Problem with evaporating battery acid

[Bigwood247]

I was told from my chemical supplier that he sold me 93% rooto drain opener so I put it into my deplating cell and ran a batch of gold plated scrap to try it out but soon after I began deplating the acid turned a clear blue and started depositing copper on my lead cathode so I concluded that he sold me battery acid in a rooto bottle. So now I had a clear blue soulition of dilute sulfuric with a bit of black gold powder in the cell I then proceeded with evaporating the dilute sulfuric And it was going well until the end I ended up with a really dark brown almost black conctrated sulfuric I'm not new to the refining game as I have processed over 4 kilos of silver through electrolysis and had them assayed at over .995 purity but I'm lost now why has my sulfuric turned brown/black ??? I need help ASAP thanks alot Sean

 

[jeneje]

Why would a chemical supplier sell you battery acid? Pure H2SO4 is 98% CP. The color change is due to the evaporation of H2O, I think. If I am wrong I will be corrected by a senior member. I use 98% CP in my cell and I Have no problem with it.

Ken

 

[Bigwood247]

Why would a chemical supplier sell you battery acid? Pure H2SO4 is 98% CP. The color change is due to the evaporation of H2O, I think. If I am wrong I will be corrected by a senior member. I use 98% CP in my cell and I Have no problem with it.

Ken

He's just a person on eBay I deal with not really a " supplier" more of a person that sells chemicals and ships them through the postal service

 

[jeneje]

Do you have a local supplier near you? I deal with greenway chemical here in TN, they have good prices, if you can I would suggest trying to get 98% H2SO4 it really does eliminate the guesswork when using a gold cell.

The H2SO4 in my cell is black, I am as I type decanting it after several uses de-plating a few lbs of plated jewelry. The great thing about this is I can keep on using the acid over and over with no worry as long as I keep it covered, just adding fresh as needed.

Ken

 

[Bigwood247]

Do you have a local supplier near you? I deal with greenway chemical here in TN, they have good prices, if you can I would suggest trying to get 98% H2SO4 it really does eliminate the guesswork when using a gold cell.

The H2SO4 in my cell is black, I am as I type decanting it after several uses de-plating a few lbs of plated jewelry. The great thing about this is I can keep on using the acid over and over with no worry as long as I keep it covered, just adding fresh as needed.

Ken

I'm from Windsor Ontario Canada and its hard to find a chemical supplier that sells to a non business

 

[Alchymist]

Why would a chemical supplier sell you battery acid? Pure H2SO4 is 98% CP. The color change is due to the evaporation of H2O, I think. If I am wrong I will be corrected by a senior member. I use 98% CP in my cell and I Have no problem with it.

Ken

No, the color change is NOT from evaporation of H2O, but is typically from decomposition of organic matter. If you store your concentrated sulfuric acid in a plastic bottle (PE or PP), the bottle soon start to change color, and after some time the acid changes color too. The color is probably carbon left over when the material decompose.
If you need to concentrate your acid, you can heat it slowly until the water is evaporated. Just remember, that hot concentrated sulfuric acid is VERY NASTY stuff, that eats through skin and many types of gloves in just seconds, and if you drop water in it, you make a steam explosion that splatters the acid everywhere.

 

[Bigwood247]

Thanks alot I let the acid sit over night and the next day it was black still but it had a grey/white coating on the bottom of my glass I think that it was copper oxide from when I evaporated the dilute sulfuric with copper in it as I concentrated it the copper sulfate precipated out I cleaned the white powder and ran a batch of pins and it worked great so thanks everyone the moral if this whole thread was to buy my chemicals directly from suppliers and not a person on eBay

 

[Bigwood247]

Here's the gold I got so far from my cell I went across the border to Detroit and brought back some liquid fire drain opener and with a little hassle I got it into Canada lol but I stripped some military spec high yeild scrap and refined the black powder I finally got my cell running great now all I need is the batter charger that I just ordered from lazersteves webpage. Right now I'm using a 6 amp 6 volt charger I can only run line 200 grams at a time but it works for now

 

[Bigwood247]

I evaporated battery acid today to 1/3 it's content and I weighed 10 ml of it on my double digit jewelery scale if 1 ml of 90+ sulfuric is suspose to weigh 1.80 grams my 10 ml should weigh 18 grams when I weighed it and subtracted the empty bottle it weighed 20.1 grams did I over evaporate it or is scale just off I doubt it's my scale as I have a very accurate one does this mean I have over 98% sulfuric I thought I read somewhere on the fourm that u can't get it past 98% because it will just start evaporating along with the water ??? Does anyone know what is going on here ??

 

[FrugalRefiner]

My first thought would be to question the accuracy of the 10 ml volume measurement. How did you determine that it was 10 ml? As dense as sulfuric acid is, it would only take a 1 ml error in volume to account for most of the extra weight. Sulfuric acid has a different meniscus than water if you were using a graduated cylinder. Add a little scale error - I'm not saying that your scale isn't accurate, but if it has 0.1 gram accuracy, that means it can be off 0.1 gram on each use. So you might account for up to 0.2 gram error there (0.1 when weighing the empty container, another 0.1 when weighing it with acid).

You are correct that you cannot over concentrate sufuric acid. It's probably just the result of cumulative error.

Dave