Sciencemadness Discussion Board

Making the H2/Cl2 Explosion More Interesting

AJKOER - 29-8-2021 at 08:35

So, how can we make the popular web videos on the hydrogen/chlorine explosion more colorful, powerful or theoretically interesting?

First, a warning as H2/Cl2 can form a dangerous explosive mixture, so as to mitigate potential danger, I recommend the use of only small amounts (say, a test tube) of hydrogen and chlorine gas in a well-ventilated setting for experimentation. Further, for safety a deflated clear plastic bag devoid of any air/oxygen contamination (which may cancel the chain reaction detonation mechanism).

Also, accidental detonation can occur apparently via several paths, for example, a reference at https://www.chlorineinstitute.org/stewardship/chlorine/other... to quote:

"The reaction of chlorine and hydrogen can be initiated by direct sunlight, other sources of ultraviolet light, static electricity, or sharp impact."

and also produce a shock wave with associated high temperatures and possible container shrapnel.

With all appropriate safety measures in place, one usually exposes the H2/Cl2 gas mix to a LED light consisting of UV light, or a spark. This results in a chain reaction based explosion. Also, sunlight exposure may also result in unintended detonation in situations where there is a higher amount of reflective UV rays (as, for example, from a lake, ocean, snow,..).

Normally Chlorine gas (see https://en.wikipedia.org/wiki/Chlorine) has some coloration against a white background. However, due to hydrogen dilution, likely less visible, so close-up photography is likely a good idea. One may try increasing the chlorine concentration to alleviate the coloration issue, as per a source (see https://webwiser.nlm.nih.gov/substance?substanceId=338&c...) , to quote:

"mixture of hydrogen and chlorine is exploded by almost any form of energy (heat, sunlight, sparks etc). Explosive range: 5-95%."

Also, one may try dissolving the Cl2 in CCl4 (this may also help with the O2 contamination which stops the chain reaction) for a more colorful liquid/gas explosion.

Now, there are many associated available videos online (see here https://www.google.com/search?q=video+on+hydrogen+chlorine+g... ).

A novel new embodiment, yet to be personally verified (albeit, the associated chemistry appears sound) is the reaction between chlorine (absence of any oxygen), hydrogen gas in a vessel which is detonated by adding a select metal (Al, Mg, Zn,...) imbued with hydrogen.

To construct the latter, for example, the insertion of Aluminum or Magnesium metal in HCl (see https://utw10193.utweb.utexas.edu/Archive/RuoffsPDFs/352.pdf ) will, at least temporarily, possess an active surface presence of absorbed hydrogen (see commentary by ScienceDirect at https://www.sciencedirect.com/topics/engineering/atomic-hydr... and more extensive material by De Gruyter (see https://www.degruyter.com/document/doi/10.1351/PAC-REP-09-10... ).

As per a source already noted, various dry metal hydrides can ignite in chlorine, so this likely results in a detonation of the mixture.

Further, to increase the actual power of the explosion, the selected use of metal hydrides, in powder form, to augment has been noted in the literature (see https://www.sciencedirect.com/science/article/pii/S221491472...).

Comments and any other ideas are welcomed.

metalresearcher - 29-8-2021 at 11:18

Nighthawkinglight describes an HHO electrolysis device in this video https://youtu.be/d85OX6yEwE0 and further on het describes a single (dangerous !) 2 H2 + O2 output. You can dissolve table salt instead of KOH and make the perfect (but even more dangerous !) H2 + Cl2 mixture.
But you can put an empty transparent plastic bag on the output and put it in full sunlight or have a blackled flashlight / laser ready to initiate explosion. Keep a safe distance (at least a few meters) before turning on the power. Use a face shield and do not use glassware as shattering will injure !
I have never done this and cannot find suitable Youtube videos, but this will probably work.

[Edited on 2021-8-29 by metalresearcher]

Junk_Enginerd - 29-8-2021 at 12:56

Is really only chlorine gas generated that way? I was under the impression that electrolysis of NaCl in water generates a mix of hydrogen and chlorine on the cathode. Not sure what the ratio of this mix is dictated by, but I guess salt concentration and cathode material?

Morgan - 29-8-2021 at 15:49

If not mentioned, there's the demo using the light from burning Mg ribbon to set it off.

