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Magpie
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That's an excellent description!
I have an excellent machinist on retainer. I'll ask him to work up a cost estimate for the cap. What metal do you want it made of?
The single most important condition for a successful synthesis is good mixing - Nicodem
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Melgar
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Quote: Originally posted by Magpie  | That's an excellent description!
I have an excellent machinist on retainer. I'll ask him to work up a cost estimate for the cap. What metal do you want it made of?
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Yeah, I did my undergraduate degree in mechanical engineering, chemistry is more of a hobby for me. Not much formal chemistry background, unless
you're talking chemistry of steel. Soooo much of it. And soooo boring.
There would need to be a hole in the top, for the hydrogen inlet. I'd have to think about what the best way would be to add the inlet, in which a tube
extends from the inlet to the bottom of the vessel. Maybe a barbed connector, with the tube replaceable? A brass cap might be best, since most of
the connectors I'm finding are brass, and I seem to remember galvanic corrosion problems with brass and aluminum. Steel would be too hard to machine
to be worth the improved strength, especially for a non-standard threaded hole. I didn't even notice the double-helix thread until I went to measure
it, now I'm thinking it might be better to just strengthen the existing cap with some sort of outer shell.
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Magpie
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Then seal the shell to the cap with epoxy?
The single most important condition for a successful synthesis is good mixing - Nicodem
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zed
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I have a fair amount of experience producing Pt catalysts, via the action of NaBH4 on Chloroplatinic acid in ethanol.
Fast, easy, reliable, and a very active catalyst. Reducing the need for pressure.
Still........ The best catalyst/solvent combination....for any given hydrogenation, is probably what worked for someone else, for exactly the same
substrate, sometime in the past. At least, as a place to start.
These matters can be very fussy. As in; reduction goes smoothly with Raney Nickel in ethanol, but utterly fails in methanol.....Or Visa Versa. Or,
the substrate, might poison Nickel, or poison Platinum, and be reduced nicely with Pd/C. But, only in glacial acetic acid.
Great when you get all yer ducks lined up right. But, sometimes it takes a while to work out all of the little details.
Looking forward to hearing your results.
PS. How do you plan to agitate your vessel? If the information is there....I missed it. Either shaking or stirring works fine. Just curious.
[Edited on 14-6-2017 by zed]
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Melgar
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Oh yeah, I was going to find a copper pipe cap that could cover my plastic bottle cap, drill a hole through, then either use acrylic resin or epoxy to
strengthen it and hold it there. I know I want both a pressure gauge and a proper pneumatic quick-connection on the cap.
Today I added some of this activated aluminum alloy (like Al/Hg but nontoxic) to a sturdy, glass 10mm vial, half full of a mixture of acetonitrile and
water, then screwed the cap on tight and put it inside a plastic jar, to contain debris if the pressure got too high. With a vial that small,
there's no way it would, but it still would have made me nervous just sitting on a shelf next to me. Well, before that, I added a very small speck of
of PdCl2, and made sure it went into solution. Eventually the bubbles were almost too tiny to see, and I opened it up, releasing a lot of pressure in
the process. It smelled a lot like nitromethane being reduced, but slightly different. Blowing HCl vapors across the mouth of the open vial
generated a white mist. I'm not sure if that signifies an amine, or if a hydroxylamine might also be possible. Though, I didn't think that was an
intermediate in nitrile reductions.
Stirring would just be magnetic, if it needed to be for any length of time. Easy enough to mount an alnico magnet on a DC motor with epoxy.
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Melgar
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I've been gradually collecting parts for this, and I finally got everything together. Only two probems: the check valve leaks and the pressure gauge
stays at zero no matter what.
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NEMO-Chemistry
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Ive used small Kabota tractor (micro tractor) front wheel inner tubes to store both Hydrogen and Methane. Seems to keep the Hydrogen in for a good
time as well
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Bert
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Totally not related to the primary topic... But the blown up boiler mentioned in the 3rd post? It did not blow up due to a simple over pressure
bursting of the container.
It blew up because it cracked or otherwise leaked and the pressure FELL.
A whole lot of water in a boiler at working pressure, which has a temperature higher than boiling point at atmospheric pressure develops a leak, rapid
pressure drop and the water flashes to steam. Kaboom.
Failure modes. Not always what you expected.
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Magpie
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| Quote: Originally posted by Melgar | | I've been gradually collecting parts for this, and I finally got everything together. Only two probems: the check valve leaks and the pressure gauge
stays at zero no matter what. |
If the check valve leaks you will build no pressure and the gauge will read zero, right?
The single most important condition for a successful synthesis is good mixing - Nicodem
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Melgar
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No. When there's pressure on the inlet, the check valve may as well be a straight tube. Also, because the gauge doesn't work, I'm reluctant to
pressurize it at all, because I have no idea what the pressure ever is. The pressure gauge was designed to be on an air compressor, but my first
tests were only with air, although some water got in the tubes since for some reason I felt the need to have liquid in the bottle. That happened
after I removed the pressure, the check valve leaked, and air pressure forced water backwards through everything.
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NEMO-Chemistry
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| Quote: Originally posted by Bert | Totally not related to the primary topic... But the blown up boiler mentioned in the 3rd post? It did not blow up due to a simple over pressure
bursting of the container.
It blew up because it cracked or otherwise leaked and the pressure FELL.
A whole lot of water in a boiler at working pressure, which has a temperature higher than boiling point at atmospheric pressure develops a leak, rapid
pressure drop and the water flashes to steam. Kaboom.
Failure modes. Not always what you expected. |
Wow, cant say you do things by halves can they lol. I would have shat myself with that 
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Melgar
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| Quote: Originally posted by Bert | A whole lot of water in a boiler at working pressure, which has a temperature higher than boiling point at atmospheric pressure develops a leak, rapid
pressure drop and the water flashes to steam. Kaboom.
Failure modes. Not always what you expected. |
Even though we understand water better than probably any other fluid, (or at least think we do) water is somewhat of an anomaly among fluids. If I'm
not mistaken, no other compound with a similar molecular weight has such a high boiling point. Hydrogen bonds hold it in liquid phase up to its
boiling point, but as soon as it boils, those hydrogen bonds disappear, and the resulting steam has a pressure on the order of what methane would have
at that temperature.
Hydrogen bonds take some time to form in a condensing gas, but can be broken instantly if conditions are right. When superheated water flashes to
steam, it's all converted to a gas at once, and the molecules fly apart. Adiabatic cooling comes into play, but isn't able to cool it enough to
condense the water unless hydrogen bonding comes into play. And since hydrogen bonds aren't especially quick to form, the steam has a brief interval
during which it behaves similar to how methane would at that temperature.
At least I believe this is the mechanism. I wrote it down to get it straight in my head.
The first step in the process of learning something is admitting that you don't know it already.
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