how do I make silver nitrate

Wyndham · Dec 4, 2009

Silver nitrate sells for about $25 gram. As a potter I have a special glaze that calls for 6% silver nitrate or I might be able to use silver chloride as well.
My question is using pure silver how much silver will dissolve into what volume of nitric acid and then do i let it evaporate to crystals? Would Muriatic acid and silver work for the chloride.
Is there a better method?
If I were to use sterling scrap would i use AP to get the sterling into solution, but what would i use to drop the silver so I would have pure silver.
I wanted to ask before using the wrong volumne of acid. I also have an outdoor work area for ventilation and safety.
Thanks for any help in this matter Wyndham

butcher · Dec 4, 2009

I am kind of unclear what you need silver nitrate, or silver chloride or silver powders for your project,

silver chloride is insoluble, and a chloride oxidizes the silver and can not really dissolve it.
silver would be insoluble in acid peroxide, or HCl, unless a really strong oxidizer, and heat was used, this is not a good way to get silver chloride.

if you wanted silver chloride, dissolve the silver in nitric acid first to make silver nitrate, then precipitate it out by adding HCl, it will look like cottage cheese, this chloride of silver should not be melted without conversion, as melt would produce chlorine gas, and can carry your silver away with this gas,

a piece of copper in the silver nitrate solution will make the silver come out of solution looking like pepper (this can be melted back to silver metal without conversion.

I have a bad memory I think somebody said HNO3 1610 mL/#cu this maybe another can answer better,

Harold_V · Dec 4, 2009

A liter of nitric acid in a liter of water will easily dissolve 30 troy ounces of pure silver.

All you need do to recover the silver as nitrate crystals is to allow the solution to cool. Crystals will grow readily from a concentrated solution. So fast, in fact, that you can watch them grow. If they fail to grow, evaporate the solution, reducing its volume by 50%, then allow it to cool once again.

Assuming you need pure silver, but have only a silver alloy, one of the things you can do is dissolve the material in your possession, using only a minimum amount of acid, so it is all consumed in the process. Use (distilled) water sparingly, but do include a small percentage. When the material has digested, allowing it to cool will cause silver nitrate crystals to grow. In the process, they will reject any other metals in solution. When all of the silver has converted to crystals, the solution can be poured off, then the crystals dissolved in hot distilled water. Allow the solution to cool, where it once again will grow silver nitrate crystals. If it fails to do so, evaporate excess water.

By repeating the above cycle, you can purify the silver, each time eliminating any traces of impurities.

Key to success is having concentrated solutions, and in consuming all of the acid that is present. You can judge that by heating the solution and allowing it to work until it no longer emits fumes, but there are traces of the starting metal still not dissolved.

Harold

goldsilverpro · Dec 5, 2009

I agree totally with what Harold said. I always used the figure of 100 ozs of silver being soluble in 1 gallon of nitric (about 1 gram silver per 1.2 ml nitric), which is pretty close to Harold's numbers. In any case, like Harold said, use an excess of silver - when the nitric stops working, there should still be some undissolved silver. Silver nitrate is about 9 times more soluble when the solution is hot than when it cools.

Wyndham · Dec 5, 2009

Thanks for the info . In the glaze that I am using, which is called a crystalline glaze, Zinc silicate crystals grow in the glaze that is held at 2100 deg f for 4 hrs and slowly cooled.Coloring oxides like cobalt(.5%) or iron or other coloring oxides produce the different colors. The glaze has a excess of zinc(25%) and combines with the silica as it cools forming the random crystals.
I'll post a link, might or might not work. The picture is about 2/3 down the page.
http://s3.excoboard.com/exco/thread.php?forumid=64484&threadid=694767
The silver nitrate produces a golden metallic crystal when the glaze is reheated to 1800 deg f and reduced by introducing excess hydrocarbon into the kiln, changing a copper green to a red and the silver from a clear to a metallic luster.
I also found a company called salt lake metals that sells silver nitrate for about $1/gram after i posted the question. That's cheaper than I can make it. A ceramic supplier had the $25/gram price, wish i had that kind of markup on my pottery.
Thanks again and I'll archive this info for future use. Wyndham