03-24-2009, 09:37 PM
pgandw Wrote:jim currie Wrote:i have over 30 pages of info i have looked up on the web will try to condense them down to a reasonable size of post to back up my findings .
While you are doing so, please learn a little about alloys. Representing the characteristics of an alloy, which nickel silver is, by its component elements is incorrect, to put it nicely. Confusing an alloy with its component elements will cause you to fail chemistry and engineering classes. Insisting everybody else is wrong, and only you are correctly interpreting the research is not a great way to make friends and influence enemies.
Nickel silver was engineered by Germans in a contest to imitate an imported Chinese metal. Nickel silver, as the name implies, is an ideal substrate for silver plating, and is also used without plating in inexpensive cutlery because of its resistance to visible tarnish (oxidation) to its silver color despite immersion in dishwasher solutions and temperatures.
And depending on where you live and the environment of your train room, oxidation and the yellow color were the bane of brass rail track. Unfortunately, the rate of oxidation of brass is very dependent on the specifics of the environment so experiences vary widely with brass rail. Some can use brass rail quite successfully; other will have nothing but continuous cleaning chores with brass rail.
Fred Wright
•Chemical Vs. Physical Change
A Closer Look: Chemical Vs. Physical Change
Physical change: Although some extensive properties (like shape, phase, etc.) of the material change, the material itself is the same before and after the change. The change can be “undone.”
Ice melting: an example of physical change.
Chemical change: The substances present at the beginning of the change are not present at the end; new substances are formed. The change cannot be “undone.”
A nail rusting: an example of chemical change.
Mass conservation: Mass is neither created nor destroyed.
What are the macroscopic and microscopic differences between physical and chemical changes?
Macroscopic Definition Microscopic Definition
Physical Change The matter is the same.
The original matter can be recovered. The particles of the substance are rearranged.
Chemical Change The matter is different.
The old matter is no longer present. The original matter cannot be recovered.
The particles of the substance are broken apart, and the atoms are rearranged into new particles, forming a new substance.
Is the distinction always “clear-cut”?
There are many cases where the distinctions between physical changes and chemical changes are unclear. For example:
The dissolution of salt in water: This seems like a physical change because we know we can recover the salt from the water. However, if we look at the microscopic level, we see that the two types of atoms in salt, sodium and chlorine, separate from one another. In this example, we don’t have a new substance, therefore this salt in solution doesn’t fit the microscopic definition of a chemical change; but we also don’t have the substance in its original form — a stack of alternating sodium and chlorine atoms. Does this mean the change is half chemical and half physical? Though it has aspects of a chemical change, scientists would still classify the dissolution of salt as a physical change.
The creation of a metal alloy: If we melt two types of metal together, we create an alloy metal that has different properties than either of its components (e.g., heat conductivity, electrical conductivity, density, etc.). This might lead us to think that we’ve witnessed a chemical change. In fact, a new particle is not created by melting two metals together. This indicates they did not undergo a chemical reaction. Brass, for example, is about 60% copper and 40% zinc, and is composed of individual copper and zinc atoms (i.e., there is no “smallest unit” that is still brass). There is no such thing as a brass molecule.
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as far as making friends i don't give a hoot i just want some solid evidence to substantiate the claims of NS rail