Recovering Any Valuable Metals From Unknown Metal(S)

[dcapone2004]

So, I have a few pounds of an unknown metal that I am trying to determine if any of it contains any precious/valuable metals.  There is a descent a good quantity of it is silver and maybe even some gold as the metal was left behind from a jeweler along with several pieces of finished jewelry.

 

The jewelry itself is sterling silver with rhodium plating (according to the markings).  Additionally there are some gold plated pieces and some what I would venture to guess is brass molds.

 

The question is, since I officially have no idea what the metals may be (the majority of it is silver colored), what would be the best strategy to determine if any of it is silver or a silver alloy?

 

My thought process is to create shot out of it and heat it in concentrated (31, not 37 since it is a cheap starting point) hydrochloric acid.  If everything dissolves, when then it is fairly worthless.  Alternatively, if they is remaining unreacted metal, there should be a fairly high confidence that the metal is silver or some type of silver alloy.  Would this thinking be incorrect?  What other silver colored metals would not dissolve in hydrochloric acid?

 

From there, the plan was to rinse with distilled water and attempt to react with nitric acid and precipitate with copper wire.

 

Is this plan ok?  Is there a better way to go about this that would not be overly expensive (like buying an XRF analyzer)?

 

Thanks for any feedback.

[HydrogenBond]

You might try what Archimedes figured out and did. Back in ancient times, the King had a crown made. He wanted to know how much gold was in the crown. It was very odd shaped and it was hard to calculate the volume. Archimedes was given the task. 

 

Archimedes, while taking a bath, noticed that an object that is submerged in water, will displace its volume; eureka! Once he understood this, he took the crown and submerged it in water, to get its volume. Knowing the weight of the crown, he divided that by the volume, and calculated the density. Knowing the density of gold, he then calculated the percent of gold.

 

A less dangerous first approximation may be to submerge samples into a bucket of water, and measure the displacement to calculate the exact volume. You can have the water filled to an overflow so any displace water will overflow through a tube, into a collection bucket, to be weighed/measures in real time; beaker or scale. 

 

Then you calculate the mass/volume to give you a density. If you know the density of iron, brass, gold and silver, you can sort of get an estimate of the possible value. 

Edited April 23, 2015 by HydrogenBond