4 I'll probably also make, just for the fun of it,
as I already have a liter of that as well- but I can't buy more of it, that's the issue, and it's the fun of the synthesis that matters to me.
About activated carbon: This could work, but it could aswell not work at all.
Ullmann says that the type and quality of the charcoal is extremely important, as the wrong charcoal requires higher temperatures for satisfactory
operation. Charcoal from hardwood is preferred, and beech is hardwood I think.
Activated carbon is something else than charcoal.
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garage chemist
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Unfortunately, my digital camera broke. So I will probably not be able to take pictures of the improved CS2 synthesis tomorrow, unless I can borrow
another digicam from someone.
So I hope you won't be disappointed if I can only add a written report of my changes in the apparatus and method and how they affected the results of
the synthesis.
What I will do is connect the sulfur boiling flask to the quartz tube via a bent adapter so I can fill in more sulfur, and lead the offgas from the
condenser through a cold trap cooled by ice and salt.
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woelen
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Great job!
Garage chemist, I can only say WOW to what you have achieved! I think it is a great achievement that you can do this in a safe manner in a home lab,
and it indeed shows that home chemistry can be done at a high level!
I am looking forward to read about your improved setup and your experiences with that. This is not the type of home chemistry I can do (lack of
resources and lack of suitable place to build up such setups), but I really enjoy reading about it.
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DJF90
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Well done garage chemist, you must be thoroughly pleased with your progress and the amount of crystal clear carbon disulphide you have produced (44g
is about 34ml yes?). So whats next? First SO3, now CS2, perhaps the next obstacle for you is white phosphorus?  Keep up the good work; your write ups are always a pleasure to read and also well written 
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Formatik
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Very well done, garage chemist. I've tried to make CS2 in pipes and also found that the dry sulfur mixed with carbon, it tends to vaporize prematurely
unreacted and cause quite a smell. Do you think it would work to use a separatory funnel and "drip" a padded and pressed mixture of sulfur and carbon
onto a hot metal in a pipe and quickly close the funnel and the CS2 leads out into a condenser? Like this.
[Edited on 25-5-2008 by Schockwave]
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not_important
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you really need to lead the sulfur over heated carbon, or heat the sulfur so hot that it heats the surface of the carbon high enough to promote the
reaction Attempting to heat a mix using most heat sources will result in the sulfur vapourising before the mixture gets hot enough to react much.
You could try blowing powdered sulfur and carbon through an thin arc, like the old nitrogen fixing furnaces. But that sounds more difficult than the
hot tube method.
-------
If you were to lead steam over the charcoal at 200 to 300 C for awhile, most hydrocarbons should be removed. Follow that with CO2 during the time you
preheat the charcoal to reaction temperature and you should oxidise away any remaining combined hydrogen.
Note that sugar charcoal is very low in mineral content, and if you don't live in the USA is pretty cheap to make.
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Sauron
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Admirable work, guys!
Muted only by the modest amount of product.
If a liter, or ten liters, CS2 is needed, purchase would still be the only practical option. I doubt that you would want to do this 20 times to get a
liter of CS2 and scaleup does not seem very practical. The hazards will still be there in any case.
CS2 is some of my favorite stuff as you both will know from reading my posts. For making CCl4, or for use as a solvent, it has unique properties. But
I need rather a lot of it.
Sic gorgeamus a los subjectatus nunc.
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Jor
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| Quote: | Originally posted by DJF90
Well done garage chemist, you must be thoroughly pleased with your progress and the amount of crystal clear carbon disulphide you have produced (44g
is about 34ml yes?). So whats next? First SO3, now CS2, perhaps the next obstacle for you is white phosphorus? Keep up the good work; your write ups are always a pleasure to read and also well written |
Garage chemist already made White P
I think the writeup is on versuchschemie.
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garage chemist
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Alright, did the synthesis again. I put a bent adapter between sulfur boiler flask and pipe entry.
Result: The sulfur vapor didn't ever reach the pipe entry no matter how long I heated. Even wrapping glass wool around the adapter to serve as thermal
insulation did not improve the situation.
The glass at about 450°C simply radiated too much heat.
I then got a 500ml flask, poured the molten sulfur into it (amazingly, the flask survived having molten sulfur poured into it)
and directly attached it to the pipe entry. This did hold the 150g of sulfur I was using without spilling into the pipe.
Heating this with the bunsen burner did only produce very low flux through the tube- the flask also radiated too much heat. The sulfur was condensing
at the upper half of the flask.
Things seemed bad, but then I got an idea: I have a bunsen burner made for natural gas, which has a far lower specific combustion heat than propane,
and an accordingly larger nozzle.
When hooked up to propane, it makes a 40cm high flame!
I then used this as the heating source, which was actually *too* powerful, I had to throttle it down somewhat in order to get a sensible sulfur flow
through the tube.
CS2 was again condensing steadily on the walls of the receiver flask.
