In light of recent events I have a few questions How reliable is the Ice cube testing method and how accurate is the rare earth magnet? Can the rare earth magnet be fooled? I read where that the ice cube method doesnt always work....opinions?
You didn't say what type/size of objects you were concerned about. The rare earth magnet effect is very difficult to differentiate, unless it is something like a flat full silver object. Paramagnetism is known and can show easily in carefully done experiments, but, with only subjective input by the experimenter ( usually the owner can see it well) ,it is hazy. People easily 'see' it if they know something about the object such as its an ASE or a brand name bar than an unmarked one. The Ice-cube method is also based on properties of silver, but even 50% silver will be faster than base metals alloys, but slower than pure. When we do thermodynamics of solids in chem experiments, to identify properties or mix of metals, the answers from beginners are all over the scale at first but get better over time. It would be even worse if they just used an ice cube with no other measurable restrictions, such as was the ice cube made from degassed water or did it have bubbles within, was the ambient temperature exactly the same for both samples, etc. That is why the sources do not say , ..it will melt 22% faster or anything, just 'faster'. In summary they could work, but I myself would not base any outcome such as buying or trading on it, unless lab conditions were used, and time is more important for me. Jim
In this circumstance it is a standing liberty quarter I ask about, the rare earth magnet is something im not familiar with nor is the ice method. For example if I wanted to determine whether or not something like a standing liberty quarter is real can the rare earth magnet determine it?
A rare earth magnet is generally neodymium. It doesn't hold the metal vertically, the metal is allowed to slide over the surface and it appears to slow down, or vertical nearby the magnet and a deviation in its direction as it passes the magnet. Such magnets are often found in hobby shops and shops like lowes and home depot. Be cautious with them. I would not slide a collector type of coin over a metal magnet.
Off topic, sorry - just wanted to say I'm super impressed with your chem and Spanish skills! (back on topic now) I always figured the best method for metal testing was specific gravity - but can this be fooled with a tricky alloy?
Specific gravity is (if you'll pardon the pun) the gold standard test. The ice cube and magnet tests are less direct, they depend on characteristics of silver not present to the same extent in the base metals used in counterfeits. For example, silver is a good conductor of heat (better than copper, or gold, especially better than tin and zinc) German silver (used for many contemporary counterfeits) is an alloy of copper, nickel and zinc, which conducts heat about 1/20th as well as pure silver (Interestingly worse than any of it's components). http://www.engineersedge.com/properties_of_metals.htm But the lab measurements are done by applying heat to the face of a smooth bar and measuring the temperature rise at the other end - which we can't do for a coin. With the ice cube test you are doing an indirect measurement - how well heat is conducted from the (rough) face through the (rough) reverse and into whatever heat sink the coin/bar is sitting on. That's why it's best done in parallel - two bars resting on the same heat sink, two ice cubes. If the melt time is significantly different or substantially the same, they are different or same composition (could, of course BOTH be counterfeit).
I dont know about the ice cube method. But i have a neodymium magnet that is about 4 inches long. I place the coin on it and tip it until the coin slides down. At the very end just before it falls off, a silver coin will seem to want to stick to it just for a split second. However copper will do the same thing. Heres a video i found: https://www.google.com/url?sa=t&sou...kSIg2OAKUIK2wx4uA&sig2=3Tb0_9LywUPduQ1M9Wsrpg
