Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

White Gold

  1. Feb 15, 2010 #1
    Is this Wikipedia diagram of white gold alloy wrong? The contributing proportions of Cu, Au and Ag seem to add up to 150% for equal portions of each metal.


    This is from the Wikipedia article http://en.wikipedia.org/wiki/Colored_gold#White_gold"
    Last edited by a moderator: Apr 24, 2017
  2. jcsd
  3. Feb 16, 2010 #2


    User Avatar

    It is not wrong, it's just harder to read.

    Any alloy is a point on the diagram, which is then transformed into 3 proportions of each totaling 100%.

    The way to read. Set a random point or what alloy you want. from that point draw 3 lines parallel to the sides of the triangle. The %'s will be clearly visible and totaling 100%.
  4. Feb 17, 2010 #3
    OK. Now I see it, now that you've stated it that way. The equipotential lines pinwheel counterclockwise and it seems to work out correctly.

    For 33.3% of each it works out and the axes intersect in the center of the triange. Pinwheel to the right, instead, and you get 66,7% of each. I think the wikipedia contributors need to work a little harder in their presentation!
  5. Feb 17, 2010 #4


    User Avatar

    Staff: Mentor

    Wikipedia has its quirks, but don't blame it for your own lack of knowledge :wink: This method of presenting properties of three component mixtures predates wikipedia, see for example http://www.sv.vt.edu/classes/MSE2094_NoteBook/96ClassProj/experimental/ternary2.html [Broken]
    Last edited by a moderator: May 4, 2017
  6. Feb 17, 2010 #5


    User Avatar

    The rotaion can be clockwise too it all depends on the way you set the 0 to 100 % on each side. i'm sure there is a convention about this but, it's just the same and can appear sometimes.
  7. Feb 18, 2010 #6
    Yeah, that was a bit harsh of me. The criticism of experts working for free should be gentle.

    So I went to your quoted web site and it said this,

    "Reading the compositions of iron, chromium and nickel at any point on the stainless steel ternary phase diagram in Fig. 2 is simple. Instead of drawing one tie-line, as in a binary phase diagram , three lines are drawn, each parallel to a side of the triangle and going through the point in question. Extend the lines so they pass through an axes. To find the iron composition, the line drawn parallel to the axis opposite the Fe vertex is the one needed. The percent iron is then read off the axis."

    OK. So we keep the vertex at x=0 in mind and draw the equipotentials of x so they are parallel to the axis opposite x=0. That helps.

    And thanks Lok. That makes sense.
    Last edited: Feb 18, 2010
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook