Experiment Question

[Tristan]

Alot of you know what Im working on, but I have some questions that need to be resolved. If you dont know, Im recreating the Miller-Urey Experiment. Pretty intense. The glassblower said this:

"I would recommend a heating mantle or an oil bath. Don't use an open flame. You might shock and break the flask due to the high coefficient of expansion of Pyrex Glass.
Oil Bath is the safe to work with. "

So how does an oil bath work? Anyone ever use one? Explain.

Thanks
Tristan

 

[Idle Mind]

I would imagine that you it would be the same as a water bath. You apply the heat to the oil, and immerse the flask in the oil. All this is doing is creating a buffer so you aren't applying heat directly to the glassware.

The chemistry department should have a water bath that you could use.

 

[Hercules Rockefeller]

I'm recreating the Miller-Urey Experiment. Pretty intense.

Indeed!

Please keep us informed as to your progress. But I hope you’re going to design the experiment a bit better than they did. There has been a recent wave of skepticism concerning the Miller-Urey experiment. The primary concern is that it is now believed that the early earth's atmosphere was not a predominantly reducing atmosphere as they simulated in their reaction vessel. Another objection is that this experiment required a tremendous amount of energy. They simulated constant lightning storms. Whilst such storms were extremely common on the primitive Earth, it is not believed that they were continuous as the Miller/Urey experiment portrayed.

 

[Tristan]

The primary concern is that it is now believed that the early earth's atmosphere was not a predominantly reducing atmosphere as they simulated in their reaction vessel.

Elaborate please

They simulated constant lightning storms.

I suppose I could just turn the power supply off at regular/irregular intervals to simulate a non-constant supply of energy.

Thanks!
Tristan

 

[Hercules Rockefeller]

Elaborate please

I’m sorry but I have no real knowledge of this topic other than the basics. A reducing atmosphere (such as the one thought to be present with the primitive earth) is one that contains lots of methane and ammonia. These molecules reduce free oxygen (O₂) down to other oxygen containing molecules (H₂O?). So a reducing atmosphere has no molecular oxygen. These were the conditions that Urey-Miler simulated.

In recent times there have been a lot of scientists arguing that the primitive Earth did not have a reducing atmosphere. No one thinks that there was any molecular oxygen, but many are now arguing that there was no significant methane or ammonia either.

Try Googling with terms such as “reducing atmosphere” or “reducing atmosphere Miller Urey” etc etc. I found this very quickly which seems very relevant and interesting......

<a href="http://www.physics.vanderbilt.edu/astrocourses/ast201/atmospheres.html" target="new">http://www.physics.vanderbilt.edu/astrocourses/ast201/atmospheres.html</a>

Another question that is now being debated is related to where the organic molecules that precipitated life actually came from. The Urey-Miller experiment with a reducing atmosphere suggests that biological molecules arose from reactions involving methane and ammonia molecules. But if methane and ammonia weren’t present, where did amino acids and sugars come from? A growing idea is that they came from comet and meteorite impacts. We now know that these objects contain large amounts of such biological molecules (simple sugar precursors and even simple amino acids) and that they were continuously bombarding the early Earth.

It’s a fascinating area! I wish I had the time to learn more about it.<P>

 

[Tristan]

Ok, so I have one more question. There is one thing that keeps me from doing this experiment right now: Oxygen... Its incredibly hard to remove from the system. So what If I just used Nitrogen, CO2, and water, would I get anything? Would molecular oxygen really inhibit the formation of any organic compounds?

Later
T

 

[pilpaX]

use vacum to get rif of oxygen.
And didn´t life start in H2S enviorment?

 

[hypatia]

Ok, so I have one more question. There is one thing that keeps me from doing this experiment right now: Oxygen... Its incredibly hard to remove from the system. So what If I just used Nitrogen, CO2, and water, would I get anything? Would molecular oxygen really inhibit the formation of any organic compounds?

Later
T

Oxygen is actually a fairly reactive substance. As I understand it, the only reason we don't usually see spontaneous oxidation reactions happening all around us is that the susceptible compounds were all quickly oxidized once O2 became a significant component of the atmosphere, leaving only those compounds that were stable in its presence.

But, if you'll forgive my stupidity, why is it so difficult to remove from the chamber? Can't you just flush with an N2/CO2 mix until the oxygen is gone, and then seal the chamber?

 

[Tristan]

Yeah, but there is water in the 500cc flask... that is boiled to circulate the gases through the appartus and provide another componet for the reaction. And water has dissolved oxygen in it. From all acounts, its not as easy as it sounds... Hypatia, I was thinking just that, flooding with N2, but apparently its not that east.

Later
T

 

[hypatia]

Yeah, but there is water in the 500cc flask... that is boiled to circulate the gases through the appartus and provide another componet for the reaction. And water has dissolved oxygen in it. From all acounts, its not as easy as it sounds... Hypatia, I was thinking just that, flooding with N2, but apparently its not that east.

Later
T

Can you use degassed water in the reaction? For gas-sensitive reactions, we usually pretreat the water by leaving it under a vacuum for a while (I just stick an open 50-ml tube of water in the vacuum flask), tapping out the bubbles on the side every hour or so until they no longer form.