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lead oxide from electrolysis reaction?


PyroNinjaah

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-So I was trying to make lead oxide for various purposes (star recipes, making lead nitrate for a lead dioxide anode...etc) and I thought electrolysis would be the easiest way. I added 3 spoonfuls of potassium nitrate to a 250 ml beaker and used a graphite cathode and lead anode. The anode made no bubbles and a white lead hydroxide/oxide precipitate formed which fell to the bottom of the beaker. The cathode formed bubbles of hydrogen and started to form a layer of spongy lead dioxide.

-My thoughts were that the lead at the anode was oxidized to lead ions and water was reduced to hydrogen and hydroxide ions at the cathode.

-Some lead ions might stay in the solution thanks to the nitrate ions increasing the solubility of the lead compound, and thus could be plated out at the cathode and be oxidized by the nitrate.

-All seemed fine, and then the lead dioxide stopped being formed after about an hour but everything else was normal as it was. (Maybe the nitrate ions were used up and so lead ions couldn't stay in solution until they reached the cathode?)

-Suddenly, the lead dioxide started forming again after another half an hour.

-After an hour after this, the solution started smelling like strong ammonia.

-After I stopped the reaction and filtered off the lead hydroxide, I decided to nuetralize the ammonia with hydrochloric acid (i just felt like doing it). The solution didn't chnge after the first small adition of acid, but apon further additions, lots of nitrogen monoxide was developed that bubbled out of solution and turned into nitrogen dioxide in the air.

 

-I am pretty sure this strange chain of events is due to the reduction of the nitrate ions, but does anyone actually know what is going on? And what is the final compound that formed nitrogen monoxide when hydrochloric acid was added to it?

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Why did you add potassium nitrate to your solution? Lead dioxide is formed on the anode when a lead anode is electrolyzed in an acidic solution, usually weak sulfuric acid (6-10%). Unfortunately, for you, this forms a coating that stays on the anode. This process is commonly used to create nonsoluble anodes for chrome plating. I have been doing experiments to form solid lead anodes for a perchlorate cell by doing this. The problem is that there are two differing crystalline forms of lead dioxide; alpha and beta. Beta is the preferred form for perch production and I have been experimenting with different parameters in the electrolysis cell to form only beta with very limited success, so far. If you want to try plating lead dioxide on a substrate this might help you: http://www.reocities.com/lllwolly/further/sauce1.html

Edited by MadMat
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Thanks, that is a great resource. Sorry for not replying earlier, but I wasn't home due to the holiday. I added potassium nitrate to the solution as an electrolyte. I didn't think about the nitrate being reduced. Sodium hydroxide or maybe a carbonate would probably have worked out better. I have heard about making lead dioxide anodes with dilute sulphuric acid, but many have said that the coating peels off quickly in a chlorate cell. Please share if you manage to refine the process to where the anodes work in a chlorate cell.
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