PDA

View Full Version : homebuilt vAg electrode?



Pages : 1 [2]

Photo Engineer
10-11-2012, 10:45 AM
The electrode should be clean to start with, and the plating should be done under dim light. After all, you are forming a silver halide. It is light sensitive.

PE

kb3lms
10-13-2012, 05:23 PM
Some better results!

Today, I re-plated the RE and the Bromide electrode under safelight. Now the 0.1M KBr solution gives a reading of -68.0 t -68.5 mV. Ambient temperature was 20C so according to the chart, that should give a reading of about -62.56 mV. Since my solution has sat for a few days there may have been some evaporation and it could now be at higher concentration and/or it could have been a bit off in the first place. Later this evening I will make fresh solutions and get new readings as Kirk suggests above.

-- Jason

Photo Engineer
10-13-2012, 06:23 PM
Jason;

You are as close as I get sometimes, with an offset of about 6 mv.

You should only apply voltage (plate) the Silver electrode, and you do it with another Silver electrode in the halide you wish to plate it with.

PE

kb3lms
10-13-2012, 07:33 PM
PE,

Yes, sorry. I meant that I re-applied plating to silver electrode in KBr (.17M) and also replated the reference electrode in KCl (0.05M). My reference electrode was built from the instructions in the article I posted above. It seems to work quite well. Compared with the RE in my Hanna pH meter, the readings are about the same.

Also, just for the record, my silver wire is 14 gauge .9999 fine silver bought off the big auction site. Quite sure the real seller is one of the references given in other posts here. 14 gauge is sturdy enough to use for the electrodes.

-- Jason

kb3lms
10-13-2012, 07:41 PM
Also, for anyone following this thread, here are instructions (courtesy of RIT) for plating the silver electrode using a piece of equipment they have, or more likely had. All it really did was run the plating process for a fixed four minutes. There is a description in one of the papers I found giving some description of the machine.

https://www.dropbox.com/s/w50e1hm3a56hvri/plating.pdf

Also, while their method of cleaning the electrode does work, I am just cleaning mine with scothbrite. Works great and it gets nice and shiny. Initially I did sand down the sharp edge left by the wire cutters but have not sanded since.

Photo Engineer
10-13-2012, 08:33 PM
Well, the restriction on the length of exposed plated Silver is not a hard and fast rule.

Also, the HANNA meter electrode is not ideal for this measurement. My RE is a HANNA Ag/Ag/Cl electrode build as a RE and it works fine.

PE

Kirk Keyes
10-14-2012, 04:44 PM
I used to perform Total Organic Halide analysis, and we had a silver electrode in it that we would clean using Ajax Powder, which has chlorine in it, well, probably as chloramine-T which releases free chlorine in water solution. The Ajax was nice as it had fine grit for scrubbing the crap off the silver electrode and I'm sure plated it somewhat as well!