Sciencemadness Discussion Board

Preparation of Hydrogen chloride gas via electrochemical methods

phendrol - 15-6-2012 at 03:07

While surfing the internet I found this:
Quote:
Hydrogen chloride can be prepared using electrochemical methods. In this regards, hydrogen chloride can be prepared by first, electrolyzing a mixture of Epsom salt and pickling salt, and then passing the gas mixture produced, into a mixture of hexane containing aluminum foil pieces. The aluminum foil acts as a catalyst, causing hydrogen gas to combine with chlorine gas, forming hydrogen chloride.

Place 300 milliliters (10.1 fluid oz.) of dry hexane and 20 grams (0.70 oz.) of aluminum foil pieces into the appropriate round bottom flask, and then dissolve 200 grams (7 oz.) of Epsom salt into 1000 milliliters (3.8 fluid oz.) of cold water, and thereafter, add and dissolve 95 grams (3.4 oz.) of pickling salt. Now, pour this salt solution into an open cell, and then electrolysis the mixture at 6 to 12 volt at 6 to 12 amp for a period ranging from 12 to 18 hours. During the electrolysis process, a moderate, yet steady stream of chlorine gas (mixed with hydrogen and oxygen) will be steadily evolved and carried over.



Now my questions are:

1. Can i use a different solvent than hexane (petroleum ether for example)?

2. Can I use a NaCl solution instead of a mix of epsom salts and NaCl?

greenenergy - 17-6-2012 at 11:27

I guess the magnesium sulfate absorbs any potential H20 from the hexane. (becomes saturated with H anyways makes it easier for electorlysis?) and that the depropination factor of hexane prevents the hydride interacting with the sodium from the NaCl to form Naoh which would cause the chlorine to react and form sodium hypochlorite. (sodium hypochlorite will slowly have its chlorine atoms vaporize though eventually leaving a NAOH solution)

I dont see why to just use two electrochemical cells seperated by a u bridge this way you can for example; have two cells filled with super-saturated brine water (hint: add salt to the point it is no longer soluble in the water, heat in microwave for 1 minute, add more salt repeat until NO more salt mixxes it should be so salty it should have a mild chlorine-ish smell.

if two cells containing salt water are used and the circuit completed with a U-bridge than sodium hydroxide will form at one cell and chlorine gas at the other. The cell containing the sodium hydroxide will become very basic and the other acidic as the chlorine saturates with the water (it is somewhat water-soluable) as the water absorbs chlorine the hydrogen atoms within should form HCL. rerember that HCL is volatile and that when the chlorine escapes it will leave small clouds of hydrogen chloride (put a PH paper in front of a bottle of HCL and you will notice


it is essentially the opposite of a batery instead of using an acid/alkaline reaction to produce energy you use elecrtical energy to create to a chemical reaction
hope this potentially helps. although your post ws much interesting. the aluminum electrolytic action is a first for me and it is awesome to know. thanks for sharing:cool:

dann2 - 17-6-2012 at 14:40

Quote: Originally posted by phendrol  
While surfing the internet I found this:

Quote:
Hydrogen chloride can be prepared using
.................and oxygen) will be steadily evolved and carried over.




Where did you read THAT?

peach - 17-6-2012 at 17:23

It's 2am and I should be in bed by now, but isn't the Epsom salt there to push the chlorine out, rather than allowing it to form hypochlorite etc so easily in an undivided cell? If you electrolyse NaCl alone, you'll end up making dilute bleach.

Hydrochloric acid onto manganese dioxide will generate a stream of chlorine. If you choose that method, I highly recommend you hang onto the resulting manganese chloride, run it through a filter paper and you should have pink manganese chloride. If there's black grit in the filter paper, that's either activated carbon or sand or both, and the manganese dioxide is likely from rinsed battery paste; ditch the filter cake if so (it's pretty much worthless / harmless gunk). If the filtrate is yellow / brown / black, that's iron contamination (common from battery paste derived dioxide), selectively precipitate it out and retain the pink chloride. If you heat the chloride, it'll release more chlorine, go back to dioxide and can go back through the process.

I think it'd be better to build yourself a membrane separated cell for generating the chlorine if you plan on doing it regularly / need lots / like building things. I'd quite like to make one.

Or, sulphuric onto table salt will yield clean and direct hydrogen chloride. Even small generators with a handful of salt and cups worth of sulphuric will generate a considerable amount of it, enough that it'd cost over a hundred squids (that's English pounds) if bought in a lecture bottle.

If you need a lot of hydrogen chloride, you can buy 5kg bulk cylinders of it for somewhere in the region of £200. You will need to talk to a specialist gas supplier about that, as it usually requires / benefits from some form of training / checks due to the risk they present; it's not like buying acetylene or argon, e.g. it'll need to go buy hazmat delivery etc.

wireshark - 2-2-2013 at 19:24

Pretty cool. Anhydrous HCl without using precious sulfuric. I'd be interested to try this when I get the chance. I know you're probably gone, but it's curious where you got this from. It's probably not primary literature, seeing as imperial units are bothered to be typed and ambiguous chemical names are used.

elementcollector1 - 11-2-2013 at 09:35

Quote: Originally posted by peach  
If you choose that method, I highly recommend you hang onto the resulting manganese chloride, run it through a filter paper and you should have pink manganese chloride. If there's black grit in the filter paper, that's either activated carbon or sand or both, and the manganese dioxide is likely from rinsed battery paste; ditch the filter cake if so (it's pretty much worthless / harmless gunk). If the filtrate is yellow / brown / black, that's iron contamination (common from battery paste derived dioxide), selectively precipitate it out and retain the pink chloride. If you heat the chloride, it'll release more chlorine, go back to dioxide and can go back through the process.


This isn't as easy as it looks on paper, and according to the chlorine thread in Prepublications, yields are low compared to trichloroisocyanuric acid.

How 'hot' is the reaction between H2 and Cl2? Hot enough to shatter a glass flask? I was thinking a 3-neck glass flask could be filled with hydrogen and chlorine from 2 of the necks, with the third leading to a closed gas outlet. When the gases had finished reacting, the outlet could be opened into cold distilled water.



[Edited on 11-2-2013 by elementcollector1]

[Edited on 11-2-2013 by elementcollector1]