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Biologists often use a CO2 incubator - it's a chamber that not
only maintains a constant chamber, but also maintains a
constant CO2 concentration, typically around 5%. This is
necessary because many cultured cells grow best at these
higher CO2 concentrations.
A CO2 incubator is normally fed
from a CO2 cylinder. A
solenoid valve opens to let CO2 in, when necessary, and the
chamber itself is more-or-less airtight to limit the loss of
However, this is a huge faff. You have to have a big (eg
CO2 cylinder, which is typically rented from a supplier; it
to have a leak-free connection to the incubator; and you
to replace the cylinder when it gets low. If it runs out over
weekend, it can be bad news for your cells. So an ideal
has _two_ cylinders connected to a gadget that
switches from the empty cylinder to the full one, ensuring
continuity of supply.
Now, all this is a bit silly. CO2 is very easy to make by
combustion. So, I suggest a better way.
Inside the incubator, we place a little battery-powered or
mains-fed gizmo consisting of a alcohol burner, an electronic
ignition, and a snuffer. It also has a CO2 sensor (like current
CO2 incubators). When the CO2 level falls, the electronic
igniter lights the wick, burning alcohol to produce CO2.
a couple of seconds, the snuffer drops down over the wick to
extinguish the flame. If the CO2 level is still too low, the
process repeats every few minutes.
One problem is that the burning will raise the temperature
the incubator, which would be very bad. However, if the
small flame is active for only a couple of seconds every few
minutes, the heater control of the incubator will
and the temperature deviation will be negligible.
A level sensor can warn the user when the alcohol needs
topping up. No CO2 cylinders or automated changeover
are needed. It also means that you can run a CO2 incubator
in locations too remote for regular cylinder deliveries.
[bs0u0155, Aug 26 2019]
...from different chemicals [Frankx, Oct 08 2019]
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||Potential bun, but I want to see some math about how much
the flame will affect the carbon dioxide concentration and
||Well, I don't have the math but I do have an experiment.
Burning an alcohol-soaked tissue in my CO2 incubator for
about 5 seconds sent the CO2 concentration up into the 10s
of percent, and caused a brief blip of about 5°C. +5°C is
completely unacceptable, but I also produced far too much
CO2. I think a much smaller flame for a couple of seconds
would give me 5% CO2 for a temperature rise of maybe
0.5°C. An even smaller flame in short bursts would reach
5% CO2 without a significant temperature change.
||If you were really worried about temperature fluctuations,
you could have the burner thermally isolated from the
chamber, and just chimnify the resulting CO2-rich gas into
the chamber. But I don't think that would be necessary.
||A look at the numbers, Aigas charge us about $1.80/kg for
CO2, Decon charge about $15/kg for EtOH, now a kg of
EtOH = 2 kg of CO2 when combusted, but it still turns out
dramatically expensive. Then there's doing the
combustion in a clean way, you'll have water to deal
with, and worse there's non-CO2 combustion products,
just a little CO for example could mess things up.
||Now, HCl is cheap, and baking soda can be bought for
~$1/kg. Dosing is a microcontroller and a cheap
peristaltic pump. No flames, purity guaranteed.
||One problem I have with incubators, they can only INCREASE
CO2. A total pain, I blame the cancer people who have cells
that can't be bothered actually doing any real respiration.
Consequently, if you have a full incubator of cells that
actually use their mitochondria, the CO2 can go above 5%
over the weekend.
||Another tactic, used by labs with relaxed attitudes, is to
have a nice healthy bacterial colony living in the water at
the bottom. Always an interesting smell come monday.
||//$15/kg for EtOH// Jeezus that's cheap! Where exactly
did you find that? I pay a fortune for 96% ethanol, even
without duty. But, we can use methanol instead, which I
believe is much cheaper.
||Agreed, CO would be bad - but how much CO is produced
when burning alcohol in what is essentially air? As for water
- many incubators are humidified anyway.
||The baking soda/HCl option is sort of nice, but not as simple
as an alcohol burner. And the main consideration was not
cost (which won't be great in any case) but faff.
