dew129,
First, you are using way to much acid. You only need about 1.2 ml of concentrated nitric per gram of silver, maybe 35 to 40 ml for an ounce of silver. This is why your silver isn't cementing out when you put your copper in. There is still a LOT of free nitric acid left. The silver won't cement out until all the nitric acid has been consumed.
Second, You said:
i then place it in my container and add my nitric acid just above the pile of silver in the container. I then put the container on a hot plate...
Are you using concentrated acid - around 68%? Are you adding any distilled water to dilute your acid? Are you covering your container while it's hot?
Since you are getting blue crystals that disappear when you add water, I'm guessing your solution is too concentrated. We usually use 50% concentrated acid along with 50% distilled water when digesting silver. If you are already adding it you may just be losing too much to evaporation while your solution is hot.
Here is my suggestion for the future. Put your cleaned pieces in the container. Figure out how much acid you think you'll need - around 35 to 40 ml. per oz. Add that much distilled water to your container. Heat it. Now add a small amount of the acid - just a few milliliters at first. Then cover the container with a watch glass or saucer. When the reaction dies down, add a bit more of the acid. Repeat until all the silver is digested. Use only enough acid to dissolve the silver. Let the solution cool, filter it and cement out your silver.
You can still recover the silver you've already dissolved. First, bring the volume of your solution to about 3 cups by adding distilled water. Then, just add small amounts of silver to the solution and let them dissolve. This will consume any excess acid that still remains. Give each addition of silver plenty of time to react. Heating will speed the process. When no more silver dissolves, cool, filter to remove any undissolved material, and cement with copper.
Since you're new here, I'd also like to offer the following advice. The first rule is to be safe in everything you do. Before you jump into any of the processes you see discussed here, be sure you understand the potential hazards and do everything you can to minimize the risks. Read EVERYTHING in the
Safety section of the forum, especially the Dealing with Waste topic. No amount of precious metal is worth jeopardizing your health or the health of those around you.
I strongly encourage all new members to follow the
Guided Tour created by LazerSteve. It will provide an introduction to the forum and numerous valuable links including the General Reactions List. Be sure to follow the link to his web site as he has many outstanding videos, a collection of great reference documents, and he sells a lot of the supplies needed to get started including detailed instructional DVDs. Samuel-a also has a lot of videos, guides and tutorials at his web site
Gold-N-Scrap.
Download C.M. Hoke's book
Refining Precious Metal Wastes. You'll see her book mentioned repeatedly here on the forum for good reason. It is probably the best book ever written for the beginner who wants to learn refining. It is written in layman's terms and will provide a solid foundation that will help you understand everything you read here on the forum. You'll also find a tremendous amount of information in the two Forum Handbooks compiled by aflacglobal,
Forum Handbook Vol 1 and
Forum Handbook Vol 2.
Best of luck,
Dave
Edit, I just reread your posts and saw that you are using home made nitric acid, so my comments regarding concentrated acid do not apply in this case.
