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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: hohenheim on August 01, 2011, 02:27:15 PM

Title: Mercury electrode oxyde?
Post by: hohenheim on August 01, 2011, 02:27:15 PM
Here is what I did for a chlorite:

(http://img837.imageshack.us/img837/8949/electrolysis.jpg)

When I pass 3v through the solution, mercury forms a non conductive layer so the current stopped to flow.
At first I tought it was an oxyde of some metal that formed an amalgam with mercury, I removed it but it continued to form indefinitely.
Since the MgO has an orangish color. what could be the dark grey scrap I got?


Thank you
Title: Re: Mercury electrode oxyde?
Post by: hohenheim on August 04, 2011, 04:33:21 PM
Is it that hard?
Title: Re: Mercury electrode oxyde?
Post by: DevaDevil on August 05, 2011, 11:01:02 AM
yes it is, as "brine" is not a very well-defined system. was it pure sodium chloride solution? mixed metal-chlorides, or seawater, which has tons of ions of all kinds in it?

3 volt is a large current, and so there are many reactions that may happen. yes, mercury oxide is orange, but for example mercury sulfate, mercury chloride etc. are white.
As I said, many options available
Title: Re: Mercury electrode oxyde?
Post by: hohenheim on August 08, 2011, 03:54:07 PM
Thanks for the information, I didn't tought about the voltage I'll try with 1.6v.

I used a distilled water saturated with table salt.
Title: Re: Mercury electrode oxyde?
Post by: Benzenelover on August 09, 2011, 12:43:21 AM
Was the salt iodized?
Title: Re: Mercury electrode oxyde?
Post by: hohenheim on August 09, 2011, 09:55:02 AM
Yes I suppose, does it matter? since only a tiny quantity is present, Like I said the layer keeps forming until all the mercury is transformed.
Title: Re: Mercury electrode oxyde?
Post by: DevaDevil on August 09, 2011, 01:57:48 PM
mercury iodide is very insoluble, that is why it matters. if mercury cations are formed, iodide in solution may cause it to crystallize out as mercury iodide.

solubility product of Hg2I2: 5.33 x 10-29
solubility product of HgI2: 2.82 x 10-29
Title: Re: Mercury electrode oxyde?
Post by: Benzenelover on August 09, 2011, 02:15:11 PM
Not to mention iodized salt tends to have all kinds of other contaminants, such as anti caking agents.
Title: Re: Mercury electrode oxyde?
Post by: hohenheim on August 09, 2011, 10:00:19 PM
I understand, So this is necessarly due to contaminants in the electrolyte?
So is there any other way making chlorine? I tried stainless steel but it degrades quickly, the graphite too.
Title: Re: Mercury electrode oxyde?
Post by: Hunter2 on August 10, 2011, 12:56:19 AM
Quote
3 volt is a large current,

Volt is not a current, current is measured in Ampere.

For this problem I would suggest to measure the current with an Amperemeter in series.
The voltage is only the force to drive the current through.
Title: Re: Mercury electrode oxyde?
Post by: DevaDevil on August 10, 2011, 09:55:43 AM
Quote from: Hunter2 on August 10, 2011, 12:56:19 AM
Quote
3 volt is a large current,

Volt is not a current, current is measured in Ampere.

For this problem I would suggest to measure the current with an Amperemeter in series.
The voltage is only the force to drive the current through.

my bad, slip of the keys