Metallophile - 29-8-2021 at 19:38

Quote: Originally posted by Junk_Enginerd  
Is really only chlorine gas generated that way? I was under the impression that electrolysis of NaCl in water generates a mix of hydrogen and chlorine on the cathode. Not sure what the ratio of this mix is dictated by, but I guess salt concentration and cathode material?


Wouldn't the chlorine be formed at the anode along with oxygen? I imagine the ratio is dependent on Cl- concentration, and maybe voltage?


[Edited on 8/30/2021 by Metallophile]

woelen - 30-8-2021 at 00:48

From personal experience I know that electrolysis of NaCl produces a mix of Cl2 and O2 at the anode. The higher the voltage, used for the electrolysis cell, the more oxygen is produced. I once collected 100 ml or so of the anode-gas and one could clearly see the green color of Cl2, but when the bottle was immersed top down under water and some solution of NaOH was injected into the Cl2 gas, then only 80% or so of the gas dissolved. The remaining gas is colorless and when a glowing piece of wood is kept in the remaining gas, there is a brief strong glowing, indicating a higher oxygen concentration. So, the remaining gas must be oxygen.

@Junk_Enginerd: At the cathode you only get hydrogen (and hydroxide ions in solution). Formation of Cl2 requires strongly oxidizing conditions and those only exist at the anode.

katyushaslab - 30-8-2021 at 03:36

The demo I recall of the H2/Cl2 mix in a bag was usually set off with a photoflash from a camera.

Morgan - 30-8-2021 at 12:30

If you could find an account of the discovery by early chemists that might add interest. I recall some scant info of carrying flasks covered with black cloths outside into the sunlight and setting them off.

I wonder if a few specks of this Pt on alumina would be another way to trigger the mixture? One time in a clear gallon jug with methanol vapor I tapped the tiniest speck above the neck and a half dozen tiny flecks softly floated down into the vessel glowing like embers. Instead of a typical whoosh bottle effect, it went off with a loud bang.
https://youtu.be/h3lS3TBuntw

Or maybe a fiber from a hand warmer which heats suddenly on contact with methanol.
https://youtu.be/UtkEfzpZ4Sg

[Edited on 30-8-2021 by Morgan]

Junk_Enginerd - 31-8-2021 at 02:53

Quote: Originally posted by woelen  
From personal experience I know that electrolysis of NaCl produces a mix of Cl2 and O2 at the anode. The higher the voltage, used for the electrolysis cell, the more oxygen is produced. I once collected 100 ml or so of the anode-gas and one could clearly see the green color of Cl2, but when the bottle was immersed top down under water and some solution of NaOH was injected into the Cl2 gas, then only 80% or so of the gas dissolved. The remaining gas is colorless and when a glowing piece of wood is kept in the remaining gas, there is a brief strong glowing, indicating a higher oxygen concentration. So, the remaining gas must be oxygen.

@Junk_Enginerd: At the cathode you only get hydrogen (and hydroxide ions in solution). Formation of Cl2 requires strongly oxidizing conditions and those only exist at the anode.


Oh, yes of course it's on the anode. If the H2/Cl2 ratio is controlled by voltage, that means it consequently is controlled by

  1. Salt concentration/conductivity
  2. Electrode area
  3. Current
  4. Electrode gap


So as concentrated salt solution as possible, as large electrode plates as possible, spaced as close as possible, electrolyzed with as low current as possible will result in the highest chlorine generation possible.

AJKOER - 31-8-2021 at 04:11

I can up with an interesting idea to explore, per a source (https://onlinelibrary.wiley.com/doi/full/10.1002/est2.35):

" In this form, hydrogen can be stored by absorption (metal hydrides and complex hydrides) and adsorption (carbon materials). Compared to absorption, adsorption of hydrogen on carbon materials is observed to be more favorable in terms of storage capacity. Taking in to account of these facts, in this short review, an overview on hydrogen adsorption on activated carbon..."

Also, per a source (https://webwiser.nlm.nih.gov/substance?substanceId=338&c...) noted previously to quote:

"The mixture of /activated carbon and chlorine/ spontaneously ignites in the dry state."

So, an interesting embodiment of the H2/Cl2 interaction could be the sudden combining of activated carbon treated with H2 gas, and say Cl2 dissolved in, for example, benzene or toluene or CCl4 (see https://pubs.acs.org/doi/10.1021/je00024a019). Best investigated only in small amounts (toxic/explosive/thermal hazard) in a well-ventilated setting with appropriate safety measures in place.

