Posted: 10/17/2008 3:22:03 PM EDT
|
I received this awhile back and was told it's silver. It was obviously formed by liquid poured into a mold at some point. When I received it, it was a uniform silver color, but over time it has tarnished a bit to a bronzish tint. The 15.05 is probably the weight in oz, since that feels about right. Is it silver?    |
The tarnish is a copper color. I used my shirt on the side of it and it started to polish up pretty quickly. |
|
determine its volume by putting it in a measuring cup filled with water, and use that to calculate its density. Then compare that to the density of silver. eta the density of silver is 10.49 g·cm−3 if you do the measuring I can do the calculations and unit conversions. |
Which measurements do you want from the cup? |
volume (in mL or fluid ounces) before and after you put the bar in. Try to be as accurate as you possibly can. |
The best I could do was with a plastic measuring cup. I started with 500mL, and after I put the bar in, the level was at 550mL. Not the most accurate test, but it's the best I could do with what I have. |
according to my calculation, 15.05 ounces of silver should displace a volume of about 40.67 mL. If the water was at slightly less than 550mL, i'd say you probably have silver. |
| i don't know much about metallurgy, but other metals which look somewhat similar could be nickel, zinc and lead. Nickel and zinc have much lower densities than the results we found. The density of lead is very close though. Anyone know how we could rule out lead? I think its perhaps too shiny to be lead. |
Doesnt lead have a lower melting temp than silver? Silver, pure 1761 degrees f Silver, sterling 1640 degrees f Silver, coin 1615 degrees f Lead 621 degrees f |
Just guessing, but it doesn't seem to weigh enough to be lead and it seems to be too hard. It takes quite a bit of effort to scratch it. |
Lead starts out very bright and shiny but dulls to a gray color over time. |
My uncle had it sitting on his shelf about 5 years ago, I asked him what it was and he said "I dunno, someone told me it's silver... you want it?" So I kept it. 
|
lead is only about 10% more dense than silver, so distinguishing the two by weight would be difficult. However, lead has high resistance to corrosion and a dull luster, so if the thing was tarnished but shiny after you polished it up a bit, i'd guess silver. If you have a multimeter maybe you could test it to check for electrical conductivity. Silver's is good, lead's poor. |
This has been shiny-ish silver since day one, but over time, it has tarnished to a bronzish color. It reminds me of the parts we did in the machine shop that had to be silver plated... they would tarnish to a bronze color quickly if left out. |
|
You can test for silver by using some Iron sulfide (rock hound pyrite) in hydrochloric acid. (You can find HCl at any Ace hardware, believe it or not). The small bit of the pyrite is put in enough HCl to coat the bottom of the beaker. Swirl it a bit to get the reaction started. Cover with a flat bit of cardboard. When some hydrogen sulfide gas has filled the beaker, immediately remove the top and dunk the metal to be tested into the gas (don't get it in the acid itself). Silver loves sulfide ions. It will turn brownish black dark almost immediately when it hits the vapor. DON'T breath the vapors. Best to do it outside in low wind. Of course, if you've got nitric acid you can clean up a spot with ammonia and hit it with a drop -- a creamy white precipitate (silver nitrate) indicates you've got high percentage silver, but green indicates bunches of copper mixed in. |
Lead will do the same thing.  I'm sure you don't have nitric acid around, but I used to differentiate between silver and lead: 1) Dissolve the metal sample in nitric acid. 2) Add just enough of a salt solution to get a white precipitate. 3) Add ammonia solution. 4) Silver chloride will dissolve but lead chloride does not. 
|
Its not lead; he'd be able scratch it with his fingers if it were. |
Then why bother with the H2S.
|
|
A jeweler or bullion dealer would do acid tests on it; depending on what the acid does and what color the residue turns, indicates (roughly) the percentage. If you eventually want to sell it to a jeweler/dealer, nobody is going to pay you "spot" price for silver for it. They'll have to sell it for less to offset the assay fee. They'll only sell it to an assayer* who will refine it again and sell it back into the market. And for what is a "scrap" casting like that, the jeweler may want to drill a small hole through it, and test all the hole drillings as well to make sure it's the same all the way through. *Midwest Refineries is one such place. ~ |
