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Preparation of dry hydrogen?

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LAN_403

klugesmith

Tue Mar 27 2018, 05:45AM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1714

A helium-filled mylar balloon purchased last December remained buoyant in air for months.
Now I want to re-fill it with hydrogen, and see how long the balloon can hold that gas.
The amount needed is 10 or 15 liters. On the order of 1/2 mole.

In my high school years, we filled latex balloons with hydrogen by putting aluminum foil in a solution of lye. Usually in a large glass Coke bottle, with a 10 cent deposit, because PET bottles for fizzy beverages hadn't been invented.

Now I'm asking on a forum, before generally searching the Internet, about whether anyone prefers a different reaction. People have been filling balloons with hydrogen since 1783.

I also want to try drying the hydrogen, which starts out hot and humid. Maybe bubble it through ice water before some kind of dessicant column. Suggestions are welcome!

Sulaiman

Tue Mar 27 2018, 11:03AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

I would just use what is available;
Hydrogen;
. Aluminium cooking foil + drain cleaner sodium hydroxide
. Lantern Battery zinc or iron wool + brick/concrete cleaner muriatic/hydrochloric acid
. electrolysis of water using carbon rods (painfully slow)

Scrubbing;
. pass gas through a tube loosely packed with dehumidifier calcium chloride or oven-dried cotton wool
. bubble through (drain unblocker) conc. sulphuric acid (hazardous)

I'd try BOC or welding suppliers for bottled gas as other methods will be quite slow.

the_anomaly

Tue Mar 27 2018, 12:10PM

Registered Member #19 Joined: Thu Feb 02 2006, 03:19PM
Location: Jacksonville, FL
Posts: 168

I built a fuel cell in high school and the chemistry teacher suggested zinc + citric acid with a bit of copper sulfate as a catalyst. Worked great for me and was far safer than the HCL + aluminium I had been trying. I don't have any ratios but the reaction speed is adjustable; I had a steady stream of bubbles from a half filled test tube.

Justin

Tue Mar 27 2018, 06:48PM

Registered Member #46164 Joined: Wed May 07 2014, 08:16AM
Location: California, USA
Posts: 89

Couldn't you just use electrolysis of water as a source of hydrogen?

Sulaiman

Tue Mar 27 2018, 08:25PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Usually because 2H+ + 2e- = H2
so to produce 0.5 mol H2, 1 mol e- is required = 96485 A.s

96485 A.s = 26.8 amp.hour

Hence my (painfully slow) comment above

Conundrum

Fri Mar 30 2018, 08:31AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059

yes, a fuel cell would also work.
Interestingly you can now get these quite cheaply and they have other applications.

Sulaiman

Fri Mar 30 2018, 11:57AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Conundrum wrote ...

yes, a fuel cell would also work.
Interestingly you can now get these quite cheaply and they have other applications.

but you will still need at least 26.8 A.h

(more actually as the gas will be slightly compressed, and electrolysis is rarely 100% efficient)

If you want to collect oxygen and/or hydrogen separately then I advise the use of a membrane in the cell as back-pressure on one port can force electrolyte out of the other.

I have not tried, but if you do go the electrolysis way, you could consider a HHO generator,
(all of the hydrogen and oxygen collected together)
lighter than air and MUCH more violent explosion if ignited.
CAUTION: in theory, u.v. light (sunlight) can initiate the reaction, so take care.

2Spoons

Sat Mar 31 2018, 09:22PM

Registered Member #2939 Joined: Fri Jun 25 2010, 04:25AM
Location:
Posts: 615

I wouldn't call electrolysis 'painfully' slow. I built a 4 cell electrolyser using stainless steel plates, with gas separation, and with 20A running through it the hydrogen flow was enough to sustain a flame on the end of a 20mm tube. Took 3-4 minutes to fill a plastic shopping bag (about 15l I guess) with mixed H2/O2. The bang when we ignited that was ... impressive.

Personally I'd use the Al + NaOH method to fill a balloon. There are plenty of drying agents you can use - silica gel, NaOH prills, CaO, hell probably even a bucket of dry rice would work well enough for this experiment.

klugesmith

Mon Apr 09 2018, 09:08AM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1714

Thanks, 2Spoons. On the Internet we can find work by other amateurs who got serious about electrolytic H2. I like this one -- the anode and cathode plates are separated by wet felt to keep the gases from mixing. H2 is collected in a bellows at atmospheric pressure. When that's full, a refrigeration compressor pumps the H2 into a storage tank.

Industrial hydrogen is almost all made from methane and other hydrocarbons. Mostly for non-fuel applications, since it's harder to store & contains less energy than its fossil fuel precursors.

Today I made about 7 liters of hydrogen, in a practice run, from zinc and acid.

Without much daylight time left, I deferred the chemical calculations. Broke 88 g of die-cast scrap into chunks that would fit into a 20 ounce Gatorade bottle. Made a hole in the cap for tight fit of a Tygon hose. Added 8 fl. oz. (240 ml) of diluted hydrochloric acid previously used for pickling steel. After displacing all the water from a quart-size canning jar, I started filling a much larger jar. Picture above was taken after about 8 minutes, as the bubbling slowed down.

I ended the experiment at 24 minutes, after the bubbling had almost stopped. I guess from depletion of the acid.

Later, weighed the unconsumed zinc.

Next run might be balloon-filling time. Need to contrive a dessicant column. Also figure in advance the amount of metal and acid, and beware of frothing or overheating since the acid volume and/or concentration need to be increased substantially.

Sulaiman

Tue May 08 2018, 04:50PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

klugesmith - you are a bad influence !

... due to your evil influence, I now have four 36" latex balloons and 500g drain cleaner - and I've started stockpiling aluminium cans.

I estimate that my 36" diameter balloons will need about 400 litres of hydrogen each,
I estimate about 25 aluminium cans (c14g each) and a 500g tub of drain cleaner sodium hydroxide to be sure of a little excess hydrogen.

I've not decided how to dry and neutralise (sodium hydroxide droplets) the hydrogen yet,
probably just a wad of cotton wool in a tube.

I hope to levitate 60m of stainless steel wire to act as a temporary antenna.
(UK limit for a tethered balloon)

I intend to start when I have enough cans and these arrive

as I do not want to use my nice glassware for hot sodium hydroxide.

P.S. The only carbonated drink that I buy is Ginger Beer and the plastic coating on the inside and outside of these aluminium cans is very good at resisting sodium hydroxide solution... work in progress.

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