[Edited on 31-8-2021 by AJKOER]

unionised - 31-8-2021 at 04:47

Quote: Originally posted by AJKOER  


"The mixture of /activated carbon and chlorine/ spontaneously ignites in the dry state."


[Edited on 31-8-2021 by AJKOER]

If that reaction works, why wasn't it used to make CCl4?

AJKOER - 31-8-2021 at 05:12

Unionised:

To quote from an educational source (https://chem.libretexts.org/Bookshelves/General_Chemistry/Map%3A_General_Chemistry_(Petrucci_et_al.)/27%3A_Reactions_of_Organic_Compounds/27.07%3A_Re actions_of_Alkanes ):

"The relative amounts of the various products depend on the proportion of the two reactants used. In the case of methane, a large excess of the hydrocarbon favors formation of methyl chloride as the chief product; whereas, an excess of chlorine favors formation of chloroform and carbon tetrachloride.

CH4 + Cl2 + energy → CH3Cl + CH2Cl2 + CHCl3 + CCl4 + HCl"

I also expect that burning C in Cl2 likely produces a spectrum of products. Actually, Libretexts above equation is technically wrong (being illustrative, but correctly qualifies with the word 'chief') on the relative amounts of each respective product. The heat/energy induces the creation of the Cl radical which, at random, further extracts an H atom (even from previously newly created products)...

Further, likely a question of initiating temperature (energy as you noted) as carbon combustion in O2 starts at a lower temperature than Cl2.

In the current context, the H2/Cl2 reaction and the associated flame is very hot, certainly, when the ignition has occurred, it will continue.

Actually, on further reflection, using a nonactivated carbon source is probably better to store the hydrogen and proceed to mix with the dissolved chlorine and detonate with a spark. This would likely be a more reliable path in avoiding an accident.

Here is a source available at https://backend.orbit.dtu.dk/ws/portalfiles/portal/128840669... on "High-temperature chemistry of HCl and Cl2", which relatedly, I would recommend to assist on the mechanics of the chain reaction.

[Edited on 31-8-2021 by AJKOER]

AJKOER - 3-9-2021 at 04:20

Did find an interesting source on Activated Carbon reaction mechanics here https://www.watertreatmentguide.com/activated_carbon_filtrat... to quote:

"Activated carbon can remove and destroy residual disinfectants (chlorine and chloramine) through a catalytic reduction reaction. This is a chemical reaction that involves a transfer of electrons from the activated carbon surface to the residual disinfectant. In other words, activated carbon acts as a reducing agent."

So Activated Carbon (AC) could supply an electron, e-, to a source of H+ (say water vapor):

H+ + e- = .H

and that is the same .H needed for the hydrogen/chlorine chain reaction subject to a light/energy source:

H2 + Energy = .H + .H

.H + Cl2 = HCl + .Cl

.Cl + H2 = HCl + .H

......

Note: In reference to water chemistry and chlorine presence, the formation of HCl is the alluded to increased chloride formation sourced from elemental Cl2 per AC.

With respect to gaseous chlorine, a theoretical basis to suspect that Activated Carbon in the presence of undried Cl2 and H2 could be problematic (as in ignition).
-------------------------------------

Interestingly, the proposed electron pathway for Activated Carbon appears to be accurate as to what is reported per this source https://wcponline.com/2009/06/13/chlorine-chloramine-removal... at more alkaline pH where HOCl is attacked by AC (due to the limited H+ presence). The associated chemistry I have detailed previously on this forum (see http://www.sciencemadness.org/talk/viewthread.php?tid=98989#... ) and I would note here:

Cl2 + H2O + OH- -> HOCl + H2O + Cl-

HOCl + e- -> .OHCl-

If pH >5 :

.OHCl- -> .OH + Cl-

.OH + e- -> OH-

That is, conditions favoring hypochlorous acid (which is more effective than hypochlorite) can suffer a significant long-term loss in disinfecting power (albeit, a short term powerful radical boost) in the presence of Activated Carbon.

Of more possible import, the above implies that Fenton-type transition metal chemistry (acting as a source of electrons) can be replaced by Activated Carbon.

[Edited on 3-9-2021 by AJKOER]