I also led the exhaust gas through a cold trap kept at -20°C throughout the entire synthesis.
Surprise: Less than 1ml of liquid condensed there over the course of the synthesis!
This is a very important observation. It shows that 0°C (receiver in ice bath) *IS* enough to condense about 95% of the carbon disulfide, and an
additional cold trap does not contribute significantly to yield.
So now I know that I don't have to add a cold trap in subsequent runs!
Sadly, I can't give an exact figure of yield- I spilled a significant amount of the raw, yellow CS2 while transferring it to the distilling flask.
I got about 46g of distillate, so with the loss considered, I can safely say that I had made a somewhat larger amount of CS2 this time.
This time, I also got a very large amount of unreacted sulfur in the pipe, almost large enough to flow into the receiver flask.
This might have had to do with the fact that during the second half of the synthesis, the flux of sulfur through the pipe was very strong so some of
the sulfur did not have time to react with the charcoal.
I also used somewhat coarser charcoal pieces this time as opposed to the dust I used the first time.
Next time, I will pay more attention to the grain size of the charcoal. I should screen it to 1-3mm grain size- I need to get some sieves for this.
I have abandoned the bent adapter idea in favor of a 500ml flask heated by the propane-fueled natural gas burner.
This allows me to react 150g of sulfur at a time, which is enough for my purposes.
I will also have to pay attention to the speed with which I distill the sulfur over the charcoal. Too fast, and most of it won't react.
@ Jor: Yes I have made white P, but only from red P, which was easy.
The hard part will be to make it by reduction of a phosphate.
Yes DJF90, you are right with your assumption.
Maybe Fleaker will be faster than me- but I will also be trying to reduce phosphates soon.
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DJF90
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Good luck in your adventures garage chemist... Unfortunately I myself am in no position to be doing any serious experimenting yet, still building up a
collection of glassware  Nearly there though .
Using a larger flask (and probably some sort of support for it) do you think it would be possible to scale up and make about 100ml (abbout 120g IRC)
of CS2 at a time? This would probably make the whole process more efficient in terms of energy used to heat the charcoal bed. The only major problems
I can forsee are:
1) There will be not enough thermal energy provided to the larger amount of sulphur to allow sufficient vaporisation (although your burner should be
able to handle it )
2)There may not be enough capacity in the furnace tube for the quantities of charcoal needed to make this much CS2 in one batch. If this is the case
then the only real solution I can see is to work in smaller batches, unless you have the facilities to make a longer tube furnace (and have a longer
tube).
However the amount of CS2 you make in one batch is of a reasonable size. What I would like to ask is how long the whole procedure takes, from setting
up the apparatus, allowing the tube furnace to reach temperature, do the reaction, let everything cool down, and then clean up? Are the sulphur
"deposits" easy to clean away?
[Edited on 27-5-2008 by DJF90]
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Sauron
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Garage chemist, I would suggest a short fat tube furnace with a vycor or quartz tube to contain the sulfur melt directly connected to your long thing
tube furnace through a spherical joint (allowing you yo angle the sulfur tube downward to prevent spilliage of melt). You can then electrically heat
both the S and the C, allowing you to control the conditions better. The S tube is heated around its entire circumferance so you won't have the
thermal losses that plague scaleup with the spherical flasks, and you won't have the hassles of the taper joints with differential thermal expansion
coefficients.
Sic gorgeamus a los subjectatus nunc.
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quantumcorespacealchemyst
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using Anthracite
What is the prediction for using powdered/crushed Anthracite?
another quick question, what about firing As4S4(Realgar) with coke?
[Edited on 23-2-2015 by quantumcorespacealchemyst]
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Oscilllator
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You will die. I can almost guarantee it.
On a happier note, I noticed some images fall off the back of a truck the other day. Perhaps a mod could restore them to their rightful place?
http://imgur.com/a/tLh2K
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blogfast25
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Of all the sulphides he had to choose an arsenic based one. Poetic justice? Darwin Award pending?
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Oscilllator
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I think a darwin award would be in order. A 20 second google search confirmed the boiling point of arsenic trioxide, on of the many delicious products
no doubt produced by burning sulfur-arsenic compounds.
With regards to anthracite though, I don't think it would work particularly well unless it was ball-milled, because of it's low surface area. I
suspect that garage chemist's method works despite the low reactivity of charcoal because of it high surface area and perhaps because of residual
functional groups attached to the charcoal.
These groups (e.g. hydroxide) are what make activated carbon unsuited for gunpowder production despite it's extremely high surface area because
activated carbon is essentially pure carbon, as opposed to wood charcoal.
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Magpie
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Quote: Originally posted by garage chemist  | | Yes, Len and I did collaborate in person. He made a trip to europe and visited me, some german labware suppliers, and friends in europe.
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Oh, how I wish I could have been there to meet and learn from these masters.
The single most important condition for a successful synthesis is good mixing - Nicodem
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