||See link, we get it even cheaper via the hospital
pharmacy, but the lady who orders is on hols, so I have no
idea exactly how much. It still involves a fax machine for
||I know many incubators are humidified, but you have to
be able to deal with an excess. Actually, there needs to
be an auto-top up on incubators. I have one on my fish
tank, they're not pricey.
||HCl/Limestone? Could use an XYZ controlled dropper to
slowly acid etch your own face into a block of stone.
||Or, how about using Pd/Pt catalysis for oxidation of the
natural gas? no flame, entirely gaseous. The only problem
I can think of is the sulfur compounds they put in the gas.
Buggers a lot of catalysts right up and probably cells too.
||Ah, America. Land of the home and the brave of the free. I
guess high ethanol prices are a UK thing. I forget the last
price I paid but it was over £200 for 2.5l of 96%.
||Natural gas - does bottled gas have sulphur? I guess it must
have a sulphur-containing odorant (since it still smells bad).
Otherwise it would be a good solution; you could use the same
camping-gas cylinders that you use for lab bunsens.
||They put the stinky stuff in everything that might get near a
consumer. Still, a great commercial opportunity to sell
activated charcoal filters. No CO2, just recurring filters...
||I was about to name methyl mercaptan as the "stinky stuff" (as stated in Wikipedia), but thought I'd check. It's not. Natural gas odourant (in the UK) is a mixture of 80% 2-Methylpropane-2-thiol (TBM, (CH3)3CSH) with 20% methylthiomethane (DMS, (CH3)2S).
||"a mixture of rotten eggs with a cabbage-like smell"
||Fascinating article [link]
||Acetylene is about as unsaturated as you can conveniently get, and is cheaply and widely available. A suitable metallic catalyst should give you all the CO2 you want at the flip of a valve.
||[bs0], can I just thank you? Your comment made me look
again at lab ethanol prices, and I found an alternative (from
the same bloody supplier!) at 1/2.8th the price. Since this
will save me a couple of grand a year, please feel free to buy
yourself a drink.
||// at 1/2.8th the price.// I'll get 1/2.8th of a drink and
make up the difference with lab EtOH and a dash of
tryptone for beery authenticity... Actually, I could probably
survive on that in a pinch, like boozy Soylent.
||Hmm. Never tried tryptone. Limonene or benzaldehyde yes,
but only in extreme moderation.
||Wouldn't it be cheaper to buy methylated spirit, if you're
just burning it?
||Though you might have to get it through accounts
||For a while, here, we had to fill in a special form for our
ethanol from stores, saying exactly what we wanted to
use it for. Since we're unlikely to use 2.5 litres of any
solvent up in one go, and in any case I didn't know what
we'd need it for next, I wrote down the maximally
comprehensive phrase "preparation of alcoholic
solutions". It was allowed.
||//cheaper to buy methylated spirit// it would, though its
denaturants may contain sulphur and other junk. Isopropyl
alcohol or straight methanol would do too, for this
||(But if you mean for my applications - I use it like any other
molecular biologist, for solutions, precipitations etc.)
||Incidentally, one place I worked at also had a procedure of
justifying ethanol issue. I once filled in the form with "I
intend to drink it"; needless to say, nobody noticed or cared
and I got my 2.5l. The same place had a form for ordering
non-standard radiolabelled compounds; I put "dirty bomb",
but that one did get picked up.
||Requisition for 10 boxes of 7.62mm ammunition: In the "Required for :" box was written "Overthrow of the State by violent means. Long Live the People's Revolution ! "
||Needless to say, we smiled and approved it.
||We have checked several times, but it seems the Revolution hasn't started yet. If it doesn't get going soon, we will go and ask for the ammunition back.
// , like boozy Soylent //
||Oooh, you should post that ...
||//but it seems the Revolution hasn't started yet// I believe
they're going to ask for an extension.
||That sounds nice. Are there any architect's drawings we can look at ?
||Will there be a Shrubbery ?
||Good idea though [MB]. How about using a small
flask of home-brew as your CO2 source? Added